Initial vcom TUI prototype

internal/fs/preview.go

@@ -0,0 +1,204 @@
+package vfs
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	_ "image/gif"
+	_ "image/jpeg"
+	_ "image/png"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type PreviewKind string
+
+const (
+	PreviewKindEmpty     PreviewKind = "empty"
+	PreviewKindDirectory PreviewKind = "directory"
+	PreviewKindText      PreviewKind = "text"
+	PreviewKindImage     PreviewKind = "image"
+	PreviewKindBinary    PreviewKind = "binary"
+	PreviewKindError     PreviewKind = "error"
+)
+
+type Metadata struct {
+	Path        string
+	Kind        string
+	Size        int64
+	SizeKnown   bool
+	ModifiedAt  string
+	CreatedAt   string
+	Permissions string
+	ImageFormat string
+	ImageSize   string
+	Extension   string
+}
+
+type Preview struct {
+	Kind     PreviewKind
+	Title    string
+	Body     string
+	Metadata Metadata
+}
+
+type PreviewOptions struct {
+	ShowHidden            bool
+	DirsFirst             bool
+	SortBy                string
+	SortReverse           bool
+	MaxPreviewBytes       int64
+	DirectoryPreviewLimit int
+	HumanReadableSize     bool
+}
+
+func BuildPreview(entry Entry, options PreviewOptions) Preview {
+	preview := Preview{
+		Kind:  PreviewKindEmpty,
+		Title: entry.DisplayName(),
+		Metadata: Metadata{
+			Path:        entry.Path,
+			Kind:        kindLabel(entry),
+			Permissions: Permissions(entry.Mode),
+			ModifiedAt:  ShortTime(entry.ModifiedAt),
+			CreatedAt:   "n/a",
+			Extension:   entry.Extension,
+		},
+	}
+
+	if entry.CreatedKnown {
+		preview.Metadata.CreatedAt = ShortTime(entry.CreatedAt)
+	}
+
+	if entry.IsDir {
+		preview.Kind = PreviewKindDirectory
+		preview.Metadata.Size = entry.Size
+		preview.Metadata.SizeKnown = entry.DirSizeKnown
+		preview.Body = buildDirectoryPreview(entry.Path, options)
+		return preview
+	}
+
+	preview.Metadata.Size = entry.Size
+	preview.Metadata.SizeKnown = true
+
+	file, err := os.Open(entry.Path)
+	if err != nil {
+		preview.Kind = PreviewKindError
+		preview.Body = fmt.Sprintf("Could not open file:\n\n%s", err)
+		return preview
+	}
+	defer file.Close()
+
+	buffer := new(bytes.Buffer)
+	if _, err := io.CopyN(buffer, file, options.MaxPreviewBytes); err != nil && err != io.EOF {
+		preview.Kind = PreviewKindError
+		preview.Body = fmt.Sprintf("Could not read preview:\n\n%s", err)
+		return preview
+	}
+
+	data := buffer.Bytes()
+	if format, dimensions, ok := detectImage(data); ok {
+		preview.Kind = PreviewKindImage
+		preview.Metadata.ImageFormat = format
+		preview.Metadata.ImageSize = dimensions
+		preview.Body = fmt.Sprintf(
+			"Image preview is metadata-only for now.\n\nFormat: %s\nDimensions: %s\nPath: %s",
+			format,
+			dimensions,
+			entry.Path,
+		)
+		return preview
+	}
+
+	if IsBinarySample(data) {
+		preview.Kind = PreviewKindBinary
+		preview.Body = "Binary file detected.\n\nSafe inline preview is disabled for this file type."
+		return preview
+	}
+
+	preview.Kind = PreviewKindText
+	preview.Body = strings.ReplaceAll(string(data), "\t", "    ")
+	return preview
+}
+
+func buildDirectoryPreview(path string, options PreviewOptions) string {
+	entries, err := ListDir(path, ListOptions{
+		ShowHidden:  options.ShowHidden,
+		DirsFirst:   options.DirsFirst,
+		SortBy:      options.SortBy,
+		SortReverse: options.SortReverse,
+	})
+	if err != nil {
+		return fmt.Sprintf("Could not list directory:\n\n%s", err)
+	}
+	if len(entries) == 0 {
+		return "Directory is empty."
+	}
+
+	var lines []string
+	for _, entry := range entries {
+		if entry.IsParent {
+			continue
+		}
+		icon := previewIcon(entry)
+
+		size := ""
+		if !entry.IsDir {
+			if options.HumanReadableSize {
+				size = HumanSize(entry.Size)
+			} else {
+				size = fmt.Sprintf("%d", entry.Size)
+			}
+		}
+
+		lines = append(lines, fmt.Sprintf("%s %-36s %12s %s", icon, entry.DisplayName(), size, ShortTime(entry.ModifiedAt)))
+		if len(lines) >= options.DirectoryPreviewLimit {
+			lines = append(lines, "…")
+			break
+		}
+	}
+
+	return strings.Join(lines, "\n")
+}
+
+func previewIcon(entry Entry) string {
+	switch entry.Category() {
+	case "directory":
+		return ""
+	case "config":
+		return ""
+	case "text":
+		return "󰈙"
+	case "image":
+		return "󰋩"
+	case "executable":
+		return "󰆍"
+	case "archive":
+		return ""
+	default:
+		return "󰈔"
+	}
+}
+
+func detectImage(data []byte) (string, string, bool) {
+	cfg, format, err := image.DecodeConfig(bytes.NewReader(data))
+	if err != nil {
+		return "", "", false
+	}
+	return format, fmt.Sprintf("%dx%d", cfg.Width, cfg.Height), true
+}
+
+func kindLabel(entry Entry) string {
+	switch {
+	case entry.IsParent:
+		return "parent"
+	case entry.IsDir:
+		return "directory"
+	case entry.Extension != "":
+		return "file"
+	default:
+		return strings.TrimPrefix(filepath.Ext(entry.Name), ".")
+	}
+}