// Dross improvements — versioned CSS-layer changes with instant rollback.
import { pool } from '../pool.js';
const q = (text, params) => pool.query(text, params);

// Same exfil guards as elsewhere: an approved improvement still can't phone home
// or pull remote CSS. Pure visual tweaks only.
const BANNED = /url\s*\(|@import|@charset|expression\s*\(|behavior\s*:|javascript:/i;
const MAX_CSS = 20_000;

export function validateCss(css) {
  if (typeof css !== 'string' || !css.trim()) return 'css required';
  if (css.length > MAX_CSS) return `css too large (max ${MAX_CSS} chars)`;
  if (BANNED.test(css)) return 'css may not use url()/@import/expression — visual tweaks only';
  return null;
}

export async function create({ summary, css }) {
  const { rows } = await q(
    `INSERT INTO dross_improvements (summary, css) VALUES ($1, $2) RETURNING *`,
    [String(summary).slice(0, 200), css]);
  return rows[0];
}

export async function list() {
  const { rows } = await q(
    `SELECT id, summary, status, created_at, decided_at, length(css) AS css_len
       FROM dross_improvements ORDER BY created_at DESC LIMIT 100`);
  return rows;
}

export async function get(id) {
  const { rows } = await q(`SELECT * FROM dross_improvements WHERE id = $1`, [id]);
  return rows[0] ?? null;
}

// pending→active (approve) · active→rolled_back · rolled_back→active (restore) · pending→rejected
const TRANSITIONS = {
  approve: { from: ['pending'], to: 'active' },
  rollback: { from: ['active'], to: 'rolled_back' },
  restore: { from: ['rolled_back'], to: 'active' },
  reject: { from: ['pending'], to: 'rejected' },
};

export async function transition(id, verb, actor) {
  const t = TRANSITIONS[verb];
  if (!t) return null;
  const { rows } = await q(
    `UPDATE dross_improvements SET status = $1, decided_at = now(), decided_by = $2
      WHERE id = $3 AND status = ANY($4) RETURNING *`,
    [t.to, actor ?? 'owner', id, t.from]);
  return rows[0] ?? null;
}

export async function activeCss() {
  const { rows } = await q(
    `SELECT summary, css FROM dross_improvements WHERE status = 'active' ORDER BY created_at`);
  return rows.map((r) => `/* dross: ${r.summary.replace(/\*\//g, '')} */\n${r.css}`).join('\n\n');
}