// supply-chain-recheck.mjs — Periodic re-audit of installed dependencies
// Parses lockfiles (package-lock.json, yarn.lock, requirements.txt, Pipfile.lock)
// and checks against blocklists, OSV.dev batch API, and typosquat detection.
//
// Unlike pre-install-supply-chain.mjs (hook, checks at install time),
// this scanner checks what's ALREADY installed — catching deps that became
// compromised after installation.
//
// Scanner prefix: SCR
// OWASP coverage: LLM03 (Supply Chain), ASI04, AST06, MCP04
// Zero external dependencies — Node.js builtins only.

import { readFile } from 'node:fs/promises';
import { join, dirname } from 'node:path';
import { existsSync, readFileSync } from 'node:fs';
import { fileURLToPath } from 'node:url';
import { finding, scannerResult } from './lib/output.mjs';
import { SEVERITY } from './lib/severity.mjs';
import { levenshtein, tokenize, tokenOverlap, TYPOSQUAT_SUSPICIOUS_TOKENS } from './lib/string-utils.mjs';
import {
  NPM_COMPROMISED, PIP_COMPROMISED, CARGO_COMPROMISED, GEM_COMPROMISED,
  isCompromised, extractOSVSeverity, queryOSVBatch, OSV_ECOSYSTEM_MAP,
} from './lib/supply-chain-data.mjs';

const __dirname = dirname(fileURLToPath(import.meta.url));

// ---------------------------------------------------------------------------
// Top-package knowledge base loader (for typosquat detection)
// ---------------------------------------------------------------------------

let _topPackages = null;
let _typosquatAllowlist = null;

async function loadTopPackages() {
  if (_topPackages) return _topPackages;
  const knowledgePath = join(__dirname, '..', 'knowledge', 'top-packages.json');
  try {
    const raw = await readFile(knowledgePath, 'utf8');
    _topPackages = JSON.parse(raw);
  } catch {
    _topPackages = { npm: [], pypi: [] };
  }
  return _topPackages;
}

async function loadTyposquatAllowlist() {
  if (_typosquatAllowlist) return _typosquatAllowlist;
  const allowPath = join(__dirname, '..', 'knowledge', 'typosquat-allowlist.json');
  try {
    const raw = await readFile(allowPath, 'utf8');
    const data = JSON.parse(raw);
    _typosquatAllowlist = {
      npm: new Set((data.npm || []).map(n => n.toLowerCase().replace(/[_.-]/g, '-'))),
      pypi: new Set((data.pypi || []).map(n => n.toLowerCase().replace(/[_.-]/g, '-'))),
    };
  } catch {
    _typosquatAllowlist = { npm: new Set(), pypi: new Set() };
  }
  return _typosquatAllowlist;
}

// ---------------------------------------------------------------------------
// Lockfile parsers — extract { name, version, ecosystem } tuples
// ---------------------------------------------------------------------------

/**
 * Parse package-lock.json (v2/v3 format with packages field).
 * @param {string} filePath - Absolute path to package-lock.json
 * @returns {Promise<{ name: string, version: string, ecosystem: string }[]>}
 */
async function parsePackageLock(filePath) {
  const deps = [];
  try {
    const raw = await readFile(filePath, 'utf8');
    const lock = JSON.parse(raw);

    // v3 format: packages object
    const packages = lock.packages || {};
    for (const [key, info] of Object.entries(packages)) {
      if (key === '') continue; // Root package
      const name = key.replace(/^node_modules\//, '');
      if (name && info.version) {
        deps.push({ name, version: info.version, ecosystem: 'npm' });
      }
    }

    // v1 fallback: dependencies object
    if (deps.length === 0 && lock.dependencies) {
      for (const [name, info] of Object.entries(lock.dependencies)) {
        if (info.version) {
          deps.push({ name, version: info.version, ecosystem: 'npm' });
        }
      }
    }
  } catch { /* parse error — skip */ }
  return deps;
}

/**
 * Parse yarn.lock (v1 format).
 * Extracts package name and resolved version from each entry.
 * @param {string} filePath - Absolute path to yarn.lock
 * @returns {Promise<{ name: string, version: string, ecosystem: string }[]>}
 */
async function parseYarnLock(filePath) {
  const deps = [];
  try {
    const raw = await readFile(filePath, 'utf8');
    const lines = raw.split('\n');
    let currentPkg = null;

    for (const line of lines) {
      // Package header: "pkg@^1.0.0", "pkg@1.0.0:" or "@scope/pkg@^1.0.0":
      if (!line.startsWith(' ') && !line.startsWith('#') && line.includes('@')) {
        const trimmed = line.replace(/[":]/g, '').trim();
        if (trimmed.startsWith('@')) {
          // Scoped: @scope/pkg@version
          const rest = trimmed.slice(1);
          const atIdx = rest.indexOf('@');
          if (atIdx > 0) currentPkg = '@' + rest.slice(0, atIdx);
        } else {
          const atIdx = trimmed.indexOf('@');
          if (atIdx > 0) currentPkg = trimmed.slice(0, atIdx);
        }
      }
      // Version line: "  version "1.2.3""
      const versionMatch = line.match(/^\s+version\s+"([^"]+)"/);
      if (versionMatch && currentPkg) {
        deps.push({ name: currentPkg, version: versionMatch[1], ecosystem: 'npm' });
        currentPkg = null;
      }
    }
  } catch { /* parse error — skip */ }
  return deps;
}

/**
 * Parse requirements.txt (pip format).
 * @param {string} filePath - Absolute path to requirements.txt
 * @returns {Promise<{ name: string, version: string|null, ecosystem: string }[]>}
 */
async function parseRequirementsTxt(filePath) {
  const deps = [];
  try {
    const raw = await readFile(filePath, 'utf8');
    for (const rawLine of raw.split('\n')) {
      const line = rawLine.trim();
      if (!line || line.startsWith('#') || line.startsWith('-')) continue;
      const eqIdx = line.indexOf('==');
      if (eqIdx > 0) {
        deps.push({ name: line.slice(0, eqIdx).trim(), version: line.slice(eqIdx + 2).trim(), ecosystem: 'pip' });
      } else {
        const match = line.match(/^([a-zA-Z0-9_.-]+)/);
        if (match) deps.push({ name: match[1], version: null, ecosystem: 'pip' });
      }
    }
  } catch { /* parse error — skip */ }
  return deps;
}

/**
 * Parse Pipfile.lock (JSON format).
 * @param {string} filePath - Absolute path to Pipfile.lock
 * @returns {Promise<{ name: string, version: string, ecosystem: string }[]>}
 */
async function parsePipfileLock(filePath) {
  const deps = [];
  try {
    const raw = await readFile(filePath, 'utf8');
    const lock = JSON.parse(raw);
    for (const section of ['default', 'develop']) {
      const packages = lock[section] || {};
      for (const [name, info] of Object.entries(packages)) {
        const version = typeof info === 'object' && info.version
          ? info.version.replace(/^==/, '')
          : null;
        if (version) {
          deps.push({ name, version, ecosystem: 'pip' });
        }
      }
    }
  } catch { /* parse error — skip */ }
  return deps;
}

// ---------------------------------------------------------------------------
// Checks
// ---------------------------------------------------------------------------

/**
 * Check all dependencies against blocklists.
 * @param {{ name: string, version: string, ecosystem: string }[]} deps
 * @param {string} lockfile - Source lockfile name for finding references
 * @returns {object[]} findings
 */
function checkBlocklists(deps, lockfile) {
  const results = [];
  const lists = { npm: NPM_COMPROMISED, pip: PIP_COMPROMISED, cargo: CARGO_COMPROMISED, gem: GEM_COMPROMISED };

  for (const dep of deps) {
    const blocklist = lists[dep.ecosystem];
    if (!blocklist) continue;
    if (isCompromised(blocklist, dep.name, dep.version)) {
      results.push(finding({
        scanner: 'SCR',
        severity: SEVERITY.CRITICAL,
        title: `Compromised dependency: ${dep.name}@${dep.version || '*'}`,
        description:
          `"${dep.name}"${dep.version ? '@' + dep.version : ''} in ${lockfile} is on the known-compromised blocklist. ` +
          `This package/version is associated with supply chain attacks (malware, data exfiltration, or sabotage).`,
        file: lockfile,
        evidence: `${dep.name}@${dep.version || 'any'} in ${dep.ecosystem} blocklist`,
        owasp: 'LLM03',
        recommendation:
          `Remove "${dep.name}" immediately. If this was a transitive dependency, find and remove ` +
          `the parent package that requires it. Audit your system for signs of compromise.`,
      }));
    }
  }
  return results;
}

/**
 * Check dependencies against OSV.dev batch API for known vulnerabilities.
 * @param {{ name: string, version: string, ecosystem: string }[]} deps
 * @param {string} lockfile
 * @returns {{ findings: object[], offline: boolean }}
 */
async function checkOSV(deps, lockfile) {
  // Only query deps that have a version (OSV requires version)
  const queryable = deps.filter(d => d.version && OSV_ECOSYSTEM_MAP[d.ecosystem]);
  if (queryable.length === 0) return { findings: [], offline: false };

  const { results, offline } = await queryOSVBatch(queryable);
  if (offline) return { findings: [], offline: true };

  const findings = [];
  for (let i = 0; i < results.length; i++) {
    const vulns = results[i]?.vulns || [];
    if (vulns.length === 0) continue;

    const dep = queryable[i];
    let hasCritical = false;

    for (const vuln of vulns) {
      const severity = extractOSVSeverity(vuln);
      const sevConst = severity === 'CRITICAL' ? SEVERITY.CRITICAL
        : severity === 'HIGH' ? SEVERITY.HIGH
        : SEVERITY.MEDIUM;

      if (severity === 'CRITICAL') hasCritical = true;

      findings.push(finding({
        scanner: 'SCR',
        severity: sevConst,
        title: `Known vulnerability: ${dep.name}@${dep.version} (${vuln.id})`,
        description:
          `${vuln.id}: ${(vuln.summary || vuln.details || 'No description').slice(0, 200)}. ` +
          `Found in ${lockfile}.`,
        file: lockfile,
        evidence: `${vuln.id} — ${dep.name}@${dep.version}`,
        owasp: 'LLM03',
        recommendation:
          `Upgrade "${dep.name}" to a patched version. Check ${vuln.id} for fix details.`,
      }));
    }
  }
  return { findings, offline: false };
}

/**
 * Check npm dependencies for typosquatting against top packages.
 * @param {{ name: string, version: string, ecosystem: string }[]} deps
 * @param {string[]} topList - Normalized top package names
 * @param {number} topCutoff - Top N for stricter matching
 * @param {string} ecosystem
 * @param {string} lockfile
 * @returns {object[]}
 */
function checkTyposquatting(deps, topList, topCutoff, ecosystem, lockfile, allowlist) {
  const results = [];
  const checked = new Set();

  for (const dep of deps) {
    if (dep.ecosystem !== ecosystem) continue;
    const normalized = dep.name.toLowerCase().replace(/[_.-]/g, '-');
    if (checked.has(normalized)) continue;
    checked.add(normalized);

    // Skip known legitimate packages
    if (allowlist && allowlist.has(normalized)) continue;

    let closestDist = Infinity;
    let closestPkg = null;
    let closestIdx = Infinity;

    for (let i = 0; i < topList.length; i++) {
      const topPkg = topList[i];
      if (normalized === topPkg) { closestPkg = null; break; } // Exact match — legit
      if (Math.abs(normalized.length - topPkg.length) > 2) continue;

      const dist = levenshtein(normalized, topPkg);
      if (dist < closestDist || (dist === closestDist && i < closestIdx)) {
        closestDist = dist;
        closestPkg = topPkg;
        closestIdx = i;
      }
    }

    if (!closestPkg) continue;

    if (closestDist === 1) {
      results.push(finding({
        scanner: 'SCR',
        severity: SEVERITY.HIGH,
        title: `Possible typosquatting: "${dep.name}" vs "${closestPkg}" (edit distance 1)`,
        description:
          `"${dep.name}" in ${lockfile} is 1 character away from the popular ${ecosystem} package "${closestPkg}". ` +
          `Typosquatting packages impersonate popular libraries to execute malicious code.`,
        file: lockfile,
        evidence: `"${dep.name}" → "${closestPkg}" (Levenshtein: 1)`,
        owasp: 'LLM03',
        recommendation:
          `Verify "${dep.name}" is the intended package. If you meant "${closestPkg}", correct the dependency.`,
      }));
    } else if (closestDist === 2 && closestIdx < topCutoff) {
      results.push(finding({
        scanner: 'SCR',
        severity: SEVERITY.MEDIUM,
        title: `Potential typosquatting: "${dep.name}" vs "${closestPkg}" (edit distance 2)`,
        description:
          `"${dep.name}" in ${lockfile} is 2 characters away from the popular ${ecosystem} package "${closestPkg}" ` +
          `(top ${topCutoff} by downloads).`,
        file: lockfile,
        evidence: `"${dep.name}" → "${closestPkg}" (Levenshtein: 2)`,
        owasp: 'LLM03',
        recommendation:
          `Confirm "${dep.name}" is the correct package. Check publish date and author on the registry.`,
      }));
    } else {
      // B7 (v7.2.0): token-overlap fallback. Catches typosquats with edit
      // distance >= 3 that contain all tokens of a popular package plus a
      // suspicious suffix (e.g. `lodash-utils` vs `lodash`).
      const tokenFinding = checkTyposquatTokenOverlap(dep, normalized, topList, topCutoff, ecosystem, lockfile);
      if (tokenFinding) results.push(tokenFinding);
    }
  }
  return results;
}

function checkTyposquatTokenOverlap(dep, normalized, topList, topCutoff, ecosystem, lockfile) {
  const declaredTokens = new Set(tokenize(normalized));
  if (declaredTokens.size < 2) return null;

  const suspiciousSuffixes = TYPOSQUAT_SUSPICIOUS_TOKENS.filter(t => declaredTokens.has(t));
  if (suspiciousSuffixes.length === 0) return null;

  const limit = Math.min(topCutoff, topList.length);
  for (let i = 0; i < limit; i++) {
    const topPkg = topList[i];
    if (normalized === topPkg) return null;
    const topTokens = tokenize(topPkg);
    if (topTokens.length === 0) continue;
    const allContained = topTokens.every(t => declaredTokens.has(t));
    if (!allContained) continue;
    if (topTokens.length === declaredTokens.size) continue;
    const overlap = tokenOverlap(normalized, topPkg);
    if (overlap < 0.66) continue;
    return finding({
      scanner: 'SCR',
      severity: SEVERITY.MEDIUM,
      title: `Possible typosquatting via token-overlap: "${dep.name}" vs "${topPkg}"`,
      description:
        `"${dep.name}" in ${lockfile} contains all tokens of the popular ${ecosystem} package ` +
        `"${topPkg}" plus a suspicious suffix (${suspiciousSuffixes.join(', ')}). ` +
        `This is a common typosquat pattern: attackers register popular-name-plus-suffix ` +
        `packages to capture installs.`,
      file: lockfile,
      evidence: `"${dep.name}" tokens ⊃ "${topPkg}" tokens; suffix=${suspiciousSuffixes.join(',')}; overlap=${overlap.toFixed(2)}`,
      owasp: 'LLM03',
      recommendation:
        `Verify "${dep.name}" is intentional. If you meant "${topPkg}", correct the dependency. ` +
        `If "${dep.name}" is a legitimate utility, add it to knowledge/typosquat-allowlist.json under "${ecosystem}".`,
    });
  }
  return null;
}

// ---------------------------------------------------------------------------
// Main scanner export
// ---------------------------------------------------------------------------

/**
 * Scan targetPath lockfiles for supply chain issues.
 *
 * Detection categories:
 *   1. Blocklist matches (known compromised packages)     — CRITICAL
 *   2. OSV.dev CVE/advisory detection (batch API)         — CRITICAL/HIGH/MEDIUM
 *   3. Typosquatting against top packages                 — HIGH/MEDIUM
 *
 * Lockfiles parsed: package-lock.json, yarn.lock, requirements.txt, Pipfile.lock
 *
 * @param {string} targetPath   - Absolute root path being scanned
 * @param {object} discovery    - Unused (scanner reads lockfiles by convention)
 * @returns {Promise<object>}   - scannerResult envelope
 */
export async function scan(targetPath, discovery) {
  const startMs = Date.now();
  const allFindings = [];
  let filesScanned = 0;
  let osvOffline = false;

  // Discover lockfiles
  const lockfiles = [
    { path: join(targetPath, 'package-lock.json'), parser: parsePackageLock, name: 'package-lock.json', ecosystem: 'npm' },
    { path: join(targetPath, 'yarn.lock'), parser: parseYarnLock, name: 'yarn.lock', ecosystem: 'npm' },
    { path: join(targetPath, 'requirements.txt'), parser: parseRequirementsTxt, name: 'requirements.txt', ecosystem: 'pip' },
    { path: join(targetPath, 'Pipfile.lock'), parser: parsePipfileLock, name: 'Pipfile.lock', ecosystem: 'pip' },
  ];

  // Also check for requirements-*.txt variants
  for (const variant of ['requirements-dev.txt', 'requirements-prod.txt', 'requirements.lock']) {
    const varPath = join(targetPath, variant);
    if (existsSync(varPath)) {
      lockfiles.push({ path: varPath, parser: parseRequirementsTxt, name: variant, ecosystem: 'pip' });
    }
  }

  const presentLockfiles = lockfiles.filter(l => existsSync(l.path));

  if (presentLockfiles.length === 0) {
    return scannerResult('supply-chain-recheck', 'skipped', [], 0, Date.now() - startMs);
  }

  try {
    // Load top packages and allowlist for typosquat detection
    const [topPkgs, allowlist] = await Promise.all([loadTopPackages(), loadTyposquatAllowlist()]);
    const npmTop = topPkgs.npm.map(n => n.toLowerCase().replace(/[_.-]/g, '-'));
    const pypiTop = topPkgs.pypi.map(n => n.toLowerCase().replace(/[_.-]/g, '-'));

    // Parse all lockfiles
    const allDeps = [];
    for (const lockfile of presentLockfiles) {
      filesScanned++;
      const deps = await lockfile.parser(lockfile.path);

      // 1. Blocklist check
      allFindings.push(...checkBlocklists(deps, lockfile.name));

      // 3. Typosquat check
      if (lockfile.ecosystem === 'npm') {
        allFindings.push(...checkTyposquatting(deps, npmTop, 200, 'npm', lockfile.name, allowlist.npm));
      } else if (lockfile.ecosystem === 'pip') {
        allFindings.push(...checkTyposquatting(deps, pypiTop, 100, 'pip', lockfile.name, allowlist.pypi));
      }

      allDeps.push(...deps.map(d => ({ ...d, lockfile: lockfile.name })));
    }

    // 2. OSV.dev batch check (all deps from all lockfiles at once)
    const osvDeps = allDeps.filter(d => d.version);
    if (osvDeps.length > 0) {
      const osvResult = await checkOSV(osvDeps, 'lockfiles');

      if (osvResult.offline) {
        osvOffline = true;
        allFindings.push(finding({
          scanner: 'SCR',
          severity: SEVERITY.INFO,
          title: 'OSV.dev unreachable — CVE check skipped',
          description:
            'Could not reach the OSV.dev API. Blocklist and typosquat checks were performed, ' +
            'but known vulnerability (CVE) detection was skipped. Re-run when network is available.',
          owasp: 'LLM03',
          recommendation: 'Re-run the scanner when network connectivity is restored.',
        }));
      } else {
        // Re-tag findings with correct lockfile names
        for (const f of osvResult.findings) {
          // Find the dep this finding refers to
          const depMatch = f.evidence?.match(/^(\S+)\s*—\s*(\S+?)@/);
          if (depMatch) {
            const depName = depMatch[2];
            const sourceDep = allDeps.find(d => d.name === depName);
            if (sourceDep) {
              f.file = sourceDep.lockfile;
            }
          }
          allFindings.push(f);
        }
      }
    }

    const durationMs = Date.now() - startMs;
    const result = scannerResult('supply-chain-recheck', 'ok', allFindings, filesScanned, durationMs);
    if (osvOffline) result.osv_offline = true;
    return result;

  } catch (err) {
    const durationMs = Date.now() - startMs;
    return scannerResult('supply-chain-recheck', 'error', allFindings, filesScanned, durationMs, err.message);
  }
}