import { BaseSchema } from '@adonisjs/lucid/schema'
import { packSegments, unpackSegments } from '#lib/nzb/segments'

const BATCH = 5000

/**
 * Segment lists compressed (CONCEPT.md D31): `files.message_ids` (jsonb,
 * ~38 bytes per segment after pglz) becomes `files.segments` (zstd, ~20),
 * plus `first_message_id` for the lookups the old expression index served.
 * Run with the workers stopped; reclaim the space with VACUUM FULL files.
 */
export default class extends BaseSchema {
  static disableTransactions = true

  async up() {
    await this.db.rawQuery(`ALTER TABLE files ADD COLUMN IF NOT EXISTS segments bytea, ADD COLUMN IF NOT EXISTS first_message_id text`)
    let last = 0
    let done = 0
    while (true) {
      const { rows } = await this.db.rawQuery(
        `SELECT id, message_ids FROM files WHERE id > ? AND segments IS NULL ORDER BY id LIMIT ?`,
        [last, BATCH]
      )
      if (rows.length === 0) break
      const ids: number[] = []
      const packed: Buffer[] = []
      const firsts: (string | null)[] = []
      for (const row of rows) {
        const segments = Object.entries((row.message_ids ?? {}) as Record<string, { id: string; size?: number }>)
          .map(([number, s]) => ({ number: Number(number), id: s.id, size: Number(s.size ?? 0) }))
          .sort((a, b) => a.number - b.number)
        ids.push(Number(row.id))
        packed.push(packSegments(segments))
        firsts.push(segments[0]?.id ?? null)
      }
      await this.db.rawQuery(
        `UPDATE files f SET segments = v.segments, first_message_id = v.first
         FROM unnest(?::bigint[], ?::bytea[], ?::text[]) AS v(id, segments, first) WHERE f.id = v.id`,
        [ids, packed, firsts] as any
      )
      last = ids[ids.length - 1]
      done += rows.length
      if (done % 100_000 < BATCH) console.log(`Packed the segments of ${done} files.`)
    }
    await this.db.rawQuery(`ALTER TABLE files ALTER COLUMN segments SET NOT NULL`)
    await this.db.rawQuery(`CREATE INDEX CONCURRENTLY IF NOT EXISTS files_first_message_id_idx ON files (first_message_id)`)
    await this.db.rawQuery(`DROP INDEX CONCURRENTLY IF EXISTS files_first_segment_idx`)
    await this.db.rawQuery(`ALTER TABLE files DROP COLUMN message_ids`)
  }

  async down() {
    await this.db.rawQuery(`ALTER TABLE files ADD COLUMN IF NOT EXISTS message_ids jsonb`)
    const { rows } = await this.db.rawQuery(`SELECT id, segments FROM files`)
    for (const row of rows) {
      const json = Object.fromEntries(unpackSegments(row.segments).map((s) => [s.number, { id: s.id, size: s.size }]))
      await this.db.rawQuery(`UPDATE files SET message_ids = ? WHERE id = ?`, [JSON.stringify(json), row.id])
    }
    await this.db.rawQuery(`ALTER TABLE files ALTER COLUMN message_ids SET NOT NULL`)
    await this.db.rawQuery(`CREATE INDEX IF NOT EXISTS files_first_segment_idx ON files ((message_ids->'1'->>'id'))`)
    await this.db.rawQuery(`DROP INDEX IF EXISTS files_first_message_id_idx`)
    await this.db.rawQuery(`ALTER TABLE files DROP COLUMN segments, DROP COLUMN first_message_id`)
  }
}