import type { DiffSegment } from '../types/diff.js';
/**
* DiffFormatter provides different formatting options for diff output
* to optimize readability and token usage based on use case.
*/
export class DiffFormatter {
/**
* Format diff in unified format (similar to git diff)
* Shows additions and removals with context lines
* @param segments Array of diff segments
* @param context Number of context lines to show around changes
* @returns Formatted diff string
*/
formatUnified(segments: DiffSegment[], context = 3): string {
if (segments.length === 0) {
return '';
}
const lines: string[] = [];
let hasChanges = false;
for (const segment of segments) {
const processedSegment = this.processUnifiedSegment(
segment,
lines,
hasChanges,
context
);
hasChanges = processedSegment.hasChanges;
if (processedSegment.shouldBreak) {
break;
}
}
return hasChanges ? lines.join('\n') : '';
}
private processUnifiedSegment(
segment: DiffSegment,
lines: string[],
hasChanges: boolean,
context: number
): { hasChanges: boolean; shouldBreak: boolean } {
if (segment.type === 'add') {
this.addUnifiedLines(segment, lines, '+ ');
return { hasChanges: true, shouldBreak: false };
}
if (segment.type === 'remove') {
this.addUnifiedLines(segment, lines, '- ');
return { hasChanges: true, shouldBreak: false };
}
if (segment.type === 'equal' && hasChanges) {
return this.processEqualSegment(segment, lines, context);
}
return { hasChanges, shouldBreak: false };
}
private addUnifiedLines(
segment: DiffSegment,
lines: string[],
prefix: string
): void {
for (const line of segment.value.split('\n')) {
if (line || segment.value.endsWith('\n')) {
lines.push(`${prefix}${line}`);
}
}
}
private processEqualSegment(
segment: DiffSegment,
lines: string[],
context: number
): { hasChanges: boolean; shouldBreak: boolean } {
const contextLines = segment.value.split('\n');
const showLines = Math.min(context, contextLines.length);
for (let j = 0; j < showLines && j < contextLines.length - 1; j++) {
lines.push(` ${contextLines[j]}`);
}
const shouldBreak = contextLines.length > showLines;
return { hasChanges: true, shouldBreak };
}
/**
* Format diff in split format showing removals and additions separately
* @param segments Array of diff segments
* @returns Formatted diff string
*/
formatSplit(segments: DiffSegment[]): string {
const { removedLines, addedLines } = this.extractSplitLines(segments);
return this.buildSplitOutput(removedLines, addedLines);
}
private extractSplitLines(segments: DiffSegment[]): {
removedLines: string[];
addedLines: string[];
} {
const removedLines: string[] = [];
const addedLines: string[] = [];
for (const segment of segments) {
if (segment.type === 'remove') {
this.addSplitLines(segment, removedLines);
} else if (segment.type === 'add') {
this.addSplitLines(segment, addedLines);
}
}
return { removedLines, addedLines };
}
private addSplitLines(segment: DiffSegment, targetLines: string[]): void {
for (const line of segment.value.split('\n')) {
if (line || segment.value.endsWith('\n')) {
targetLines.push(line);
}
}
}
private buildSplitOutput(
removedLines: string[],
addedLines: string[]
): string {
const result: string[] = [];
this.addSplitSection(result, removedLines, '--- Removed');
this.addSplitSection(result, addedLines, '+++ Added', result.length > 0);
return result.join('\n');
}
private addSplitSection(
result: string[],
lines: string[],
header: string,
addSeparator = false
): void {
if (lines.length > 0) {
if (addSeparator) {
result.push('');
}
result.push(header);
result.push(...lines);
}
}
/**
* Format diff in minimal format showing only the changes
* @param segments Array of diff segments
* @returns Formatted diff string
*/
formatMinimal(segments: DiffSegment[]): string {
const changes: string[] = [];
for (const segment of segments) {
if (segment.type === 'add') {
changes.push(`+${segment.value}`);
} else if (segment.type === 'remove') {
changes.push(`-${segment.value}`);
}
}
return changes.join('');
}
}
