import db from '@adonisjs/lucid/services/db'
import logger from '@adonisjs/core/services/logger'
import { par2ReleaseName } from '#lib/release/index'
import { looksRandom } from '#lib/release/random'

/** Releases of a set further apart than this (posted) aren't one upload: a repost is merged separately (decision d). */
const MAX_SPREAD_MS = 48 * 3600 * 1000
/** Between rounds. */
const ROUND_MS = 60_000
/** A round looks back this far past the previous one's start (rows committed while it ran). */
const OVERLAP_MS = 60_000

export interface MergeRound {
  sets: number
  merges: number
  releases: number
}

interface Member {
  id: number
  release_key: string
  group_id: number
  files: number
  posted_at: Date | null
  readable: boolean
}

/**
 * The par2 merge (REBUILD.md, phase 2): releases whose files a par2 set
 * describes are one upload. Obfuscated uploads post each file under a name of
 * its own ("[9/20] - "14f5999a7bd4680b0720e524cac0b3b5"", hep: 13,232
 * one-file releases), so the header pass can't group them; the prober reads
 * each such file's first article (a `lone` candidate) and stores the MD5 of
 * its first 16 KiB, and a par2 body's file list holds the same hash per file,
 * whatever the file was renamed to. Releases in one group, posted within
 * MAX_SPREAD_MS of a release that holds the set's par2, become the one with
 * the most files: its chunks, probe candidates, inspections and hashes, the
 * sums of its counts, and when none of them has a readable name the name the
 * par2's file names share. Each merge is kept in release_merges.
 */
export class Par2Merger {
  private stopped = false
  private since = new Date(0)

  stop() {
    this.stopped = true
  }

  async run() {
    while (!this.stopped) {
      const started = Date.now()
      try {
        const round = await this.round()
        if (round.merges > 0) logger.info(`Merged ${round.releases} releases into ${round.merges} by par2 set (${round.sets} sets checked).`)
      } catch (error: any) {
        logger.error(`Par2 merge round failed: ${error.message}`)
      }
      for (let waited = Date.now() - started; waited < ROUND_MS && !this.stopped; waited += 1000) await new Promise((r) => setTimeout(r, 1000))
    }
  }

  /** The sets with something new since the last round: a par2 found, or a hash of one of their files. */
  async round(): Promise<MergeRound> {
    const { rows: now } = await db.rawQuery(`SELECT now() AS at`)
    const since = new Date(this.since.getTime() - OVERLAP_MS)
    const { rows } = await db.rawQuery(
      `SELECT set_id FROM par2_sets WHERE created_at >= ?
       UNION
       SELECT f.set_id FROM file_hashes h JOIN par2_files f ON f.hash16k = h.hash16k AND f.length = h.size WHERE h.created_at >= ?`,
      [since, since]
    )
    const round: MergeRound = { sets: rows.length, merges: 0, releases: 0 }
    for (const { set_id: setId } of rows) {
      if (this.stopped) return round
      const merged = await this.mergeSet(setId.trim())
      if (merged > 0) {
        round.merges++
        round.releases += merged + 1
      }
    }
    this.since = now[0].at
    return round
  }

  /** Merges the releases of one set; how many went into another. */
  async mergeSet(setId: string): Promise<number> {
    return db.transaction(async (trx) => {
      const { rows: holders } = await trx.rawQuery(
        `SELECT r.id, r.release_key, r.group_id, r.files, r.posted_at, r.readable FROM par2_sets s JOIN releases r ON r.id = s.release_id
         WHERE s.set_id = ? ORDER BY r.id`,
        [setId]
      )
      const anchor: Member | undefined = holders[0]
      if (!anchor) return 0
      const at = (r: Member) => (r.posted_at ? new Date(r.posted_at).getTime() : null)
      const near = (r: Member) => r.group_id === anchor.group_id && (at(r) === null || at(anchor) === null || Math.abs(at(r)! - at(anchor)!) <= MAX_SPREAD_MS)
      const { rows: matches } = await trx.rawQuery(
        `SELECT f.file_id, r.id, r.release_key, r.group_id, r.files, r.posted_at, r.readable
         FROM par2_files f JOIN file_hashes h ON h.hash16k = f.hash16k AND h.size = f.length JOIN releases r ON r.id = h.release_id
         WHERE f.set_id = ?`,
        [setId]
      )
      // A file of the set that matches more than one release nearby is ambiguous: files that share their first
      // 16 KiB and size (131 uploads of 1 GiB test files "kantodoNNN.bin" matched one set's single file and became
      // one release of 1,284 files; LOG.md 2026-10-12 (16)). A plain repost of the same file stays apart too.
      const byFile = new Map<string, Map<string, Member>>()
      for (const m of matches.filter(near)) {
        const releases = byFile.get(m.file_id) ?? new Map<string, Member>()
        releases.set(String(m.id), m)
        byFile.set(m.file_id, releases)
      }
      const found = new Map<string, Member>()
      for (const r of holders.filter(near)) found.set(String(r.id), r)
      for (const releases of byFile.values()) if (releases.size === 1) for (const [id, r] of releases) found.set(id, r)
      if (found.size < 2) return 0
      // Locked in id order (the batch store and other rounds take the same rows).
      const { rows: locked } = await trx.rawQuery(`SELECT id FROM releases WHERE id = ANY(?) ORDER BY id FOR UPDATE`, [[...found.keys()]])
      const members: Member[] = locked.map((r: { id: string }) => found.get(String(r.id))!)
      if (members.length < 2) return 0
      const target = members.reduce((a, b) => (Number(b.files) > Number(a.files) ? b : a))
      const others = members.filter((m) => m.id !== target.id).map((m) => Number(m.id))
      const name = members.every((m) => !m.readable) ? await this.setName(trx, setId) : undefined

      await trx.rawQuery(
        `INSERT INTO release_merges (from_id, from_key, into_id, set_id, files)
         SELECT id, release_key, ?, ?, files FROM releases WHERE id = ANY(?)`,
        [target.id, setId, others]
      )
      for (const table of ['release_chunks', 'probe_candidates', 'release_inspections', 'file_hashes']) {
        await trx.rawQuery(`UPDATE ${table} SET release_id = ? WHERE release_id = ANY(?)`, [target.id, others])
      }
      // A set held by the target already isn't held twice.
      await trx.rawQuery(`DELETE FROM par2_sets WHERE release_id = ANY(?) AND set_id IN (SELECT set_id FROM par2_sets WHERE release_id = ?)`, [others, target.id])
      await trx.rawQuery(`UPDATE par2_sets SET release_id = ? WHERE release_id = ANY(?)`, [target.id, others])
      await trx.rawQuery(
        `UPDATE releases t SET
           files = t.files + s.files, segments = t.segments + s.segments, bytes = t.bytes + s.bytes, chunks = t.chunks + s.chunks,
           first_article = least(t.first_article, s.first_article), last_article = greatest(t.last_article, s.last_article),
           posted_at = least(t.posted_at, s.posted_at), last_posted_at = greatest(t.last_posted_at, s.last_posted_at),
           first_seen_at = least(t.first_seen_at, s.first_seen_at), last_seen_at = greatest(t.last_seen_at, s.last_seen_at),
           readable = t.readable OR s.readable, has_par2 = t.has_par2 OR s.has_par2, passworded = t.passworded OR s.passworded,
           file_total = greatest(t.file_total, s.file_total), inner_name = coalesce(t.inner_name, s.inner_name),
           name = coalesce(nullif(?, ''), t.name)
         FROM (SELECT sum(files) AS files, sum(segments) AS segments, sum(bytes) AS bytes, sum(chunks) AS chunks,
                 min(first_article) AS first_article, max(last_article) AS last_article, min(posted_at) AS posted_at,
                 max(last_posted_at) AS last_posted_at, min(first_seen_at) AS first_seen_at, max(last_seen_at) AS last_seen_at,
                 bool_or(readable) AS readable, bool_or(has_par2) AS has_par2, bool_or(passworded) AS passworded,
                 max(file_total) AS file_total, max(inner_name) AS inner_name
               FROM releases WHERE id = ANY(?)) s
         WHERE t.id = ?`,
        [name ?? '', others, target.id]
      )
      // Completeness as the settler decides it, once settled.
      await trx.rawQuery(
        `UPDATE releases SET complete = CASE WHEN file_total IS NULL THEN NULL ELSE files >= file_total END WHERE id = ? AND settled_at IS NOT NULL`,
        [target.id]
      )
      await trx.rawQuery(`DELETE FROM releases WHERE id = ANY(?)`, [others])
      return others.length
    })
  }

  /** The name a set's files share (par2ReleaseName), for an upload none of whose names is readable. */
  private async setName(trx: any, setId: string): Promise<string | undefined> {
    const { rows } = await trx.rawQuery(`SELECT name FROM par2_files WHERE set_id = ?`, [setId])
    const name = par2ReleaseName(rows.map((r: { name: string }) => r.name))
    // A par2 made after the renaming names the random names again.
    return name && !looksRandom(name) ? name.slice(0, 255) : undefined
  }
}