package main

import (
	"archive/tar"
	"compress/gzip"
	"flag"
	"fmt"
	"io"
	"os"
	"path/filepath"
)

func main() {
	// Define command line flags
	sourceDir := flag.String("source", "", "Source directory to compress")
	outputFile := flag.String("output", "output.tar.gz", "Output tarball filename")
	prefixDir := flag.String("prefix", "myapp", "Directory prefix in tarball")
	flag.Parse()

	if *sourceDir == "" {
		fmt.Println("Please specify a source directory using -source")
		flag.Usage()
		os.Exit(1)
	}

	err := createTarball(*sourceDir, *outputFile, *prefixDir)
	if err != nil {
		fmt.Printf("Error creating tarball: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Successfully created %s with prefix %s\n", *outputFile, *prefixDir)
}

func createTarball(sourceDir, outputFile, prefix string) error {
	// Create output file
	out, err := os.Create(outputFile)
	if err != nil {
		return err
	}
	defer out.Close()

	// Create gzip writer
	gw := gzip.NewWriter(out)
	defer gw.Close()

	// Create tar writer
	tw := tar.NewWriter(gw)
	defer tw.Close()

	// Resolve absolute source path to handle relative symlinks correctly
	sourceDir, err = filepath.Abs(sourceDir)
	if err != nil {
		return err
	}

	// Walk through source directory
	err = filepath.Walk(sourceDir, func(filePath string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		// Get relative path to use in the tarball
		relPath, err := filepath.Rel(sourceDir, filePath)
		if err != nil {
			return err
		}

		// Create tar header using original file info
		header, err := tar.FileInfoHeader(info, "")
		if err != nil {
			return err
		}

		// Update the name with the prefix and relative path
		header.Name = filepath.Join(prefix, relPath)

		// Special handling for symbolic links
		if info.Mode()&os.ModeSymlink != 0 {
			// Read link target
			linkTarget, err := os.Readlink(filePath)
			if err != nil {
				return err
			}

			// Store the link target in the header
			header.Linkname = linkTarget

			// Make sure the link type is set correctly
			header.Typeflag = tar.TypeSymlink
		}

		// Write header
		if err := tw.WriteHeader(header); err != nil {
			return err
		}

		// If it's a file (not a directory or symlink), copy contents
		if !info.IsDir() && info.Mode()&os.ModeSymlink == 0 {
			file, err := os.Open(filePath)
			if err != nil {
				return err
			}
			defer file.Close()

			_, err = io.Copy(tw, file)
			if err != nil {
				return err
			}
		}

		return nil
	})

	return err
}