#!/usr/bin/env node

/// /////////////////////////////////////////////////////////////////////////////
//
// run this scrips as
//
// REDIS_GC_MODE=lazy \
//   REDIS_GC_CONNECTION=localhost:6379 \
//   REDIS_GC_CHUNK=1000 \
//   ./redis-gc
//
// or use an .env file to set the environment variables
//
// scheduled as: every 3 minutes lazy, every 15 minutes strict
//
// */3 * * * * export REDIS_GC_MODE=lazy REDIS_GC_LAZY_CHUNK=100; /redis-gc
// */15 * * * * export REDIS_GC_MODE=strict REDIS_GC_CHUNK=100; /redis-gc
//
/// /////////////////////////////////////////////////////////////////////////////

// TODO test

if (process.argv[2]) {
  require('dotenv').config({ path: process.argv[2] })
}

const fs = require('fs').promises
const path = require('path')
const os = require('os')
const Redis = require('ioredis')
const { createStorage } = require('async-cache-dedupe')

const log = require('pino')()

const mode = process.env.REDIS_GC_MODE || 'lazy'
const connection = process.env.REDIS_GC_CONNECTION || 'redis://localhost:6379'
const chunk = process.env.REDIS_GC_CHUNK ? Number(process.env.REDIS_GC_CHUNK) : 1000
const lazyChunk = process.env.REDIS_GC_LAZY_CHUNK ? Number(process.env.REDIS_GC_LAZY_CHUNK) : 1000

async function main () {
  const start = Date.now()
  // retrieve last cursor
  let cursor = process.env.REDIS_GC_LAZY_CURSOR ? Number(process.env.REDIS_GC_LAZY_CURSOR) : undefined
  if (!cursor && mode === 'lazy') {
    try {
      cursor = await fs.readFile(path.join(os.tmpdir(), 'mercurius-cache-gc'), 'utf8')
      cursor = Number(cursor)
    } catch (e) { }
  }

  const client = new Redis(connection)
  const storage = createStorage('redis', { log, client, invalidation: true })
  const report = await storage.gc(mode, { chunk, lazy: { chunk: lazyChunk, cursor } })

  // need to save cursor to complete the iteration in lazy mode
  if (mode === 'lazy') {
    await fs.writeFile(path.join(os.tmpdir(), 'mercurius-cache-gc'), String(report.cursor ?? 0), 'utf8')
  }

  const d = Date.now() - start
  log.info({ msg: `gc done in ${d} ms`, mode, report })

  await client.end()
}

main()