beaker-saved-archive-storage.js

import path from 'path'
import raf from 'random-access-file'
import multi from 'multi-random-access'
import pda from 'pauls-dat-api'

module.exports = function (metadataDir, contentDir) {
  return {
    metadata: function (name, opts) {
      return raf(path.join(metadataDir, 'metadata', name))
    },
    content: function (name, opts, archive) {
      if (!archive) archive = opts
      if (name === 'data') return createStorage(archive, metadataDir, contentDir)
      return raf(path.join(metadataDir, 'content', name))
    }
  }
}

function createStorage (archive, metadataDir, contentDir) {
  var historyStorage = raf(path.join(metadataDir, 'content', name))
  return multi({limit: 128}, locate)

  function locate (offset, cb) {
    archive.ready(async function (err) {
      if (err) return cb(err)

      // locate the metadata (stat) info
      var entry
      try {
        entry = await pda.findEntryByContentBlock(archive, offset)
        if (!entry) throw new Error('Could not locate data')
      } catch (err) {
        return cb(err)
      }

      // look up the latest version of this file
      var latestSt = await pda.stat(archive, entry.name)

      // fallback to history storage if not latest
      if (latestSt.offset > entry.start) {
        return cb({
          start: entry.start,
          end: entry.end,
          storage: historyStorage
        })
      }

      // use the content directory
      cb(null, {
        start: entry.bytesStart,
        end: entry.bytesEnd,
        storage: raf(path.join(contentDir, entry.name))
      })
    })
  }
}