Add syntax highlighting to text previews

go.mod

@@ -3,6 +3,7 @@ module vcom
 go 1.26.0
 
 require (
+	github.com/alecthomas/chroma/v2 v2.23.1
 	github.com/charmbracelet/bubbles v0.21.0
 	github.com/charmbracelet/bubbletea v1.3.10
 	github.com/charmbracelet/lipgloss v1.1.0
@@ -17,6 +18,7 @@ require (
 	github.com/charmbracelet/x/ansi v0.10.1 // indirect
 	github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd // indirect
 	github.com/charmbracelet/x/term v0.2.1 // indirect
+	github.com/dlclark/regexp2 v1.11.5 // indirect
 	github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f // indirect
 	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect

go.sum

@@ -1,3 +1,5 @@
+github.com/alecthomas/chroma/v2 v2.23.1 h1:nv2AVZdTyClGbVQkIzlDm/rnhk1E9bU9nXwmZ/Vk/iY=
+github.com/alecthomas/chroma/v2 v2.23.1/go.mod h1:NqVhfBR0lte5Ouh3DcthuUCTUpDC9cxBOfyMbMQPs3o=
 github.com/atotto/clipboard v0.1.4 h1:EH0zSVneZPSuFR11BlR9YppQTVDbh5+16AmcJi4g1z4=
 github.com/atotto/clipboard v0.1.4/go.mod h1:ZY9tmq7sm5xIbd9bOK4onWV4S6X0u6GY7Vn0Yu86PYI=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiErDT4WkJ2k=
@@ -16,6 +18,8 @@ github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd h1:vy0G
 github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd/go.mod h1:xe0nKWGd3eJgtqZRaN9RjMtK7xUYchjzPr7q6kcvCCs=
 github.com/charmbracelet/x/term v0.2.1 h1:AQeHeLZ1OqSXhrAWpYUtZyX1T3zVxfpZuEQMIQaGIAQ=
 github.com/charmbracelet/x/term v0.2.1/go.mod h1:oQ4enTYFV7QN4m0i9mzHrViD7TQKvNEEkHUMCmsxdUg=
+github.com/dlclark/regexp2 v1.11.5 h1:Q/sSnsKerHeCkc/jSTNq1oCm7KiVgUMZRDUoRu0JQZQ=
+github.com/dlclark/regexp2 v1.11.5/go.mod h1:DHkYz0B9wPfa6wondMfaivmHpzrQ3v9q8cnmRbL6yW8=
 github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f h1:Y/CXytFA4m6baUTXGLOoWe4PQhGxaX0KpnayAqC48p4=
 github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f/go.mod h1:vw97MGsxSvLiUE2X8qFplwetxpGLQrlU1Q9AUEIzCaM=
 github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69Aj6K7nkY=

internal/fs/preview.go

@@ -11,6 +11,11 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+
+	"github.com/alecthomas/chroma/v2"
+	"github.com/alecthomas/chroma/v2/formatters"
+	"github.com/alecthomas/chroma/v2/lexers"
+	"github.com/alecthomas/chroma/v2/styles"
 )
 
 type PreviewKind string
@@ -38,10 +43,11 @@ type Metadata struct {
 }
 
 type Preview struct {
-	Kind     PreviewKind
+	Kind      PreviewKind
-	Title    string
+	Title     string
-	Body     string
+	Body      string
-	Metadata Metadata
+	PlainBody string
+	Metadata  Metadata
 }
 
 type PreviewOptions struct {
@@ -52,6 +58,7 @@ type PreviewOptions struct {
 	MaxPreviewBytes       int64
 	DirectoryPreviewLimit int
 	HumanReadableSize     bool
+	ThemeName             string
 }
 
 func BuildPreview(entry Entry, options PreviewOptions) Preview {
@@ -77,6 +84,7 @@ func BuildPreview(entry Entry, options PreviewOptions) Preview {
 		preview.Metadata.Size = entry.Size
 		preview.Metadata.SizeKnown = entry.DirSizeKnown
 		preview.Body = buildDirectoryPreview(entry.Path, options)
+		preview.PlainBody = preview.Body
 		return preview
 	}
 
@@ -87,6 +95,7 @@ func BuildPreview(entry Entry, options PreviewOptions) Preview {
 	if err != nil {
 		preview.Kind = PreviewKindError
 		preview.Body = fmt.Sprintf("Could not open file:\n\n%s", err)
+		preview.PlainBody = preview.Body
 		return preview
 	}
 	defer file.Close()
@@ -95,6 +104,7 @@ func BuildPreview(entry Entry, options PreviewOptions) Preview {
 	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)
+		preview.PlainBody = preview.Body
 		return preview
 	}
 
@@ -109,20 +119,64 @@ func BuildPreview(entry Entry, options PreviewOptions) Preview {
 			dimensions,
 			entry.Path,
 		)
+		preview.PlainBody = preview.Body
 		return preview
 	}
 
 	if IsBinarySample(data) {
 		preview.Kind = PreviewKindBinary
 		preview.Body = "Binary file detected.\n\nSafe inline preview is disabled for this file type."
+		preview.PlainBody = preview.Body
 		return preview
 	}
 
 	preview.Kind = PreviewKindText
-	preview.Body = strings.ReplaceAll(string(data), "\t", "    ")
+	preview.PlainBody = strings.ReplaceAll(string(data), "\t", "    ")
+	preview.Body = highlightText(entry.Path, preview.PlainBody, options.ThemeName)
 	return preview
 }
 
+func highlightText(path string, source string, themeName string) string {
+	lexer := lexers.Match(path)
+	if lexer == nil {
+		lexer = lexers.Analyse(source)
+	}
+	if lexer == nil {
+		return source
+	}
+
+	iterator, err := chroma.Coalesce(lexer).Tokenise(nil, source)
+	if err != nil {
+		return source
+	}
+
+	style := styles.Get(chromaStyleName(themeName))
+	if style == nil {
+		return source
+	}
+
+	var output bytes.Buffer
+	if err := formatters.TTY16m.Format(&output, style, iterator); err != nil {
+		return source
+	}
+	return output.String()
+}
+
+func chromaStyleName(themeName string) string {
+	switch strings.ToLower(strings.TrimSpace(themeName)) {
+	case "catppuccin-mocha":
+		return "catppuccin-mocha"
+	case "tokyo-night":
+		return "tokyonight-night"
+	case "gruvbox-dark":
+		return "gruvbox"
+	case "nord-frost":
+		return "nord"
+	default:
+		return "catppuccin-mocha"
+	}
+}
+
 func buildDirectoryPreview(path string, options PreviewOptions) string {
 	entries, err := ListDir(path, ListOptions{
 		ShowHidden:  options.ShowHidden,

internal/ui/model.go

@@ -513,6 +513,7 @@ func (m Model) loadPreviewCmd() tea.Cmd {
 		MaxPreviewBytes:       m.cfg.Preview.MaxPreviewBytes,
 		DirectoryPreviewLimit: m.cfg.Preview.DirectoryPreviewLimit,
 		HumanReadableSize:     m.cfg.Browser.HumanReadableSize,
+		ThemeName:             m.cfg.UI.Theme,
 	}
 
 	return func() tea.Msg {
@@ -952,7 +953,10 @@ func renderPreviewPane(preview vfs.Preview, viewportModel *viewport.Model, cfg c
 }
 
 func renderSelectionPane(preview vfs.Preview, viewportModel *viewport.Model, palette theme.Palette, width int, height int) string {
-	content := preview.Body
+	content := preview.PlainBody
+	if strings.TrimSpace(content) == "" {
+		content = preview.Body
+	}
 	viewportModel.Width = max(width, 1)
 	viewportModel.Height = max(height, 1)
 	viewportModel.SetContent(content)