#!/usr/bin/env node
// =============================================================
// whynot-design CLI — consumer drift-check (WHYNOT-WP-0003 · T05)
//
// Runs IN A CONSUMING REPO:  npx @whynot/design drift
//
// Compares the consumer's adopted sync-point (.whynot-design.lock) against the
// installed package's ir/manifest.json (or an explicit --manifest), and reports
// added / changed / removed components + token changes. Read-only against the
// package; the only file it writes is .whynot-design.lock (and only on --update).
//
// This is the DOWNSTREAM mirror of the upstream adapter drift
// (adapters/ADAPTER_CONTRACT.md) — same report shape, same exit codes:
//   0  in sync          2  usage/config error          3  drift detected
// =============================================================
import { readFileSync, writeFileSync, existsSync } from "node:fs";
import { join, dirname, resolve, isAbsolute } from "node:path";
import { fileURLToPath } from "node:url";

const PKG_ROOT = join(dirname(fileURLToPath(import.meta.url)), "..");
const EXIT = { OK: 0, USAGE: 2, DRIFT: 3 };

function fail(msg) {
  process.stderr.write(`whynot-design: ${msg}\n`);
  process.exit(EXIT.USAGE);
}

function readJson(path, label) {
  if (!existsSync(path)) fail(`${label} not found at ${path}`);
  try {
    return JSON.parse(readFileSync(path, "utf8"));
  } catch (e) {
    fail(`${label} at ${path} is not valid JSON: ${e.message}`);
  }
}

function parseArgs(argv) {
  const args = { _: [], flags: {} };
  for (let i = 0; i < argv.length; i++) {
    const a = argv[i];
    if (a === "--json" || a === "--update") args.flags[a.slice(2)] = true;
    else if (a === "--lock" || a === "--manifest" || a === "--version") args.flags[a.slice(2)] = argv[++i];
    else if (a.startsWith("--")) fail(`unknown flag ${a}`);
    else args._.push(a);
  }
  return args;
}

function resolvePath(p, base) {
  return isAbsolute(p) ? p : resolve(base, p);
}

// ---------- drift core ----------
// Compare an adopted lock against a target manifest. Pure; reused for --json,
// the human report, and --update. Mirrors the adapter drift component shape.
function computeDrift(lock, manifest) {
  const adopted = lock.manifestHashes.components || {};
  const current = Object.fromEntries(manifest.components.map((c) => [c.name, c.hash]));
  const groupOf = Object.fromEntries(manifest.components.map((c) => [c.name, c.group]));

  const names = [...new Set([...Object.keys(adopted), ...Object.keys(current)])].sort();
  const components = [];
  for (const name of names) {
    if (!(name in adopted)) components.push({ name, group: groupOf[name], status: "added" });
    else if (!(name in current)) components.push({ name, status: "removed" });
    else if (adopted[name] !== current[name]) components.push({ name, group: groupOf[name], status: "changed", from: adopted[name], to: current[name] });
    else components.push({ name, group: groupOf[name], status: "ok" });
  }

  const tokensChanged = lock.manifestHashes.tokens !== manifest.tokensHash;
  const drifted = tokensChanged || components.some((c) => c.status !== "ok");

  return {
    tool: "@whynot/design drift",
    generatedAt: new Date().toISOString(),
    adopted: { designVersion: lock.designVersion, adoptedAt: lock.adoptedAt },
    target: { designVersion: manifest.designVersion, generatedAt: manifest.generatedAt },
    schemaVersionMismatch: lock.manifestSchemaVersion !== manifest.schemaVersion
      ? { adopted: lock.manifestSchemaVersion, target: manifest.schemaVersion }
      : null,
    tokens: { status: tokensChanged ? "changed" : "ok" },
    components,
    drift: drifted,
  };
}

function lockFromManifest(manifest) {
  return {
    designVersion: manifest.designVersion,
    adoptedAt: new Date().toISOString(),
    manifestSchemaVersion: manifest.schemaVersion,
    manifestHashes: {
      tokens: manifest.tokensHash,
      components: Object.fromEntries(manifest.components.map((c) => [c.name, c.hash])),
    },
  };
}

function printHuman(report) {
  const out = [];
  out.push(`whynot-design drift`);
  out.push(`  adopted: ${report.adopted.designVersion}  (${report.adopted.adoptedAt})`);
  out.push(`  target:  ${report.target.designVersion}  (${report.target.generatedAt})`);
  if (report.schemaVersionMismatch) {
    out.push(`  ! manifest schemaVersion differs (${report.schemaVersionMismatch.adopted} → ${report.schemaVersionMismatch.target}); hashes may not be directly comparable.`);
  }
  out.push("");

  const added = report.components.filter((c) => c.status === "added");
  const changed = report.components.filter((c) => c.status === "changed");
  const removed = report.components.filter((c) => c.status === "removed");

  out.push(`Tokens:     ${report.tokens.status === "changed" ? "changed" : "unchanged"}`);
  out.push(`Components:  +${added.length} added · ~${changed.length} changed · -${removed.length} removed · ${report.components.length} total`);
  if (added.length) out.push(`  + ${added.map((c) => c.name).join(", ")}`);
  if (changed.length) out.push(`  ~ ${changed.map((c) => c.name).join(", ")}`);
  if (removed.length) out.push(`  - ${removed.map((c) => c.name).join(", ")}`);
  out.push("");

  if (report.drift) {
    out.push(`Drift detected vs your adopted sync-point.`);
    out.push(`Adopt this version:  npx @whynot/design drift --update`);
  } else {
    out.push(`In sync with ${report.target.designVersion}. No drift.`);
  }
  process.stdout.write(out.join("\n") + "\n");
}

// ---------- drift command ----------
function cmdDrift(args) {
  const cwd = process.cwd();
  const lockPath = resolvePath(args.flags.lock || ".whynot-design.lock", cwd);
  const manifestPath = args.flags.manifest
    ? resolvePath(args.flags.manifest, cwd)
    : join(PKG_ROOT, "ir", "manifest.json");

  const manifest = readJson(manifestPath, "ir/manifest.json");
  if (!Array.isArray(manifest.components) || typeof manifest.tokensHash !== "string") {
    fail(`${manifestPath} is not a valid ir/manifest.json`);
  }
  if (args.flags.version && manifest.designVersion !== args.flags.version) {
    fail(`--version ${args.flags.version} does not match the resolved manifest (designVersion ${manifest.designVersion}). Install that version or point --manifest at it.`);
  }

  // First adopt: no lock yet. --update bootstraps it; otherwise guide the user.
  if (!existsSync(lockPath)) {
    if (args.flags.update) {
      writeFileSync(lockPath, JSON.stringify(lockFromManifest(manifest), null, 2) + "\n");
      if (args.flags.json) process.stdout.write(JSON.stringify({ adopted: manifest.designVersion, created: true }, null, 2) + "\n");
      else process.stdout.write(`Adopted ${manifest.designVersion} as the initial sync-point → ${lockPath}\n`);
      return EXIT.OK;
    }
    fail(`no .whynot-design.lock found. Adopt the installed version first:\n  npx @whynot/design drift --update`);
  }

  const lock = readJson(lockPath, ".whynot-design.lock");
  if (!lock.manifestHashes || !lock.manifestHashes.components) {
    fail(`${lockPath} is missing manifestHashes.components`);
  }

  const report = computeDrift(lock, manifest);

  if (args.flags.update) {
    writeFileSync(lockPath, JSON.stringify(lockFromManifest(manifest), null, 2) + "\n");
    if (args.flags.json) process.stdout.write(JSON.stringify({ ...report, updated: true }, null, 2) + "\n");
    else {
      printHuman(report);
      process.stdout.write(`\nAdopted ${manifest.designVersion} → ${lockPath}\n`);
    }
    return EXIT.OK; // --update reconciles, so it always lands in sync
  }

  if (args.flags.json) process.stdout.write(JSON.stringify(report, null, 2) + "\n");
  else printHuman(report);

  return report.drift ? EXIT.DRIFT : EXIT.OK;
}

// ---------- dispatch ----------
function main() {
  const argv = process.argv.slice(2);
  const args = parseArgs(argv);
  const cmd = args._[0];

  if (!cmd || cmd === "help" || args.flags.help) {
    process.stdout.write(`whynot-design — consumer-side design-system tooling

Usage:
  npx @whynot/design drift [options]      Report changes since your adopted sync-point

Options:
  --update            Adopt the target version as the new sync-point (writes .whynot-design.lock)
  --json              Machine-readable output
  --manifest <path>   Diff against an explicit ir/manifest.json (default: the installed package's)
  --version <x.y.z>   Assert the resolved manifest is this version (guards against the wrong install)
  --lock <path>       Path to the consumer lock (default: ./.whynot-design.lock)

Exit codes:  0 in sync · 2 usage/config error · 3 drift detected
`);
    return EXIT.OK;
  }

  if (cmd === "drift") return cmdDrift(args);
  fail(`unknown command '${cmd}'. Try: npx @whynot/design help`);
}

process.exit(main());