package main

import (
	"context"
	"errors"
	"fmt"
	"log"
	"net"
	"net/http"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"git.nianxx.cn/wangxuming/NianAIGC/backend/internal/application"
	"git.nianxx.cn/wangxuming/NianAIGC/backend/internal/settings"
)

const shutdownTimeout = 10 * time.Second

func main() {
	if err := run(); err != nil {
		log.Fatal(err)
	}
}

func run() error {
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()

	getenv, err := runtimeGetenv(os.Getenv)
	if err != nil {
		return fmt.Errorf("load Go backend runtime settings: %w", err)
	}
	app, err := application.New(application.Options{Context: ctx, Getenv: getenv})
	if err != nil {
		return fmt.Errorf("initialize Go backend: %w", err)
	}
	defer app.Close()

	server := &http.Server{
		Addr:              listenAddress(getenv),
		Handler:           app.Handler(),
		ReadHeaderTimeout: 5 * time.Second,
	}

	serveErr := make(chan error, 1)
	go func() {
		log.Printf("zhinian-api foundation listening on %s", server.Addr)
		serveErr <- server.ListenAndServe()
	}()

	select {
	case err := <-serveErr:
		if errors.Is(err, http.ErrServerClosed) {
			return nil
		}
		return fmt.Errorf("serve Go backend: %w", err)
	case <-ctx.Done():
	}

	shutdownCtx, cancel := context.WithTimeout(context.Background(), shutdownTimeout)
	defer cancel()
	if err := server.Shutdown(shutdownCtx); err != nil {
		return fmt.Errorf("shut down Go backend: %w", err)
	}
	if err := <-serveErr; err != nil && !errors.Is(err, http.ErrServerClosed) {
		return fmt.Errorf("serve Go backend: %w", err)
	}
	return nil
}

func runtimeGetenv(process func(string) string) (func(string) string, error) {
	path := strings.TrimSpace(process("ZHINIAN_SETTINGS_FILE"))
	if path == "" {
		path = ".env.local"
	}
	values := map[string]string{}
	for _, key := range settings.RuntimeSettingKeys() {
		if value := process(key); value != "" {
			values[key] = value
		}
	}
	merged, err := settings.LoadEnvironment(path, values)
	if err != nil {
		return nil, err
	}
	return func(name string) string {
		if value, exists := merged[name]; exists {
			return value
		}
		return process(name)
	}, nil
}

func listenAddress(getenv func(string) string) string {
	host := strings.TrimSpace(getenv("GO_BACKEND_HOST"))
	if host == "" {
		host = "127.0.0.1"
	}
	port := strings.TrimSpace(getenv("GO_BACKEND_PORT"))
	if port == "" {
		port = "8080"
	}
	return net.JoinHostPort(host, port)
}