import {z} from 'zod'

export type GetApiForecastDemandTotalWeekAheadArgs = {from: string, to: string, format?: ('json' | 'xml' | 'csv') | undefined};

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

export const insightsApiModelsResponsesTransparencyWeekAheadTotalLoadPerBiddingZone = z.object({publishTime: z.string().optional(), forecastDate: z.string().optional(), forecastWeek: z.number().int().optional(), minimumPossible: z.number().optional(), maximumAvailable: z.number().optional()});

export const insightsApiModelsMetadataApiResponseSourceMetadata = z.object({datasets: z.array(z.string()).nullable().optional()});

export const insightsApiModelsResponsesResponseWithMetadata1InsightsApiModelsResponsesTransparencyWeekAheadTotalLoadPerBiddingZone = z.object({data: z.array(insightsApiModelsResponsesTransparencyWeekAheadTotalLoadPerBiddingZone).nullable().optional(), metadata: insightsApiModelsMetadataApiResponseSourceMetadata.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
};

/**
 * Week-ahead total load forecast (WATL/B0630)
 * 
 * GET /forecast/demand/total/week-ahead
 */
export const getApiForecastDemandTotalWeekAhead = async (args: GetApiForecastDemandTotalWeekAheadArgs, options?: GetApiForecastDemandTotalWeekAheadOptions) => {
const {baseUrl = "https://data.elexon.co.uk/bmrs/api/v1", fetch: fetchFn = fetch} = options ?? {}

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

if (args.from != null) query.append("from", String(args.from))
if (args.to != null) query.append("to", String(args.to))
if (args.format != null) query.append("format", String(args.format))

const url = `${baseUrl.replace(/\/+$/, '')}/forecast/demand/total/week-ahead${query.size > 0 ? `?${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(insightsApiModelsResponsesResponseWithMetadata1InsightsApiModelsResponsesTransparencyWeekAheadTotalLoadPerBiddingZone, await res.json())
};