ipfs-repo/src/utils/level.js

IPFS Repo implementation

import { NotFoundError } from '../errors.js'

/**
 * @typedef {import('interface-datastore').Datastore} Datastore
 * @typedef {import('interface-datastore').Key} Key
 */

/**
 * @param {Key} key
 * @param {function (Key): Promise<boolean>} has
 * @param {Datastore} store
 * @returns {Promise<boolean>}
 */
export async function hasWithFallback (key, has, store) {
  const result = await has(key)

  if (result) {
    return result
  }

  // Newer versions of level.js changed the key type from Uint8Array|string
  // to Uint8Array  so fall back to trying Uint8Arrays if we are using level.js
  // and the string version of the key did not work
  const levelJs = findLevelJs(store)

  if (!levelJs) {
    return false
  }

  return new Promise((resolve, reject) => {
    // drop down to IndexDB API, otherwise level-js will monkey around with the keys/values
    // @ts-ignore
    const req = levelJs.store('readonly').get(key.toString())
    req.transaction.onabort = () => {
      reject(req.transaction.error)
    }
    req.transaction.oncomplete = () => {
      resolve(Boolean(req.result))
    }
  })
}

/**
 * @param {import('interface-datastore').Key} key
 * @param {function (Key): Promise<Uint8Array>} get
 * @param {function (Key): Promise<boolean>} has
 * @param {import('interface-datastore').Datastore} store
 * @returns {Promise<Uint8Array>}
 */
export async function getWithFallback (key, get, has, store) {
  if (await has(key)) {
    return get(key)
  }

  // Newer versions of level.js changed the key type from Uint8Array|string
  // to Uint8Array so fall back to trying Uint8Arrays if we are using level.js
  // and the string version of the key did not work
  const levelJs = findLevelJs(store)

  if (!levelJs) {
    throw new NotFoundError()
  }

  return new Promise((resolve, reject) => {
    // drop down to IndexDB API, otherwise level-js will monkey around with the keys/values
    // @ts-ignore
    const req = levelJs.store('readonly').get(key.toString())
    req.transaction.onabort = () => {
      reject(req.transaction.error)
    }
    req.transaction.oncomplete = () => {
      if (req.result) {
        return resolve(req.result)
      }

      reject(new NotFoundError())
    }
  })
}

/**
 * Level dbs wrap level dbs that wrap level dbs. Find a level-js
 * instance in the chain if one exists.
 *
 * @param {Datastore} store
 * @returns {Datastore | undefined}
 */
function findLevelJs (store) {
  let db = store

  // @ts-ignore
  while (db.db || db.child) {
    // @ts-ignore
    db = db.db || db.child

    // `Level` is only present in the browser, in node it is LevelDOWN
    // @ts-ignore
    if (db.type === 'level-js' || db.constructor.name === 'Level') {
      return db
    }
  }
}