package main

import (
	"crypto/md5"
	"encoding/hex"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
)

const (
	manifestUrl      = "https://updater.project-epoch.net/api/manifest"
	defaultWowPath   = "/path/to/wow"
	defaultLaunchCmd = "not configured"
)

func main() {
	var (
		helpFlag       bool
		updateOnlyFlag bool
	)
	flag.BoolVar(&helpFlag, "h", false, "Print help")
	flag.BoolVar(&updateOnlyFlag, "u", false, "Only update the client, do not launch")
	flag.Parse()

	if helpFlag {
		flag.CommandLine.SetOutput(os.Stdout)
		flag.PrintDefaults()
		os.Exit(0)
	}

	config, err := setupConfig()
	if err != nil {
		log.Fatal(err)
	}

	if config.WowDir == defaultWowPath {
		log.Fatalf("WowDir in %s is still the default setting, exiting", cfgPath)
	}

	count, err := downloadUpdate(config)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Printf("Updated %d files\n", count)

	if updateOnlyFlag {
		os.Exit(0)
	}

	if config.LaunchCmd == defaultLaunchCmd {
		log.Fatalf("LaunchCmd in %s is still the default setting, exiting\n", cfgPath)
	}

	fmt.Printf("Starting Epoch....\n", count)

	switch runtime.GOOS {
	case "darwin":
		exec.Command("open", config.LaunchCmd).Run()
	case "linux":
		exec.Command(config.LaunchCmd).Run()
	}
}

func downloadUpdate(config *Config) (int, error) {
	var c int

	manifest, err := getManifest()
	if err != nil {
		log.Fatalf("Failed to get manifest: %v\n", err)
	}

	for _, file := range manifest.Files {
		path := strings.ReplaceAll(file.Path, `\`, `/`)
		path = strings.TrimLeft(path, `\`)

		localPath := filepath.Join(config.WowDir, path)
		localDir := filepath.Dir(localPath)
		if _, err = os.Stat(localDir); os.IsNotExist(err) {
			os.MkdirAll(localDir, 0755)
		}

		if _, err = os.Stat(localPath); err == nil {
			data, err := os.ReadFile(localPath)
			if err != nil {
				return c, err
			}
			hashBytes := md5.Sum(data)
			hash := hex.EncodeToString(hashBytes[:])
			if hash == file.Hash {
				continue
			}
		}

		fmt.Printf("Updating %s...\n", file.Path)

		outFile, err := os.Create(localPath)
		if err != nil {
			return c, err
		}
		defer outFile.Close()

		resp, err := http.Get(file.URL)
		if err != nil {
			return c, err
		}
		defer resp.Body.Close()
		if resp.StatusCode != http.StatusOK {
			return c, fmt.Errorf("failed to download update from %s, status code: %d", file.URL, resp.StatusCode)
		}

		_, err = io.Copy(outFile, resp.Body)
		if err != nil {
			return c, err
		}

		c += 1
	}

	return c, nil
}