Put everything in src directories

packages/util/src/Zaps.ts

@@ -0,0 +1,126 @@
+import {hexToBech32} from '@welshman/lib'
+import type {TrustedEvent} from './Events'
+import {Tags} from "./Tags"
+
+const DIVISORS = {
+  m: BigInt(1e3),
+  u: BigInt(1e6),
+  n: BigInt(1e9),
+  p: BigInt(1e12),
+}
+
+const MAX_MILLISATS = BigInt("2100000000000000000")
+
+const MILLISATS_PER_BTC = BigInt(1e11)
+
+export const hrpToMillisat = (hrpString: string) => {
+  let divisor, value
+  if (hrpString.slice(-1).match(/^[munp]$/)) {
+    divisor = hrpString.slice(-1)
+    value = hrpString.slice(0, -1)
+  } else if (hrpString.slice(-1).match(/^[^munp0-9]$/)) {
+    throw new Error("Not a valid multiplier for the amount")
+  } else {
+    value = hrpString
+  }
+
+  if (!value.match(/^\d+$/)) throw new Error("Not a valid human readable amount")
+
+  const valueBN = BigInt(value)
+
+  const millisatoshisBN = divisor
+    ? (valueBN * MILLISATS_PER_BTC) / (DIVISORS as any)[divisor]
+    : valueBN * MILLISATS_PER_BTC
+
+  if (
+    (divisor === "p" && !(valueBN % BigInt(10) === BigInt(0))) ||
+    millisatoshisBN > MAX_MILLISATS
+  ) {
+    throw new Error("Amount is outside of valid range")
+  }
+
+  return millisatoshisBN
+}
+
+export const getInvoiceAmount = (bolt11: string) => {
+  const hrp = bolt11.match(/lnbc(\d+\w)/)
+  const bn = hrpToMillisat(hrp![1])
+  return Number(bn)
+}
+
+export const getLnUrl = (address: string) => {
+  if (address.startsWith("lnurl1")) {
+    return address
+  }
+
+  // If it's a regular url, just encode it
+  if (address.includes("://")) {
+    return hexToBech32("lnurl", address)
+  }
+
+  // Try to parse it as a lud16 address
+  if (address.includes("@")) {
+    const [name, domain] = address.split("@")
+
+    if (domain && name) {
+      return hexToBech32("lnurl", `https://${domain}/.well-known/lnurlp/${name}`)
+    }
+  }
+
+  return null
+}
+
+export type Zapper = {
+  lnurl: string
+  pubkey: string,
+  callback: string
+  minSendable: number
+  maxSendable: number
+  nostrPubkey: string
+  allowsNostr: boolean
+}
+
+export type Zap = {
+  request: TrustedEvent
+  response: TrustedEvent,
+  invoiceAmount: number
+}
+
+export const zapFromEvent = (response: TrustedEvent, zapper: Zapper) => {
+  const responseMeta = Tags.fromEvent(response).asObject()
+
+  let zap: Zap
+  try {
+    zap = {
+      response,
+      invoiceAmount: getInvoiceAmount(responseMeta.bolt11),
+      request: JSON.parse(responseMeta.description),
+    }
+  } catch (e) {
+    return null
+  }
+
+  // Don't count zaps that the user sent himself
+  if (zap.request.pubkey === zapper.pubkey) {
+    return null
+  }
+
+  const {amount, lnurl} = Tags.fromEvent(zap.request).asObject()
+
+  // Verify that the zapper actually sent the requested amount (if it was supplied)
+  if (amount && parseInt(amount) !== zap.invoiceAmount) {
+    return null
+  }
+
+  // If the sending client provided an lnurl tag, verify that too
+  if (lnurl && lnurl !== zapper.lnurl) {
+    return null
+  }
+
+  // Verify that the request actually came from the recipient's zapper
+  if (zap.response.pubkey !== zapper.nostrPubkey) {
+    return null
+  }
+
+  return zap
+}