import {z} from 'zod'

export type JsonRpcRequest = {jsonrpc: '2.0', id?: (string | number | null) | undefined, method: 'SendMessage' | 'GetTask' | 'ListTasks' | 'CancelTask', params: {[key: string]: unknown}};

export type CreateApiA2aArgs = {'A2A-Version'?: '1.0' | undefined, body: JsonRpcRequest};

export type CreateApiA2aOptions = {baseUrl?: string | undefined, fetch?: typeof fetch | undefined};

export const jsonRpcResponse = z.object({jsonrpc: z.literal("2.0"), id: z.union([z.string(), z.number().int()]).nullable(), result: z.unknown(), error: z.object({code: z.number().int(), message: z.string(), data: z.unknown()}).optional()});

export const validateResponse = async <Output>(
  schema: {
    readonly '~standard': {
      readonly validate: (value: unknown) => ({ readonly value: Output; readonly issues?: undefined } | { readonly issues: ReadonlyArray<{ readonly message: string; readonly path?: ReadonlyArray<PropertyKey | { readonly key: PropertyKey }> | undefined }> }) | Promise<{ readonly value: Output; readonly issues?: undefined } | { readonly issues: ReadonlyArray<{ readonly message: string; readonly path?: ReadonlyArray<PropertyKey | { readonly key: PropertyKey }> | undefined }> }>
    }
  },
  value: unknown
): Promise<Output> => {
  const result = await schema['~standard'].validate(value)

  if (result.issues !== undefined) {
    const detail = result.issues
      .map(({ message, path }) =>
        path?.length
          ? `${path.map((segment) => String(typeof segment === 'object' ? segment.key : segment)).join('.')}: ${message}`
          : message
      )
      .join('; ')

    throw new Error(`Response does not match the schema: ${detail}`, { cause: { issues: result.issues } })
  }

  return result.value
};

/**
 * Send an A2A 1.0 JSON-RPC request
 * 
 * POST /a2a
 */
export const createApiA2a = async (args: CreateApiA2aArgs, options?: CreateApiA2aOptions) => {
const {baseUrl = "https://api.temp.md", fetch: fetchFn = fetch} = options ?? {}

const query = new URLSearchParams()
const headers = new Headers()
headers.set('content-type', "application/json")
headers.set('accept', "application/a2a+json")

if (args['A2A-Version'] != null) headers.set("A2A-Version", String(args['A2A-Version']))

const url = `${baseUrl.replace(/\/+$/, '')}/a2a${query.size > 0 ? `?${query}` : ''}`

const res = await fetchFn(url, {method: "POST", headers, body: JSON.stringify(args.body)})

if (!res.ok) throw new Error(`Request failed with status ${res.status}`, {cause: {status: res.status, body: await res.text()}})

return validateResponse(jsonRpcResponse, await res.json())
};