Add exchange rate feature with multi-currency transactions and transfers support (#1099)

Co-authored-by: Pedro J. Aramburu <pedro@joakin.dev>

app/javascript/controllers/exchange_rate_form_controller.js

@@ -0,0 +1,298 @@
+import { Controller } from "@hotwired/stimulus";
+
+export default class extends Controller {
+  static targets = [
+    "amount",
+    "destinationAmount",
+    "date",
+    "exchangeRateContainer",
+    "exchangeRateField",
+    "convertDestinationDisplay",
+    "calculateRateDisplay"
+  ];
+
+  static values = {
+    exchangeRateUrl: String,
+    accountCurrencies: Object
+  };
+
+  connect() {
+    this.sourceCurrency = null;
+    this.destinationCurrency = null;
+    this.activeTab = "convert";
+
+    if (!this.hasRequiredExchangeRateTargets()) {
+      return;
+    }
+
+    this.checkCurrencyDifference();
+  }
+
+  hasRequiredExchangeRateTargets() {
+    return this.hasDateTarget;
+  }
+
+  checkCurrencyDifference() {
+    const context = this.getExchangeRateContext();
+
+    if (!context) {
+      this.hideExchangeRateField();
+      return;
+    }
+
+    const { fromCurrency, toCurrency, date } = context;
+
+    if (!fromCurrency || !toCurrency) {
+      this.hideExchangeRateField();
+      return;
+    }
+
+    this.sourceCurrency = fromCurrency;
+    this.destinationCurrency = toCurrency;
+
+    if (fromCurrency === toCurrency) {
+      this.hideExchangeRateField();
+      return;
+    }
+
+    this.fetchExchangeRate(fromCurrency, toCurrency, date);
+  }
+
+  onExchangeRateTabClick(event) {
+    const btn = event.target.closest("button[data-id]");
+    if (!btn) {
+      return;
+    }
+
+    const nextTab = btn.dataset.id;
+
+    if (nextTab === this.activeTab) {
+      return;
+    }
+
+    this.activeTab = nextTab;
+
+    if (this.activeTab === "convert") {
+      this.clearCalculateRateFields();
+    } else if (this.activeTab === "calculateRate") {
+      this.clearConvertFields();
+    }
+  }
+
+  onAmountChange() {
+    this.onAmountInputChange();
+  }
+
+  onSourceAmountChange() {
+    this.onAmountInputChange();
+  }
+
+  onAmountInputChange() {
+    if (!this.hasAmountTarget) {
+      return;
+    }
+
+    if (this.activeTab === "convert") {
+      this.calculateConvertDestination();
+    } else {
+      this.calculateRateFromAmounts();
+    }
+  }
+
+  onConvertSourceAmountChange() {
+    this.calculateConvertDestination();
+  }
+
+  onConvertExchangeRateChange() {
+    this.calculateConvertDestination();
+  }
+
+  calculateConvertDestination() {
+    if (!this.hasAmountTarget || !this.hasExchangeRateFieldTarget || !this.hasConvertDestinationDisplayTarget) {
+      return;
+    }
+
+    const amount = Number.parseFloat(this.amountTarget.value);
+    const rate = Number.parseFloat(this.exchangeRateFieldTarget.value);
+
+    if (amount && rate && rate !== 0) {
+      const destAmount = (amount * rate).toFixed(2);
+      this.convertDestinationDisplayTarget.textContent = this.destinationCurrency ? `${destAmount} ${this.destinationCurrency}` : destAmount;
+    } else {
+      this.convertDestinationDisplayTarget.textContent = "-";
+    }
+  }
+
+  onCalculateRateSourceAmountChange() {
+    this.calculateRateFromAmounts();
+  }
+
+  onCalculateRateDestinationAmountChange() {
+    this.calculateRateFromAmounts();
+  }
+
+  calculateRateFromAmounts() {
+    if (!this.hasAmountTarget || !this.hasDestinationAmountTarget || !this.hasCalculateRateDisplayTarget || !this.hasExchangeRateFieldTarget) {
+      return;
+    }
+
+    const amount = Number.parseFloat(this.amountTarget.value);
+    const destAmount = Number.parseFloat(this.destinationAmountTarget.value);
+
+    if (amount && destAmount && amount !== 0) {
+      const rate = destAmount / amount;
+      const formattedRate = this.formatExchangeRate(rate);
+      this.calculateRateDisplayTarget.textContent = formattedRate;
+      this.exchangeRateFieldTarget.value = rate.toFixed(14);
+    } else {
+      this.calculateRateDisplayTarget.textContent = "-";
+      this.exchangeRateFieldTarget.value = "";
+    }
+  }
+
+  formatExchangeRate(rate) {
+    let formattedRate = rate.toFixed(14);
+    formattedRate = formattedRate.replace(/(\.\d{2}\d*?)0+$/, "$1");
+
+    if (!formattedRate.includes(".")) {
+      formattedRate += ".00";
+    } else if (formattedRate.match(/\.\d$/)) {
+      formattedRate += "0";
+    }
+
+    return formattedRate;
+  }
+
+  clearConvertFields() {
+    if (this.hasExchangeRateFieldTarget) {
+      this.exchangeRateFieldTarget.value = "";
+    }
+    if (this.hasConvertDestinationDisplayTarget) {
+      this.convertDestinationDisplayTarget.textContent = "-";
+    }
+  }
+
+  clearCalculateRateFields() {
+    if (this.hasDestinationAmountTarget) {
+      this.destinationAmountTarget.value = "";
+    }
+    if (this.hasCalculateRateDisplayTarget) {
+      this.calculateRateDisplayTarget.textContent = "-";
+    }
+    if (this.hasExchangeRateFieldTarget) {
+      this.exchangeRateFieldTarget.value = "";
+    }
+  }
+
+  async fetchExchangeRate(fromCurrency, toCurrency, date) {
+    if (this.exchangeRateAbortController) {
+      this.exchangeRateAbortController.abort();
+    }
+
+    this.exchangeRateAbortController = new AbortController();
+    const signal = this.exchangeRateAbortController.signal;
+
+    try {
+      const url = new URL(this.exchangeRateUrlValue, window.location.origin);
+      url.searchParams.set("from", fromCurrency);
+      url.searchParams.set("to", toCurrency);
+      if (date) {
+        url.searchParams.set("date", date);
+      }
+
+      const response = await fetch(url, { signal });
+      const data = await response.json();
+
+      if (!this.isCurrentExchangeRateState(fromCurrency, toCurrency, date)) {
+        return;
+      }
+
+      if (!response.ok) {
+        if (this.shouldShowManualExchangeRate(data)) {
+          this.showManualExchangeRateField();
+        } else {
+          this.hideExchangeRateField();
+        }
+        return;
+      }
+
+      if (data.same_currency) {
+        this.hideExchangeRateField();
+      } else {
+        this.sourceCurrency = fromCurrency;
+        this.destinationCurrency = toCurrency;
+        this.showExchangeRateField(data.rate);
+      }
+    } catch (error) {
+      if (error.name === "AbortError") {
+        return;
+      }
+
+      console.error("Error fetching exchange rate:", error);
+      this.hideExchangeRateField();
+    }
+  }
+
+  showExchangeRateField(rate) {
+    if (this.hasExchangeRateFieldTarget) {
+      this.exchangeRateFieldTarget.value = this.formatExchangeRate(rate);
+    }
+    if (this.hasExchangeRateContainerTarget) {
+      this.exchangeRateContainerTarget.classList.remove("hidden");
+    }
+
+    this.calculateConvertDestination();
+  }
+
+  showManualExchangeRateField() {
+    const context = this.getExchangeRateContext();
+    this.sourceCurrency = context?.fromCurrency || null;
+    this.destinationCurrency = context?.toCurrency || null;
+
+    if (this.hasExchangeRateFieldTarget) {
+      this.exchangeRateFieldTarget.value = "";
+    }
+    if (this.hasExchangeRateContainerTarget) {
+      this.exchangeRateContainerTarget.classList.remove("hidden");
+    }
+
+    this.calculateConvertDestination();
+  }
+
+  shouldShowManualExchangeRate(data) {
+    if (!data || typeof data.error !== "string") {
+      return false;
+    }
+
+    return data.error === "Exchange rate not found" || data.error === "Exchange rate unavailable";
+  }
+
+  hideExchangeRateField() {
+    if (this.hasExchangeRateContainerTarget) {
+      this.exchangeRateContainerTarget.classList.add("hidden");
+    }
+    if (this.hasExchangeRateFieldTarget) {
+      this.exchangeRateFieldTarget.value = "";
+    }
+    if (this.hasConvertDestinationDisplayTarget) {
+      this.convertDestinationDisplayTarget.textContent = "-";
+    }
+    if (this.hasCalculateRateDisplayTarget) {
+      this.calculateRateDisplayTarget.textContent = "-";
+    }
+    if (this.hasDestinationAmountTarget) {
+      this.destinationAmountTarget.value = "";
+    }
+
+    this.sourceCurrency = null;
+    this.destinationCurrency = null;
+  }
+
+  getExchangeRateContext() {
+    throw new Error("Subclasses must implement getExchangeRateContext()");
+  }
+
+  isCurrentExchangeRateState(_fromCurrency, _toCurrency, _date) {
+    throw new Error("Subclasses must implement isCurrentExchangeRateState()");
+  }
+}