handle encoding/decoding spontpays

services/gunDB/contact-api/schema.js

@@ -1,6 +1,11 @@
 /**
  * @format
  */
+const logger = require('winston')
+const isFinite = require('lodash/isFinite')
+const isNumber = require('lodash/isNumber')
+const isNaN = require('lodash/isNaN')
+
 /**
  * @typedef {object} HandshakeRequest
  * @prop {string} from Public key of the requestor.
@@ -410,3 +415,105 @@ exports.isOrderResponse = o => {
 
   return obj.type === 'err' || obj.type === 'invoice'
 }
+
+/**
+ * @typedef {import('./schema-types').EncSpontPayment} EncSpontPayment
+ */
+
+const ENC_SPONT_PAYMENT_PREFIX = '$$__SHOCKWALLET__SPONT__PAYMENT__'
+
+/**
+ * @param {string} s
+ * @returns {s is EncSpontPayment}
+ */
+const isEncodedSpontPayment = s => s.indexOf(ENC_SPONT_PAYMENT_PREFIX) === 0
+
+exports.isEncodedSpontPayment = isEncodedSpontPayment
+
+/**
+ * @typedef {object} SpontaneousPayment
+ * @prop {number} amt
+ * @prop {string} memo
+ * @prop {string} preimage
+ */
+
+/**
+ *
+ * @param {EncSpontPayment} sp
+ * @throws {Error} If decoding fails.
+ * @returns {SpontaneousPayment}
+ */
+exports.decodeSpontPayment = sp => {
+  try {
+    const [preimage, amtStr, memo] = sp
+      .slice(ENC_SPONT_PAYMENT_PREFIX.length)
+      .split('__')
+
+    if (typeof preimage !== 'string') {
+      throw new TypeError('Could not parse preimage')
+    }
+
+    if (typeof amtStr !== 'string') {
+      throw new TypeError('Could not parse amt')
+    }
+
+    if (typeof memo !== 'string') {
+      throw new TypeError('Could not parse memo')
+    }
+
+    const amt = Number(amtStr)
+
+    if (!isNumber(amt)) {
+      throw new TypeError(`Could parse amount as a number, not a number?`)
+    }
+
+    if (isNaN(amt)) {
+      throw new TypeError(`Could not amount as a number, got NaN.`)
+    }
+
+    if (!isFinite(amt)) {
+      throw new TypeError(
+        `Amount was correctly parsed, but got a non finite number.`
+      )
+    }
+
+    return {
+      amt,
+      memo,
+      preimage
+    }
+  } catch (err) {
+    logger.debug(`Encoded spontaneous payment: ${sp}`)
+    logger.error(err)
+    throw err
+  }
+}
+
+/**
+ *
+ * @param {number} amt
+ * @param {string} memo
+ * @param {string} preimage
+ * @returns {EncSpontPayment}
+ */
+exports.encodeSpontaneousPayment = (amt, memo, preimage) => {
+  if (amt <= 0) {
+    throw new RangeError('Amt must be greater than zero')
+  }
+
+  if (memo.length < 1) {
+    throw new TypeError('Memo must be populated')
+  }
+
+  if (preimage.length < 1) {
+    throw new TypeError('preimage must be populated')
+  }
+
+  const enc = `${ENC_SPONT_PAYMENT_PREFIX}__${amt}__${memo}__${preimage}`
+
+  if (isEncodedSpontPayment(enc)) {
+    return enc
+  }
+
+  throw new Error('isEncodedSpontPayment(enc) false')
+}