hypercore-list/index.js

An ordered collection of hypercores

const { once } = require('events')
const cenc = require('compact-encoding')
const SubEncoder = require('sub-encoder')
const idEnc = require('hypercore-id-encoding')
const RehosterDb = require('hypercore-rehoster/db')

class HypercoreList {
  constructor (bee) {
    this.bee = bee

    const subEncoder = new SubEncoder('collection')
    this.entriesEncs = {
      keyEncoding: subEncoder,
      valueEncoding: cenc.array(cenc.fixed32)
    }
    this.titleEncs = {
      keyEncoding: subEncoder,
      valueEncoding: cenc.string
    }

    this.rehosterDb = new RehosterDb(this.bee)
  }

  async setTitle (title) {
    await this.bee.put('TITLE', title, {
      ...this.titleEncs,
      cas: (prev, next) => prev !== next // no useless appends if it's the same
    })
  }

  async getTitle () {
    return this._getWithWaiting('TITLE', this.titleEncs)
  }

  async setEntries (orderedEntries, { description } = {}) {
    if (!description) description = `List entry for ${idEnc.normalize(this.bee.key)}`

    if (!this.bee.opened) await this.bee.ready()
    const bufferEntries = []
    const rehosterEntries = new Map()
    for (const key of orderedEntries) {
      bufferEntries.push(idEnc.decode(key))
      rehosterEntries.set(key, { description })
    }

    let inserted = true
    await this.bee.put('ENTRIES', bufferEntries, {
      ...this.entriesEncs,
      cas: (prev, next) => {
        if (!prev) return true // only if none exists, for simplicity (TODO:)
        inserted = false
        return false
      }
    })

    if (!inserted) throw new Error('Updating the entries is not yet supported (TODO)')

    const synced = await this.rehosterDb.sync(rehosterEntries)
    if (!synced) throw new Error('Logical error in hypercore-collection.setEntries')
  }

  async getEntries () {
    return this._getWithWaiting('ENTRIES', this.entriesEncs)
  }

  async _getWithWaiting (key, opts = {}) {
    // TODO: timeout option with sensible default
    const watcher = await this.bee.getAndWatch(key, opts)
    try {
      if (watcher.node) {
        return watcher.node.value
      } else {
        await once(watcher, 'update')
        return watcher.node.value
      }
    } finally {
      await watcher.close()
    }
  }
}

module.exports = HypercoreList