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index.js
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index.js
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var Nanocomponent = require('nanocomponent')
var morph = require('nanomorph')
var onidle = require('on-idle')
var onload = require('on-load')
var assert = require('assert')
const STATUS = Object.freeze({
UNFETCHED: Symbol('UNFETCHED'),
FETCHING: Symbol('FETCHING'),
FETCHED: Symbol('FETCHED')
})
module.exports = Nanofetcher
function Nanofetcher () {
if (!(this instanceof Nanofetcher)) return new Nanofetcher()
this._status = STATUS.UNFETCHED
this._data = null
this._dataID = null
this._createdID = null
this._prefetchCbs = []
this._promisify = false
assert.notEqual(
this.constructor.name,
'nanofetcher',
'nanofetcher: set Component.prototype.constructor = Component'
)
assert.ok(
!this.constructor.prototype.hasOwnProperty('createElement'),
'nanofetcher: createElement should not be defined'
)
assert.ok(
!this.constructor.prototype.hasOwnProperty('identity'),
'nanofetcher: identity should be a static method'
)
this.createElement = this._createElement
Nanocomponent.call(this)
}
Nanofetcher.prototype = Object.create(Nanocomponent.prototype)
Nanofetcher.prototype.constructor = Nanofetcher
Nanofetcher.prototype._createElement = function () {
var args = new Array(arguments.length)
for (var i = 0; i < arguments.length; i++) args[i] = arguments[i]
var id = this.constructor.identity.apply(null, args)
assert.equal(
typeof id,
'string',
'nanofetcher.render: Component.identity should return type string'
)
// createElement id should match the id of previously fetched or fetching data,
// unless an element has already been created for the (now stale) data
if (this._status == STATUS.FETCHED || this._status == STATUS.FETCHING) {
assert.ok(
id == this._dataID || this._dataID == this._createdID,
'nanofetcher.render: called with different arguments than nanofetch.prefetch'
)
if (id != this._dataID) {
this._data = null
this._dataID = null
this._status = STATUS.UNFETCHED
}
}
if (this._status == STATUS.UNFETCHED) {
if (this.init) this.init.apply(this, args)
}
this._createdID = id
var el
if (this._status == STATUS.FETCHED) {
el = this.hydrate.call(this, this._data)
if (this._hasWindow && this.done) { onload(el, this.done.bind(this), () => {}, this._ncID) }
} else {
el = this.placeholder.call(this)
if (this._hasWindow) onload(el, this._load.bind(this), () => {}, this._ncID)
}
return el
}
Nanofetcher.prototype._load = function () {
if (this._status == STATUS.UNFETCHED) {
onidle(() => {
var cb = this.done || (() => {})
this._handleFetch(this._createdID, cb)
})
} else if (this._status == STATUS.FETCHED) {
// only happens if fetching finishes after createElement but before onload fires
morph(this.element, this.hydrate.call(this, this._data))
if (this.done) this.done.call(this)
} else {
// STATUS.FETCHING
if (this.done) this._prefetchCbs.push(this.done.bind(this))
}
}
Nanofetcher.prototype._handleFetch = function (id, cb) {
this._status = STATUS.FETCHING
this._dataID = id
var promise = this.fetch.call(this, _cb.bind(this))
if (promise && typeof promise.then === 'function') {
this._promisify = true
promise.then(data => _cb.call(this, null, data)).catch(_cb)
}
function _cb (err, data) {
if (err) {
this._status = STATUS.UNFETCHED
this._dataID = null
cb(err)
}
if (id != this._dataID) {
return
}
this._data = data
this._status = STATUS.FETCHED
if (this.element) morph(this.element, this.hydrate.call(this, this._data))
cb()
}
}
Nanofetcher.prototype.prefetch = function () {
// this is a bit of sleight-of-hand to support
// both callbacks and promises, depending on whether
// fetch returns a promise or not
// if it does, this._promisify will be true and maybeCb
// is actually the last createElement argument
// if fetch does not return a promise, then maybeCb
// must be a callback
var maybeCb = arguments[arguments.length - 1]
var args = []
for (var i = 0; i < arguments.length; i++) args.push(arguments[i])
var id = this.constructor.identity.apply(null, args)
assert.equal(
typeof id,
'string',
'nanofetcher.prefetch: Component.identity should return type string'
)
// prefetch id should match the id of previously fetched or fetching data,
// unless an element has already been created for the (now stale) data
if (this._status == STATUS.FETCHED || this._status == STATUS.FETCHING) {
assert.ok(
id == this._dataID || this._dataID == this._createdID,
'nanofetcher.prefetch: called twice with different arguments'
)
if (id != this._dataID) {
this._data = null
this._dataID = null
this._status = STATUS.UNFETCHED
}
}
if (this._status == STATUS.FETCHED) {
if (this._promisify) {
return Promise.resolve()
} else {
assert.equal(
typeof maybeCb,
'function',
'nanofetcher.prefetch: last argument must be callback'
)
return maybeCb()
}
} else if (this._status == STATUS.FETCHING) {
return handleReturn.call(this)
} else {
if (this.init) this.init.apply(this, args)
this._handleFetch(id, err => {
// callback all prefetch calls at the same time
for (var i = 0; i < this._prefetchCbs.length; i++) {
if (err) this._prefetchCbs[i](err)
this._prefetchCbs[i]()
}
})
return handleReturn.call(this)
}
function handleReturn () {
if (this._promisify) {
return new Promise((resolve, reject) => {
this._prefetchCbs.push(_cb)
function _cb (err, data) {
if (err) return reject(err)
return resolve()
}
})
} else {
assert.equal(
typeof maybeCb,
'function',
'nanofetcher.prefetch: last argument must be callback'
)
this._prefetchCbs.push(maybeCb)
}
}
}
Nanofetcher.identity = function () {
throw new Error('nanofetcher: static method identity should be implemented!')
}
Nanofetcher.prototype.fetch = function () {
throw new Error('nanofetcher: fetch should be implemented!')
}
Nanofetcher.prototype.placeholder = function () {
throw new Error('nanofetcher: placeholder should be implemented!')
}
Nanofetcher.prototype.hydrate = function () {
throw new Error('nanofetcher: hydrate should be implemented!')
}