[FEATURE] Support pathfinding by source amount

Also adds tests for `QuotingClient#quotePathFrom{Destination,Source}`.

Paves the way for interledger-deprecated/five-bells-sender#24.

package.json

@@ -57,6 +57,7 @@
     "eslint-plugin-standard": "^1.3.0",
     "istanbul": "^0.4.0",
     "mocha": "^2.3.2",
+    "nock": "^7.0.2",
     "randomgraph": "^0.1.3",
     "spec-xunit-file": "0.0.1-3",
     "supertest": "^1.1.0"

src/pathfinder.js

@@ -67,9 +67,11 @@ class Pathfinder {
 
     log.info('findPath found ' + paths.length + ' paths')
 
-    const pathsQuotes = yield this.quotingClient.quotePathsFromDestination({
-      destinationAccount: params.destinationAccount,
-      destinationAmount: params.destinationAmount
+    const pathsQuotes = yield this.quotingClient.quotePaths({
+      source_account: params.sourceAccount,
+      source_amount: params.sourceAmount,
+      destination_account: params.destinationAccount,
+      destination_amount: params.destinationAmount
       // TODO add other params like destination expiry duration
     }, paths)
 
@@ -82,11 +84,16 @@ class Pathfinder {
     return cheapestPath
   }
 
-  // params -
-  //   sourceLedger
-  //   destinationLedger
-  //   destinationAmount
-  //   destinationAccount (optional)
+  /**
+   * @param {Object} params
+   * @param {String} params.sourceLedger
+   * @param {String} params.destinationLedger
+   * @param {String} params.sourceAmount - either this or destinationAmount is required
+   * @param {String} params.destinationAmount - either this or sourceAmount is required
+   * @param {String} params.sourceAccount - provided with sourceAmount (optional)
+   * @param {String} params.destinationAccount - provided with destinationAmount (optional)
+   * @returns {Promise<[Quote]>}
+   */
   findPath (params) { return co(this._findPath.bind(this), params) }
 }
 

src/quoting-client.js

@@ -2,63 +2,77 @@
 
 const request = require('superagent')
 const uuid = require('uuid4')
+const _ = require('lodash')
 
 class QuotingClient {
   constructor (crawler) {
-    const _this = this
-
     this.crawler = crawler
     this.pairs = {}
-
-    this.crawler.on('pair', function (pair) {
-      _this.handleTradingPair(pair)
-    })
+    this.crawler.on('pair', this._handleTradingPair.bind(this))
   }
 
-  handleTradingPair (pair) {
+  _handleTradingPair (pair) {
     this.pairs[pair.source + ';' + pair.destination] = pair.uri
   }
 
-  * quotePathFromDestination (params, path) {
-    path = path.slice()
-
-    let payments = []
-    let destination = path.pop()
-    let destinationAccount = params.destinationAccount
-    let destinationAmount = params.destinationAmount
-    let destinationExpiryDuration = params.destinationExpiryDuration ||
-      path.length + 2
-
-    while (path.length) {
-      let source = path.pop()
-      let trader = this.pairs[source + ';' + destination]
+  quotePaths (params, paths) {
+    if (params.destination_amount) {
+      return this.quotePathsFromDestination(params, paths)
+    }
+    if (params.source_amount) {
+      return this.quotePathsFromSource(params, paths)
+    }
+    throw new Error('requires sourceAmount or destinationAmount')
+  }
 
-      let query = {
-        source_ledger: source,
-        destination_ledger: destination,
-        destination_account: destinationAccount,
-        destination_amount: destinationAmount,
-        destination_expiry_duration: destinationExpiryDuration
-      }
+  quotePathsFromDestination (params, paths) {
+    return paths.map((path) => this.quotePathFromDestination(params, path))
+  }
 
-      let payment = yield this.getTraderQuote(trader, query)
-      let paymentUuid = uuid()
-      payment.id = trader + '/payments/' + paymentUuid
+  quotePathsFromSource (params, paths) {
+    return paths.map((path) => this.quotePathFromSource(params, path))
+  }
 
+  * quotePathFromDestination (params, path) {
+    params = _.clone(params)
+    path = path.slice()
+    const payments = []
+    params.destination_expiry_duration = params.destination_expiry_duration || path.length + 1
+    params.destination_ledger = path.pop()
+    params.source_ledger = path.pop()
+    while (params.source_ledger) {
+      const payment = yield this.getTraderQuote(params)
       payments.unshift(payment)
-      destination = source
-      destinationAmount = payment.source_transfers[0].credits[0].amount
-      destinationAccount = payment.source_transfers[0].credits[0].account
-      destinationExpiryDuration = payment.source_transfers[0].expiry_duration
+      params = {
+        source_ledger: path.pop(),
+        destination_ledger: params.source_ledger,
+        destination_amount: payment.source_transfers[0].credits[0].amount,
+        destination_account: payment.source_transfers[0].credits[0].account,
+        destination_expiry_duration: payment.source_transfers[0].expiry_duration
+      }
     }
-
     return payments
   }
 
-  quotePathsFromDestination (params, paths) {
-    return paths.map((path) => {
-      return this.quotePathFromDestination(params, path)
-    })
+  * quotePathFromSource (params, path) {
+    params = _.clone(params)
+    path = path.slice()
+    const payments = []
+    params.source_expiry_duration = params.source_expiry_duration || 2 * path.length
+    params.source_ledger = path.shift()
+    params.destination_ledger = path.shift()
+    while (params.destination_ledger) {
+      const payment = yield this.getTraderQuote(params)
+      payments.push(payment)
+      params = {
+        source_ledger: params.destination_ledger,
+        destination_ledger: path.shift(),
+        source_amount: payment.destination_transfers[0].debits[0].amount,
+        source_account: payment.destination_transfers[0].debits[0].account,
+        source_expiry_duration: payment.destination_transfers[0].expiry_duration
+      }
+    }
+    return payments
   }
 
   /**
@@ -71,15 +85,17 @@ class QuotingClient {
    *  destination_asset
    *  destination_amount or source_amount
    */
-  * getTraderQuote (trader, quoteOpts) {
-    let res = yield request
+  * getTraderQuote (quoteOpts) {
+    const trader = this.pairs[quoteOpts.source_ledger + ';' + quoteOpts.destination_ledger]
+    const res = yield request
       .get(trader + '/quote')
       .query(quoteOpts)
     if (res.status >= 400) {
       throw new Error('Server Error: ' + res.status + ' ' + res.body)
     }
-
-    return res.body
+    const payment = res.body
+    payment.id = trader + '/payments/' + uuid()
+    return payment
   }
 }
 

test/fixtures/from-destination.json

@@ -0,0 +1,39 @@
+{
+  "quoteArgs23": {
+    "source_ledger": "http://ledger2.example",
+    "destination_ledger": "http://ledger3.example",
+    "destination_account": "http://ledger3.example/accounts/bob",
+    "destination_amount": "100",
+    "destination_expiry_duration": 1000
+  },
+
+  "quoteArgs12": {
+    "source_ledger": "http://ledger1.example",
+    "destination_ledger": "http://ledger2.example",
+    "destination_account": "http://ledger2.example/accounts/trader23",
+    "destination_amount": "90",
+    "destination_expiry_duration": 2000
+  },
+
+  "quote23": {
+    "source_transfers": [{
+      "debits": [{"amount": "100"}],
+      "credits": [{
+        "account": "http://ledger2.example/accounts/trader23",
+        "amount": "90"
+      }],
+      "expiry_duration": 2000
+    }]
+  },
+
+  "quote12": {
+    "source_transfers": [{
+      "debits": [{"amount": "90"}],
+      "credits": [{
+        "account": "http://ledger1.example/accounts/trader12",
+        "amount": "80"
+      }],
+      "expiry_duration": 3000
+    }]
+  }
+}

test/fixtures/from-source.json

@@ -0,0 +1,39 @@
+{
+  "quoteArgs12": {
+    "source_ledger": "http://ledger1.example",
+    "destination_ledger": "http://ledger2.example",
+    "source_account": "http://ledger1.example/accounts/alice",
+    "source_amount": "80",
+    "source_expiry_duration": 3000
+  },
+
+  "quoteArgs23": {
+    "source_ledger": "http://ledger2.example",
+    "destination_ledger": "http://ledger3.example",
+    "source_account": "http://ledger2.example/accounts/trader12",
+    "source_amount": "90",
+    "source_expiry_duration": 2000
+  },
+
+  "quote12": {
+    "destination_transfers": [{
+      "debits": [{
+        "account": "http://ledger2.example/accounts/trader12",
+        "amount": "90"
+      }],
+      "credits": [{"amount": "90"}],
+      "expiry_duration": 2000
+    }]
+  },
+
+  "quote23": {
+    "destination_transfers": [{
+      "debits": [{
+        "account": "http://ledger3.example/accounts/trader23",
+        "amount": "100"
+      }],
+      "credits": [{"amount": "90"}],
+      "expiry_duration": 1000
+    }]
+  }
+}