/**
 * shared 层内部工具，不对外导出。
 *
 * HTTP / WebSocket 收到的一切都先当 unknown，再用这些收窄函数校验；
 * 直接断言会把服务端字段改名这类问题推迟到运行期某个深处才炸。
 */

/**
 * FormData / Blob（含 File）/ URLSearchParams 不是普通对象：
 * 展开或 JSON 序列化都会丢掉内容，必须原样交给 fetch（报名表导入就是被展平才丢文件）。
 */
export function isRawBody(value: unknown): value is FormData | Blob | URLSearchParams {
  if (typeof FormData !== 'undefined' && value instanceof FormData) return true
  if (typeof Blob !== 'undefined' && value instanceof Blob) return true
  if (typeof URLSearchParams !== 'undefined' && value instanceof URLSearchParams) return true
  return false
}

export function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === 'object' && value !== null && !Array.isArray(value) && !isRawBody(value)
}

export function readString(source: unknown, key: string): string | null {
  if (!isRecord(source)) return null
  const value = source[key]
  return typeof value === 'string' ? value : null
}

export function asRecord(value: unknown): Record<string, unknown> {
  return isRecord(value) ? value : {}
}

/** 依次取第一个可用值：容忍服务端把数字写成字符串（settings 表存的是文本）。 */
export function firstString(...values: unknown[]): string | null {
  for (const value of values) {
    if (typeof value === 'string') return value
  }
  return null
}

export function firstNumber(def: number, ...values: unknown[]): number {
  const found = firstNumberOrNull(...values)
  return found === null ? def : found
}

export function firstNumberOrNull(...values: unknown[]): number | null {
  for (const value of values) {
    if (typeof value === 'number' && Number.isFinite(value)) return value
    if (typeof value === 'string' && value.trim() !== '') {
      const parsed = Number(value)
      if (Number.isFinite(parsed)) return parsed
    }
  }
  return null
}

export function firstBool(def: boolean, ...values: unknown[]): boolean {
  for (const value of values) {
    if (typeof value === 'boolean') return value
    if (typeof value === 'number') return value !== 0
    if (typeof value === 'string') {
      const normalized = value.trim().toLowerCase()
      if (normalized === 'true' || normalized === '1' || normalized === 'yes' || normalized === 'on') {
        return true
      }
      if (normalized === 'false' || normalized === '0' || normalized === 'no' || normalized === 'off') {
        return false
      }
    }
  }
  return def
}

export function emptyToNull(value: string | null): string | null {
  return value === null || value.trim() === '' ? null : value
}