text: 'use strict'
  
  const BB = require('bluebird')
  
  const fetch = require('npm-registry-fetch')
  const LRU = require('lru-cache')
  const optCheck = require('../../util/opt-check')
  
  // Corgis are cute. 🐕🐶
  const CORGI_DOC = 'application/vnd.npm.install-v1+json; q=1.0, application/json; q=0.8, */*'
  const JSON_DOC = 'application/json'
  
  module.exports = packument
  function packument (spec, opts) {
    opts = optCheck(opts)
  
    const registry = fetch.pickRegistry(spec, opts)
    const uri = registry.replace(/\/?$/, '/') + spec.escapedName
  
    return fetchPackument(uri, registry, spec, opts)
  }
  
  const MEMO = new LRU({
    length: m => m._contentLength,
    max: 200 * 1024 * 1024, // 200MB
    maxAge: 30 * 1000 // 30s
  })
  
  module.exports.clearMemoized = clearMemoized
  function clearMemoized () {
    MEMO.reset()
  }
  
  function fetchPackument (uri, registry, spec, opts) {
    const mem = pickMem(opts)
    const accept = opts.fullMetadata ? JSON_DOC : CORGI_DOC
    const memoKey = `${uri}~(${accept})`
    if (mem && !opts.preferOnline && mem.has(memoKey)) {
      return BB.resolve(mem.get(memoKey))
    }
  
    return fetch(uri, opts.concat({
      headers: {
        'pacote-req-type': 'packument',
        'pacote-pkg-id': `registry:${spec.name}`,
        accept
      },
      spec
    }, opts, {
      // Force integrity to null: we never check integrity hashes for manifests
      integrity: null
    })).then(res => res.json().then(packument => {
      packument._cached = res.headers.has('x-local-cache')
      packument._contentLength = +res.headers.get('content-length')
      // NOTE - we need to call pickMem again because proxy
      //        objects get reused!
      const mem = pickMem(opts)
      if (mem) {
        mem.set(memoKey, packument)
      }
      return packument
    })).catch(err => {
      if (err.code === 'E404' && !opts.fullMetadata) {
        return fetchPackument(uri, registry, spec, opts.concat({
          fullMetadata: true
        }))
      } else {
        throw err
      }
    })
  }
  
  class ObjProxy {
    get (key) { return this.obj[key] }
    set (key, val) { this.obj[key] = val }
  }
  
  // This object is used synchronously and immediately, so
  // we can safely reuse it instead of consing up new ones
  const PROX = new ObjProxy()
  function pickMem (opts) {
    if (!opts || !opts.memoize) {
      return MEMO
    } else if (opts.memoize.get && opts.memoize.set) {
      return opts.memoize
    } else if (typeof opts.memoize === 'object') {
      PROX.obj = opts.memoize
      return PROX
    } else {
      return null
    }
  }
  