From 71dfeaebe9795697b7699acecd4ba9b96e433f08 Mon Sep 17 00:00:00 2001
From: partisan <none@noone.no>
Date: Tue, 1 Jul 2025 22:06:49 +0200
Subject: [PATCH] Added fallback for currency instant answers

---
 ia-currency.go | 106 +++++++++++++++++++++++++++++++++----------------
 1 file changed, 72 insertions(+), 34 deletions(-)

diff --git a/ia-currency.go b/ia-currency.go
index 2f1de37..8618055 100644
--- a/ia-currency.go
+++ b/ia-currency.go
@@ -4,7 +4,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"log"
 	"net/http"
 	"regexp"
 	"strconv"
@@ -17,6 +16,7 @@ import (
 var (
 	exchangeRates      = make(map[string]float64)
 	nextUpdateTime     time.Time
+	lastUpdateTime     time.Time
 	exchangeCacheMutex sync.RWMutex
 	allCurrencies      []string
 )
@@ -26,47 +26,83 @@ type CurrencyAPIResponse struct {
 	Rates map[string]float64 `json:"rates"`
 }
 
-// UpdateExchangeRates fetches and caches currency rates
+var primaryURL = "https://open.er-api.com/v6/latest/USD"
+var backupURL = "https://api.frankfurter.app/latest?base=USD"
+
+func fetchRates(url string) ([]byte, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	return io.ReadAll(resp.Body)
+}
+
 func UpdateExchangeRates() error {
 	exchangeCacheMutex.Lock()
 	defer exchangeCacheMutex.Unlock()
 
-	// Use a reliable free API with good rate limits
-	resp, err := http.Get("https://open.er-api.com/v6/latest/USD")
-	if err != nil {
-		return err
-	}
-	defer resp.Body.Close()
+	var (
+		rates    map[string]float64
+		nextTime time.Time
+		fallback bool
+	)
 
-	body, err := io.ReadAll(resp.Body)
-	if err != nil {
-		return err
+	// Try primary API
+	body, err := fetchRates(primaryURL)
+	if err == nil {
+		var res struct {
+			Result             string             `json:"result"`
+			Rates              map[string]float64 `json:"rates"`
+			TimeNextUpdateUnix int64              `json:"time_next_update_unix"`
+		}
+		if err := json.Unmarshal(body, &res); err == nil && res.Result == "success" && len(res.Rates) > 0 {
+			rates = res.Rates
+			nextTime = time.Unix(res.TimeNextUpdateUnix, 0)
+		} else {
+			printWarn("Primary API response invalid or empty, falling back to backup")
+			fallback = true
+		}
+	} else {
+		printWarn("Primary API fetch failed: %v", err)
+		fallback = true
 	}
 
-	var apiResponse struct {
-		Result             string             `json:"result"`
-		Rates              map[string]float64 `json:"rates"`
-		TimeNextUpdateUnix int64              `json:"time_next_update_unix"`
-	}
-	if err := json.Unmarshal(body, &apiResponse); err != nil {
-		return err
+	// Try backup API if needed
+	if fallback {
+		body, err := fetchRates(backupURL)
+		if err != nil {
+			return fmt.Errorf("both rate fetches failed: %v", err)
+		}
+
+		var res struct {
+			Base  string             `json:"base"`
+			Date  string             `json:"date"`
+			Rates map[string]float64 `json:"rates"`
+		}
+		if err := json.Unmarshal(body, &res); err != nil {
+			return fmt.Errorf("backup API response unmarshal failed: %v", err)
+		}
+		if len(res.Rates) == 0 {
+			return fmt.Errorf("backup API returned empty rates")
+		}
+
+		rates = res.Rates
+		nextTime = time.Now().Add(6 * time.Hour)
 	}
 
-	if apiResponse.Result != "success" {
-		return fmt.Errorf("API error: %s", apiResponse.Result)
-	}
+	// Finalize
+	exchangeRates = rates
+	nextUpdateTime = nextTime
+	lastUpdateTime = time.Now()
 
-	// Cache the rates
-	exchangeRates = apiResponse.Rates
-	nextUpdateTime = time.Unix(apiResponse.TimeNextUpdateUnix, 0)
-
-	// Update list of all currencies
 	allCurrencies = make([]string, 0, len(exchangeRates))
-	for currency := range exchangeRates {
-		allCurrencies = append(allCurrencies, currency)
+	for c := range exchangeRates {
+		allCurrencies = append(allCurrencies, c)
 	}
 
 	printDebug("Updated currency rates: %d currencies cached", len(allCurrencies))
+	printDebug("Next currency update at: %s", nextUpdateTime.Format(time.RFC1123))
 	return nil
 }
 
@@ -76,7 +112,7 @@ func PrecacheAllCurrencyPairs() {
 	defer exchangeCacheMutex.RUnlock()
 
 	if len(exchangeRates) == 0 {
-		log.Println("Skipping precache - no rates available")
+		printWarn("Skipping precache: no currency rates available")
 		return
 	}
 
@@ -99,11 +135,13 @@ func PrecacheAllCurrencyPairs() {
 func GetExchangeRate(from, to string) (float64, bool) {
 	// Auto-update cache if expired
 	if time.Now().After(nextUpdateTime) {
-		err := UpdateExchangeRates()
-		if err != nil {
-			printWarn("Currency update failed: %v", err)
-			// Postpone next attempt to avoid hammering API
-			nextUpdateTime = time.Now().Add(5 * time.Minute)
+		// Avoid excessive updates within 1 min
+		if time.Since(lastUpdateTime) > time.Minute {
+			err := UpdateExchangeRates()
+			if err != nil {
+				printWarn("Currency update failed: %v", err)
+				nextUpdateTime = time.Now().Add(5 * time.Minute)
+			}
 		}
 	}