/**
 * CalDAV broker poller — runs every 5 minutes via node-cron.
 *
 * Responsibilities (D-13, D-02):
 *   - Load all member_credentials (N-credential per-member model)
 *   - Decrypt each app password via decryptPassword (T-03-04 — never log the decrypted value)
 *   - Create a tsdav client per credential, fetch calendars via PROPFIND
 *   - For each calendar: compare current ctag to stored ctag
 *       → ctag unchanged (and non-null): SKIP (no DB write, no Fastmail round-trip)
 *       → ctag changed or null: call syncCalendar (REPORT → ical.js → DB upsert)
 *
 * runPoll is exported for unit testing (inject mocks via vi.mock at the module level).
 * startBrokerPoller wraps it in node-cron's 5-minute schedule.
 *
 * Source: https://github.com/node-cron/node-cron (v4 stable basic API)
 */

import { schedule } from 'node-cron'
import { and, eq } from 'drizzle-orm'
import { db } from '../db/client.js'
import { memberCredentials, calendars } from '../db/schema.js'
import { decryptPassword } from './crypto.js'
import { createFastmailClient } from './client.js'
import { syncCalendar } from './sync.js'

/**
 * Runs one full poll cycle:
 *   1. Load all member credentials
 *   2. For each credential: decrypt, create client, fetch calendars
 *   3. For each calendar: check ctag; skip if unchanged, sync if changed
 *
 * Errors for individual credentials are caught and logged (not re-thrown),
 * so one bad credential does not stop processing for others.
 */
export async function runPoll(): Promise<void> {
  const creds = await db.select().from(memberCredentials)

  for (const cred of creds) {
    try {
      // Decrypt before client creation (T-03-04: never expose decrypted value in logs)
      const appPassword = decryptPassword(cred.encryptedPassword)

      const client = await createFastmailClient(cred.fastmailEmail, appPassword)
      const davCalendars = await client.fetchCalendars()

      for (const davCal of davCalendars) {
        // Look up the stored calendar row to get the known ctag (D-13).
        // BUG B: scope by (userId, url). The two members share one Fastmail account
        // (D-16), so the same collection URL exists for both. A url-only predicate
        // matched the OTHER member's row → wrong ctag compared, and syncCalendar
        // wrote events under the wrong calendar. Match on this member's row only.
        const [stored] = await db
          .select()
          .from(calendars)
          .where(and(eq(calendars.userId, cred.userId), eq(calendars.url, davCal.url)))
          .limit(1)

        // ctag/syncToken: defensive null handling (Pitfall #6)
        const knownCtag = stored?.ctag ?? null
        const currentCtag = (davCal.ctag ?? davCal.syncToken ?? null) as string | null

        // Skip if ctag is present on both sides and unchanged
        if (currentCtag !== null && currentCtag === knownCtag) {
          continue
        }

        await syncCalendar(client, davCal, cred.userId)
      }
    } catch (err) {
      // Log the error but do NOT log the app password or key (T-03-04)
      console.error(
        `[broker/poller] Error processing credential id=${cred.id} (${cred.fastmailEmail}):`,
        err instanceof Error ? err.message : String(err),
      )
    }
  }
}

/**
 * Starts the 5-minute background polling schedule.
 * Call once at API startup (Plan 04 wires this into index.ts).
 */
export function startBrokerPoller(): void {
  schedule('*/5 * * * *', () => {
    runPoll().catch((err: unknown) => {
      console.error('[broker/poller] Unhandled runPoll error:', err)
    })
  })
}