'use strict'

/**
 * 安全协议唯一使用的 canonical JSON。对象键按字典序排列，null/undefined 字段省略；
 * 非 JSON 协议值、数组空位和不确定的对象形态直接拒绝。
 */
function canonicalJson(value) {
  if (value === null) return 'null'
  if (typeof value === 'string' || typeof value === 'boolean') return JSON.stringify(value)
  if (typeof value === 'number') {
    if (!Number.isFinite(value)) throw new TypeError('Canonical JSON requires finite numbers')
    return JSON.stringify(value)
  }
  if (Array.isArray(value)) {
    for (let index = 0; index < value.length; index += 1) {
      if (!Object.prototype.hasOwnProperty.call(value, index) || value[index] === undefined) {
        throw new TypeError('Canonical JSON arrays cannot contain holes or undefined')
      }
    }
    return `[${value.map(canonicalJson).join(',')}]`
  }
  if (value && typeof value === 'object') {
    const prototype = Object.getPrototypeOf(value)
    if (prototype !== Object.prototype && prototype !== null) {
      throw new TypeError('Canonical JSON only supports plain objects')
    }
    const keys = Reflect.ownKeys(value)
    if (keys.some(key => typeof key === 'symbol')) {
      throw new TypeError('Canonical JSON does not support symbol keys')
    }
    for (const key of keys) {
      const descriptor = Object.getOwnPropertyDescriptor(value, key)
      if (!descriptor?.enumerable || !('value' in descriptor)) {
        throw new TypeError('Canonical JSON only supports enumerable data properties')
      }
    }
    return `{${keys
      .filter(key => value[key] !== null && value[key] !== undefined)
      .sort()
      .map(key => `${JSON.stringify(key)}:${canonicalJson(value[key])}`)
      .join(',')}}`
  }
  throw new TypeError(`Canonical JSON does not support ${typeof value}`)
}

module.exports = { canonicalJson }