const router = require('express-promise-router')()
const db = require('../db')
const ensureAdmin = require('./middleware/ensureAdmin')
const fs = require('fs');
const path = require('path');

const cacheRoot = path.join(__dirname, '../cache/images')

fs.promises.mkdir(cacheRoot, {recursive: true})
  .catch(() => console.error("Could not create image cache dir: " + cacheRoot));

const memCache = {};

async function writeImageFile(uuid, size, data) {
  if(size !== 'thumb' && size !== 'large')
    throw new Error(`Unknown image size ${size}`);

  await fs.promises.writeFile(path.join(cacheRoot, `${uuid}-${size}`), data);
}

async function getImage(uuid, size) {
  // If we've already stored a mime type, that means we've written the file to disk
  if(memCache[`${uuid}-${size}`]?.mime_type) {
    return {
      file: fs.createReadStream(path.join(cacheRoot, `${uuid}-${size}`)),
      mime_type: memCache[`${uuid}-${size}`].mime_type
    }
  }

  // If we've stored a promise, that means we're currently retrieving it from the db
  if(memCache[`${uuid}-${size}`]?.dbPromise) {
    return await memCache[`${uuid}-${size}`]?.dbPromise;
  }

  // Otherwise, retrieve it from the DB, and then write it to disk
  const record = memCache[`${uuid}-${size}`] = {};
  record.dbPromise = db.item.getImage(uuid, size);

  const image = await record.dbPromise;
  await writeImageFile(uuid, size, image.file);

  record.mime_type = image.mime_type;
  delete record.dbPromise;

  return image;
}

router.get('/:uuid/:size', async (req, res) => {
  const image = await getImage(req.params.uuid, req.params.size)

  const cacheSeconds = 60 * 60 * 24;
  res.set('Cache-Control', cacheSeconds);
  res.set('Content-Type', image.mime_type)

  if(Buffer.isBuffer(image.file))
    res.end(image.file)
  else if (typeof image.file.pipe === 'function')
    image.file.pipe(res)
  else
    throw new Error("Unable to send file to user");
})

router.post('/:uuid/featured', ensureAdmin, async (req, res) => {
  const item = await db.item.setFeatured(req.params.uuid)
  res.json(item)
})

router.delete('/:uuid', ensureAdmin, async (req, res) => {
  const item = await db.item.removeImage(req.params.uuid)
  res.json(item)
})

module.exports = router