const CID = require('cids')
const multihashes = require('multihashes')
const assert = require('assert')
function isValidCID (link) {
try {
CID.isCID(new CID(link))
} catch (e) {
return false
}
return true
}
function isObject (obj) {
return typeof obj === 'object' && obj !== null
}
function clearObject (myObject) {
for (var member in myObject) {
delete myObject[member]
}
}
module.exports = class Graph {
/**
* @param {Object} ipfsDag an instance of [ipfs.dag](https://github.com/ipfs/interface-ipfs-core/tree/master/API/dag#dag-api)
*/
constructor (ipfsDag) {
assert(ipfsDag, 'ipld-graph must have an instance of ipfs.dag')
this._dag = ipfsDag
this._loading = new Map()
}
_loadCID (node, link) {
const loadingOp = this._loading.get(link)
if (loadingOp) {
return loadingOp
} else {
const promise = new Promise(async (resolve, reject) => {
const cid = new CID(link)
node.options = {}
node.options.format = cid.codec
node.options.hashAlg = multihashes.decode(cid.multihash).name
let value = (await this._dag.get(cid)).value
if (value && typeof value.toJSON === 'function') {
value = value.toJSON()
}
node['/'] = value
this._loading.delete(link)
resolve()
})
this._loading.set(link, promise)
return promise
}
}
/**
* sets a value on a root object given its path
* @param {Object} node
* @param {String} path
* @param {*} value
* @return {Promise}
*/
async set (node, path, value) {
value = {
'/': value
}
path = path.split('/')
const last = path.pop()
let {
value: foundVal,
remainderPath: remainder,
parent
} = await this._get(node, path)
// if the found value is a litaral attach an object to the parent object
if (!isObject(foundVal)) {
const pos = path.length - remainder.length - 1
const name = path.slice(pos, pos + 1)[0]
foundVal = parent[name] = {}
}
// extend the path for the left over path names
for (const name of remainder) {
foundVal = foundVal[name] = {}
}
foundVal[last] = value
return node
}
/**
* traverses an object's path and returns the resulting value in a Promise
* @param {Object} node
* @param {String} path
* @return {Promise}
*/
async get (node, path) {
path = path.split('/')
const {value} = await this._get(node, path)
return value
}
async _get (node, path) {
let parent = node
path = path.slice(0)
while (1) {
const link = node['/']
// if there is a link, traverse throught it
if (isValidCID(link)) {
await this._loadCID(node, link)
} else {
if (link !== undefined) {
// link is a POJO
node = link
}
// traverse through POJOs
if (!path.length) {
break
}
const name = path.shift()
const edge = node[name]
node = edge
if (isObject(edge)) {
parent = node
} else {
break
}
}
}
return {
value: node,
remainderPath: path,
parent: parent
}
}
/**
* Resolves all the links in an object and does so recusivly for N `level`
* @param {Object} node
* @param {Integer} levels
* @return {Promise}
*/
async tree (node, levels = 1) {
const orignal = node
const link = node['/']
if (isValidCID(link)) {
await this._loadCID(node, link)
node = node['/']
}
if (levels && isObject(node)) {
levels--
const promises = []
for (const name in node) {
const edge = node[name]
promises.push(this.tree(edge, levels))
}
await Promise.all(promises)
}
return orignal
}
async _flush (node, opts) {
const awaiting = []
if (isObject(node)) {
for (const name in node) {
const edge = node[name]
awaiting.push(this._flush(edge, opts))
}
await Promise.all(awaiting)
const link = node['/']
if (link !== undefined && !isValidCID(link)) {
let options = Object.assign(opts, node.options)
delete node.options
return this._dag.put(link, options).then(cid => {
const str = cid.toBaseEncodedString()
node['/'] = str
})
}
}
}
/**
* flush an object to ipfs returning the resulting CID in a promise
* @param {Object} node
* @param {Object} opts - encoding options for [`dag.put`](https://github.com/ipfs/interface-ipfs-core/tree/master/API/dag#dagput)
* @param {Function} opts.onHash - a callback that happens on each merklized node. It is given two arguments `hash` and `node` which is the node that was hashed
* @return {Promise}
*/
async flush (node, opts = {}) {
const defaults = {
format: 'dag-cbor',
hashAlg: 'sha2-256'
}
Object.assign(opts, defaults)
if (!node['/']) {
const oldRoot = Object.assign({}, node)
clearObject(node)
node['/'] = oldRoot
}
await this._flush(node, opts)
return node
}
}
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