#!/usr/bin/env bun

/**

* slop-diff: show NEW slop-scan findings introduced on this branch.

*

* Runs slop-scan on HEAD and on the merge-base, then diffs the results

* to show only findings that were added. Line-number-insensitive comparison

* so shifting code doesn't create false positives.

*

* Usage:

* bun run slop:diff # diff against main

* bun run slop:diff origin/release # diff against another base

*/

import { spawnSync } from 'child_process';

import * as fs from 'fs';

import * as os from 'os';

import * as path from 'path';

const base = process.argv[2] || 'main';

// 1. Find changed files

const diffResult = spawnSync('git', ['diff', '--name-only', `${base}...HEAD`], {

encoding: 'utf-8', timeout: 10000,

});

const changedFiles = new Set(

(diffResult.stdout || '').trim().split('\n').filter(Boolean)

);

if (changedFiles.size === 0) {

console.log('No files changed vs', base, '— nothing to check.');

process.exit(0);

}

// 2. Run slop-scan on HEAD

const scanHead = spawnSync('npx', ['slop-scan', 'scan', '.', '--json'], {

encoding: 'utf-8', timeout: 120000, shell: true,

});

if (!scanHead.stdout) {

console.log('slop-scan not available. Install: npm i -g slop-scan');

process.exit(0);

}

let headReport: any;

try { headReport = JSON.parse(scanHead.stdout); } catch {

console.log('slop-scan returned invalid JSON.'); process.exit(0);

}

// 3. Get base branch findings using git stash approach

// Check out base versions of changed files, scan, then restore

const mergeBase = spawnSync('git', ['merge-base', base, 'HEAD'], {

encoding: 'utf-8', timeout: 5000,

}).stdout?.trim();

// Fingerprint: strip line numbers so shifting code doesn't create false positives

// "line 142: empty catch, boundary=none" -> "empty catch, boundary=none"

function stripLineNum(evidence: string): string {

return evidence.replace(/^line \d+: /, '').replace(/ at line \d+ /, ' ');

}

// Count evidence items per (rule, file, stripped-evidence) for the base

const baseCounts = new Map<string, number>();

if (mergeBase) {

// Create temp worktree for base scan

const tmpWorktree = path.join(os.tmpdir(), `slop-base-${Date.now()}`);

const wtResult = spawnSync('git', ['worktree', 'add', '--detach', tmpWorktree, mergeBase], {

encoding: 'utf-8', timeout: 30000,

});

if (wtResult.status === 0) {

// Copy slop-scan config if it exists

const configFile = 'slop-scan.config.json';

if (fs.existsSync(configFile)) {

try { fs.copyFileSync(configFile, path.join(tmpWorktree, configFile)); } catch {}

}

const scanBase = spawnSync('npx', ['slop-scan', 'scan', tmpWorktree, '--json'], {

encoding: 'utf-8', timeout: 120000, shell: true,

});

if (scanBase.stdout) {

try {

const baseReport = JSON.parse(scanBase.stdout);

for (const f of baseReport.findings) {

// Remap worktree paths back to repo-relative

const realPath = f.path.replace(tmpWorktree + '/', '');

if (!changedFiles.has(realPath)) continue;

for (const ev of f.evidence || []) {

const key = `${f.ruleId}|${realPath}|${stripLineNum(ev)}`;

baseCounts.set(key, (baseCounts.get(key) || 0) + 1);

}

}

} catch {}

}

// Clean up worktree

spawnSync('git', ['worktree', 'remove', '--force', tmpWorktree], {

timeout: 10000,

});

}

}

// 4. Find genuinely new findings

// For each evidence item on HEAD, check if the base had the same (rule, file, stripped-evidence).

// Use counts to handle duplicates: if base had 2 and HEAD has 3, that's 1 new.

const headCounts = new Map<string, { count: number; evidence: string[] }>();

const headFindings = headReport.findings.filter((f: any) => changedFiles.has(f.path));

for (const f of headFindings) {

for (const ev of f.evidence || []) {

const key = `${f.ruleId}|${f.path}|${stripLineNum(ev)}`;

const entry = headCounts.get(key) || { count: 0, evidence: [] };

entry.count++;

entry.evidence.push(ev);

headCounts.set(key, entry);

}

}

// Compute net new

type NewFinding = { ruleId: string; filePath: string; evidence: string };

const newFindings: NewFinding[] = [];

let removedCount = 0;

for (const [key, entry] of headCounts) {

const baseCount = baseCounts.get(key) || 0;

const netNew = entry.count - baseCount;

if (netNew > 0) {

const [ruleId, filePath] = key.split('|');

// Take the last N evidence items as the "new" ones

for (const ev of entry.evidence.slice(-netNew)) {

newFindings.push({ ruleId, filePath, evidence: ev });

}

}

}

for (const [key, baseCount] of baseCounts) {

const headCount = headCounts.get(key)?.count || 0;

if (headCount < baseCount) removedCount += baseCount - headCount;

}

// 5. Print results

if (newFindings.length === 0) {

if (removedCount > 0) {

console.log(`\n slop-scan: no new findings. Removed ${removedCount} pre-existing findings.\n`);

} else {

console.log(`\n slop-scan: no new findings in ${changedFiles.size} changed files.\n`);

}

process.exit(0);

}

console.log(`\n── slop-scan: ${newFindings.length} new findings (+${newFindings.length} / -${removedCount}) ──\n`);

// Group by file, then by rule

const grouped = new Map<string, Map<string, string[]>>();

for (const { ruleId, filePath, evidence } of newFindings) {

if (!grouped.has(filePath)) grouped.set(filePath, new Map());

const rules = grouped.get(filePath)!;

if (!rules.has(ruleId)) rules.set(ruleId, []);

rules.get(ruleId)!.push(evidence);

}

for (const [filePath, rules] of grouped) {

console.log(` ${filePath}`);

for (const [ruleId, evidence] of rules) {

console.log(` ${ruleId}:`);

for (const ev of evidence) {

console.log(` ${ev}`);

}

}

}

console.log(`\n Net: +${newFindings.length} new, -${removedCount} removed\n`);