import type { H3Event } from 'h3'
import type { output, ZodObject, ZodType } from 'zod'

async function readRawJson(event: H3Event): Promise<Record<string, unknown>> {
  const raw = await readRawBody(event, 'utf8')
  if (!raw) return {}
  try { return JSON.parse(raw) }
  catch { throw createError({ statusCode: 400, message: '请求体不是合法的 JSON' }) }
}

function validationError(issues: { path: PropertyKey[], message: string }[]) {
  const first = issues[0]
  return createError({ statusCode: 400, message: `参数错误：${first?.path.map(String).join('.') || ''} ${first?.message || ''}`.trim() })
}

export async function readJson<T>(event: H3Event, schema: ZodType<T>): Promise<T> {
  const parsed = schema.safeParse(await readRawJson(event))
  if (!parsed.success) throw validationError(parsed.error.issues)
  return parsed.data
}

/**
 * 读取部分更新的请求体：只保留请求中实际出现的字段
 * （zod 4 中 optional 包裹的 default 仍会生效，直接 partial() 会把缺省字段覆盖成默认值）
 */
export async function readPatch<S extends ZodObject>(event: H3Event, schema: S): Promise<Partial<output<S>>> {
  const data = await readRawJson(event)
  const parsed = schema.partial().safeParse(data)
  if (!parsed.success) throw validationError(parsed.error.issues)
  const result = parsed.data as Record<string, unknown>
  const out: Record<string, unknown> = {}
  for (const k of Object.keys(data)) {
    if (k in result) out[k] = result[k]
  }
  return out as Partial<output<S>>
}

export function param(event: H3Event, name = 'id') {
  const v = getRouterParam(event, name)
  if (!v) throw createError({ statusCode: 400, message: `缺少参数 ${name}` })
  return v
}