import {z} from 'zod'

export type GetApiMetricsArgs = {search?: string | undefined, category?: ('Cases' | 'Testing' | 'Healthcare' | 'Deaths' | 'Vaccinations') | undefined, tags?: string | undefined, exact?: boolean | undefined, Accept: 'application/json'};

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

export const metrics = z.array(z.object({last_update: z.string(), metric: z.string(), metric_name: z.string(), category: z.string(), deprecated: z.string().nullable().optional(), doc_last_modified: z.string().nullable().optional(), tags: z.array(z.string())}));

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
};

/**
 * Metric search
 * 
 * GET /metrics
 */
export const getApiMetrics = async (args: GetApiMetricsArgs, options?: GetApiMetricsOptions) => {
const {baseUrl = "https://api.coronavirus.data.gov.uk/generic", fetch: fetchFn = fetch} = options ?? {}

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

if (args.search != null) query.append("search", String(args.search))
if (args.category != null) query.append("category", String(args.category))
if (args.tags != null) query.append("tags", String(args.tags))
if (args.exact != null) query.append("exact", String(args.exact))
if (args.Accept != null) headers.set("Accept", String(args.Accept))

const url = `${baseUrl.replace(/\/+$/, '')}/metrics${query.size > 0 ? `?${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(metrics, await res.json())
};