package utils

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"runtime"
	"strings"
	"time"
)

const (
	// GitHub API endpoint for latest release
	githubReleasesURL = "https://api.github.com/repos/lukaszraczylo/semver-generator/releases/latest"
	// Request timeout for HTTP requests
	requestTimeout = 10 * time.Second
)

// ReleaseInfo contains information about a GitHub release
type ReleaseInfo struct {
	TagName string         `json:"tag_name"`
	HTMLURL string         `json:"html_url"`
	Name    string         `json:"name"`
	Assets  []ReleaseAsset `json:"assets"`
}

// ReleaseAsset contains information about a release asset
type ReleaseAsset struct {
	Name               string `json:"name"`
	BrowserDownloadURL string `json:"browser_download_url"`
}

// httpClient is the HTTP client used for requests (allows mocking in tests)
var httpClient = &http.Client{
	Timeout: requestTimeout,
}

// CheckLatestRelease checks for the latest release version using REST API
// Returns the latest version tag and true if successful, empty string and false otherwise
func CheckLatestRelease() (string, bool) {
	release, err := fetchLatestRelease(context.Background())
	if err != nil {
		Debug("Unable to check latest release", map[string]interface{}{"error": err.Error()})
		return "", false
	}

	version := normalizeVersion(release.TagName)
	return version, true
}

// UpdatePackage downloads and installs the latest version
func UpdatePackage() bool {
	Info("Checking for updates", nil)

	release, err := fetchLatestRelease(context.Background())
	if err != nil {
		Error("Unable to fetch latest release", map[string]interface{}{"error": err.Error()})
		return false
	}

	downloadURL := findBinaryAsset(release.Assets)
	if downloadURL == "" {
		Error("Unable to find binary for current platform", map[string]interface{}{
			"os":   runtime.GOOS,
			"arch": runtime.GOARCH,
		})
		return false
	}

	Info("Downloading update", map[string]interface{}{
		"version": release.TagName,
		"url":     downloadURL,
	})

	// Download to temp file
	tempFile, err := downloadBinary(downloadURL)
	if err != nil {
		Error("Unable to download binary", map[string]interface{}{"error": err.Error()})
		return false
	}
	defer os.Remove(tempFile) // Clean up temp file on failure

	// Get current binary path
	currentBinary, err := os.Executable()
	if err != nil {
		Error("Unable to get current binary path", map[string]interface{}{"error": err.Error()})
		return false
	}

	// Replace current binary
	if err := replaceBinary(tempFile, currentBinary); err != nil {
		Error("Unable to replace binary", map[string]interface{}{"error": err.Error()})
		return false
	}

	Info("Update successful", map[string]interface{}{
		"version": release.TagName,
	})
	return true
}

// fetchLatestRelease fetches the latest release info from GitHub REST API
func fetchLatestRelease(ctx context.Context) (*ReleaseInfo, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, githubReleasesURL, nil)
	if err != nil {
		return nil, err
	}

	req.Header.Set("Accept", "application/vnd.github.v3+json")
	req.Header.Set("User-Agent", "semver-generator")

	resp, err := httpClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("GitHub API returned status %d", resp.StatusCode)
	}

	var release ReleaseInfo
	if err := json.NewDecoder(resp.Body).Decode(&release); err != nil {
		return nil, err
	}

	return &release, nil
}

// findBinaryAsset finds the download URL for the current platform
func findBinaryAsset(assets []ReleaseAsset) string {
	// Build expected binary name pattern
	// Format: semver-gen-{version}-{os}-{arch}.tar.gz or just semver-gen-{os}-{arch}
	osName := runtime.GOOS
	archName := runtime.GOARCH

	for _, asset := range assets {
		name := strings.ToLower(asset.Name)
		// Match patterns like "semver-gen-1.0.0-darwin-arm64.tar.gz" or "semver-gen-darwin-arm64"
		if strings.Contains(name, osName) && strings.Contains(name, archName) {
			// Prefer tar.gz archives
			if strings.HasSuffix(name, ".tar.gz") {
				return asset.BrowserDownloadURL
			}
		}
	}

	// Fallback: try to find any matching binary without tar.gz
	for _, asset := range assets {
		name := strings.ToLower(asset.Name)
		if strings.Contains(name, osName) && strings.Contains(name, archName) {
			// Skip checksums
			if strings.Contains(name, "checksum") || strings.HasSuffix(name, ".sha256") || strings.HasSuffix(name, ".md5") {
				continue
			}
			return asset.BrowserDownloadURL
		}
	}

	return ""
}

// downloadBinary downloads the binary to a temp file and returns the path
func downloadBinary(url string) (string, error) {
	resp, err := httpClient.Get(url)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("download failed with status %d", resp.StatusCode)
	}

	// Create temp file
	tempFile, err := os.CreateTemp("", "semver-generator-update-*")
	if err != nil {
		return "", err
	}
	tempPath := tempFile.Name()

	// Check if it's a tar.gz archive
	if strings.HasSuffix(url, ".tar.gz") {
		// For tar.gz, we need to extract the binary
		if err := extractTarGz(resp.Body, tempFile); err != nil {
			_ = tempFile.Close()
			_ = os.Remove(tempPath)
			return "", err
		}
	} else {
		// Direct binary download
		if _, err := io.Copy(tempFile, resp.Body); err != nil {
			_ = tempFile.Close()
			_ = os.Remove(tempPath)
			return "", err
		}
	}

	if err := tempFile.Close(); err != nil {
		_ = os.Remove(tempPath)
		return "", err
	}
	return tempPath, nil
}

// extractTarGz extracts the semver-generator binary from a tar.gz archive
func extractTarGz(r io.Reader, destFile *os.File) error {
	// For simplicity, we'll download the whole archive to a temp file first,
	// then use tar command to extract. This avoids adding archive/tar dependency.

	// Create temp archive file
	archiveFile, err := os.CreateTemp("", "semver-generator-archive-*.tar.gz")
	if err != nil {
		return err
	}
	archivePath := archiveFile.Name()
	defer os.Remove(archivePath)

	if _, err := io.Copy(archiveFile, r); err != nil {
		_ = archiveFile.Close()
		return err
	}
	if err := archiveFile.Close(); err != nil {
		return err
	}

	// Extract using tar command
	extractDir, err := os.MkdirTemp("", "semver-generator-extract-*")
	if err != nil {
		return err
	}
	defer os.RemoveAll(extractDir)

	// Use tar to extract
	cmd := fmt.Sprintf("tar -xzf %s -C %s", archivePath, extractDir)
	if err := runCommand(cmd); err != nil {
		return fmt.Errorf("failed to extract archive: %w", err)
	}

	// Find the binary in the extracted files
	// Support both new name (semver-generator) and old name (semver-gen) for backwards compatibility
	binaryPath := ""
	entries, err := os.ReadDir(extractDir)
	if err != nil {
		return err
	}

	// First try to find semver-generator (new name)
	for _, entry := range entries {
		if entry.Name() == "semver-generator" {
			binaryPath = fmt.Sprintf("%s/%s", extractDir, entry.Name())
			break
		}
	}

	// Fallback to semver-gen (old name) for older releases
	if binaryPath == "" {
		for _, entry := range entries {
			if entry.Name() == "semver-gen" {
				binaryPath = fmt.Sprintf("%s/%s", extractDir, entry.Name())
				break
			}
		}
	}

	if binaryPath == "" {
		return fmt.Errorf("binary not found in archive (looked for semver-generator and semver-gen)")
	}

	// Copy the binary to the destination
	srcFile, err := os.Open(binaryPath)
	if err != nil {
		return err
	}
	defer srcFile.Close()

	// Seek to beginning of dest file and truncate
	if _, err := destFile.Seek(0, 0); err != nil {
		return err
	}
	if err := destFile.Truncate(0); err != nil {
		return err
	}

	if _, err := io.Copy(destFile, srcFile); err != nil {
		return err
	}

	return nil
}

// runCommand runs a shell command
func runCommand(cmdStr string) error {
	return runCommandFunc(cmdStr)
}

// runCommandFunc is the function used to run commands (allows mocking in tests)
var runCommandFunc = func(cmdStr string) error {
	cmd := exec.Command("sh", "-c", cmdStr)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}

// replaceBinary replaces the current binary with the new one
func replaceBinary(newBinary, currentBinary string) error {
	// Make the new binary executable
	// #nosec G302 -- 0755 is required for executable binaries
	if err := os.Chmod(newBinary, 0755); err != nil {
		return err
	}

	// Rename (atomic on most systems)
	if err := os.Rename(newBinary, currentBinary); err != nil {
		// If rename fails (e.g., cross-device), try copy
		return copyFile(newBinary, currentBinary)
	}

	return nil
}

// copyFile copies a file from src to dst
// Note: This function is only called internally with controlled paths from
// os.CreateTemp and os.Executable, not with user-supplied paths.
func copyFile(src, dst string) error {
	// #nosec G304 -- src is from os.CreateTemp, not user input
	srcFile, err := os.Open(src)
	if err != nil {
		return err
	}
	defer srcFile.Close()

	// #nosec G304 -- dst is from os.Executable, not user input
	dstFile, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer dstFile.Close()

	if _, err := io.Copy(dstFile, srcFile); err != nil {
		return err
	}

	// Make executable
	// #nosec G302 -- 0755 is required for executable binaries
	return os.Chmod(dst, 0755)
}

// normalizeVersion removes 'v' or 'V' prefix and trims whitespace
func normalizeVersion(v string) string {
	v = strings.TrimSpace(v)
	v = strings.TrimPrefix(v, "v")
	v = strings.TrimPrefix(v, "V")
	return v
}