Cargo.toml

@@ -77,6 +77,8 @@ features = [
   "LucideBug",
   "LucideCheck",
   "LucideCheckCircle",
+  "LucideClipboardCheck",
+  "LucideClipboardCopy",
   "LucideFlame",
   "LucideLink",
   "LucideList",

public/format.js

@@ -0,0 +1,15 @@
+export function formatNumber(value, thousands, places, prefix, suffix) {
+  const aval = Math.abs(value);
+  const neg = value < 0;
+
+  const formatter = new Intl.NumberFormat(undefined, {
+    style: "decimal",
+    useGrouping: thousands ? "always" : false,
+    minimumFractionDigits: places,
+  });
+
+  const res =
+    (neg ? "-" : "") + (prefix || "") + formatter.format(aval) + (suffix || "");
+
+  return res;
+}

src/components.rs

@@ -7,3 +7,10 @@ pub mod layout;
 pub mod render;
 pub mod seo;
 pub mod title;
+
+pub mod fields {
+    pub mod currency;
+    pub mod label;
+    pub mod number;
+    pub mod toggle;
+}

src/components/display.rs

@@ -1 +1,2 @@
 pub mod bar_chart;
+pub mod clipboard;

src/components/display/clipboard.rs

@@ -0,0 +1,51 @@
+use yew::{function_component, html, use_effect_with_deps, use_state, Callback, Html, Properties};
+use yew_hooks::use_clipboard;
+use yew_icons::{Icon, IconId};
+
+#[derive(Properties, PartialEq)]
+pub struct CopyToClipboardProps {
+    pub value: String,
+    pub format: Option<String>,
+}
+
+#[function_component(CopyToClipboard)]
+pub fn copy_to_clipboard(props: &CopyToClipboardProps) -> Html {
+    let copied = use_state(|| false);
+    let clipboard = use_clipboard();
+
+    let onclick = {
+        let value = props.value.clone();
+        let format = props.format.clone();
+        let copied = copied.clone();
+
+        Callback::from(move |_| {
+            clipboard.write(value.clone().into_bytes(), format.clone());
+            copied.set(true);
+        })
+    };
+
+    {
+        let copied = copied.clone();
+        use_effect_with_deps(
+            move |_| {
+                copied.set(false);
+            },
+            props.value.clone(),
+        );
+    }
+
+    html! {
+        <button type="button" title="Copy to clipboard" {onclick}>
+            <Icon
+                icon_id={
+                    if *copied {
+                        IconId::LucideClipboardCheck
+                    } else {
+                        IconId::LucideClipboardCopy
+                    }
+                }
+                width={"1em".to_string()}
+                height={"1em".to_string()} />
+        </button>
+    }
+}

src/components/fields/currency.rs

@@ -0,0 +1,40 @@
+use web_sys::HtmlSelectElement;
+use yew::{function_component, html, Callback, Html, Properties, TargetCast};
+
+use crate::model::currency::{Currency, CURRENCIES};
+
+#[derive(Properties, PartialEq)]
+pub struct CurrencySelectProps {
+    pub value: Currency,
+    pub onchange: Callback<Currency>,
+}
+
+#[function_component(CurrencySelect)]
+pub fn currency_select(props: &CurrencySelectProps) -> Html {
+    let onchange = {
+        let onchange = props.onchange.clone();
+
+        Callback::from(move |event: yew::Event| {
+            onchange.emit(
+                event
+                    .target_dyn_into::<HtmlSelectElement>()
+                    .expect("target")
+                    .value()
+                    .parse::<Currency>()
+                    .expect("currency"),
+            );
+        })
+    };
+
+    html! {
+        <select {onchange}>
+            {
+                for CURRENCIES.iter().map(|currency| html! {
+                    <option value={currency.to_string()} selected={*currency == props.value}>
+                        {currency.to_string()}
+                    </option>
+                })
+            }
+        </select>
+    }
+}

src/components/fields/label.rs

@@ -0,0 +1,24 @@
+use yew::{classes, function_component, html, AttrValue, Children, Classes, Html, Properties};
+
+#[derive(Properties, PartialEq)]
+pub struct LabelProps {
+    pub title: AttrValue,
+    #[prop_or_default]
+    pub class: Classes,
+    #[prop_or_default]
+    pub children: Children,
+}
+
+#[function_component(Label)]
+pub fn label(props: &LabelProps) -> Html {
+    let class = classes!("flex", "flex-col", "gap-2", props.class.clone());
+
+    html! {
+        <div class={class}>
+            <label class="text-sm font-medium">
+                {props.title.clone()}
+            </label>
+            {props.children.clone()}
+        </div>
+    }
+}

src/components/fields/number.rs

@@ -0,0 +1,237 @@
+use wasm_bindgen::{prelude::wasm_bindgen, JsValue};
+use web_sys::FocusEvent;
+use yew::{
+    classes, function_component, html, use_node_ref, use_state, AttrValue, Callback, Classes, Html,
+    Properties, TargetCast,
+};
+use yew_hooks::use_timeout;
+use yew_icons::{Icon, IconId};
+
+#[wasm_bindgen(module = "/public/format.js")]
+extern "C" {
+    #[wasm_bindgen(catch, js_name = formatNumber)]
+    pub fn format_number(
+        value: f64,
+        thousands: bool,
+        places: usize,
+        prefix: Option<&str>,
+        suffix: Option<&str>,
+    ) -> Result<String, JsValue>;
+}
+
+#[derive(Properties, PartialEq)]
+pub struct NumberProps {
+    pub icon_left: Option<IconId>,
+    pub icon_right: Option<IconId>,
+
+    pub icon_left_class: Option<Classes>,
+    pub icon_right_class: Option<Classes>,
+
+    #[prop_or_default]
+    pub class: Classes,
+    pub id: Option<AttrValue>,
+    pub name: Option<AttrValue>,
+    pub placeholder: Option<AttrValue>,
+
+    #[prop_or_default]
+    pub value: f64,
+
+    #[prop_or_default]
+    pub disabled: bool,
+    #[prop_or_default]
+    pub thousands: bool,
+    #[prop_or_default]
+    pub places: usize,
+    pub prefix: Option<AttrValue>,
+    pub suffix: Option<AttrValue>,
+
+    pub onfocus: Option<Callback<FocusEvent>>,
+    pub onblur: Option<Callback<FocusEvent>>,
+    pub onchange: Option<Callback<Option<f64>>>,
+    pub oninput: Option<Callback<Option<f64>>>,
+}
+
+#[function_component(Number)]
+pub fn number(props: &NumberProps) -> Html {
+    let mut classes = Classes::from("text-right");
+
+    let icon_left = if let Some(icon) = props.icon_left {
+        classes.push("icon-left");
+        Some(html! {
+            <Icon
+                icon_id={icon}
+                class={classes!("group-focus-within:text-indigo-300",
+                                props.icon_left_class.clone())} />
+        })
+    } else {
+        None
+    };
+
+    let icon_right = if let Some(icon) = props.icon_right {
+        classes.push("icon-right");
+        Some(html! {
+            <Icon
+                icon_id={icon}
+                class={classes!("group-focus-within:text-indigo-300",
+                                props.icon_right_class.clone())} />
+        })
+    } else {
+        None
+    };
+
+    classes.extend(props.class.clone());
+
+    let value = props.value;
+
+    // Create a state variable that we will use to store the value that the user enters into the
+    // input element. We use this so that we only need to validate input when the user focuses away
+    // from the input (or presses <Enter>). The default value for this state is the initial value
+    // of the number field, formatted for reasonable input.
+    let input_value = {
+        let places = props.places;
+        use_state(move || {
+            format_number(value, false, places, None, None).expect("format_numbert to work")
+        })
+    };
+
+    // We need to keep track of whether the field is focused, which we do with this state variable.
+    // When the user focuses and unfocuses the control, we toggle this state variable.
+    let focused = use_state(|| false);
+
+    // We also want to keep track of a reference to our <input> element, so that we can select the
+    // text when the user focuses the input. Doing this in the event handler is not having the
+    // desired effect without a small delay.
+    let input_ref = use_node_ref();
+
+    let timeout = {
+        let focused = focused.clone();
+        let input_ref = input_ref.clone();
+
+        use_timeout(
+            move || {
+                if *focused {
+                    input_ref
+                        .cast::<web_sys::HtmlInputElement>()
+                        .expect("<input> not attached to reference")
+                        .select();
+                }
+            },
+            50,
+        )
+    };
+
+    let parse_input = {
+        let places = props.places;
+        let input_value = input_value.clone();
+        let onchange = props.onchange.clone();
+
+        Callback::from(move |()| {
+            let value = if let Ok(value) = (*input_value).parse::<f64>() {
+                // Update the text value of the input to match our parsed number. We only format to
+                // the desired number of places here, so we don't force the user to cursor around
+                // formatting characters and thousand separators.
+                input_value.set(
+                    format_number(value, false, places, None, None)
+                        .expect("Number formatting to work"),
+                );
+
+                Some(value)
+            } else {
+                None
+            };
+
+            if let Some(onchange) = &onchange {
+                onchange.emit(value);
+            }
+        })
+    };
+
+    let onfocus = {
+        let timeout = timeout.clone();
+        let focused = focused.clone();
+
+        Callback::from(move |_| {
+            focused.set(true);
+            timeout.reset();
+        })
+    };
+
+    let onblur = {
+        let focused = focused.clone();
+        let parse_input = parse_input.clone();
+
+        Callback::from(move |_| {
+            focused.set(false);
+            parse_input.emit(());
+        })
+    };
+
+    let onchange = { Callback::from(move |_| parse_input.emit(())) };
+
+    let oninput = {
+        let input_value = input_value.clone();
+        let oninput = props.oninput.clone();
+
+        Callback::from(move |event: yew::InputEvent| {
+            let Some(el) = event.target_dyn_into::<web_sys::HtmlInputElement>() else {
+                log::error!("No <input> element found in event");
+                return;
+            };
+
+            let value = el.value();
+            input_value.set(value.clone());
+
+            if let Some(oninput) = &oninput {
+                oninput.emit(value.parse::<f64>().ok());
+            }
+        })
+    };
+
+    // If the field is focused, then we want to allow the user to work with their own value, as a
+    // string. if the field is not focused, then we want to render the number value using the
+    // prefix, suffix, thousands separator and places.
+    let rendered = if *focused {
+        (*input_value).clone()
+    } else {
+        format_number(
+            value,
+            props.thousands,
+            props.places,
+            props.prefix.as_deref(),
+            props.suffix.as_deref(),
+        )
+        .expect("format_number to work")
+    };
+
+    let id = props.id.clone();
+    let name = props.name.clone();
+    let placeholder = props.placeholder.clone();
+
+    let input = html! {
+        <input
+            ref={input_ref}
+            class={classes}
+            type="text"
+            id={id}
+            name={name}
+            placeholder={placeholder}
+            disabled={props.disabled}
+            value={rendered}
+            {onfocus}
+            {onblur}
+            {onchange}
+            {oninput} />
+    };
+
+    if icon_left.is_some() || icon_right.is_some() {
+        html! {
+            <div class="input-icons group">
+                {icon_left}
+                {input}
+                {icon_right}
+            </div>
+        }
+    } else {
+        input
+    }
+}

src/components/fields/toggle.rs

@@ -0,0 +1,48 @@
+use yew::{classes, function_component, html, AttrValue, Callback, Classes, Html, Properties};
+
+#[derive(Properties, PartialEq)]
+pub struct ToggleProps {
+    #[prop_or_default]
+    pub label: AttrValue,
+    pub value: bool,
+    #[prop_or_default]
+    pub classes: Classes,
+    #[prop_or_default]
+    pub disabled: bool,
+    pub onchange: Callback<bool>,
+}
+
+#[function_component(Toggle)]
+pub fn toggle(props: &ToggleProps) -> Html {
+    let onclick = {
+        let onchange = props.onchange.clone();
+        let value = props.value;
+        let disabled = props.disabled;
+
+        Callback::from(move |_| {
+            if disabled {
+                return;
+            }
+
+            onchange.emit(!value);
+        })
+    };
+
+    html! {
+        <div class="flex flex-row items-center gap-2">
+            <div class={classes!("toggle",
+                                 if props.value { "active" } else { "inactive" },
+                                 if props.disabled { "disabled" } else { "" },
+                                 props.classes.clone())}
+                 {onclick}>
+                 <div class="toggle-background" />
+                <div class="toggle-inner" />
+            </div>
+            if !props.label.is_empty() {
+                <div>
+                    {props.label.clone()}
+                </div>
+            }
+        </div>
+    }
+}

src/components/layout/footer.rs

@@ -65,6 +65,9 @@ pub fn footer(_: &FooterProps) -> Html {
                             rel="noreferrer">
                             {"Mastodon"}
                         </a>
+                        <Link<Route> classes="hover:text-neutral-50" to={Route::PositionSize}>
+                            {"Position Size Calculator"}
+                        </Link<Route>>
                         <Link<Route> classes="hover:text-neutral-50" to={Route::Analytics}>
                             {"Analytics"}
                         </Link<Route>>

src/model.rs

@@ -6,8 +6,14 @@ use yew::{function_component, html, use_memo, Children, ContextProvider, Html, P
 macros::tags!("content/tags.yaml");
 
 pub mod blog;
+pub mod currency;
 pub mod pages;
 
+pub mod trading {
+    pub mod account;
+    pub mod position;
+}
+
 #[derive(Properties, PartialEq)]
 pub struct ProvideTagsProps {
     #[prop_or_default]

src/model/currency.rs

@@ -0,0 +1,149 @@
+use std::{collections::HashMap, fmt::Display, str::FromStr};
+
+use gloo::net::http::Request;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Hash, Serialize, Deserialize)]
+pub enum Currency {
+    AUD,
+    CAD,
+    EUR,
+    GBP,
+    JPY,
+    USD,
+}
+
+impl Default for Currency {
+    fn default() -> Self {
+        Self::USD
+    }
+}
+
+impl Display for Currency {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "{}",
+            match self {
+                Currency::AUD => "AUD",
+                Currency::CAD => "CAD",
+                Currency::EUR => "EUR",
+                Currency::GBP => "GBP",
+                Currency::JPY => "JPY",
+                Currency::USD => "USD",
+            }
+        )
+    }
+}
+
+impl FromStr for Currency {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "AUD" => Ok(Currency::AUD),
+            "CAD" => Ok(Currency::CAD),
+            "EUR" => Ok(Currency::EUR),
+            "GBP" => Ok(Currency::GBP),
+            "JPY" => Ok(Currency::JPY),
+            "USD" => Ok(Currency::USD),
+            _ => Err(()),
+        }
+    }
+}
+
+impl Currency {
+    pub fn symbol(&self) -> &'static str {
+        match self {
+            Currency::AUD => "$",
+            Currency::CAD => "$",
+            Currency::EUR => "€",
+            Currency::GBP => "£",
+            Currency::JPY => "¥",
+            Currency::USD => "$",
+        }
+    }
+}
+
+pub static CURRENCIES: &[Currency] = &[
+    Currency::AUD,
+    Currency::CAD,
+    Currency::EUR,
+    Currency::GBP,
+    Currency::JPY,
+    Currency::USD,
+];
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct ExchangeRates {
+    /// The base currency
+    pub base: Currency,
+    /// The rates converting from `base` to the target currency
+    pub rates: HashMap<Currency, f64>,
+}
+
+impl Default for ExchangeRates {
+    fn default() -> Self {
+        Self::new(Currency::default())
+    }
+}
+
+impl ExchangeRates {
+    pub fn new(base: Currency) -> Self {
+        let mut rates = HashMap::new();
+        rates.insert(base, 1.0);
+        Self { base, rates }
+    }
+}
+
+#[derive(Debug, Deserialize)]
+struct ExchangeRateResult {
+    success: bool,
+    base: String,
+    date: String,
+    rates: HashMap<String, f64>,
+}
+
+pub async fn get_exchange_rates(
+    base: Currency,
+    target: Option<Currency>,
+) -> Result<ExchangeRates, &'static str> {
+    let symbols = target.as_ref().map(Currency::to_string).unwrap_or_else(|| {
+        CURRENCIES
+            .iter()
+            .map(Currency::to_string)
+            .collect::<Vec<_>>()
+            .join(",")
+    });
+
+    let res = Request::get(&format!(
+        "https://api.exchangerate.host/latest?base={base}&symbols={symbols}"
+    ))
+    .send()
+    .await
+    .map_err(|err| {
+        log::error!("Failed to send request to api.exchangerate.host: {err:?}");
+        "Failed to send request to api.exchangerate.host"
+    })?
+    .json::<ExchangeRateResult>()
+    .await
+    .map_err(|err| {
+        log::error!("Failed to parse response from api.exchangerate.host: {err:?}");
+        "Failed to parse response from api.exchangerate.host"
+    })?;
+
+    let mut rates = HashMap::new();
+    for (symbol, rate) in res.rates {
+        match symbol.parse() {
+            Ok(currency) => {
+                rates.insert(currency, rate);
+            }
+
+            Err(err) => {
+                log::error!("Failed to parse currency symbol '{symbol}' from api.exchangerate.host: {err:?}");
+            }
+        }
+    }
+
+    Ok(ExchangeRates { base, rates })
+}

src/model/trading/account.rs

@@ -0,0 +1,98 @@
+use std::rc::Rc;
+
+use gloo::storage::Storage;
+use serde::{Deserialize, Serialize};
+use yew::Reducible;
+
+use crate::model::currency::{Currency, ExchangeRates};
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct Account {
+    pub places: usize,
+    pub currency: Currency,
+    pub exchange_rates: ExchangeRates,
+    pub amount: f64,
+    pub margin_risk: f64,
+    pub position_risk: f64,
+}
+
+impl Default for Account {
+    fn default() -> Self {
+        let currency = Currency::GBP;
+
+        Self {
+            places: 4,
+            currency,
+            exchange_rates: ExchangeRates::new(currency),
+            amount: 500.0,
+            margin_risk: 0.01,
+            position_risk: 0.01,
+        }
+    }
+}
+
+pub enum AccountAction {
+    SetPlaces { places: usize },
+    SetCurrency { currency: Currency },
+    SetExchangeRates { exchange_rates: ExchangeRates },
+    SetAmount { amount: f64 },
+    SetMarginRisk { risk: f64 },
+    SetPositionRisk { risk: f64 },
+}
+
+impl Reducible for Account {
+    type Action = AccountAction;
+
+    fn reduce(self: Rc<Self>, action: Self::Action) -> Rc<Self> {
+        match action {
+            AccountAction::SetPlaces { places } => Self {
+                places,
+                ..(*self).clone()
+            },
+
+            AccountAction::SetCurrency { currency } => Self {
+                currency,
+                ..(*self).clone()
+            },
+
+            AccountAction::SetExchangeRates { exchange_rates } => Self {
+                exchange_rates,
+                ..(*self).clone()
+            },
+
+            AccountAction::SetAmount { amount } => Self {
+                amount,
+                ..(*self).clone()
+            },
+
+            AccountAction::SetMarginRisk { risk } => Self {
+                margin_risk: risk,
+                ..(*self).clone()
+            },
+
+            AccountAction::SetPositionRisk { risk } => Self {
+                position_risk: risk,
+                ..(*self).clone()
+            },
+        }
+        .into()
+    }
+}
+
+impl Account {
+    pub fn load() -> Self {
+        match gloo::storage::LocalStorage::get("trading.account") {
+            Ok(stored) => stored,
+            Err(err) => {
+                log::error!("Failed to retrieve trading account from local storage: {err:?}");
+                return Self::default();
+            }
+        }
+    }
+
+    pub fn save(&self) {
+        if let Err(err) = gloo::storage::LocalStorage::set("trading.account", self) {
+            log::error!("Failed to store trading account in local storage: {err:?}");
+        }
+    }
+}

src/model/trading/position.rs

@@ -0,0 +1,364 @@
+use std::{fmt::Display, rc::Rc, str::FromStr};
+
+use yew::Reducible;
+
+use crate::model::currency::Currency;
+
+use super::account::Account;
+
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub enum Direction {
+    Buy,
+    Sell,
+}
+
+impl Display for Direction {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::Buy => write!(f, "Buy"),
+            Self::Sell => write!(f, "Sell"),
+        }
+    }
+}
+
+impl FromStr for Direction {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "Buy" => Ok(Self::Buy),
+            "Sell" => Ok(Self::Sell),
+            _ => Err(()),
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct Position {
+    pub position_currency: Currency,
+    pub quote_currency: Currency,
+    pub conversion: f64,
+    pub open_price: f64,
+    pub quantity: Option<f64>,
+    pub direction: Direction,
+    pub margin: f64,
+    pub take_profit: Option<f64>,
+    pub stop_loss: Option<f64>,
+}
+
+impl Default for Position {
+    fn default() -> Self {
+        Self {
+            position_currency: Currency::GBP,
+            quote_currency: Currency::GBP,
+            conversion: 1.0,
+            open_price: 0.0,
+            quantity: None,
+            direction: Direction::Buy,
+            margin: 0.05,
+            take_profit: None,
+            stop_loss: None,
+        }
+    }
+}
+
+pub enum PositionAction {
+    SetPositionCurrency { currency: Currency },
+    SetQuoteCurrency { currency: Currency },
+    SetConversion { conversion: f64 },
+    SetOpenPrice { price: f64 },
+    SetQuantity { quantity: Option<f64> },
+    SetDirection { direction: Direction },
+    SetMargin { margin: f64 },
+    SetTakeProfit { price: Option<f64> },
+    SetStopLoss { price: Option<f64> },
+}
+
+impl Reducible for Position {
+    type Action = PositionAction;
+
+    fn reduce(self: Rc<Self>, action: Self::Action) -> Rc<Self> {
+        match action {
+            PositionAction::SetPositionCurrency { currency } => Self {
+                position_currency: currency,
+                ..(*self).clone()
+            },
+
+            PositionAction::SetQuoteCurrency { currency } => Self {
+                quote_currency: currency,
+                ..(*self).clone()
+            },
+
+            PositionAction::SetConversion { conversion } => Self {
+                conversion,
+                ..(*self).clone()
+            },
+
+            PositionAction::SetOpenPrice { price } => Self {
+                open_price: price,
+                ..(*self).clone()
+            },
+
+            PositionAction::SetQuantity { quantity } => Self {
+                quantity,
+                ..(*self).clone()
+            },
+
+            PositionAction::SetDirection { direction } => Self {
+                direction,
+                ..(*self).clone()
+            },
+
+            PositionAction::SetMargin { margin } => Self {
+                margin,
+                ..(*self).clone()
+            },
+
+            PositionAction::SetTakeProfit { price } => Self {
+                take_profit: price,
+                ..(*self).clone()
+            },
+
+            PositionAction::SetStopLoss { price } => Self {
+                stop_loss: price,
+                ..(*self).clone()
+            },
+        }
+        .into()
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct PositionSize {
+    /// Funds available under margin risk (in account currency)
+    pub available: f64,
+    /// Funds available under margin risk (in position currency)
+    pub available_position: f64,
+    /// Funds available under margin risk (in quote currency)
+    pub available_quote: f64,
+    /// Margin available under margin risk (in account currency)
+    pub margin: f64,
+    /// Margin available (in position currency)
+    pub margin_position: f64,
+    /// margin available (in quote currency)
+    pub margin_quote: f64,
+    /// Quantity affordable at position price (in units)
+    pub affordable: f64,
+    /// Optional actual position size margin risk
+    pub actual: Option<ActualPositionSize>,
+}
+
+impl PositionSize {
+    pub fn compute(account: &Account, position: &Position) -> Self {
+        let p_rate = account
+            .exchange_rates
+            .rates
+            .get(&position.position_currency)
+            .copied()
+            .unwrap_or(1.0);
+        let q_rate = position.conversion;
+        let available = account.amount * account.margin_risk;
+        let available_position = available * p_rate;
+        let available_quote = available_position * q_rate;
+
+        let margin = available
+            / if position.margin == 0.0 {
+                1.0
+            } else {
+                position.margin
+            };
+
+        let margin_position = margin * p_rate;
+        let margin_quote = margin_position * q_rate;
+
+        let affordable = if position.open_price == 0.0 {
+            0.0
+        } else {
+            margin_quote / position.open_price
+        };
+
+        Self {
+            available,
+            available_position,
+            available_quote,
+            margin,
+            margin_position,
+            margin_quote,
+            affordable,
+            actual: position.quantity.map(|quantity| {
+                ActualPositionSize::compute(account, position, quantity, p_rate, q_rate)
+            }),
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct ActualPositionSize {
+    /// The actual quote cost (in quote currency)
+    pub cost_quote: f64,
+    /// The actual position cost (in position currency)
+    pub cost_position: f64,
+    /// The actual position cost (in account currency)
+    pub cost: f64,
+    /// The account margin required (percent)
+    pub margin: f64,
+}
+
+impl ActualPositionSize {
+    pub fn compute(
+        account: &Account,
+        position: &Position,
+        quantity: f64,
+        q_rate: f64,
+        p_rate: f64,
+    ) -> Self {
+        let cost_quote = quantity * position.open_price * position.margin;
+        let cost_position = cost_quote / q_rate;
+        let cost = cost_position / p_rate;
+        let margin = cost / account.amount;
+
+        Self {
+            cost_quote,
+            cost_position,
+            cost,
+            margin,
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct StopLoss {
+    /// Funds available under position risk (in account currency)
+    pub available: f64,
+    /// Funds available under position risk (in position currency)
+    pub available_position: f64,
+    /// Funds available under position risk (in quote currency)
+    pub available_quote: f64,
+    /// Specified position size
+    pub quantity: f64,
+    /// Required stop-loss distance
+    pub distance: f64,
+    /// Optional actual stop-loss assessment
+    pub actual: Option<ActualStopLoss>,
+}
+
+impl StopLoss {
+    pub fn compute(account: &Account, position: &Position, quantity: f64) -> Self {
+        let p_rate = account
+            .exchange_rates
+            .rates
+            .get(&position.position_currency)
+            .copied()
+            .unwrap_or(1.0);
+        let q_rate = position.conversion;
+        let available = account.amount * account.position_risk;
+        let available_position = available * p_rate;
+        let available_quote = available_position * q_rate;
+        let distance = if quantity == 0.0 {
+            0.0
+        } else {
+            available_quote / quantity
+        };
+
+        Self {
+            available,
+            available_position,
+            available_quote,
+            quantity,
+            distance,
+            actual: if let Some(stop_loss) = position.stop_loss {
+                Some(ActualStopLoss::compute(
+                    account, position, quantity, p_rate, q_rate, stop_loss,
+                ))
+            } else {
+                None
+            },
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct ActualStopLoss {
+    /// The actual stop-loss distance (in position currency)
+    pub distance: f64,
+    /// The possible loss
+    pub loss: f64,
+    /// The actual position risk (percent)
+    pub risk: f64,
+}
+
+impl ActualStopLoss {
+    pub fn compute(
+        account: &Account,
+        position: &Position,
+        quantity: f64,
+        p_rate: f64,
+        q_rate: f64,
+        stop_loss: f64,
+    ) -> Self {
+        let distance = match position.direction {
+            Direction::Buy => position.open_price - stop_loss,
+            Direction::Sell => stop_loss - position.open_price,
+        };
+
+        let loss = (distance * quantity) / (p_rate * q_rate);
+        let risk = loss / account.amount;
+
+        Self {
+            distance,
+            loss,
+            risk,
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct StopLossQuantity {
+    /// Funds available under position risk (in account currency)
+    pub available: f64,
+    /// Funds available under position risk (in position currency)
+    pub available_position: f64,
+    /// Funds available under position risk (in quote currency)
+    pub available_quote: f64,
+    /// Computed stop loss distance (in position currency)
+    pub distance: f64,
+    /// Amount that can be bought at the given stop loss (in units)
+    pub affordable: f64,
+    /// Required margin for that amount (in account currency)
+    pub margin: f64,
+}
+
+impl StopLossQuantity {
+    pub fn compute(account: &Account, position: &Position) -> Self {
+        let distance = if let Some(stop_loss) = position.stop_loss {
+            match position.direction {
+                Direction::Buy => position.open_price - stop_loss,
+                Direction::Sell => stop_loss - position.open_price,
+            }
+        } else {
+            0.0
+        };
+
+        let p_rate = account
+            .exchange_rates
+            .rates
+            .get(&position.position_currency)
+            .copied()
+            .unwrap_or(1.0);
+        let q_rate = position.conversion;
+        let available = account.amount * account.position_risk;
+        let available_position = available * p_rate;
+        let available_quote = available_position * q_rate;
+        let affordable = available_quote / distance;
+        let margin = (affordable * position.open_price * position.margin) / (p_rate * q_rate);
+
+        Self {
+            available,
+            available_position,
+            available_quote,
+            distance,
+            affordable,
+            margin,
+        }
+    }
+}

src/pages.rs

@@ -13,6 +13,10 @@ mod analytics {
     pub mod dashboard;
 }
 
+mod trading {
+    pub mod position_size;
+}
+
 #[derive(Debug, Clone, PartialEq, Sequence, Routable)]
 pub enum Route {
     #[at("/")]
@@ -27,6 +31,8 @@ pub enum Route {
     Disclaimer,
     #[at("/analytics")]
     Analytics,
+    #[at("/trading/position-size")]
+    PositionSize,
     #[not_found]
     #[at("/404")]
     NotFound,
@@ -46,6 +52,7 @@ impl Route {
             Self::Disclaimer => html! { <disclaimer::Page /> },
             Self::NotFound => html! { <not_found::Page /> },
             Self::Analytics => html! { <analytics::dashboard::Page /> },
+            Self::PositionSize => html! { <trading::position_size::Page /> },
         }
     }
 }

src/pages/trading/position_size.rs

@@ -0,0 +1,814 @@
+use web_sys::HtmlSelectElement;
+use yew::{
+    function_component, html, use_context, use_effect, use_effect_with_deps, use_reducer, Callback,
+    Children, ContextProvider, Html, Properties, TargetCast, UseReducerHandle,
+};
+use yew_hooks::{use_async, UseAsyncHandle};
+
+use crate::{
+    components::fields::{
+        currency::CurrencySelect,
+        label::Label,
+        number::{format_number, Number},
+        toggle::Toggle,
+    },
+    model::{
+        currency::get_exchange_rates,
+        trading::{
+            account::{Account, AccountAction},
+            position::{Direction, Position, PositionAction, PositionSize, StopLossQuantity},
+        },
+    },
+};
+
+type AccountHandle = UseReducerHandle<Account>;
+type PositionHandle = UseReducerHandle<Position>;
+
+#[function_component(AccountInfo)]
+fn account_info() -> Html {
+    let account = use_context::<AccountHandle>().expect("AccountHandle");
+
+    let currency_change = {
+        let account = account.clone();
+        Callback::from(move |currency| account.dispatch(AccountAction::SetCurrency { currency }))
+    };
+
+    let amount_change = {
+        let account = account.clone();
+        Callback::from(move |amount| {
+            if let Some(amount) = amount {
+                account.dispatch(AccountAction::SetAmount { amount })
+            }
+        })
+    };
+
+    let margin_risk_change = {
+        let account = account.clone();
+        Callback::from(move |risk| {
+            if let Some(risk) = risk {
+                account.dispatch(AccountAction::SetMarginRisk { risk: risk / 100.0 })
+            }
+        })
+    };
+
+    let position_risk_change = {
+        let account = account.clone();
+        Callback::from(move |risk| {
+            if let Some(risk) = risk {
+                account.dispatch(AccountAction::SetPositionRisk { risk: risk / 100.0 })
+            }
+        })
+    };
+
+    let places_change = {
+        let account = account.clone();
+        Callback::from(move |places| {
+            if let Some(places) = places {
+                let places = places as usize;
+                account.dispatch(AccountAction::SetPlaces { places })
+            }
+        })
+    };
+
+    html! {
+        <div class="flex flex-col gap-8 border border-primary rounded-md p-4">
+            <h1 class="text-2xl font-semibold">{"Account Information"}</h1>
+            <div class="grid grid-cols-2 items-center gap-4">
+                <Label title="Account Currency">
+                    <CurrencySelect
+                        value={account.currency}
+                        onchange={currency_change} />
+                </Label>
+                <Label title="Account Value">
+                    <Number
+                        thousands={true}
+                        prefix={account.currency.symbol()}
+                        places={account.places}
+                        value={account.amount}
+                        oninput={amount_change} />
+                </Label>
+                <Label title="Margin Risk">
+                    <Number
+                        value={account.margin_risk * 100.0}
+                        places={0}
+                        suffix="%"
+                        onchange={margin_risk_change} />
+                </Label>
+                <Label title="Position Risk">
+                    <Number
+                        value={account.position_risk * 100.0}
+                        places={0}
+                        suffix="%"
+                        onchange={position_risk_change} />
+                </Label>
+                <Label title="Decimal Places">
+                    <Number
+                        value={account.places as f64}
+                        places={0}
+                        suffix=" digits"
+                        onchange={places_change} />
+                </Label>
+            </div>
+        </div>
+    }
+}
+
+#[function_component(PositionInfo)]
+fn position_info() -> Html {
+    let account = use_context::<AccountHandle>().expect("AccountHandle");
+    let position = use_context::<PositionHandle>().expect("PositionHandle");
+
+    let position_currency_change = {
+        let position = position.clone();
+        Callback::from(move |currency| {
+            position.dispatch(PositionAction::SetPositionCurrency { currency })
+        })
+    };
+
+    let quote_currency_change = {
+        let position = position.clone();
+        Callback::from(move |currency| {
+            position.dispatch(PositionAction::SetQuoteCurrency { currency })
+        })
+    };
+
+    let margin_change = {
+        let position = position.clone();
+        Callback::from(move |margin| {
+            if let Some(margin) = margin {
+                position.dispatch(PositionAction::SetMargin {
+                    margin: margin / 100.0,
+                });
+            }
+        })
+    };
+
+    let open_price_change = {
+        let position = position.clone();
+        Callback::from(move |price| {
+            if let Some(price) = price {
+                position.dispatch(PositionAction::SetOpenPrice { price });
+            }
+        })
+    };
+
+    let direction_change = {
+        let position = position.clone();
+        Callback::from(move |event: yew::Event| {
+            let direction = event
+                .target_dyn_into::<HtmlSelectElement>()
+                .expect("target")
+                .value()
+                .parse::<Direction>()
+                .expect("direction");
+            position.dispatch(PositionAction::SetDirection { direction })
+        })
+    };
+
+    let quantity_toggle = {
+        let position = position.clone();
+        Callback::from(move |enabled| {
+            position.dispatch(PositionAction::SetQuantity {
+                quantity: if enabled { Some(1.0) } else { None },
+            });
+        })
+    };
+
+    let quantity_change = {
+        let position = position.clone();
+        Callback::from(move |quantity| {
+            if let Some(quantity) = quantity {
+                if position.quantity.is_some() {
+                    position.dispatch(PositionAction::SetQuantity {
+                        quantity: Some(quantity),
+                    });
+                }
+            }
+        })
+    };
+
+    let affordable_click = {
+        let account = account.clone();
+        let position = position.clone();
+        Callback::from(move |_| {
+            if position.quantity.is_none() {
+                return;
+            }
+
+            let PositionSize { affordable, .. } = PositionSize::compute(&account, &position);
+            position.dispatch(PositionAction::SetQuantity {
+                quantity: Some(affordable),
+            });
+        })
+    };
+
+    let stop_loss_click = {
+        let account = account.clone();
+        let position = position.clone();
+        Callback::from(move |_| {
+            if position.quantity.is_none() {
+                return;
+            }
+
+            let StopLossQuantity { affordable, .. } =
+                StopLossQuantity::compute(&account, &position);
+            position.dispatch(PositionAction::SetQuantity {
+                quantity: Some(affordable),
+            });
+        })
+    };
+
+    let stop_loss_toggle = {
+        let position = position.clone();
+        Callback::from(move |enabled| {
+            position.dispatch(PositionAction::SetStopLoss {
+                price: if enabled {
+                    Some(position.open_price)
+                } else {
+                    None
+                },
+            });
+        })
+    };
+
+    let stop_loss_change = {
+        let position = position.clone();
+        Callback::from(move |price| {
+            if let Some(price) = price {
+                if position.stop_loss.is_some() {
+                    position.dispatch(PositionAction::SetStopLoss { price: Some(price) });
+                }
+            }
+        })
+    };
+
+    let stop_loss_distance_change = {
+        let position = position.clone();
+        Callback::from(move |distance| {
+            if let Some(distance) = distance {
+                if position.stop_loss.is_some() {
+                    position.dispatch(PositionAction::SetStopLoss {
+                        price: Some(match position.direction {
+                            Direction::Buy => position.open_price - distance,
+                            Direction::Sell => position.open_price + distance,
+                        }),
+                    });
+                }
+            }
+        })
+    };
+
+    let take_profit_toggle = {
+        let position = position.clone();
+        Callback::from(move |enabled| {
+            position.dispatch(PositionAction::SetTakeProfit {
+                price: if enabled {
+                    Some(position.open_price)
+                } else {
+                    None
+                },
+            });
+        })
+    };
+
+    let take_profit_change = {
+        let position = position.clone();
+        Callback::from(move |price| {
+            if let Some(price) = price {
+                if position.take_profit.is_some() {
+                    position.dispatch(PositionAction::SetTakeProfit { price: Some(price) });
+                }
+            }
+        })
+    };
+
+    let take_profit_distance_change = {
+        let position = position.clone();
+        Callback::from(move |distance| {
+            if let Some(distance) = distance {
+                if position.take_profit.is_some() {
+                    position.dispatch(PositionAction::SetTakeProfit {
+                        price: Some(match position.direction {
+                            Direction::Buy => position.open_price + distance,
+                            Direction::Sell => position.open_price - distance,
+                        }),
+                    });
+                }
+            }
+        })
+    };
+
+    let tp_distance = match position.take_profit {
+        None => 0.0,
+        Some(tp) => match position.direction {
+            Direction::Buy => tp - position.open_price,
+            Direction::Sell => position.open_price - tp,
+        },
+    };
+
+    let sl_distance = match position.stop_loss {
+        None => 0.0,
+        Some(sl) => match position.direction {
+            Direction::Buy => position.open_price - sl,
+            Direction::Sell => sl - position.open_price,
+        },
+    };
+
+    let position_exchange = if account.currency != position.position_currency {
+        format!(
+            "Position ({}→{} {})",
+            account.currency,
+            position.position_currency,
+            format_number(
+                account
+                    .exchange_rates
+                    .rates
+                    .get(&position.position_currency)
+                    .copied()
+                    .unwrap_or(0.0),
+                false,
+                account.places,
+                Some(position.position_currency.symbol()),
+                None
+            )
+            .expect("format_number")
+        )
+    } else {
+        "Position".to_string()
+    };
+
+    let quote_exchange = if position.quote_currency != position.position_currency {
+        format!(
+            "Quote ({}→{} {})",
+            position.position_currency,
+            position.quote_currency,
+            format_number(
+                position.conversion,
+                false,
+                account.places,
+                Some(position.quote_currency.symbol()),
+                None
+            )
+            .expect("format_number")
+        )
+    } else {
+        "Quote".to_string()
+    };
+
+    let position_margin = if position.margin != 0.0 {
+        format!("Position Margin ({:.0}x leverage)", 1.0 / position.margin)
+    } else {
+        "Position Margin".to_string()
+    };
+
+    html! {
+        <div class="flex flex-col gap-8 border border-primary rounded-md p-4">
+            <h1 class="text-2xl font-semibold">{"Position Information"}</h1>
+            <div class="grid grid-cols-2 items-center gap-4">
+                <div class="grid grid-cols-2 gap-4">
+                    <Label title={position_exchange}>
+                        <CurrencySelect
+                            value={position.position_currency}
+                            onchange={position_currency_change} />
+                    </Label>
+                    <Label title={quote_exchange}>
+                        <CurrencySelect
+                            value={position.quote_currency}
+                            onchange={quote_currency_change} />
+                    </Label>
+                </div>
+                <Label title={position_margin}>
+                    <Number
+                        value={position.margin * 100.0}
+                        places={2}
+                        suffix="%"
+                        oninput={margin_change} />
+                </Label>
+                <Label title="Position Direction">
+                    <select onchange={direction_change}>
+                        <option
+                            value={Direction::Buy.to_string()}
+                            selected={position.direction == Direction::Buy}>
+                            {"Buy"}
+                        </option>
+                        <option
+                            value={Direction::Sell.to_string()}
+                            selected={position.direction == Direction::Sell}>
+                            {"Sell"}
+                        </option>
+                    </select>
+                </Label>
+                <Label title="Open Price">
+                    <Number
+                        value={position.open_price}
+                        thousands={true}
+                        places={account.places}
+                        prefix={position.quote_currency.symbol()}
+                        oninput={open_price_change} />
+                </Label>
+                <Label title="Quantity" class="col-start-1">
+                    <div class="flex flex-row gap-4">
+                        <Toggle
+                            value={position.quantity.is_some()}
+                            onchange={quantity_toggle} />
+                        <Number
+                            class="grow"
+                            value={position.quantity.unwrap_or_default()}
+                            thousands={true}
+                            places={4}
+                            suffix=" units"
+                            disabled={position.quantity.is_none()}
+                            oninput={quantity_change} />
+                    </div>
+                </Label>
+                <div class="flex flex-row gap-2 pt-7">
+                    <button
+                        type="button"
+                        class="button"
+                        onclick={affordable_click}
+                        disabled={position.quantity.is_none() || position.open_price == 0.0}>
+                        {"Affordable Quantity"}
+                    </button>
+                    <button
+                        type="button"
+                        class="button"
+                        onclick={stop_loss_click}
+                        disabled={position.stop_loss.is_none() || sl_distance == 0.0}>
+                        {"Stop Loss Quantity"}
+                    </button>
+                </div>
+                <Label title="Stop Loss">
+                    <div class="flex flex-row gap-4">
+                        <Toggle
+                            value={position.stop_loss.is_some()}
+                            onchange={stop_loss_toggle} />
+                        <Number
+                            class="grow"
+                            value={position.stop_loss.unwrap_or_default()}
+                            thousands={true}
+                            places={account.places}
+                            prefix={position.quote_currency.symbol()}
+                            disabled={position.stop_loss.is_none()}
+                            onchange={stop_loss_change} />
+                    </div>
+                </Label>
+                <Label title="Stop Loss Distance">
+                    <Number
+                        value={sl_distance}
+                        thousands={true}
+                        places={account.places}
+                        prefix={position.quote_currency.symbol()}
+                        disabled={position.stop_loss.is_none()}
+                        onchange={stop_loss_distance_change} />
+                </Label>
+                <Label title="Take Profit">
+                    <div class="flex flex-row gap-4">
+                        <Toggle
+                            value={position.take_profit.is_some()}
+                            onchange={take_profit_toggle} />
+                        <Number
+                            class="grow"
+                            value={position.take_profit.unwrap_or_default()}
+                            thousands={true}
+                            places={account.places}
+                            prefix={position.quote_currency.symbol()}
+                            disabled={position.take_profit.is_none()}
+                            onchange={take_profit_change} />
+                    </div>
+                </Label>
+                <Label title="Take Profit Distance">
+                    <Number
+                        value={tp_distance}
+                        thousands={true}
+                        places={account.places}
+                        prefix={position.quote_currency.symbol()}
+                        disabled={position.take_profit.is_none()}
+                        onchange={take_profit_distance_change} />
+                </Label>
+            </div>
+        </div>
+    }
+}
+
+#[function_component(ReportPositionSize)]
+fn report_position_size() -> Html {
+    let account = use_context::<AccountHandle>().expect("AccountHandle");
+    let position = use_context::<PositionHandle>().expect("PositionHandle");
+
+    let PositionSize {
+        available,
+        available_position,
+        available_quote,
+        margin,
+        margin_position,
+        margin_quote,
+        affordable,
+        actual,
+    } = PositionSize::compute(&account, &position);
+
+    let ac = account.currency.symbol();
+    let pc = position.position_currency.symbol();
+    let qc = position.quote_currency.symbol();
+    let ap = account.currency != position.position_currency;
+    let pq = position.position_currency != position.quote_currency;
+
+    let actual = if let Some(actual) = actual {
+        html! {
+            <div class="table">
+                <table class="table tighter borderless">
+                    <tbody>
+                        <tr>
+                            <th colspan="2" class="text-left">{"Actual Quantity"}</th>
+                        </tr>
+                        <tr>
+                            <th class="text-left font-normal pl-4">
+                                {"Actual cost of opening a position of "}
+                                {format_number(
+                                    position.quantity.unwrap_or_default(),
+                                    true, 2, None, None
+                                ).expect("format_number")}
+                                {" units at "}
+                                {format_number(
+                                    position.open_price, true,
+                                    account.places, Some(qc), None
+                                ).expect("format_number")}
+                            </th>
+                            <td class="text-right">
+                                {format_number(
+                                    position.quantity.unwrap_or_default() * position.open_price,
+                                    true, account.places, Some(qc), None
+                                ).expect("format_number")}
+                            </td>
+                        </tr>
+                        <tr>
+                            <th class="text-left font-normal pl-4">
+                                {"Amount of margin required at "}
+                                {format_number(
+                                    position.margin * 100.0, true,
+                                    2, None, Some("%")
+                                ).expect("format_number")}
+                                {format!(" position margin ({:.0}x leverage)",
+                                        1.0 / if position.margin == 0.0 {
+                                            1.0
+                                        } else {
+                                            position.margin
+                                        },
+                                )}
+                            </th>
+                            <td class="text-right">
+                                {format_number(
+                                    actual.cost_quote, true,
+                                    account.places, Some(qc), None
+                                ).expect("format_number")}
+                            </td>
+                        </tr>
+                        if pq {
+                            <tr>
+                                <th />
+                                <td>
+                                    {format_number(
+                                        actual.cost_position, true,
+                                        account.places, Some(pc), None
+                                    ).expect("format_number")}
+                                </td>
+                            </tr>
+                        }
+                        if ap {
+                            <tr>
+                                <th />
+                                <td>
+                                    {format_number(
+                                        actual.cost, true,
+                                        account.places, Some(ac), None
+                                    ).expect("format_number")}
+                                </td>
+                            </tr>
+                        }
+                    </tbody>
+                </table>
+            </div>
+        }
+    } else {
+        html! {}
+    };
+
+    html! {
+        <div class="flex flex-col gap-8 border border-primary rounded-md p-4">
+            <h1 class="text-2xl font-semibold">{"Position Size Information"}</h1>
+            <div class="table">
+                <table class="table tighter borderless">
+                    <tbody>
+                        <tr>
+                            <th colspan="2" class="text-left">{"Margin Risk"}</th>
+                        </tr>
+                        <tr>
+                            <th class="text-left font-normal pl-4">
+                                {"Amount of account available under margin risk"}
+                            </th>
+                            <td class="text-right">
+                                {format_number(available, true,
+                                               account.places, Some(ac), None
+                                ).expect("format_number")}
+                            </td>
+                        </tr>
+                        if ap {
+                            <tr>
+                                <th class="text-left font-normal pl-4">
+                                    {"Available account under margin risk in the position currency"}
+                                </th>
+                                <td class="text-right">
+                                    {format_number(
+                                            available_position, true,
+                                            account.places, Some(pc), None
+                                    ).expect("format_number")}
+                                </td>
+                            </tr>
+                        }
+                        if pq {
+                            <tr>
+                                <th class="text-left font-normal pl-4">
+                                    {"Available account under margin risk in the quote currency"}
+                                </th>
+                                <td class="text-right">
+                                    {format_number(
+                                            available_quote, true,
+                                            account.places, Some(qc), None
+                                    ).expect("format_number")}
+                                </td>
+                            </tr>
+                        }
+                    </tbody>
+                </table>
+            </div>
+
+            <div class="table">
+                <table class="table tighter borderless">
+                    <tbody>
+                        <tr>
+                            <th colspan="2" class="text-left">{"Position Margin and Amount"}</th>
+                        </tr>
+                        <tr>
+                            <th class="text-left font-normal pl-4">
+                                {"Available amount with a "}
+                                {format_number(
+                                        position.margin * 100.0,
+                                        true, 2, None, Some("%")
+                                ).expect("format_number")}
+                                {" position margin"}
+                            </th>
+                            <td class="text-right">
+                                {format_number(
+                                        margin, true,
+                                        account.places, Some(ac), None
+                                ).expect("format_number")}
+                            </td>
+                        </tr>
+                        if ap {
+                            <tr>
+                                <th class="text-left font-normal pl-4">
+                                    {"Available amount under position margin in position currency"}
+                                </th>
+                                <td class="text-right">
+                                    {format_number(
+                                            margin_position, true,
+                                            account.places, Some(pc), None
+                                    ).expect("format_number")}
+                                </td>
+                            </tr>
+                        }
+                        if pq {
+                            <tr>
+                                <th class="text-left font-normal pl-4">
+                                    {"Available amount under position margin in quote currency"}
+                                </th>
+                                <td class="text-right">
+                                    {format_number(
+                                            margin_quote, true,
+                                            account.places, Some(qc), None
+                                    ).expect("format_number")}
+                                </td>
+                            </tr>
+                        }
+                        <tr>
+                            <th class="text-left font-normal pl-4">
+                                {"Position size available at open price of "}
+                                {format_number(
+                                        position.open_price, true,
+                                        account.places, Some(qc), None
+                                ).expect("format_number")}
+                                {" with margin of "}
+                                {format_number(
+                                        margin_quote, true,
+                                        account.places, Some(qc), None
+                                ).expect("format_number")}
+                            </th>
+                            <td class="text-right">
+                                {format_number(
+                                        affordable, true,
+                                        2, None, Some(" units")
+                                ).expect("format_number")}
+                            </td>
+                        </tr>
+                    </tbody>
+                </table>
+            </div>
+
+            {actual}
+        </div>
+    }
+}
+
+#[derive(Properties, PartialEq)]
+struct AccountProviderProps {
+    #[prop_or_default]
+    pub children: Children,
+}
+
+#[function_component(AccountProvider)]
+fn account_provider(props: &AccountProviderProps) -> Html {
+    let account = use_reducer(Account::default);
+
+    let get_exchange_rates: UseAsyncHandle<(), &'static str> = {
+        let account = account.clone();
+        use_async(async move {
+            let rates = get_exchange_rates(account.currency, None).await?;
+            account.dispatch(AccountAction::SetExchangeRates {
+                exchange_rates: rates,
+            });
+            Ok(())
+        })
+    };
+
+    use_effect_with_deps(
+        move |_| {
+            get_exchange_rates.run();
+        },
+        account.currency,
+    );
+
+    html! {
+        <ContextProvider<AccountHandle> context={account}>
+            {props.children.clone()}
+        </ContextProvider<AccountHandle>>
+    }
+}
+
+#[derive(Properties, PartialEq)]
+struct PositionProviderProps {
+    #[prop_or_default]
+    pub children: Children,
+}
+
+#[function_component(PositionProvider)]
+fn position_provider(props: &PositionProviderProps) -> Html {
+    let position = use_reducer(Position::default);
+
+    let get_exchange_rates: UseAsyncHandle<(), &'static str> = {
+        let position = position.clone();
+        use_async(async move {
+            let rates =
+                get_exchange_rates(position.position_currency, Some(position.quote_currency))
+                    .await?;
+            position.dispatch(PositionAction::SetConversion {
+                conversion: rates
+                    .rates
+                    .get(&position.quote_currency)
+                    .copied()
+                    .unwrap_or(1.0),
+            });
+            Ok(())
+        })
+    };
+
+    use_effect_with_deps(
+        move |_| {
+            get_exchange_rates.run();
+        },
+        (position.position_currency, position.quote_currency),
+    );
+
+    html! {
+        <ContextProvider<PositionHandle> context={position}>
+            {props.children.clone()}
+        </ContextProvider<PositionHandle>>
+    }
+}
+
+#[function_component(Page)]
+pub fn page() -> Html {
+    html! {
+        <AccountProvider>
+            <PositionProvider>
+                <div class="container mx-auto my-20">
+                    <div class="grid grid-cols-2 gap-8">
+                        <AccountInfo />
+                        <PositionInfo />
+                    </div>
+                    <div class="grid grid-cols-2 gap-8 mt-8">
+                        <ReportPositionSize />
+                    </div>
+                </div>
+            </PositionProvider>
+        </AccountProvider>
+    }
+}

style/main.css

@@ -1,5 +1,9 @@
 @import "tailwind.css";
 
+:root {
+  --toggle-size: 2rem;
+}
+
 @layer components {
   body {
     @apply bg-white text-neutral-800;
@@ -20,6 +24,10 @@
     }
   }
 
+  label {
+    @apply font-semibold;
+  }
+
   select,
   input[type="text"],
   input[type="number"],
@@ -27,7 +35,9 @@
     @apply border-primary rounded-md;
     @apply text-neutral-800 placeholder:text-neutral-300;
     @apply dark:bg-zinc-800 dark:text-neutral-200 dark:placeholder:text-neutral-700;
+    @apply disabled:bg-gray-200 dark:disabled:bg-zinc-900 dark:disabled:text-neutral-500;
     @apply focus:outline-none focus:ring focus:ring-offset-2 focus:ring-opacity-50 focus:ring-slate-400;
+    @apply transition;
 
     &:disabled {
       @apply text-neutral-500 dark:text-neutral-500;
@@ -35,6 +45,80 @@
     }
   }
 
+  .input-icons {
+    @apply relative;
+
+    svg:first-child,
+    svg:last-child {
+      @apply pointer-events-none absolute top-1/2 -mt-2.5 text-gray-300 dark:text-gray-500;
+    }
+
+    svg:first-child {
+      @apply left-3;
+    }
+
+    svg:last-child {
+      @apply right-3;
+    }
+
+    select,
+    input[type="text"],
+    input[type="number"],
+    input[type="password"] {
+      &.icon-left {
+        @apply pl-10;
+      }
+
+      &.icon-right {
+        @apply pr-10;
+      }
+    }
+  }
+
+  .toggle {
+    @apply block relative cursor-pointer;
+
+    width: calc(2 * var(--toggle-size));
+    height: var(--toggle-size);
+
+    &.active {
+      .toggle-background {
+        @apply bg-slate-800 dark:bg-indigo-300;
+      }
+
+      .toggle-inner {
+        right: 0rem;
+      }
+    }
+
+    .toggle-background {
+      @apply absolute bg-slate-300 dark:bg-gray-600;
+
+      width: calc(2 * var(--toggle-size));
+      height: calc(0.5 * var(--toggle-size));
+      top: calc(0.25 * var(--toggle-size));
+
+      border-radius: calc(0.5 * var(--toggle-size));
+
+      transition: background-color 0.125s ease-in-out;
+    }
+
+    .toggle-inner {
+      @apply absolute bg-white;
+
+      width: var(--toggle-size);
+      height: var(--toggle-size);
+      top: 0;
+      right: var(--toggle-size);
+
+      border-radius: calc(0.5 * var(--toggle-size));
+      border: 1px solid rgba(0, 0, 0, 0.25);
+      box-shadow: 1px 1px 2px rgba(0, 0, 0, 0.25);
+
+      transition: right 0.125s ease-in-out;
+    }
+  }
+
   .markdown {
     @apply flex flex-col;
     @apply font-sans font-normal text-lg print:text-base;
@@ -259,6 +343,10 @@
       @apply text-neutral-600 dark:text-neutral-400;
     }
 
+    div.table {
+      @apply mb-6;
+    }
+
     blockquote {
       @apply w-full mb-6 border-l-4 border-l-blue-400 px-8;
 
@@ -360,12 +448,11 @@
   }
 
   table {
-    @apply min-w-full mb-6 border-collapse table-auto;
+    @apply min-w-full border-collapse table-auto;
 
     thead {
       @apply bg-transparent dark:bg-neutral-800;
       @apply dark:text-white;
-      @apply border-b border-neutral-500;
 
       tr {
         th {
@@ -388,8 +475,6 @@
 
     tbody {
       tr {
-        @apply border-b border-neutral-400 dark:border-neutral-600;
-
         td {
           @apply whitespace-nowrap px-6 py-4;
 
@@ -414,5 +499,22 @@
         @apply px-3 py-2;
       }
     }
+
+    &.tighter {
+      thead tr th,
+      tbody tr td {
+        @apply px-1 py-1;
+      }
+    }
+
+    &:not(.borderless) {
+      thead {
+        @apply border-b border-neutral-500;
+      }
+
+      tbody tr {
+        @apply border-b border-neutral-400 dark:border-neutral-600;
+      }
+    }
   } /* table */
 }