1 files changed, 104 insertions, 7 deletions

diff --git a/internal/lume/zip.go b/internal/lume/zip.go
index b3b331f..cecfb38 100644
--- a/internal/lume/zip.go
+++ b/internal/lume/zip.go
@@ -2,11 +2,32 @@ package lume
 
 import (
 	"archive/zip"
+	"compress/gzip"
+	"fmt"
 	"io"
+	"log/slog"
+	"net/http"
 	"os"
 	"path/filepath"
+	"strings"
 )
 
+const compressionGZIP = 0x69
+
+func init() {
+	zip.RegisterCompressor(compressionGZIP, func(w io.Writer) (io.WriteCloser, error) {
+		return gzip.NewWriterLevel(w, gzip.BestCompression)
+	})
+	zip.RegisterDecompressor(compressionGZIP, func(r io.Reader) io.ReadCloser {
+		rdr, err := gzip.NewReader(r)
+		if err != nil {
+			slog.Error("can't read from gzip stream", "err", err)
+			panic(err)
+		}
+		return rdr
+	})
+}
+
 // ZipFolder takes a source folder and a target zip file name
 // and compresses the folder contents into the zip file
 func ZipFolder(source, target string) error {
@@ -33,21 +54,27 @@ func ZipFolder(source, target string) error {
 			return nil
 		}
 
-		// Open the file
-		file, err := os.Open(path)
+		// Create a header from the file info
+		header, err := zip.FileInfoHeader(info)
 		if err != nil {
 			return err
 		}
-		defer file.Close()
 
-		// Create a header from the file info
-		header, err := zip.FileInfoHeader(info)
+		compressible, err := isCompressible(path)
 		if err != nil {
 			return err
 		}
 
-		// Set the compression method to deflate
-		header.Method = zip.Deflate
+		if compressible {
+			header.Method = compressionGZIP
+		}
+
+		// Open the file
+		file, err := os.Open(path)
+		if err != nil {
+			return err
+		}
+		defer file.Close()
 
 		// Set the header name to the relative path of the file
 		header.Name, err = filepath.Rel(source, path)
@@ -66,3 +93,73 @@ func ZipFolder(source, target string) error {
 		return err
 	})
 }
+
+// isCompressible checks if a file has a compressible mime type by its header and name.
+// It returns true if the file is compressible, false otherwise.
+func isCompressible(fname string) (bool, error) {
+	// Check if the file has a known non-compressible extension
+	// Source: [1]
+	nonCompressibleExt := []string{".7z", ".bz2", ".gif", ".gz", ".jpeg", ".jpg", ".mp3", ".mp4", ".png", ".rar", ".zip", ".pf_fragment", ".pf_index", ".pf_meta", ".ico"}
+
+	// Get the file extension from the name
+	ext := filepath.Ext(fname)
+
+	// Loop through the non-compressible extensions and compare with the file extension
+	for _, n := range nonCompressibleExt {
+		if ext == n {
+			// The file is not compressible by its name
+			return false, nil
+		}
+	}
+
+	compressibleExt := []string{".js", ".json", ".txt", ".dot", ".css", ".pdf", ".svg"}
+
+	// Loop through the compressible extensions and compare with the file extension
+	for _, n := range compressibleExt {
+		if ext == n {
+			// The file is compressible by its name
+			return true, nil
+		}
+	}
+
+	// A list of common mime types that are not compressible
+	// Source: [1]
+	nonCompressible := map[string]bool{
+		"application": true,
+		"image":       true,
+		"audio":       true,
+		"video":       true,
+	}
+
+	fin, err := os.Open(fname)
+	if err != nil {
+		return false, fmt.Errorf("can't read file %s: %w", fname, err)
+	}
+	defer fin.Close()
+
+	// Read the first 512 bytes of the file
+	buffer := make([]byte, 512)
+	if _, err = fin.Read(buffer); err != nil {
+		return false, fmt.Errorf("can't read from file %s: %w", fname, err)
+	}
+
+	// Detect the mime type from the buffer
+	mimeType := http.DetectContentType(buffer)
+
+	// Split the mime type by "/" and get the first part
+	parts := strings.Split(mimeType, "/")
+	if len(parts) < 2 {
+		slog.Debug("can't detect mime type of file, it's probably not compressible", "fname", fname, "mimeType", mimeType)
+		return false, nil
+	}
+	mainType := parts[0]
+
+	// Check if the main type is in the non-compressible map
+	if nonCompressible[mainType] {
+		// The file is not compressible by its header
+		return false, nil
+	}
+
+	// The file is compressible by both its header and name
+	return true, nil
+}