import type { ParsedDiff } from '../../mcp/types/codeReview.js';
import type { ContextPlan } from './planner.js';
export interface ContextFetcherOptions {
contextLines?: number;
maxCharsPerFile?: number;
}
function clamp(n: number, min: number, max: number): number {
return Math.max(min, Math.min(max, n));
}
function toMaxChars(text: string, maxChars: number): string {
if (text.length <= maxChars) return text;
return text.slice(0, maxChars) + '\n...';
}
function mergeRanges(ranges: Array<{ start: number; end: number }>): Array<{ start: number; end: number }> {
const sorted = ranges
.slice()
.sort((a, b) => a.start - b.start)
.filter(r => r.start <= r.end);
const merged: Array<{ start: number; end: number }> = [];
for (const r of sorted) {
const last = merged[merged.length - 1];
if (!last || r.start > last.end + 1) {
merged.push({ start: r.start, end: r.end });
} else {
last.end = Math.max(last.end, r.end);
}
}
return merged;
}
function formatSection(filePath: string, start: number, end: number, lines: string[]): string {
const out: string[] = [];
out.push(`Path: ${filePath}`);
out.push(`Lines ${start}-${end}`);
for (let i = start; i <= end; i++) {
const line = lines[i - 1] ?? '';
out.push(`${String(i).padStart(5, ' ')} ${line}`);
}
return out.join('\n');
}
export async function fetchPlannedContext(
diff: ParsedDiff,
plan: ContextPlan,
readFile: (filePath: string) => Promise<string>,
options: ContextFetcherOptions = {}
): Promise<string> {
const contextLines = clamp(options.contextLines ?? 20, 0, 200);
const maxCharsPerFile = clamp(options.maxCharsPerFile ?? 20000, 1000, 200000);
const blocks: string[] = [];
for (const allocation of plan.allocations) {
const file = diff.files.find(f => f.new_path === allocation.file);
if (!file) continue;
let content: string;
try {
content = await readFile(allocation.file);
} catch {
continue;
}
const allLines = content.split('\n');
const changed = Array.from(file.changed_lines.values()).sort((a, b) => a - b);
if (changed.length === 0) {
const basic = toMaxChars(content, maxCharsPerFile);
blocks.push(`Path: ${allocation.file}\nLines 1-${Math.min(allLines.length, 200)}\n${basic}`);
continue;
}
const ranges = changed.map(line => ({
start: Math.max(1, line - contextLines),
end: Math.min(allLines.length, line + contextLines),
}));
const merged = mergeRanges(ranges);
const perFileBlocks: string[] = [];
for (const r of merged) {
perFileBlocks.push(formatSection(allocation.file, r.start, r.end, allLines));
}
blocks.push(toMaxChars(perFileBlocks.join('\n\n'), maxCharsPerFile));
}
return blocks.join('\n\n---\n\n');
}
