package logger

import (
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"sync"
	"time"
)

type Level int

const (
	DEBUG Level = iota
	INFO
	WARN
	ERROR
)

const maxLogAge = 30 * 24 * time.Hour

var levelNames = map[Level]string{DEBUG: "DEBUG", INFO: "INFO", WARN: "WARN", ERROR: "ERROR"}

var (
	mu        sync.Mutex
	std       *log.Logger
	logDir    string
	logLevel  Level = INFO
	logFile   *os.File
	todayDate string
)

// Init sets up logging with daily rotation to dir/app-YYYY-MM-DD.log.
func Init(dir, level string) {
	logDir = dir
	os.MkdirAll(dir, 0755)

	switch strings.ToUpper(level) {
	case "DEBUG":
		logLevel = DEBUG
	case "WARN":
		logLevel = WARN
	case "ERROR":
		logLevel = ERROR
	default:
		logLevel = INFO
	}

	openToday()
	go dailyCleanup()
	Info("Logger initialized, level=%s, dir=%s", level, dir)
}

func openToday() {
	if logFile != nil {
		logFile.Close()
	}
	todayDate = time.Now().Format("2006-01-02")
	f, err := os.OpenFile(filepath.Join(logDir, "app-"+todayDate+".log"), os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
	if err != nil {
		log.Printf("Failed to open log file: %v, logging to stdout only", err)
		std = log.New(os.Stdout, "", 0)
		logFile = nil
		return
	}
	logFile = f
	multi := io.MultiWriter(os.Stdout, f)
	std = log.New(multi, "", 0)
}

func dailyCleanup() {
	for {
		time.Sleep(1 * time.Hour)
		// Delete old logs
		cutoff := time.Now().Add(-maxLogAge)
		entries, _ := os.ReadDir(logDir)
		for _, e := range entries {
			if strings.HasPrefix(e.Name(), "app-") && strings.HasSuffix(e.Name(), ".log") {
				dateStr := strings.TrimPrefix(strings.TrimSuffix(e.Name(), ".log"), "app-")
				if t, err := time.Parse("2006-01-02", dateStr); err == nil && t.Before(cutoff) {
					os.Remove(filepath.Join(logDir, e.Name()))
				}
			}
		}
	}
}

func Close() {
	if logFile != nil {
		logFile.Close()
	}
}

func rotateIfNeeded() {
	d := time.Now().Format("2006-01-02")
	if d != todayDate {
		mu.Lock()
		if d != todayDate {
			openToday()
		}
		mu.Unlock()
	}
}

func output(level Level, format string, args ...any) {
	if level < logLevel {
		return
	}
	rotateIfNeeded()

	msg := fmt.Sprintf(format, args...)
	now := time.Now().Format("2006-01-02 15:04:05.000")
	_, file, line, _ := runtime.Caller(2)
	short := file[strings.LastIndex(file, "/")+1:]

	lineStr := fmt.Sprintf("%s [%s] %s:%d %s", now, levelNames[level], short, line, msg)

	mu.Lock()
	if std != nil {
		std.Println(lineStr)
	}
	mu.Unlock()
}

func Debug(format string, args ...any) { output(DEBUG, format, args...) }
func Info(format string, args ...any)  { output(INFO, format, args...) }
func Warn(format string, args ...any)  { output(WARN, format, args...) }
func Error(format string, args ...any) { output(ERROR, format, args...) }

func StdLogger() *log.Logger {
	if std != nil {
		return std
	}
	return log.New(os.Stdout, "", 0)
}