package downloader

import (
	"context"
	"crypto/tls"
	"fmt"
	"io"
	"net/http"
	"os"
	"path/filepath"

	"yizhisec.com/hsv2/forge/pkg/logger"
)

// Options defines options for downloading files
type Options struct {
	// InsecureSkipVerify skips TLS certificate verification
	InsecureSkipVerify bool
	// HTTPClient allows providing a custom HTTP client
	HTTPClient *http.Client
	// OnProgress is called during download with bytes downloaded and total size
	OnProgress func(downloaded, total int64)
	// CreateDirs automatically creates parent directories if they don't exist
	CreateDirs bool
	// Overwrite allows overwriting existing files
	Overwrite bool
	FileMode  os.FileMode
}

// Option is a functional option for configuring the downloader
type Option func(*Options)

// WithInsecureSkipVerify skips TLS certificate verification
func WithInsecureSkipVerify() Option {
	return func(o *Options) {
		o.InsecureSkipVerify = true
	}
}

// WithHTTPClient sets a custom HTTP client
func WithHTTPClient(client *http.Client) Option {
	return func(o *Options) {
		o.HTTPClient = client
	}
}

// WithProgress sets a progress callback
func WithProgress(callback func(downloaded, total int64)) Option {
	return func(o *Options) {
		o.OnProgress = callback
	}
}

// WithoutCreateDirs disables automatic creation of parent directories
func WithoutCreateDirs() Option {
	return func(o *Options) {
		o.CreateDirs = false
	}
}

// WithoutOverwrite prevents overwriting existing files
func WithoutOverwrite() Option {
	return func(o *Options) {
		o.Overwrite = false
	}
}

func WithFileMode(mode os.FileMode) Option {
	return func(o *Options) {
		o.FileMode = mode
	}
}

// Download downloads a file from URL to the specified destination
func Download(ctx context.Context, url, dest string, opts ...Option) error {
	options := &Options{
		InsecureSkipVerify: false,
		CreateDirs:         true,
		Overwrite:          true,
		FileMode:           0644,
	}

	for _, opt := range opts {
		opt(options)
	}

	logger.Debug("开始下载文件: %s -> %s", url, dest)

	// Check if file exists and overwrite is disabled
	if !options.Overwrite {
		if _, err := os.Stat(dest); err == nil {
			logger.Debug("文件已存在且不允许覆盖: %s", dest)
			return fmt.Errorf("file already exists: %s", dest)
		}
	}

	// Create parent directories if needed
	if options.CreateDirs {
		dir := filepath.Dir(dest)
		if err := os.MkdirAll(dir, 0755); err != nil {
			logger.Debug("创建目录失败 %s: %v", dir, err)
			return fmt.Errorf("failed to create directory: %w", err)
		}
	}

	// Create HTTP client
	client := options.HTTPClient
	if client == nil {
		client = &http.Client{}
		if options.InsecureSkipVerify {
			logger.Debug("TLS 证书验证已禁用")
			client.Transport = &http.Transport{
				TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
			}
		}
	}

	// Create HTTP request
	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
	if err != nil {
		logger.Debug("创建请求失败: %v", err)
		return fmt.Errorf("failed to create request: %w", err)
	}

	// Execute request
	logger.Debug("发起 HTTP 请求: %s", url)
	resp, err := client.Do(req)
	if err != nil {
		logger.Debug("下载失败: %v", err)
		return fmt.Errorf("failed to download: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		logger.Debug("HTTP 状态码异常: %d", resp.StatusCode)
		return fmt.Errorf("bad status: %s", resp.Status)
	}

	// Get content length for progress reporting
	contentLength := resp.ContentLength
	logger.Debug("文件大小: %d bytes", contentLength)

	outFile, err := os.OpenFile(dest, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, options.FileMode)
	if err != nil {
		logger.Debug("创建文件失败 %s: %v", dest, err)
		return fmt.Errorf("failed to create file: %w", err)
	}
	defer outFile.Close()

	// Copy content with optional progress reporting
	var written int64
	if options.OnProgress != nil && contentLength > 0 {
		// Use progress reader
		reader := &progressReader{
			reader:   resp.Body,
			callback: options.OnProgress,
			total:    contentLength,
		}
		written, err = io.Copy(outFile, reader)
	} else {
		written, err = io.Copy(outFile, resp.Body)
	}

	if err != nil {
		logger.Debug("写入文件失败 %s: %v", dest, err)
		return fmt.Errorf("failed to write file: %w", err)
	}

	if options.FileMode != 0 {
		if err := os.Chmod(dest, options.FileMode); err != nil {
			logger.Debug("设置文件权限失败 %s: %v", dest, err)
			return fmt.Errorf("failed to set file mode: %w", err)
		}
	}

	logger.Debug("文件下载成功: %s (%d bytes)", dest, written)
	return nil
}

// progressReader wraps an io.Reader to report progress
type progressReader struct {
	reader     io.Reader
	callback   func(downloaded, total int64)
	total      int64
	downloaded int64
}

func (pr *progressReader) Read(p []byte) (int, error) {
	n, err := pr.reader.Read(p)
	pr.downloaded += int64(n)
	if pr.callback != nil {
		pr.callback(pr.downloaded, pr.total)
	}
	return n, err
}