package main

import (
	"fmt"
	"log/slog"
	"net/http"
	"net/http/httputil"
	"net/url"
	"time"

	"backend/src/internal/config"
	"backend/src/internal/logging"
)

const (
	AppName    = "Ollama Proxy"
	AppVersion = "1.0.0"
)

func main() {
	logger := logging.New("info")
	slog.SetDefault(logger)
	logger.Info(fmt.Sprintf("Starting %s version %s", AppName, AppVersion))

	cfg, err := config.LoadConfig(logger)
	if err != nil {
		logger.Error("Ошибка конфигурации", "error", err)
		return
	}

	level := logging.ParseLevel(cfg.LoggingConfig.Level)
	if level != slog.LevelInfo {
		logger.Info("Уровень логирования из env", "level", level.String())
	}
	logger = logging.New(cfg.LoggingConfig.Level)
	slog.SetDefault(logger)
	cfg.LoggingConfig.Instance = logger

	target, err := url.Parse(cfg.BackendURL)
	if err != nil {
		logger.Error("Неверный URL бэкенда", "error", err)
		return
	}

	proxy := &httputil.ReverseProxy{
		Rewrite: func(r *httputil.ProxyRequest) {
			r.SetURL(target)
			r.Out.Host = target.Host
		},
		ErrorHandler: func(w http.ResponseWriter, r *http.Request, err error) {
			logger.Error("Ошибка прокси", "method", r.Method, "path", r.URL.Path, "error", err)
			http.Error(w, "Bad Gateway", http.StatusBadGateway)
		},
	}

	handler := loggingMiddleware(logger, proxy)

	logger.Info("Прокси запущен", "addr", cfg.ListenAddr, "backend", cfg.BackendURL)
	if err := http.ListenAndServe(cfg.ListenAddr, handler); err != nil {
		logger.Error("Ошибка сервера", "error", err)
	}
}

func loggingMiddleware(logger *slog.Logger, next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		rw := &responseWriter{ResponseWriter: w, status: http.StatusOK}
		next.ServeHTTP(rw, r)
		logger.Info("запрос",
			"method", r.Method,
			"path", r.URL.Path,
			"status", rw.status,
			"duration", time.Since(start).String(),
		)
	})
}

type responseWriter struct {
	http.ResponseWriter
	status int
}

func (rw *responseWriter) WriteHeader(code int) {
	rw.status = code
	rw.ResponseWriter.WriteHeader(code)
}