package hysteria2

import (
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"

	"vpnclient/internal/coredl"
)

const githubAPILatest = "https://api.github.com/repos/apernet/hysteria/releases/latest"

// ResolveBinary finds hysteria client binary.
func ResolveBinary(binDir string) (string, error) {
	names := candidateNames()
	candidates := []string{}
	for _, name := range names {
		candidates = append(candidates,
			filepath.Join(binDir, name),
			filepath.Join(binDir, "hysteria2", name),
			filepath.Join(binDir, "hysteria", name),
		)
	}
	if exe, err := os.Executable(); err == nil {
		dir := filepath.Dir(exe)
		for _, name := range names {
			candidates = append(candidates, filepath.Join(dir, name), filepath.Join(dir, "bin", name))
		}
	}
	for _, c := range candidates {
		if st, err := os.Stat(c); err == nil && !st.IsDir() {
			return c, nil
		}
	}
	return "", fmt.Errorf("hysteria2 binary not found in %s; run install-core", binDir)
}

func candidateNames() []string {
	switch runtime.GOOS {
	case "windows":
		return []string{
			"hysteria.exe",
			"hysteria-windows-amd64.exe",
			"hysteria-windows-amd64-avx.exe",
		}
	case "darwin":
		return []string{
			"hysteria",
			"hysteria-darwin-arm64",
			"hysteria-darwin-amd64",
		}
	default:
		return []string{"hysteria", "hysteria-linux-amd64", "hysteria-linux-arm64"}
	}
}

// EnsureBinary downloads official Hysteria 2 release if missing.
func EnsureBinary(binDir string) (string, error) {
	if path, err := ResolveBinary(binDir); err == nil {
		return path, nil
	}
	if err := os.MkdirAll(binDir, 0o755); err != nil {
		return "", err
	}
	want, err := releaseAssetName()
	if err != nil {
		return "", err
	}
	fmt.Fprintf(os.Stderr, "downloading official hysteria2 release (%s)...\n", want)
	asset, all, err := findReleaseAsset(want)
	if err != nil {
		return "", err
	}
	sum, err := coredl.ResolveSHA(asset, all)
	if err != nil {
		return "", err
	}
	destName := "hysteria"
	if runtime.GOOS == "windows" {
		destName = "hysteria.exe"
	}
	dest := filepath.Join(binDir, destName)
	tmp := filepath.Join(binDir, asset.Name+".download")
	if err := coredl.DownloadAndVerify(tmp, asset.BrowserDownloadURL, sum); err != nil {
		return "", err
	}
	_ = os.Remove(dest)
	if err := os.Rename(tmp, dest); err != nil {
		_ = os.Remove(tmp)
		return "", err
	}
	_ = os.Chmod(dest, 0o755)
	if runtime.GOOS == "darwin" {
		_ = exec.Command("xattr", "-dr", "com.apple.quarantine", dest).Run()
	}
	return ResolveBinary(binDir)
}

func releaseAssetName() (string, error) {
	switch {
	case runtime.GOOS == "windows" && runtime.GOARCH == "amd64":
		return "hysteria-windows-amd64.exe", nil
	case runtime.GOOS == "windows" && runtime.GOARCH == "arm64":
		return "hysteria-windows-arm64.exe", nil
	case runtime.GOOS == "linux" && runtime.GOARCH == "amd64":
		return "hysteria-linux-amd64", nil
	case runtime.GOOS == "darwin" && runtime.GOARCH == "amd64":
		return "hysteria-darwin-amd64", nil
	case runtime.GOOS == "darwin" && runtime.GOARCH == "arm64":
		return "hysteria-darwin-arm64", nil
	default:
		return "", fmt.Errorf("unsupported platform %s/%s for hysteria2 auto-download", runtime.GOOS, runtime.GOARCH)
	}
}

func findReleaseAsset(exactName string) (coredl.ReleaseAsset, []coredl.ReleaseAsset, error) {
	_, assets, err := coredl.FetchLatestAssets(githubAPILatest)
	if err != nil {
		return coredl.ReleaseAsset{}, nil, err
	}
	var fallback coredl.ReleaseAsset
	for _, a := range assets {
		if a.Name == exactName {
			return a, assets, nil
		}
		if exactName == "hysteria-windows-amd64.exe" && a.Name == "hysteria-windows-amd64-avx.exe" {
			fallback = a
		}
	}
	if fallback.Name != "" {
		return fallback, assets, nil
	}
	for _, a := range assets {
		if strings.HasPrefix(a.Name, strings.TrimSuffix(exactName, filepath.Ext(exactName))) {
			return a, assets, nil
		}
	}
	return coredl.ReleaseAsset{}, assets, fmt.Errorf("no asset %s in hysteria release", exactName)
}