'use strict';

const fs = require('node:fs');
const path = require('node:path');
const crypto = require('node:crypto');

const META_KEYS = ['harvest', 'settings', 'nightly'];

class DiscoveryStore {
  constructor(dataDir) { this.file = path.join(path.resolve(dataDir), 'discovery.json'); }
  load() {
    try {
      const data = JSON.parse(fs.readFileSync(this.file, 'utf8'));
      if (data.schema !== 1 || !Number.isSafeInteger(data.revision) || !data.candidates || !data.feeds || !data.lastRun)
        throw new Error('Invalid discovery store schema');
      // Phase A files lack the metadata fields; default them.
      if (data.harvest === undefined) data.harvest = null;
      if (data.settings === undefined) data.settings = null;
      if (!data.nightly) data.nightly = { lastDate: null };
      return data;
    } catch (error) {
      if (error.code === 'ENOENT') return { schema: 1, revision: 0, candidates: {}, feeds: {}, lastRun: { status: 'never' },
        harvest: null, settings: null, nightly: { lastDate: null } };
      throw new Error(`Discovery store unavailable; refusing to overwrite it: ${error.message}`);
    }
  }
  publish(value) {
    const prior = this.load();
    const data = { schema: 1, revision: prior.revision + 1, candidates: value.candidates, feeds: value.feeds,
      lastRun: { status: 'success', startedAt: value.startedAt, finishedAt: new Date().toISOString(),
        candidateCount: Object.keys(value.candidates).length, examined: value.examined, clipped: value.clipped },
      harvest: prior.harvest, settings: prior.settings, nightly: prior.nightly };
    return this.write(data);
  }
  // Metadata only: each given key replaces that field; revision stays.
  patch(fields) {
    const data = this.load();
    for (const key of META_KEYS) if (key in fields) data[key] = fields[key];
    return this.write(data);
  }
  write(data) {
    fs.mkdirSync(path.dirname(this.file), { recursive: true });
    const temp = `${this.file}.${crypto.randomBytes(6).toString('hex')}.tmp`;
    try {
      fs.writeFileSync(temp, JSON.stringify(data, null, 2) + '\n', { mode: 0o600 });
      if (fs.existsSync(this.file)) fs.copyFileSync(this.file, `${this.file}.prev`);
      fs.renameSync(temp, this.file);
    } finally { try { fs.rmSync(temp, { force: true }); } catch {} }
    return data;
  }
}
module.exports = { DiscoveryStore };