import db from '@adonisjs/lucid/services/db'

/** files ids per slice: a few seconds of reads from the HDD. */
const SLICE = 100_000

/**
 * The file_keys filter (LOG.md 2026-10-06 (7)): a 64-bit hash of every
 * file_key. The insert trigger adds new keys; `fill` copies the keys of
 * files from before, in id order and a slice at a time, and marks the
 * filter complete when it reaches the files that existed when it started
 * (everything after that has been added by the trigger, which was live
 * first). FileStore uses the filter only once it is complete.
 */
class FileKeys {
  private completeSince = 0

  /** Whether every file's key is in file_keys; cached once true. */
  async complete(): Promise<boolean> {
    if (this.completeSince) return true
    const row = await db.from('file_keys_fill').where('id', 1).first()
    if (row?.complete) this.completeSince = Date.now()
    return Boolean(row?.complete)
  }

  /** Forgets the cached state (tests). */
  forget() {
    this.completeSince = 0
  }

  /** Copies keys until `budgetMs` has passed or the fill is done; returns the files read and whether it's complete. */
  async fill(budgetMs: number): Promise<{ read: number; complete: boolean; nextId: number; untilId: number }> {
    const started = Date.now()
    let state = await db.from('file_keys_fill').where('id', 1).first()
    if (!state) return { read: 0, complete: false, nextId: 0, untilId: 0 }
    if (state.until_id === null) {
      // Everything inserted from here on goes through the trigger (live since the migration).
      const [{ max }] = await db.from('files').max('id as max')
      await db.from('file_keys_fill').where('id', 1).update({ until_id: Number(max ?? 0), updated_at: new Date() })
      state = await db.from('file_keys_fill').where('id', 1).first()
    }
    let next = Number(state.next_id)
    const until = Number(state.until_id)
    let read = 0
    while (next <= until && Date.now() - started < budgetMs) {
      const to = Math.min(until, next + SLICE - 1)
      const result = await db.rawQuery(
        `INSERT INTO file_keys (key_hash)
         SELECT DISTINCT hashtextextended(file_key, 0) FROM files WHERE id BETWEEN ? AND ? AND file_key IS NOT NULL
         ON CONFLICT DO NOTHING`,
        [next, to]
      )
      read += Number(result.rowCount ?? 0)
      next = to + 1
      await db.from('file_keys_fill').where('id', 1).update({ next_id: next, complete: next > until, updated_at: new Date() })
    }
    return { read, complete: next > until, nextId: next, untilId: until }
  }
}

export default new FileKeys()