import {z} from 'zod'

export type GetApiDataArgs = {areaType: 'overview' | 'nation' | 'region' | 'nhsRegion' | 'utla' | 'ltla' | 'nhsTrust' | 'msoa', metric: Array<string>, areaCode?: string | undefined, format: 'json' | 'jsonl' | 'csv' | 'xml', release?: string | undefined};

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

export const data = z.object({body: z.array(z.object({areaType: z.string(), areaCode: z.string(), areaName: z.string(), date: z.string()})).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
};

/**
 * Data
 * 
 * GET /data
 */
export const getApiData = async (args: GetApiDataArgs, options?: GetApiDataOptions) => {
const {baseUrl = "https://api.coronavirus.data.gov.uk/v2", fetch: fetchFn = fetch} = options ?? {}

const query = new URLSearchParams()
const headers = new Headers()
headers.set('accept', "application/json")

if (args.areaType != null) query.append("areaType", String(args.areaType))
for (const item of args.metric ?? []) query.append("metric", String(item))
if (args.areaCode != null) query.append("areaCode", String(args.areaCode))
if (args.format != null) query.append("format", String(args.format))
if (args.release != null) query.append("release", String(args.release))

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

const res = await fetchFn(url, {method: "GET", headers})

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

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