import db from '@adonisjs/lucid/services/db'
import type { QueryClientContract } from '@adonisjs/lucid/types/database'
import { packSegments, unpackSegments, type Segment } from '#lib/nzb/segments'

/**
 * The only code that knows how `files` keeps its segment lists (CONCEPT.md
 * D31): compressed in `files.segments`, with the first segment's message-id
 * in the indexed `first_message_id` for lookups. Read them with
 * `segmentsOf(file)`; write new files with `FileStore.insert`.
 */

/** A new `files` row, with its segments as a list. */
export type NewFile = Record<string, unknown> & { segments: Segment[] }

const unpacked = new WeakMap<object, Segment[]>()

/** The segments of a `files` row (a row from `db.from('files')`), in order. */
export function segmentsOf(file: { segments?: Buffer | Segment[] | null }): Segment[] {
  const { segments } = file
  if (!segments) return []
  if (Array.isArray(segments)) return segments
  let list = unpacked.get(file)
  if (!list) {
    list = unpackSegments(segments)
    unpacked.set(file, list)
  }
  return list
}

/** Stored form of a segment list, for the File model's column. */
export function storedSegments(segments: Segment[]) {
  return packSegments(segments)
}

export function loadedSegments(stored: Buffer | null): Segment[] {
  return stored ? unpackSegments(stored) : []
}

class FileStore {
  /**
   * Inserts files, skipping those whose `file_key` exists. Returns the rows
   * that were inserted (id and filename).
   */
  async insert(files: NewFile[], client: Pick<QueryClientContract, 'knexQuery'> = db): Promise<{ id: number; filename: string }[]> {
    if (files.length === 0) return []
    const rows = files.map(({ segments, ...file }) => {
      const sorted = [...segments].sort((a, b) => a.number - b.number)
      return { ...file, segments: packSegments(sorted), first_message_id: sorted[0]?.id ?? null }
    })
    const inserted = await client.knexQuery().table('files').insert(rows).onConflict('file_key').ignore().returning(['id', 'filename'])
    return inserted.map((row: any) => ({ id: Number(row.id), filename: row.filename }))
  }
}

export default new FileStore()