Merge pull request #27 from kujtimiihoxha/opencode

OpenCode - Initial Implementation

1 files changed, 1047 insertions, 0 deletions

diff --git a/internal/diff/diff.go b/internal/diff/diff.go
new file mode 100644
index 000000000..7b48de25f
--- /dev/null
+++ b/internal/diff/diff.go
@@ -0,0 +1,1047 @@
+package diff
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/alecthomas/chroma/v2"
+	"github.com/alecthomas/chroma/v2/formatters"
+	"github.com/alecthomas/chroma/v2/lexers"
+	"github.com/alecthomas/chroma/v2/styles"
+	"github.com/charmbracelet/lipgloss"
+	"github.com/charmbracelet/x/ansi"
+	"github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/plumbing/object"
+	"github.com/kujtimiihoxha/opencode/internal/config"
+	"github.com/kujtimiihoxha/opencode/internal/logging"
+	"github.com/sergi/go-diff/diffmatchpatch"
+)
+
+// -------------------------------------------------------------------------
+// Core Types
+// -------------------------------------------------------------------------
+
+// LineType represents the kind of line in a diff.
+type LineType int
+
+const (
+	LineContext LineType = iota // Line exists in both files
+	LineAdded                   // Line added in the new file
+	LineRemoved                 // Line removed from the old file
+)
+
+// Segment represents a portion of a line for intra-line highlighting
+type Segment struct {
+	Start int
+	End   int
+	Type  LineType
+	Text  string
+}
+
+// DiffLine represents a single line in a diff
+type DiffLine struct {
+	OldLineNo int       // Line number in old file (0 for added lines)
+	NewLineNo int       // Line number in new file (0 for removed lines)
+	Kind      LineType  // Type of line (added, removed, context)
+	Content   string    // Content of the line
+	Segments  []Segment // Segments for intraline highlighting
+}
+
+// Hunk represents a section of changes in a diff
+type Hunk struct {
+	Header string
+	Lines  []DiffLine
+}
+
+// DiffResult contains the parsed result of a diff
+type DiffResult struct {
+	OldFile string
+	NewFile string
+	Hunks   []Hunk
+}
+
+// linePair represents a pair of lines for side-by-side display
+type linePair struct {
+	left  *DiffLine
+	right *DiffLine
+}
+
+// -------------------------------------------------------------------------
+// Style Configuration
+// -------------------------------------------------------------------------
+
+// StyleConfig defines styling for diff rendering
+type StyleConfig struct {
+	ShowHeader     bool
+	ShowHunkHeader bool
+	FileNameFg     lipgloss.Color
+	// Background colors
+	RemovedLineBg       lipgloss.Color
+	AddedLineBg         lipgloss.Color
+	ContextLineBg       lipgloss.Color
+	HunkLineBg          lipgloss.Color
+	RemovedLineNumberBg lipgloss.Color
+	AddedLineNamerBg    lipgloss.Color
+
+	// Foreground colors
+	HunkLineFg         lipgloss.Color
+	RemovedFg          lipgloss.Color
+	AddedFg            lipgloss.Color
+	LineNumberFg       lipgloss.Color
+	RemovedHighlightFg lipgloss.Color
+	AddedHighlightFg   lipgloss.Color
+
+	// Highlight settings
+	HighlightStyle     string
+	RemovedHighlightBg lipgloss.Color
+	AddedHighlightBg   lipgloss.Color
+}
+
+// StyleOption is a function that modifies a StyleConfig
+type StyleOption func(*StyleConfig)
+
+// NewStyleConfig creates a StyleConfig with default values
+func NewStyleConfig(opts ...StyleOption) StyleConfig {
+	// Default color scheme
+	config := StyleConfig{
+		ShowHeader:          true,
+		ShowHunkHeader:      true,
+		FileNameFg:          lipgloss.Color("#a0a0a0"),
+		RemovedLineBg:       lipgloss.Color("#3A3030"),
+		AddedLineBg:         lipgloss.Color("#303A30"),
+		ContextLineBg:       lipgloss.Color("#212121"),
+		HunkLineBg:          lipgloss.Color("#212121"),
+		HunkLineFg:          lipgloss.Color("#a0a0a0"),
+		RemovedFg:           lipgloss.Color("#7C4444"),
+		AddedFg:             lipgloss.Color("#478247"),
+		LineNumberFg:        lipgloss.Color("#888888"),
+		HighlightStyle:      "dracula",
+		RemovedHighlightBg:  lipgloss.Color("#612726"),
+		AddedHighlightBg:    lipgloss.Color("#256125"),
+		RemovedLineNumberBg: lipgloss.Color("#332929"),
+		AddedLineNamerBg:    lipgloss.Color("#293229"),
+		RemovedHighlightFg:  lipgloss.Color("#FADADD"),
+		AddedHighlightFg:    lipgloss.Color("#DAFADA"),
+	}
+
+	// Apply all provided options
+	for _, opt := range opts {
+		opt(&config)
+	}
+
+	return config
+}
+
+// Style option functions
+func WithFileNameFg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.FileNameFg = color }
+}
+
+func WithRemovedLineBg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.RemovedLineBg = color }
+}
+
+func WithAddedLineBg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.AddedLineBg = color }
+}
+
+func WithContextLineBg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.ContextLineBg = color }
+}
+
+func WithRemovedFg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.RemovedFg = color }
+}
+
+func WithAddedFg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.AddedFg = color }
+}
+
+func WithLineNumberFg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.LineNumberFg = color }
+}
+
+func WithHighlightStyle(style string) StyleOption {
+	return func(s *StyleConfig) { s.HighlightStyle = style }
+}
+
+func WithRemovedHighlightColors(bg, fg lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) {
+		s.RemovedHighlightBg = bg
+		s.RemovedHighlightFg = fg
+	}
+}
+
+func WithAddedHighlightColors(bg, fg lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) {
+		s.AddedHighlightBg = bg
+		s.AddedHighlightFg = fg
+	}
+}
+
+func WithRemovedLineNumberBg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.RemovedLineNumberBg = color }
+}
+
+func WithAddedLineNumberBg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.AddedLineNamerBg = color }
+}
+
+func WithHunkLineBg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.HunkLineBg = color }
+}
+
+func WithHunkLineFg(color lipgloss.Color) StyleOption {
+	return func(s *StyleConfig) { s.HunkLineFg = color }
+}
+
+func WithShowHeader(show bool) StyleOption {
+	return func(s *StyleConfig) { s.ShowHeader = show }
+}
+
+func WithShowHunkHeader(show bool) StyleOption {
+	return func(s *StyleConfig) { s.ShowHunkHeader = show }
+}
+
+// -------------------------------------------------------------------------
+// Parse Configuration
+// -------------------------------------------------------------------------
+
+// ParseConfig configures the behavior of diff parsing
+type ParseConfig struct {
+	ContextSize int // Number of context lines to include
+}
+
+// ParseOption modifies a ParseConfig
+type ParseOption func(*ParseConfig)
+
+// WithContextSize sets the number of context lines to include
+func WithContextSize(size int) ParseOption {
+	return func(p *ParseConfig) {
+		if size >= 0 {
+			p.ContextSize = size
+		}
+	}
+}
+
+// -------------------------------------------------------------------------
+// Side-by-Side Configuration
+// -------------------------------------------------------------------------
+
+// SideBySideConfig configures the rendering of side-by-side diffs
+type SideBySideConfig struct {
+	TotalWidth int
+	Style      StyleConfig
+}
+
+// SideBySideOption modifies a SideBySideConfig
+type SideBySideOption func(*SideBySideConfig)
+
+// NewSideBySideConfig creates a SideBySideConfig with default values
+func NewSideBySideConfig(opts ...SideBySideOption) SideBySideConfig {
+	config := SideBySideConfig{
+		TotalWidth: 160, // Default width for side-by-side view
+		Style:      NewStyleConfig(),
+	}
+
+	for _, opt := range opts {
+		opt(&config)
+	}
+
+	return config
+}
+
+// WithTotalWidth sets the total width for side-by-side view
+func WithTotalWidth(width int) SideBySideOption {
+	return func(s *SideBySideConfig) {
+		if width > 0 {
+			s.TotalWidth = width
+		}
+	}
+}
+
+// WithStyle sets the styling configuration
+func WithStyle(style StyleConfig) SideBySideOption {
+	return func(s *SideBySideConfig) {
+		s.Style = style
+	}
+}
+
+// WithStyleOptions applies the specified style options
+func WithStyleOptions(opts ...StyleOption) SideBySideOption {
+	return func(s *SideBySideConfig) {
+		s.Style = NewStyleConfig(opts...)
+	}
+}
+
+// -------------------------------------------------------------------------
+// Diff Parsing
+// -------------------------------------------------------------------------
+
+// ParseUnifiedDiff parses a unified diff format string into structured data
+func ParseUnifiedDiff(diff string) (DiffResult, error) {
+	var result DiffResult
+	var currentHunk *Hunk
+
+	hunkHeaderRe := regexp.MustCompile(`^@@ -(\d+),?(\d*) \+(\d+),?(\d*) @@`)
+	lines := strings.Split(diff, "\n")
+
+	var oldLine, newLine int
+	inFileHeader := true
+
+	for _, line := range lines {
+		// Parse file headers
+		if inFileHeader {
+			if strings.HasPrefix(line, "--- a/") {
+				result.OldFile = strings.TrimPrefix(line, "--- a/")
+				continue
+			}
+			if strings.HasPrefix(line, "+++ b/") {
+				result.NewFile = strings.TrimPrefix(line, "+++ b/")
+				inFileHeader = false
+				continue
+			}
+		}
+
+		// Parse hunk headers
+		if matches := hunkHeaderRe.FindStringSubmatch(line); matches != nil {
+			if currentHunk != nil {
+				result.Hunks = append(result.Hunks, *currentHunk)
+			}
+			currentHunk = &Hunk{
+				Header: line,
+				Lines:  []DiffLine{},
+			}
+
+			oldStart, _ := strconv.Atoi(matches[1])
+			newStart, _ := strconv.Atoi(matches[3])
+			oldLine = oldStart
+			newLine = newStart
+			continue
+		}
+
+		// Ignore "No newline at end of file" markers
+		if strings.HasPrefix(line, "\\ No newline at end of file") {
+			continue
+		}
+
+		if currentHunk == nil {
+			continue
+		}
+
+		// Process the line based on its prefix
+		if len(line) > 0 {
+			switch line[0] {
+			case '+':
+				currentHunk.Lines = append(currentHunk.Lines, DiffLine{
+					OldLineNo: 0,
+					NewLineNo: newLine,
+					Kind:      LineAdded,
+					Content:   line[1:],
+				})
+				newLine++
+			case '-':
+				currentHunk.Lines = append(currentHunk.Lines, DiffLine{
+					OldLineNo: oldLine,
+					NewLineNo: 0,
+					Kind:      LineRemoved,
+					Content:   line[1:],
+				})
+				oldLine++
+			default:
+				currentHunk.Lines = append(currentHunk.Lines, DiffLine{
+					OldLineNo: oldLine,
+					NewLineNo: newLine,
+					Kind:      LineContext,
+					Content:   line,
+				})
+				oldLine++
+				newLine++
+			}
+		} else {
+			// Handle empty lines
+			currentHunk.Lines = append(currentHunk.Lines, DiffLine{
+				OldLineNo: oldLine,
+				NewLineNo: newLine,
+				Kind:      LineContext,
+				Content:   "",
+			})
+			oldLine++
+			newLine++
+		}
+	}
+
+	// Add the last hunk if there is one
+	if currentHunk != nil {
+		result.Hunks = append(result.Hunks, *currentHunk)
+	}
+
+	return result, nil
+}
+
+// HighlightIntralineChanges updates lines in a hunk to show character-level differences
+func HighlightIntralineChanges(h *Hunk, style StyleConfig) {
+	var updated []DiffLine
+	dmp := diffmatchpatch.New()
+
+	for i := 0; i < len(h.Lines); i++ {
+		// Look for removed line followed by added line
+		if i+1 < len(h.Lines) &&
+			h.Lines[i].Kind == LineRemoved &&
+			h.Lines[i+1].Kind == LineAdded {
+
+			oldLine := h.Lines[i]
+			newLine := h.Lines[i+1]
+
+			// Find character-level differences
+			patches := dmp.DiffMain(oldLine.Content, newLine.Content, false)
+			patches = dmp.DiffCleanupSemantic(patches)
+			patches = dmp.DiffCleanupMerge(patches)
+			patches = dmp.DiffCleanupEfficiency(patches)
+
+			segments := make([]Segment, 0)
+
+			removeStart := 0
+			addStart := 0
+			for _, patch := range patches {
+				switch patch.Type {
+				case diffmatchpatch.DiffDelete:
+					segments = append(segments, Segment{
+						Start: removeStart,
+						End:   removeStart + len(patch.Text),
+						Type:  LineRemoved,
+						Text:  patch.Text,
+					})
+					removeStart += len(patch.Text)
+				case diffmatchpatch.DiffInsert:
+					segments = append(segments, Segment{
+						Start: addStart,
+						End:   addStart + len(patch.Text),
+						Type:  LineAdded,
+						Text:  patch.Text,
+					})
+					addStart += len(patch.Text)
+				default:
+					// Context text, no highlighting needed
+					removeStart += len(patch.Text)
+					addStart += len(patch.Text)
+				}
+			}
+			oldLine.Segments = segments
+			newLine.Segments = segments
+
+			updated = append(updated, oldLine, newLine)
+			i++ // Skip the next line as we've already processed it
+		} else {
+			updated = append(updated, h.Lines[i])
+		}
+	}
+
+	h.Lines = updated
+}
+
+// pairLines converts a flat list of diff lines to pairs for side-by-side display
+func pairLines(lines []DiffLine) []linePair {
+	var pairs []linePair
+	i := 0
+
+	for i < len(lines) {
+		switch lines[i].Kind {
+		case LineRemoved:
+			// Check if the next line is an addition, if so pair them
+			if i+1 < len(lines) && lines[i+1].Kind == LineAdded {
+				pairs = append(pairs, linePair{left: &lines[i], right: &lines[i+1]})
+				i += 2
+			} else {
+				pairs = append(pairs, linePair{left: &lines[i], right: nil})
+				i++
+			}
+		case LineAdded:
+			pairs = append(pairs, linePair{left: nil, right: &lines[i]})
+			i++
+		case LineContext:
+			pairs = append(pairs, linePair{left: &lines[i], right: &lines[i]})
+			i++
+		}
+	}
+
+	return pairs
+}
+
+// -------------------------------------------------------------------------
+// Syntax Highlighting
+// -------------------------------------------------------------------------
+
+// SyntaxHighlight applies syntax highlighting to text based on file extension
+func SyntaxHighlight(w io.Writer, source, fileName, formatter string, bg lipgloss.TerminalColor) error {
+	// Determine the language lexer to use
+	l := lexers.Match(fileName)
+	if l == nil {
+		l = lexers.Analyse(source)
+	}
+	if l == nil {
+		l = lexers.Fallback
+	}
+	l = chroma.Coalesce(l)
+
+	// Get the formatter
+	f := formatters.Get(formatter)
+	if f == nil {
+		f = formatters.Fallback
+	}
+	theme := `
+	<style name="vscode-dark-plus">
+	<!-- Base colors -->
+	<entry type="Background" style="bg:#1E1E1E"/>
+	<entry type="Text" style="#D4D4D4"/>
+	<entry type="Other" style="#D4D4D4"/>
+	<entry type="Error" style="#F44747"/>
+	<!-- Keywords - using the Control flow / Special keywords color -->
+	<entry type="Keyword" style="#C586C0"/>
+	<entry type="KeywordConstant" style="#4FC1FF"/>
+	<entry type="KeywordDeclaration" style="#C586C0"/>
+	<entry type="KeywordNamespace" style="#C586C0"/>
+	<entry type="KeywordPseudo" style="#C586C0"/>
+	<entry type="KeywordReserved" style="#C586C0"/>
+	<entry type="KeywordType" style="#4EC9B0"/>
+	<!-- Names -->
+	<entry type="Name" style="#D4D4D4"/>
+	<entry type="NameAttribute" style="#9CDCFE"/>
+	<entry type="NameBuiltin" style="#4EC9B0"/>
+	<entry type="NameBuiltinPseudo" style="#9CDCFE"/>
+	<entry type="NameClass" style="#4EC9B0"/>
+	<entry type="NameConstant" style="#4FC1FF"/>
+	<entry type="NameDecorator" style="#DCDCAA"/>
+	<entry type="NameEntity" style="#9CDCFE"/>
+	<entry type="NameException" style="#4EC9B0"/>
+	<entry type="NameFunction" style="#DCDCAA"/>
+	<entry type="NameLabel" style="#C8C8C8"/>
+	<entry type="NameNamespace" style="#4EC9B0"/>
+	<entry type="NameOther" style="#9CDCFE"/>
+	<entry type="NameTag" style="#569CD6"/>
+	<entry type="NameVariable" style="#9CDCFE"/>
+	<entry type="NameVariableClass" style="#9CDCFE"/>
+	<entry type="NameVariableGlobal" style="#9CDCFE"/>
+	<entry type="NameVariableInstance" style="#9CDCFE"/>
+	<!-- Literals -->
+	<entry type="Literal" style="#CE9178"/>
+	<entry type="LiteralDate" style="#CE9178"/>
+	<entry type="LiteralString" style="#CE9178"/>
+	<entry type="LiteralStringBacktick" style="#CE9178"/>
+	<entry type="LiteralStringChar" style="#CE9178"/>
+	<entry type="LiteralStringDoc" style="#CE9178"/>
+	<entry type="LiteralStringDouble" style="#CE9178"/>
+	<entry type="LiteralStringEscape" style="#d7ba7d"/>
+	<entry type="LiteralStringHeredoc" style="#CE9178"/>
+	<entry type="LiteralStringInterpol" style="#CE9178"/>
+	<entry type="LiteralStringOther" style="#CE9178"/>
+	<entry type="LiteralStringRegex" style="#d16969"/>
+	<entry type="LiteralStringSingle" style="#CE9178"/>
+	<entry type="LiteralStringSymbol" style="#CE9178"/>
+	<!-- Numbers - using the numberLiteral color -->
+	<entry type="LiteralNumber" style="#b5cea8"/>
+	<entry type="LiteralNumberBin" style="#b5cea8"/>
+	<entry type="LiteralNumberFloat" style="#b5cea8"/>
+	<entry type="LiteralNumberHex" style="#b5cea8"/>
+	<entry type="LiteralNumberInteger" style="#b5cea8"/>
+	<entry type="LiteralNumberIntegerLong" style="#b5cea8"/>
+	<entry type="LiteralNumberOct" style="#b5cea8"/>
+	<!-- Operators -->
+	<entry type="Operator" style="#D4D4D4"/>
+	<entry type="OperatorWord" style="#C586C0"/>
+	<entry type="Punctuation" style="#D4D4D4"/>
+	<!-- Comments - standard VSCode Dark+ comment color -->
+	<entry type="Comment" style="#6A9955"/>
+	<entry type="CommentHashbang" style="#6A9955"/>
+	<entry type="CommentMultiline" style="#6A9955"/>
+	<entry type="CommentSingle" style="#6A9955"/>
+	<entry type="CommentSpecial" style="#6A9955"/>
+	<entry type="CommentPreproc" style="#C586C0"/>
+	<!-- Generic styles -->
+	<entry type="Generic" style="#D4D4D4"/>
+	<entry type="GenericDeleted" style="#F44747"/>
+	<entry type="GenericEmph" style="italic #D4D4D4"/>
+	<entry type="GenericError" style="#F44747"/>
+	<entry type="GenericHeading" style="bold #D4D4D4"/>
+	<entry type="GenericInserted" style="#b5cea8"/>
+	<entry type="GenericOutput" style="#808080"/>
+	<entry type="GenericPrompt" style="#D4D4D4"/>
+	<entry type="GenericStrong" style="bold #D4D4D4"/>
+	<entry type="GenericSubheading" style="bold #D4D4D4"/>
+	<entry type="GenericTraceback" style="#F44747"/>
+	<entry type="GenericUnderline" style="underline"/>
+	<entry type="TextWhitespace" style="#D4D4D4"/>
+</style>
+`
+
+	r := strings.NewReader(theme)
+	style := chroma.MustNewXMLStyle(r)
+	// Modify the style to use the provided background
+	s, err := style.Builder().Transform(
+		func(t chroma.StyleEntry) chroma.StyleEntry {
+			r, g, b, _ := bg.RGBA()
+			t.Background = chroma.NewColour(uint8(r>>8), uint8(g>>8), uint8(b>>8))
+			return t
+		},
+	).Build()
+	if err != nil {
+		s = styles.Fallback
+	}
+
+	// Tokenize and format
+	it, err := l.Tokenise(nil, source)
+	if err != nil {
+		return err
+	}
+
+	return f.Format(w, s, it)
+}
+
+// highlightLine applies syntax highlighting to a single line
+func highlightLine(fileName string, line string, bg lipgloss.TerminalColor) string {
+	var buf bytes.Buffer
+	err := SyntaxHighlight(&buf, line, fileName, "terminal16m", bg)
+	if err != nil {
+		return line
+	}
+	return buf.String()
+}
+
+// createStyles generates the lipgloss styles needed for rendering diffs
+func createStyles(config StyleConfig) (removedLineStyle, addedLineStyle, contextLineStyle, lineNumberStyle lipgloss.Style) {
+	removedLineStyle = lipgloss.NewStyle().Background(config.RemovedLineBg)
+	addedLineStyle = lipgloss.NewStyle().Background(config.AddedLineBg)
+	contextLineStyle = lipgloss.NewStyle().Background(config.ContextLineBg)
+	lineNumberStyle = lipgloss.NewStyle().Foreground(config.LineNumberFg)
+
+	return
+}
+
+// -------------------------------------------------------------------------
+// Rendering Functions
+// -------------------------------------------------------------------------
+
+// applyHighlighting applies intra-line highlighting to a piece of text
+func applyHighlighting(content string, segments []Segment, segmentType LineType, highlightBg lipgloss.Color,
+) string {
+	// Find all ANSI sequences in the content
+	ansiRegex := regexp.MustCompile(`\x1b(?:[@-Z\\-_]|\[[0-9?]*(?:;[0-9?]*)*[@-~])`)
+	ansiMatches := ansiRegex.FindAllStringIndex(content, -1)
+
+	// Build a mapping of visible character positions to their actual indices
+	visibleIdx := 0
+	ansiSequences := make(map[int]string)
+	lastAnsiSeq := "\x1b[0m" // Default reset sequence
+
+	for i := 0; i < len(content); {
+		isAnsi := false
+		for _, match := range ansiMatches {
+			if match[0] == i {
+				ansiSequences[visibleIdx] = content[match[0]:match[1]]
+				lastAnsiSeq = content[match[0]:match[1]]
+				i = match[1]
+				isAnsi = true
+				break
+			}
+		}
+		if isAnsi {
+			continue
+		}
+
+		// For non-ANSI positions, store the last ANSI sequence
+		if _, exists := ansiSequences[visibleIdx]; !exists {
+			ansiSequences[visibleIdx] = lastAnsiSeq
+		}
+		visibleIdx++
+		i++
+	}
+
+	// Apply highlighting
+	var sb strings.Builder
+	inSelection := false
+	currentPos := 0
+
+	for i := 0; i < len(content); {
+		// Check if we're at an ANSI sequence
+		isAnsi := false
+		for _, match := range ansiMatches {
+			if match[0] == i {
+				sb.WriteString(content[match[0]:match[1]]) // Preserve ANSI sequence
+				i = match[1]
+				isAnsi = true
+				break
+			}
+		}
+		if isAnsi {
+			continue
+		}
+
+		// Check for segment boundaries
+		for _, seg := range segments {
+			if seg.Type == segmentType {
+				if currentPos == seg.Start {
+					inSelection = true
+				}
+				if currentPos == seg.End {
+					inSelection = false
+				}
+			}
+		}
+
+		// Get current character
+		char := string(content[i])
+
+		if inSelection {
+			// Get the current styling
+			currentStyle := ansiSequences[currentPos]
+
+			// Apply background highlight
+			sb.WriteString("\x1b[48;2;")
+			r, g, b, _ := highlightBg.RGBA()
+			sb.WriteString(fmt.Sprintf("%d;%d;%dm", r>>8, g>>8, b>>8))
+			sb.WriteString(char)
+			sb.WriteString("\x1b[49m") // Reset only background
+
+			// Reapply the original ANSI sequence
+			sb.WriteString(currentStyle)
+		} else {
+			// Not in selection, just copy the character
+			sb.WriteString(char)
+		}
+
+		currentPos++
+		i++
+	}
+
+	return sb.String()
+}
+
+// renderLeftColumn formats the left side of a side-by-side diff
+func renderLeftColumn(fileName string, dl *DiffLine, colWidth int, styles StyleConfig) string {
+	if dl == nil {
+		contextLineStyle := lipgloss.NewStyle().Background(styles.ContextLineBg)
+		return contextLineStyle.Width(colWidth).Render("")
+	}
+
+	removedLineStyle, _, contextLineStyle, lineNumberStyle := createStyles(styles)
+
+	// Determine line style based on line type
+	var marker string
+	var bgStyle lipgloss.Style
+	switch dl.Kind {
+	case LineRemoved:
+		marker = removedLineStyle.Foreground(styles.RemovedFg).Render("-")
+		bgStyle = removedLineStyle
+		lineNumberStyle = lineNumberStyle.Foreground(styles.RemovedFg).Background(styles.RemovedLineNumberBg)
+	case LineAdded:
+		marker = "?"
+		bgStyle = contextLineStyle
+	case LineContext:
+		marker = contextLineStyle.Render(" ")
+		bgStyle = contextLineStyle
+	}
+
+	// Format line number
+	lineNum := ""
+	if dl.OldLineNo > 0 {
+		lineNum = fmt.Sprintf("%6d", dl.OldLineNo)
+	}
+
+	// Create the line prefix
+	prefix := lineNumberStyle.Render(lineNum + " " + marker)
+
+	// Apply syntax highlighting
+	content := highlightLine(fileName, dl.Content, bgStyle.GetBackground())
+
+	// Apply intra-line highlighting for removed lines
+	if dl.Kind == LineRemoved && len(dl.Segments) > 0 {
+		content = applyHighlighting(content, dl.Segments, LineRemoved, styles.RemovedHighlightBg)
+	}
+
+	// Add a padding space for removed lines
+	if dl.Kind == LineRemoved {
+		content = bgStyle.Render(" ") + content
+	}
+
+	// Create the final line and truncate if needed
+	lineText := prefix + content
+	return bgStyle.MaxHeight(1).Width(colWidth).Render(
+		ansi.Truncate(
+			lineText,
+			colWidth,
+			lipgloss.NewStyle().Background(styles.HunkLineBg).Foreground(styles.HunkLineFg).Render("..."),
+		),
+	)
+}
+
+// renderRightColumn formats the right side of a side-by-side diff
+func renderRightColumn(fileName string, dl *DiffLine, colWidth int, styles StyleConfig) string {
+	if dl == nil {
+		contextLineStyle := lipgloss.NewStyle().Background(styles.ContextLineBg)
+		return contextLineStyle.Width(colWidth).Render("")
+	}
+
+	_, addedLineStyle, contextLineStyle, lineNumberStyle := createStyles(styles)
+
+	// Determine line style based on line type
+	var marker string
+	var bgStyle lipgloss.Style
+	switch dl.Kind {
+	case LineAdded:
+		marker = addedLineStyle.Foreground(styles.AddedFg).Render("+")
+		bgStyle = addedLineStyle
+		lineNumberStyle = lineNumberStyle.Foreground(styles.AddedFg).Background(styles.AddedLineNamerBg)
+	case LineRemoved:
+		marker = "?"
+		bgStyle = contextLineStyle
+	case LineContext:
+		marker = contextLineStyle.Render(" ")
+		bgStyle = contextLineStyle
+	}
+
+	// Format line number
+	lineNum := ""
+	if dl.NewLineNo > 0 {
+		lineNum = fmt.Sprintf("%6d", dl.NewLineNo)
+	}
+
+	// Create the line prefix
+	prefix := lineNumberStyle.Render(lineNum + " " + marker)
+
+	// Apply syntax highlighting
+	content := highlightLine(fileName, dl.Content, bgStyle.GetBackground())
+
+	// Apply intra-line highlighting for added lines
+	if dl.Kind == LineAdded && len(dl.Segments) > 0 {
+		content = applyHighlighting(content, dl.Segments, LineAdded, styles.AddedHighlightBg)
+	}
+
+	// Add a padding space for added lines
+	if dl.Kind == LineAdded {
+		content = bgStyle.Render(" ") + content
+	}
+
+	// Create the final line and truncate if needed
+	lineText := prefix + content
+	return bgStyle.MaxHeight(1).Width(colWidth).Render(
+		ansi.Truncate(
+			lineText,
+			colWidth,
+			lipgloss.NewStyle().Background(styles.HunkLineBg).Foreground(styles.HunkLineFg).Render("..."),
+		),
+	)
+}
+
+// -------------------------------------------------------------------------
+// Public API
+// -------------------------------------------------------------------------
+
+// RenderSideBySideHunk formats a hunk for side-by-side display
+func RenderSideBySideHunk(fileName string, h Hunk, opts ...SideBySideOption) string {
+	// Apply options to create the configuration
+	config := NewSideBySideConfig(opts...)
+
+	// Make a copy of the hunk so we don't modify the original
+	hunkCopy := Hunk{Lines: make([]DiffLine, len(h.Lines))}
+	copy(hunkCopy.Lines, h.Lines)
+
+	// Highlight changes within lines
+	HighlightIntralineChanges(&hunkCopy, config.Style)
+
+	// Pair lines for side-by-side display
+	pairs := pairLines(hunkCopy.Lines)
+
+	// Calculate column width
+	colWidth := config.TotalWidth / 2
+
+	leftWidth := colWidth
+	rightWidth := config.TotalWidth - colWidth
+	var sb strings.Builder
+	for _, p := range pairs {
+		leftStr := renderLeftColumn(fileName, p.left, leftWidth, config.Style)
+		rightStr := renderRightColumn(fileName, p.right, rightWidth, config.Style)
+		sb.WriteString(leftStr + rightStr + "\n")
+	}
+
+	return sb.String()
+}
+
+// FormatDiff creates a side-by-side formatted view of a diff
+func FormatDiff(diffText string, opts ...SideBySideOption) (string, error) {
+	diffResult, err := ParseUnifiedDiff(diffText)
+	if err != nil {
+		return "", err
+	}
+
+	var sb strings.Builder
+	config := NewSideBySideConfig(opts...)
+
+	if config.Style.ShowHeader {
+		removeIcon := lipgloss.NewStyle().
+			Background(config.Style.RemovedLineBg).
+			Foreground(config.Style.RemovedFg).
+			Render("⏹")
+		addIcon := lipgloss.NewStyle().
+			Background(config.Style.AddedLineBg).
+			Foreground(config.Style.AddedFg).
+			Render("⏹")
+
+		fileName := lipgloss.NewStyle().
+			Background(config.Style.ContextLineBg).
+			Foreground(config.Style.FileNameFg).
+			Render(" " + diffResult.OldFile)
+		sb.WriteString(
+			lipgloss.NewStyle().
+				Background(config.Style.ContextLineBg).
+				Padding(0, 1, 0, 1).
+				Foreground(config.Style.FileNameFg).
+				BorderStyle(lipgloss.NormalBorder()).
+				BorderTop(true).
+				BorderBottom(true).
+				BorderForeground(config.Style.FileNameFg).
+				BorderBackground(config.Style.ContextLineBg).
+				Width(config.TotalWidth).
+				Render(
+					lipgloss.JoinHorizontal(lipgloss.Top,
+						removeIcon,
+						addIcon,
+						fileName,
+					),
+				) + "\n",
+		)
+	}
+
+	for _, h := range diffResult.Hunks {
+		// Render hunk header
+		if config.Style.ShowHunkHeader {
+			sb.WriteString(
+				lipgloss.NewStyle().
+					Background(config.Style.HunkLineBg).
+					Foreground(config.Style.HunkLineFg).
+					Width(config.TotalWidth).
+					Render(h.Header) + "\n",
+			)
+		}
+		sb.WriteString(RenderSideBySideHunk(diffResult.OldFile, h, opts...))
+	}
+
+	return sb.String(), nil
+}
+
+// GenerateDiff creates a unified diff from two file contents
+func GenerateDiff(beforeContent, afterContent, fileName string) (string, int, int) {
+	// remove the cwd prefix and ensure consistent path format
+	// this prevents issues with absolute paths in different environments
+	cwd := config.WorkingDirectory()
+	fileName = strings.TrimPrefix(fileName, cwd)
+	fileName = strings.TrimPrefix(fileName, "/")
+	// Create temporary directory for git operations
+	tempDir, err := os.MkdirTemp("", fmt.Sprintf("git-diff-%d", time.Now().UnixNano()))
+	if err != nil {
+		logging.Error("Failed to create temp directory for git diff", "error", err)
+		return "", 0, 0
+	}
+	defer os.RemoveAll(tempDir)
+
+	// Initialize git repo
+	repo, err := git.PlainInit(tempDir, false)
+	if err != nil {
+		logging.Error("Failed to initialize git repository", "error", err)
+		return "", 0, 0
+	}
+
+	wt, err := repo.Worktree()
+	if err != nil {
+		logging.Error("Failed to get git worktree", "error", err)
+		return "", 0, 0
+	}
+
+	// Write the "before" content and commit it
+	fullPath := filepath.Join(tempDir, fileName)
+	if err = os.MkdirAll(filepath.Dir(fullPath), 0o755); err != nil {
+		logging.Error("Failed to create directory for file", "error", err)
+		return "", 0, 0
+	}
+	if err = os.WriteFile(fullPath, []byte(beforeContent), 0o644); err != nil {
+		logging.Error("Failed to write before content to file", "error", err)
+		return "", 0, 0
+	}
+
+	_, err = wt.Add(fileName)
+	if err != nil {
+		logging.Error("Failed to add file to git", "error", err)
+		return "", 0, 0
+	}
+
+	beforeCommit, err := wt.Commit("Before", &git.CommitOptions{
+		Author: &object.Signature{
+			Name:  "OpenCode",
+			Email: "[email protected]",
+			When:  time.Now(),
+		},
+	})
+	if err != nil {
+		logging.Error("Failed to commit before content", "error", err)
+		return "", 0, 0
+	}
+
+	// Write the "after" content and commit it
+	if err = os.WriteFile(fullPath, []byte(afterContent), 0o644); err != nil {
+		logging.Error("Failed to write after content to file", "error", err)
+		return "", 0, 0
+	}
+
+	_, err = wt.Add(fileName)
+	if err != nil {
+		logging.Error("Failed to add file to git", "error", err)
+		return "", 0, 0
+	}
+
+	afterCommit, err := wt.Commit("After", &git.CommitOptions{
+		Author: &object.Signature{
+			Name:  "OpenCode",
+			Email: "[email protected]",
+			When:  time.Now(),
+		},
+	})
+	if err != nil {
+		logging.Error("Failed to commit after content", "error", err)
+		return "", 0, 0
+	}
+
+	// Get the diff between the two commits
+	beforeCommitObj, err := repo.CommitObject(beforeCommit)
+	if err != nil {
+		logging.Error("Failed to get before commit object", "error", err)
+		return "", 0, 0
+	}
+
+	afterCommitObj, err := repo.CommitObject(afterCommit)
+	if err != nil {
+		logging.Error("Failed to get after commit object", "error", err)
+		return "", 0, 0
+	}
+
+	patch, err := beforeCommitObj.Patch(afterCommitObj)
+	if err != nil {
+		logging.Error("Failed to create git diff patch", "error", err)
+		return "", 0, 0
+	}
+
+	// Count additions and removals
+	additions := 0
+	removals := 0
+	for _, fileStat := range patch.Stats() {
+		additions += fileStat.Addition
+		removals += fileStat.Deletion
+	}
+
+	return patch.String(), additions, removals
+}