/**
* Git-style unified diff generator
*
* Generates readable diffs for displaying file changes.
* Used by AiderTool, RawAiderTool for dry-run previews, and collision detection.
*
* Uses the 'diff' npm package (Myers algorithm) for high-quality diffs.
*/
import { createTwoFilesPatch, structuredPatch } from 'diff';
export class DiffGenerator {
/**
* Generate git-style unified diff using Myers algorithm
*
* @param original - Original content
* @param modified - Modified content
* @param path - File path for diff header
* @returns Unified diff string
*/
generateDiff(original: string, modified: string, path: string): string {
return createTwoFilesPatch(
`a/${path}`,
`b/${path}`,
original,
modified,
'original',
'modified'
);
}
/**
* Generate compact summary of changes using Myers diff
*
* @param original - Original content
* @param modified - Modified content
* @returns Summary string with accurate line counts
*/
generateSummary(original: string, modified: string): string {
const patch = structuredPatch('file', 'file', original, modified);
let additions = 0;
let deletions = 0;
for (const hunk of patch.hunks) {
for (const line of hunk.lines) {
if (line.startsWith('+')) additions++;
else if (line.startsWith('-')) deletions++;
}
}
const parts: string[] = [];
if (additions > 0) parts.push(`+${additions}`);
if (deletions > 0) parts.push(`-${deletions}`);
return parts.length > 0 ? parts.join(', ') : 'no changes';
}
}
// ============================================================================
// Standalone functions for collision detection
// ============================================================================
import type { StaleFile } from '../types/collisionTypes.js';
/**
* Generate unified diff for a single file collision
*
* Used when displaying what changed between expected and actual content.
* Content should be UNWRAPPED for LLM readability (matches what LLM sees in cat).
*
* @param filename - File name for diff header
* @param expectedContent - Content we expected (from previous cat)
* @param actualContent - Current actual content (from remote)
* @returns Unified diff string
*/
export function generateFileDiff(
filename: string,
expectedContent: string,
actualContent: string
): string {
return createTwoFilesPatch(
`a/${filename}`,
`b/${filename}`,
expectedContent,
actualContent,
'expected (your version)',
'actual (current remote)'
);
}
/**
* Generate folder-style diff summary for multiple stale files
*
* Used in exec staleness detection to show which files have drifted.
*
* @param staleFiles - Array of stale file info
* @returns Summary string with file list and change indicators
*/
export function generateFolderDiff(staleFiles: StaleFile[]): string {
const lines = ['Files changed since last read:', ''];
for (const file of staleFiles) {
const icon =
file.action === 'deleted'
? '[-]'
: file.action === 'created_externally'
? '[+]'
: '[M]';
lines.push(`${icon} ${file.file}`);
}
return lines.join('\n');
}
/**
* Get diff statistics (additions and deletions)
*
* @param original - Original content
* @param modified - Modified content
* @returns Object with linesAdded and linesRemoved counts
*/
export function getDiffStats(
original: string,
modified: string
): { linesAdded: number; linesRemoved: number } {
const patch = structuredPatch('file', 'file', original, modified);
let linesAdded = 0;
let linesRemoved = 0;
for (const hunk of patch.hunks) {
for (const line of hunk.lines) {
if (line.startsWith('+')) linesAdded++;
else if (line.startsWith('-')) linesRemoved++;
}
}
return { linesAdded, linesRemoved };
}
