package main

import (
	"archive/zip"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
	"time"

	"github.com/sqweek/dialog"
)

var (
	installDirFlag = flag.String("dir", "", "Installation directory (default C:\\ZernMC or chosen via dialog)")
	onlineFlag     = flag.Bool("online", true, "Online mode (download JRE + files)")
	offlineFlag    = flag.Bool("offline", false, "Offline mode (unpack from adjacent zip)")
	offlineZipFlag = flag.String("offline-zip", "", "Path to offline zip for offline mode")
	shortcutFlag   = flag.Bool("shortcut", true, "Create desktop shortcut")
)

const (
	defaultInstallDir = "C:\\ZernMC"
	serverBase        = "https://api.zern.cc"
	jreZipName        = "OpenJDK21U-jre_x64_windows_hotspot_21.0.6_7.zip"
)

func main() {
	flag.Parse()

	// Offline flag overrides online
	isOnline := *onlineFlag && !*offlineFlag

	dir := *installDirFlag
	if dir == "" {
		dir = askInstallDir()
	}
	if dir == "" {
		fmt.Println("Installation cancelled")
		os.Exit(0)
	}
	fmt.Printf("Install dir: %s (online=%v)\n", dir, isOnline)

	if err := os.MkdirAll(dir, 0755); err != nil {
		fatal("Cannot create directory: %v", err)
	}

	createShortcut := *shortcutFlag
	if !isFlagSet("shortcut") {
		// ask via dialog if not explicitly flagged
		createShortcut = askShortcut()
	}

	if isOnline {
		if err := installOnline(dir, createShortcut); err != nil {
			fatal("Online install failed: %v", err)
		}
	} else {
		zipPath := *offlineZipFlag
		if zipPath == "" {
			// try to find adjacent offline zip
			zipPath = findAdjacentOfflineZip()
			if zipPath == "" {
				// ask user
				zipPath, _ = dialog.File().Title("Select ZernMC-Offline.zip").Filter("ZIP (*.zip)", "zip").Load()
			}
		}
		if zipPath == "" {
			fatal("Offline zip not specified")
		}
		if err := installOffline(dir, zipPath, createShortcut); err != nil {
			fatal("Offline install failed: %v", err)
		}
	}

	fmt.Println("\nInstallation complete!")
	fmt.Printf("Launcher: %s\\zernmc.exe\n", dir)
	fmt.Printf("Data dir: %s\\.zernmc (local files, instances)\n", os.Getenv("USERPROFILE"))
	if createShortcut {
		fmt.Println("Shortcut on desktop: ZernMC Launcher.lnk")
	}
	fmt.Println("Uninstall: run", filepath.Join(dir, "uninstall.exe"), "or delete folder")
}

func isFlagSet(name string) bool {
	found := false
	flag.Visit(func(f *flag.Flag) {
		if f.Name == name {
			found = true
		}
	})
	return found
}

func askInstallDir() string {
	// Try GUI dialog first (Windows)
	if runtime.GOOS == "windows" {
		dir, err := dialog.Directory().Title("Куда установить ZernMC").Browse()
		if err == nil && dir != "" {
			// dialog.Directory returns chosen dir; append ZernMC if not already
			if !strings.Contains(strings.ToLower(dir), "zernmc") {
				dir = filepath.Join(dir, "ZernMC")
			}
			return dir
		}
		// fallback to default if dialog fails/cancelled with empty
		fmt.Printf("Dialog cancelled or error (%v), using default %s\n", err, defaultInstallDir)
	}
	// CLI fallback
	fmt.Printf("Куда установить ZernMC [%s]: ", defaultInstallDir)
	var input string
	fmt.Scanln(&input)
	input = strings.TrimSpace(input)
	if input == "" {
		input = defaultInstallDir
	}
	return input
}

func askShortcut() bool {
	if runtime.GOOS != "windows" {
		return false
	}
	// simple yes/no dialog
	// sqweek/dialog Message does not return bool, so use question
	// fallback to true by default if dialog unavailable
	yes := dialog.Message("Создать ярлык на рабочем столе (ZernMC Launcher)?").Title("Ярлык").YesNo()
	return yes
}

func fatal(format string, args ...interface{}) {
	msg := fmt.Sprintf(format, args...)
	fmt.Fprintln(os.Stderr, msg)
	// also show dialog on Windows
	if runtime.GOOS == "windows" {
		dialog.Message(msg).Title("ZernMC Installer — Ошибка").Error()
	}
	os.Exit(1)
}

func installOnline(dir string, createShortcut bool) error {
	fmt.Println("Online installation — downloading JRE + launcher files...")
	// Step 1: download JRE zip if missing
	jreDir := filepath.Join(dir, "lib", "jre21")
	javaExe := filepath.Join(jreDir, "bin", "java.exe")
	if _, err := os.Stat(javaExe); err != nil {
		fmt.Println("Downloading JRE 21 (47 MB)...")
		jreURL := serverBase + "/launcher/download/jre"
		tmpZip := filepath.Join(os.TempDir(), jreZipName)
		if err := downloadFile(jreURL, tmpZip); err != nil {
			// fallback to direct zip from builds if server endpoint not ready
			// try alternative mirrors
			mirrors := []string{
				"https://api.zernmc.ru/launcher/download/jre",
				"https://api.zernmc.online/launcher/download/jre",
			}
			var lastErr error
			for _, m := range mirrors {
				fmt.Printf("Retry mirror %s\n", m)
				if err := downloadFile(m, tmpZip); err == nil {
					lastErr = nil
					break
				} else {
					lastErr = err
				}
			}
			if lastErr != nil {
				return fmt.Errorf("JRE download failed: %w", lastErr)
			}
		}
		fmt.Printf("Unpacking JRE to %s ...\n", jreDir)
		if err := unzip(tmpZip, dir); err != nil {
			// try alt: unzip should contain jre21/ prefix or lib/jre21?
			// our zip contains jre21/ at root, need to move to lib/jre21
			return fmt.Errorf("unzip JRE: %w", err)
		}
		// handle both zip layouts: some zips contain jre21/, some lib/jre21/
		// if tmp unzip created dir/jre21, move to lib/jre21
		candidate := filepath.Join(dir, "jre21")
		if _, err := os.Stat(candidate); err == nil {
			os.MkdirAll(filepath.Join(dir, "lib"), 0755)
			os.RemoveAll(jreDir)
			if err := os.Rename(candidate, jreDir); err != nil {
				// fallback copy
				if err := copyDir(candidate, jreDir); err != nil {
					return err
				}
				os.RemoveAll(candidate)
			}
		}
		os.Remove(tmpZip)
		if _, err := os.Stat(javaExe); err != nil {
			return fmt.Errorf("JRE unpack failed, %s not found", javaExe)
		}
		fmt.Println("JRE ready")
	} else {
		fmt.Println("JRE already present, skipping")
	}

	// Step 2: fetch meta and download launcher files
	fmt.Println("Fetching launcher meta...")
	meta, err := fetchMeta()
	if err != nil {
		return fmt.Errorf("fetch meta: %w", err)
	}
	fmt.Printf("Latest: %s (%d files)\n", meta.Version, len(meta.Files))

	for i, f := range meta.Files {
		rel := f.Path
		// skip JRE entries (should not be in meta, but just in case)
		if strings.HasPrefix(rel, "jre21/") || strings.HasPrefix(rel, "lib/jre21") {
			continue
		}
		dest := filepath.Join(dir, filepath.FromSlash(rel))
		need := true
		if fi, err := os.Stat(dest); err == nil && !fi.IsDir() {
			hash, _ := fileSHA256(dest)
			if hash == strings.TrimPrefix(f.Hash, "sha256:") {
				need = false
			}
		}
		if !need {
			continue
		}
		fmt.Printf("[%d/%d] %s (%.1f KB)\n", i+1, len(meta.Files), rel, float64(f.Size)/1024)
		if err := os.MkdirAll(filepath.Dir(dest), 0755); err != nil {
			return err
		}
		url := fmt.Sprintf("%s/launcher/file/%s/%s", serverBase, meta.Version, rel)
		// try mirrors on failure
		if err := downloadFile(url, dest); err != nil {
			// try versioned fallback (some servers use builds/ vs versions/)
			alt := fmt.Sprintf("%s/launcher/download/jar", serverBase) // not generic
			_ = alt
			return fmt.Errorf("download %s: %w", rel, err)
		}
		// verify hash
		hash, _ := fileSHA256(dest)
		if hash != strings.TrimPrefix(f.Hash, "sha256:") {
			fmt.Printf("  WARNING hash mismatch for %s\n", rel)
		}
	}

	// write build.version
	if err := os.WriteFile(filepath.Join(dir, "build.version"), []byte(meta.Version), 0644); err != nil {
		fmt.Printf("warning write build.version: %v\n", err)
	}
	// also ensure bin/zernmclauncher.jar etc are present
	fmt.Println("Launcher files ready")

	if createShortcut {
		if err := createDesktopShortcut(dir); err != nil {
			fmt.Printf("shortcut failed: %v\n", err)
		}
	}
	if err := createUninstaller(dir); err != nil {
		fmt.Printf("uninstall.exe failed: %v\n", err)
	}
	return nil
}

func installOffline(dir, zipPath string, createShortcut bool) error {
	fmt.Printf("Offline installation from %s to %s\n", zipPath, dir)
	if _, err := os.Stat(zipPath); err != nil {
		return fmt.Errorf("offline zip not found: %s", zipPath)
	}
	fmt.Println("Unpacking (98 MB, ~200 MB unpacked)...")
	if err := unzip(zipPath, dir); err != nil {
		return fmt.Errorf("unzip: %w", err)
	}
	// zip contains zernmc.exe, lib/, bin/, assets/ at root — already correct relative to dir
	// if zip contained top-level folder, handle it
	// we unzip directly to dir, so should be fine

	if createShortcut {
		if err := createDesktopShortcut(dir); err != nil {
			fmt.Printf("shortcut failed: %v\n", err)
		}
	}
	if err := createUninstaller(dir); err != nil {
		fmt.Printf("uninstall.exe failed: %v\n", err)
	}
	fmt.Println("Offline unpack complete")
	fmt.Printf("Data will be in %s\\.zernmc\n", os.Getenv("USERPROFILE"))
	return nil
}

func downloadFile(url, dest string) error {
	// support resume? simple GET
	client := &http.Client{Timeout: 120 * time.Second}
	resp, err := client.Get(url)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode != 200 {
		return fmt.Errorf("HTTP %d", resp.StatusCode)
	}
	// ensure parent
	if err := os.MkdirAll(filepath.Dir(dest), 0755); err != nil {
		return err
	}
	tmp := dest + ".tmp"
	out, err := os.Create(tmp)
	if err != nil {
		return err
	}
	defer out.Close()

	total := resp.ContentLength
	var written int64
	buf := make([]byte, 64*1024)
	start := time.Now()
	for {
		n, err := resp.Body.Read(buf)
		if n > 0 {
			if _, werr := out.Write(buf[:n]); werr != nil {
				return werr
			}
			written += int64(n)
			if total > 0 {
				pct := float64(written) / float64(total) * 100
				elapsed := time.Since(start).Seconds()
				speed := float64(written) / 1024 / 1024 / (elapsed + 0.001)
				fmt.Printf("\r  %.1f%% %.1f/%.1f MB %.1f MB/s   ", pct, float64(written)/1024/1024, float64(total)/1024/1024, speed)
			} else {
				fmt.Printf("\r  %.1f MB   ", float64(written)/1024/1024)
			}
		}
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}
	}
	fmt.Println()
	out.Close()
	// verify tmp exists
	if err := os.Rename(tmp, dest); err != nil {
		// fallback copy
		if err2 := copyFile(tmp, dest); err2 != nil {
			return err2
		}
		os.Remove(tmp)
	}
	return nil
}

func unzip(src, dest string) error {
	r, err := zip.OpenReader(src)
	if err != nil {
		return err
	}
	defer r.Close()
	for _, f := range r.File {
		fpath := filepath.Join(dest, f.Name)
		// ZipSlip protection
		if !strings.HasPrefix(fpath, filepath.Clean(dest)+string(os.PathSeparator)) {
			return fmt.Errorf("illegal file path: %s", fpath)
		}
		if f.FileInfo().IsDir() {
			os.MkdirAll(fpath, f.Mode())
			continue
		}
		if err := os.MkdirAll(filepath.Dir(fpath), 0755); err != nil {
			return err
		}
		out, err := os.OpenFile(fpath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, f.Mode())
		if err != nil {
			return err
		}
		rc, err := f.Open()
		if err != nil {
			out.Close()
			return err
		}
		_, err = io.Copy(out, rc)
		out.Close()
		rc.Close()
		if err != nil {
			return err
		}
	}
	return nil
}

func copyFile(src, dst string) error {
	in, err := os.Open(src)
	if err != nil {
		return err
	}
	defer in.Close()
	out, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer out.Close()
	_, err = io.Copy(out, in)
	return err
}

func copyDir(src, dst string) error {
	return filepath.Walk(src, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		rel, _ := filepath.Rel(path, src)
		target := filepath.Join(dst, rel)
		if info.IsDir() {
			return os.MkdirAll(target, info.Mode())
		}
		return copyFile(path, target)
	})
}

func fileSHA256(path string) (string, error) {
	f, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer f.Close()
	h := sha256.New()
	if _, err := io.Copy(h, f); err != nil {
		return "", err
	}
	return hex.EncodeToString(h.Sum(nil)), nil
}

type Meta struct {
	Version string `json:"version"`
	Files   []struct {
		Path string `json:"path"`
		Size int64  `json:"size"`
		Hash string `json:"hash"`
	} `json:"files"`
}

func fetchMeta() (*Meta, error) {
	// try /launcher/meta/{version} flow: first get version, then meta
	resp, err := http.Get(serverBase + "/launcher/version")
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()
	var verResp struct {
		Version string `json:"version"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&verResp); err != nil {
		return nil, err
	}
	ver := verResp.Version
	if ver == "" {
		ver = "1.1.1"
	}
	metaResp, err := http.Get(serverBase + "/launcher/meta/" + ver)
	if err != nil {
		return nil, err
	}
	defer metaResp.Body.Close()
	if metaResp.StatusCode != 200 {
		return nil, fmt.Errorf("meta %d", metaResp.StatusCode)
	}
	var meta Meta
	if err := json.NewDecoder(metaResp.Body).Decode(&meta); err != nil {
		return nil, err
	}
	if meta.Version == "" {
		meta.Version = ver
	}
	return &meta, nil
}

func findAdjacentOfflineZip() string {
	exe, _ := os.Executable()
	dir := filepath.Dir(exe)
	// look for ZernMC-Offline*.zip or ZernMC-win*.zip nearby
	matches, _ := filepath.Glob(filepath.Join(dir, "ZernMC-Offline*.zip"))
	if len(matches) > 0 {
		return matches[0]
	}
	matches, _ = filepath.Glob(filepath.Join(dir, "ZernMC-win*.zip"))
	if len(matches) > 0 {
		return matches[0]
	}
	// also check current dir
	matches, _ = filepath.Glob("ZernMC-Offline*.zip")
	if len(matches) > 0 {
		return matches[0]
	}
	return ""
}

func createDesktopShortcut(installDir string) error {
	if runtime.GOOS != "windows" {
		return nil
	}
	desktop := filepath.Join(os.Getenv("USERPROFILE"), "Desktop")
	if _, err := os.Stat(desktop); err != nil {
		desktop = filepath.Join(os.Getenv("USERPROFILE"), "OneDrive", "Desktop")
	}
	if _, err := os.Stat(desktop); err != nil {
		return fmt.Errorf("desktop not found")
	}
	lnk := filepath.Join(desktop, "ZernMC Launcher.lnk")
	target := filepath.Join(installDir, "zernmc.exe")
	ps := fmt.Sprintf(`$WshShell = New-Object -comObject WScript.Shell; $Shortcut = $WshShell.CreateShortcut('%s'); $Shortcut.TargetPath = '%s'; $Shortcut.WorkingDirectory = '%s'; $Shortcut.IconLocation = '%s'; $Shortcut.Save()`, lnk, target, installDir, target)
	tmp := filepath.Join(os.TempDir(), "zernmc_shortcut.ps1")
	if err := os.WriteFile(tmp, []byte(ps), 0644); err != nil {
		return err
	}
	defer os.Remove(tmp)
	cmd := exec.Command("powershell", "-ExecutionPolicy", "Bypass", "-File", tmp)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}

func createUninstaller(dir string) error {
	// create uninstall.bat and copy self as uninstall.exe
	exe, _ := os.Executable()
	uninstExe := filepath.Join(dir, "uninstall.exe")
	if exe != "" && exe != uninstExe {
		_ = copyFile(exe, uninstExe)
	}
	bat := filepath.Join(dir, "uninstall.bat")
	content := fmt.Sprintf(`@echo off
echo Uninstalling ZernMC from %s
timeout /t 2 >nul
del "%%USERPROFILE%%\Desktop\ZernMC Launcher.lnk" 2>nul
del "%%USERPROFILE%%\OneDrive\Desktop\ZernMC Launcher.lnk" 2>nul
echo Data in %%USERPROFILE%%\.zernmc will be kept.
echo To remove completely, delete %%USERPROFILE%%\.zernmc manually.
`, dir)
	_ = os.WriteFile(bat, []byte(content), 0644)
	return nil
}

func runCmd(name string, args ...string) error {
	cmd := exec.Command(name, args...)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}