/* eslint @typescript-eslint/no-unused-vars: 0 */

import sqlite3 from 'sqlite3'
import crypto from 'crypto'
import { instrument } from 'succinct-async'
import { now } from '@welshman/lib'
import type { Subscription } from './alert.js'

const DATA_DIR = process.env.DATA_DIR || '.'
const db = new sqlite3.Database(DATA_DIR + '/mailship.db')

type Param = number | string | boolean

type Row = Record<string, any>

const run = (query: string, params: Param[] = []) =>
  new Promise((resolve, reject) => {
    db.run(query, params, function (err) {
      return err ? reject(err) : resolve(this.changes > 0)
    })
  })

// prettier-ignore
const all = <T=Row>(query: string, params: Param[] = []) =>
  new Promise<T[]>((resolve, reject) => {
    db.all(query, params, (err, rows: T[]) => (err ? reject(err) : resolve(rows)))
  })

// prettier-ignore
const get = <T=Row>(query: string, params: Param[] = []) =>
  new Promise<T | undefined>((resolve, reject) => {
    db.get(query, params, (err, row) => {
      if (err) {
        reject(err)
      } else if (row) {
        resolve(row as T)
      } else {
        resolve(undefined)
      }
    })
  })

async function assertResult<T>(p: T | Promise<T>) {
  return (await p)!
}

// Migrations

export const migrate = () =>
  new Promise<void>(async (resolve, reject) => {
    try {
      db.serialize(async () => {
        await run(
          `
          CREATE TABLE IF NOT EXISTS subscriptions (
            id TEXT PRIMARY KEY,
            key TEXT NOT NULL UNIQUE,
            pubkey TEXT NOT NULL,
            email TEXT NOT NULL,
            frequency TEXT NOT NULL DEFAULT 'daily',
            created_at INTEGER NOT NULL,
            confirmed_at INTEGER,
            unsubscribed_at INTEGER,
            last_digest_at INTEGER
          )
        `
        )
        await run(
          `
          CREATE TABLE IF NOT EXISTS events (
            id TEXT NOT NULL,
            subscription_id TEXT NOT NULL,
            event JSON NOT NULL,
            relay TEXT NOT NULL,
            received_at INTEGER NOT NULL,
            PRIMARY KEY (id, subscription_id)
          )
        `
        )
        await run(
          `CREATE INDEX IF NOT EXISTS idx_events_subscription_received ON events (subscription_id, received_at)`
        )
        // Tombstone older duplicate active rows, so the unique index below can be created
        // even if a previous version of the server let races insert more than one.
        await run(
          `
          UPDATE subscriptions
          SET unsubscribed_at = created_at
          WHERE unsubscribed_at IS NULL
            AND id NOT IN (
              SELECT id FROM (
                SELECT id, ROW_NUMBER() OVER (
                  PARTITION BY pubkey ORDER BY created_at DESC, id DESC
                ) AS rn
                FROM subscriptions
                WHERE unsubscribed_at IS NULL
              )
              WHERE rn = 1
            )
        `
        )
        // At most one active subscription per pubkey. Enforced in the DB so a
        // check-then-insert race can never create duplicate digest rows.
        await run(
          `
          CREATE UNIQUE INDEX IF NOT EXISTS idx_subscriptions_active_pubkey
            ON subscriptions (pubkey)
            WHERE unsubscribed_at IS NULL
        `
        )
        resolve()
      })
    } catch (err) {
      reject(err)
    }
  })

// Subscriptions

const parseSubscription = (row: any): Subscription | undefined => {
  if (row) {
    return row as Subscription
  }
}

export const updateSubscription = instrument(
  'database.updateSubscription',
  async (existing: Subscription, email: string, frequency: string) => {
    if (existing.email === email && existing.frequency === frequency) {
      return existing
    }

    // Update by id, not pubkey, so tombstoned rows for the same account are never
    // re-activated alongside this one (the unique index would reject that anyway).
    if (existing.email === email) {
      return parseSubscription(
        await get(
          `UPDATE subscriptions SET frequency = ?, unsubscribed_at = NULL
           WHERE id = ? RETURNING *`,
          [frequency, existing.id]
        )
      )
    }

    return parseSubscription(
      await get(
        `UPDATE subscriptions SET email = ?, frequency = ?, confirmed_at = NULL, unsubscribed_at = NULL
         WHERE id = ? RETURNING *`,
        [email, frequency, existing.id]
      )
    )
  }
)

export const insertSubscription = instrument(
  'database.insertSubscription',
  async (pubkey: string, email: string, frequency: string) => {
    const existing = await getSubscriptionByPubkey(pubkey)

    if (existing) {
      return assertResult(await updateSubscription(existing, email, frequency))
    }

    try {
      return assertResult(
        parseSubscription(
          await get(
            `INSERT INTO subscriptions (id, key, pubkey, email, frequency, created_at)
             VALUES (?, ?, ?, ?, ?, ?) RETURNING *`,
            [
              crypto.randomUUID(),
              crypto.randomBytes(32).toString('hex'),
              pubkey,
              email,
              frequency,
              now(),
            ]
          )
        )
      )
    } catch (err: any) {
      // A concurrent request inserted the active subscription between our select
      // and insert. The partial unique index forces one active row per pubkey,
      // so fall back to updating the row that won the race.
      if (err.message?.includes('UNIQUE constraint')) {
        const concurrent = await getSubscriptionByPubkey(pubkey)

        if (concurrent) {
          return assertResult(await updateSubscription(concurrent, email, frequency))
        }
      }

      throw err
    }
  }
)

export const confirmSubscription = instrument(
  'database.confirmSubscription',
  async (key: string) => {
    return parseSubscription(
      await get(
        `UPDATE subscriptions SET confirmed_at = unixepoch()
         WHERE key = ? AND confirmed_at IS NULL AND unsubscribed_at IS NULL RETURNING *`,
        [key]
      )
    )
  }
)

export const unsubscribeSubscription = instrument(
  'database.unsubscribeSubscription',
  async (key: string) => {
    return parseSubscription(
      await get(
        `UPDATE subscriptions SET unsubscribed_at = unixepoch() WHERE key = ? RETURNING *`,
        [key]
      )
    )
  }
)

export const getSubscriptionById = instrument(
  'database.getSubscriptionById',
  async (id: string) => {
    return parseSubscription(await get(`SELECT * FROM subscriptions WHERE id = ?`, [id]))
  }
)

export const getSubscriptionByKey = instrument(
  'database.getSubscriptionByKey',
  async (key: string) => {
    return parseSubscription(await get(`SELECT * FROM subscriptions WHERE key = ?`, [key]))
  }
)

export const getSubscriptionByPubkey = instrument(
  'database.getSubscriptionByPubkey',
  async (pubkey: string) => {
    return parseSubscription(
      await get(`SELECT * FROM subscriptions WHERE pubkey = ? AND unsubscribed_at IS NULL`, [
        pubkey,
      ])
    )
  }
)

export const getActiveSubscriptions = instrument('database.getActiveSubscriptions', async () => {
  const rows = await all(
    `SELECT * FROM subscriptions
     WHERE confirmed_at IS NOT NULL
       AND unsubscribed_at IS NULL`
  )

  return rows.map(parseSubscription) as Subscription[]
})

export const updateLastDigestAt = instrument(
  'database.updateLastDigestAt',
  async (id: string, timestamp: number) => {
    await run(`UPDATE subscriptions SET last_digest_at = ? WHERE id = ?`, [timestamp, id])
  }
)

// Events

export type StoredEvent = {
  id: string
  subscription_id: string
  event: any
  relay: string
  received_at: number
}

export const insertEvent = instrument(
  'database.insertEvent',
  async (eventId: string, subscriptionId: string, event: any, relay: string) => {
    try {
      await run(
        `INSERT INTO events (id, subscription_id, event, relay, received_at)
         VALUES (?, ?, ?, ?, ?)`,
        [eventId, subscriptionId, JSON.stringify(event), relay, now()]
      )
      return true
    } catch (err: any) {
      // PRIMARY KEY collision = dedup, not an error
      if (err.message?.includes('UNIQUE constraint')) {
        return false
      }
      throw err
    }
  }
)

export const getEventsForSubscription = instrument(
  'database.getEventsForSubscription',
  async (subscriptionId: string, since: number) => {
    const rows = await all<StoredEvent>(
      `SELECT * FROM events
       WHERE subscription_id = ? AND received_at > ?
       ORDER BY received_at DESC`,
      [subscriptionId, since]
    )

    return rows.map((row) => ({
      ...row,
      event: JSON.parse(row.event as any),
    }))
  }
)

export const deleteEventsForSubscription = instrument(
  'database.deleteEventsForSubscription',
  async (subscriptionId: string, since: number) => {
    await run(`DELETE FROM events WHERE subscription_id = ? AND received_at > ?`, [
      subscriptionId,
      since,
    ])
  }
)

export const deleteEventsByIds = instrument(
  'database.deleteEventsByIds',
  async (subscriptionId: string, eventIds: string[]) => {
    if (eventIds.length === 0) return
    const placeholders = eventIds.map(() => '?').join(',')
    await run(
      `DELETE FROM events WHERE subscription_id = ? AND id IN (${placeholders})`,
      [subscriptionId, ...eventIds]
    )
  }
)

export const purgeEventsOlderThan = instrument(
  'database.purgeEventsOlderThan',
  async (timestamp: number) => {
    await run(`DELETE FROM events WHERE received_at < ?`, [timestamp])
  }
)