Add TypeScript domain and contract bindings

web/src/domain/fingerprint.ts

@@ -0,0 +1,77 @@
+export type JsonValue =
+  null | boolean | number | string | JsonValue[] | { [key: string]: JsonValue }
+
+export function jsonValue(value: unknown): JsonValue {
+  if (value === null || typeof value === 'boolean') return value
+  if (typeof value === 'string') {
+    assertValidUnicode(value)
+    return value
+  }
+  if (typeof value === 'number') {
+    if (!Number.isFinite(value))
+      throw new Error('canonical JSON does not permit non-finite numbers')
+    return value
+  }
+  if (Array.isArray(value)) return value.map(jsonValue)
+  if (typeof value === 'object') {
+    const prototype = Object.getPrototypeOf(value)
+    if (prototype !== Object.prototype && prototype !== null)
+      throw new Error('value is not JSON')
+    return Object.fromEntries(
+      Object.entries(value).map(([key, member]) => {
+        assertValidUnicode(key)
+        return [key, jsonValue(member)]
+      }),
+    )
+  }
+  throw new Error('value is not JSON')
+}
+
+export function canonicalJson(value: JsonValue): string {
+  if (
+    value === null ||
+    typeof value === 'boolean' ||
+    typeof value === 'string'
+  ) {
+    if (typeof value === 'string') assertValidUnicode(value)
+    return JSON.stringify(value)
+  }
+  if (typeof value === 'number') {
+    if (!Number.isFinite(value))
+      throw new Error('canonical JSON does not permit non-finite numbers')
+    return JSON.stringify(value)
+  }
+  if (Array.isArray(value)) return `[${value.map(canonicalJson).join(',')}]`
+  return `{${Object.keys(value)
+    .map((key) => {
+      assertValidUnicode(key)
+      return key
+    })
+    .sort()
+    .map((key) => `${JSON.stringify(key)}:${canonicalJson(value[key])}`)
+    .join(',')}}`
+}
+
+function assertValidUnicode(value: string): void {
+  for (let index = 0; index < value.length; index += 1) {
+    const codeUnit = value.charCodeAt(index)
+    if (codeUnit >= 0xd800 && codeUnit <= 0xdbff) {
+      const next = value.charCodeAt(index + 1)
+      if (index + 1 >= value.length || next < 0xdc00 || next > 0xdfff)
+        throw new Error('canonical JSON does not permit lone surrogates')
+      index += 1
+    } else if (codeUnit >= 0xdc00 && codeUnit <= 0xdfff) {
+      throw new Error('canonical JSON does not permit lone surrogates')
+    }
+  }
+}
+
+export async function requestFingerprint(value: JsonValue): Promise<string> {
+  const digest = await crypto.subtle.digest(
+    'SHA-256',
+    new TextEncoder().encode(canonicalJson(value)),
+  )
+  return Array.from(new Uint8Array(digest), (byte) =>
+    byte.toString(16).padStart(2, '0'),
+  ).join('')
+}