//go:build linux || freebsd
// +build linux freebsd

package file

import (
	"context"
	"io"
	"os"
	"path/filepath"
	"time"

	"codeberg.org/petrbalvin/goget/internal/core"
	"codeberg.org/petrbalvin/goget/internal/protocol"
)

// Protocol implements file:// downloads.
type Protocol struct {
	*protocol.BaseProtocol
}

// NewProtocol creates a new file protocol handler.
func NewProtocol() *Protocol {
	return &Protocol{
		BaseProtocol: protocol.NewBaseProtocol(protocol.ProtocolInfo{
			Name:        "FILE",
			Scheme:      "file",
			DefaultPort: 0,
			Features:    []string{"resume", "recursive"},
		}),
	}
}

func (p *Protocol) Download(ctx context.Context, req *core.DownloadRequest) (*core.DownloadResult, error) {
	startTime := time.Now()

	filePath := req.URL.Path
	if req.URL.Host != "" {
		filePath = filepath.Join("/", req.URL.Host, filePath)
	}
	filePath = filepath.Clean(filePath)

	info, err := os.Stat(filePath)
	if err != nil {
		return nil, core.NewFileError("failed to stat source path", err)
	}

	if info.IsDir() {
		return p.downloadDirectory(ctx, req, filePath, startTime)
	}

	src, err := os.Open(filePath)
	if err != nil {
		return nil, core.NewFileError("failed to open source file", err)
	}
	defer src.Close()

	totalSize := info.Size()
	var writer io.Writer
	var outputPath string

	if req.Writer != nil {
		writer = req.Writer
		outputPath = req.Output
	} else if req.Output == "" || req.Output == "-" {
		writer = os.Stdout
		outputPath = "-"
	} else {
		dst, err := os.Create(req.Output)
		if err != nil {
			return nil, core.NewFileError("failed to create output file", err)
		}
		defer dst.Close()
		writer = dst
		outputPath = req.Output
	}

	var written int64
	if req.Resume && outputPath != "" && outputPath != "-" {
		if fi, err := os.Stat(outputPath); err == nil {
			written = fi.Size()
			if written >= totalSize {
				return &core.DownloadResult{
					BytesDownloaded: totalSize,
					TotalSize:       totalSize,
					Duration:        time.Since(startTime),
					Protocol:        "FILE",
					OutputPath:      outputPath,
					Resumed:         true,
				}, nil
			}
			if _, err := src.Seek(written, io.SeekStart); err != nil {
				return nil, core.NewFileError("failed to seek for resume", err)
			}
		}
	}

	buf := make([]byte, 32*1024)
	for {
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		default:
		}
		n, err := src.Read(buf)
		if n > 0 {
			if _, werr := writer.Write(buf[:n]); werr != nil {
				return nil, core.NewFileError("failed to write data", werr)
			}
			written += int64(n)
			if req.ProgressCallback != nil {
				speed := float64(written) / time.Since(startTime).Seconds()
				req.ProgressCallback(written, totalSize, speed)
			}
		}
		if err == io.EOF {
			break
		}
		if err != nil {
			return nil, core.NewFileError("failed to read source file", err)
		}
	}

	duration := time.Since(startTime)
	speed := float64(written) / duration.Seconds()

	return &core.DownloadResult{
		BytesDownloaded: written,
		TotalSize:       totalSize,
		Duration:        duration,
		Protocol:        "FILE",
		Speed:           speed,
		OutputPath:      outputPath,
		Resumed:         written > 0 && req.Resume,
	}, nil
}

// downloadDirectory recursively copies a local directory.
func (p *Protocol) downloadDirectory(ctx context.Context, req *core.DownloadRequest, dirPath string, startTime time.Time) (*core.DownloadResult, error) {
	outputBase := req.Output
	if outputBase == "" {
		outputBase = filepath.Base(dirPath)
	}

	var totalBytes int64
	var fileCount int

	err := filepath.Walk(dirPath, func(path string, info os.FileInfo, err error) error {
		select {
		case <-ctx.Done():
			return ctx.Err()
		default:
		}
		if err != nil {
			return err
		}
		if info.IsDir() {
			return nil
		}
		// Calculate relative path
		rel, err := filepath.Rel(dirPath, path)
		if err != nil {
			return err
		}
		outputPath := filepath.Join(outputBase, rel)

		if err := os.MkdirAll(filepath.Dir(outputPath), 0755); err != nil {
			return err
		}

		src, err := os.Open(path)
		if err != nil {
			return err
		}
		defer src.Close()

		dst, err := os.Create(outputPath)
		if err != nil {
			return err
		}
		defer dst.Close()

		n, err := io.Copy(dst, src)
		if err != nil {
			return err
		}
		totalBytes += n
		fileCount++
		return nil
	})

	if err != nil {
		return nil, core.NewFileError("failed to copy directory recursively", err)
	}

	duration := time.Since(startTime)
	speed := float64(0)
	if duration.Seconds() > 0 {
		speed = float64(totalBytes) / duration.Seconds()
	}

	return &core.DownloadResult{
		BytesDownloaded: totalBytes,
		TotalSize:       totalBytes,
		Duration:        duration,
		Protocol:        "FILE",
		Speed:           speed,
		OutputPath:      outputBase,
		ChunksCount:     fileCount,
	}, nil
}