feat(api): wire server configuration and dependencies

backend/cmd/api/config.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"time"
+)
+
+type config struct {
+	ServerAddr       string
+	FrontendOrigin   string
+	ZarinHubEndpoint string
+	ZarinHubToken    string
+	ZarinHubTimeout  time.Duration
+	DatabasePath     string
+}
+
+func loadConfig() (config, error) {
+	return readConfig(os.Getenv)
+}
+
+func readConfig(getenv func(string) string) (config, error) {
+	token := strings.TrimSpace(getenv("ZARINHUB_ACCESS_TOKEN"))
+	if token == "" {
+		return config{}, fmt.Errorf("ZARINHUB_ACCESS_TOKEN is required")
+	}
+
+	timeoutText := valueOrDefault(
+		getenv("ZARINHUB_TIMEOUT"),
+		"5s",
+	)
+	timeout, err := time.ParseDuration(timeoutText)
+	if err != nil || timeout <= 0 {
+		return config{}, fmt.Errorf(
+			"ZARINHUB_TIMEOUT must be a positive duration",
+		)
+	}
+
+	return config{
+		ServerAddr: valueOrDefault(
+			getenv("SERVER_ADDR"),
+			"127.0.0.1:8080",
+		),
+		FrontendOrigin: valueOrDefault(
+			getenv("FRONTEND_ORIGIN"),
+			"http://127.0.0.1:3000",
+		),
+		ZarinHubEndpoint: valueOrDefault(
+			getenv("ZARINHUB_ENDPOINT"),
+			"https://zarin-hub.com/api/v5/KYC/CardToIban",
+		),
+		ZarinHubToken:   token,
+		ZarinHubTimeout: timeout,
+		DatabasePath: valueOrDefault(
+			getenv("DATABASE_PATH"),
+			"./card-to-iban.db",
+		),
+	}, nil
+}
+
+func valueOrDefault(value string, fallback string) string {
+	if strings.TrimSpace(value) == "" {
+		return fallback
+	}
+
+	return strings.TrimSpace(value)
+}