Files MCP Server

/** * Unified diff generation for change preview. * * Produces diffs in unified format (like `git diff`) for human-readable * change visualization before applying modifications. */ // ───────────────────────────────────────────────────────────── // Diff Generation // ───────────────────────────────────────────────────────────── /** * Generate a unified diff between two strings. * * Produces standard unified diff format with 3 lines of context: * - Lines starting with `-` are removed * - Lines starting with `+` are added * - Lines starting with ` ` are unchanged context * * @param oldContent - Original content * @param newContent - Modified content * @param filename - Filename for diff header (default: "file") * @returns Unified diff string, or "(no changes)" if identical * * @example * generateDiff("hello\nworld", "hello\nuniverse", "greeting.txt") * // --- a/greeting.txt * // +++ b/greeting.txt * // @@ -1,2 +1,2 @@ * // hello * // -world * // +universe */ export function generateDiff(oldContent: string, newContent: string, filename = 'file'): string { const oldLines = oldContent.split('\n'); const newLines = newContent.split('\n'); const hunks: string[] = []; let i = 0; let j = 0; while (i < oldLines.length || j < newLines.length) { // Find next difference while (i < oldLines.length && j < newLines.length && oldLines[i] === newLines[j]) { i++; j++; } if (i >= oldLines.length && j >= newLines.length) break; // Found a difference, collect the hunk const hunkStartOld = Math.max(0, i - 3); const hunkStartNew = Math.max(0, j - 3); const hunkLines: string[] = []; // Add context before for (let k = hunkStartOld; k < i; k++) { hunkLines.push(` ${oldLines[k]}`); } // Find extent of changes let oldEnd = i; let newEnd = j; let contextAfter = 0; while (oldEnd < oldLines.length || newEnd < newLines.length) { if ( oldEnd < oldLines.length && newEnd < newLines.length && oldLines[oldEnd] === newLines[newEnd] ) { contextAfter++; if (contextAfter >= 3) break; oldEnd++; newEnd++; } else { contextAfter = 0; if ( oldEnd < oldLines.length && (newEnd >= newLines.length || oldLines[oldEnd] !== newLines[newEnd]) ) { oldEnd++; } if ( newEnd < newLines.length && (oldEnd >= oldLines.length || oldLines[oldEnd - 1] !== newLines[newEnd]) ) { newEnd++; } } } // Add removed lines for (let k = i; k < oldEnd - contextAfter; k++) { hunkLines.push(`-${oldLines[k]}`); } // Add added lines for (let k = j; k < newEnd - contextAfter; k++) { hunkLines.push(`+${newLines[k]}`); } // Add context after for (let k = 0; k < contextAfter && oldEnd - contextAfter + k < oldLines.length; k++) { hunkLines.push(` ${oldLines[oldEnd - contextAfter + k]}`); } if (hunkLines.length > 0) { const header = `@@ -${hunkStartOld + 1},${oldEnd - hunkStartOld} +${hunkStartNew + 1},${newEnd - hunkStartNew} @@`; hunks.push(`${header}\n${hunkLines.join('\n')}`); } i = oldEnd; j = newEnd; } if (hunks.length === 0) { return '(no changes)'; } return `--- a/${filename}\n+++ b/${filename}\n${hunks.join('\n')}`; } // ───────────────────────────────────────────────────────────── // Diff Analysis // ───────────────────────────────────────────────────────────── /** * Count lines added and removed in a diff. * * @param diff - Unified diff string * @returns Count of added and removed lines * * @example * const diff = generateDiff("a\nb", "a\nc\nd"); * countDiffLines(diff) * // { added: 2, removed: 1 } */ export function countDiffLines(diff: string): { added: number; removed: number } { const lines = diff.split('\n'); let added = 0; let removed = 0; for (const line of lines) { if (line.startsWith('+') && !line.startsWith('+++')) added++; if (line.startsWith('-') && !line.startsWith('---')) removed++; } return { added, removed }; }