import {z} from 'zod'

export type GetApiEloCalculatorArgs = {yourRating: number, opponentRating: number, result: 'win' | 'draw' | 'loss', system?: ('fide' | 'chesscom' | 'lichess') | undefined, kFactor?: number | undefined};

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

export const eloResponse = z.object({yourRating: z.number().int().optional(), opponentRating: z.number().int().optional(), result: z.enum(["win", "draw", "loss"]).optional(), system: z.enum(["fide", "chesscom", "lichess"]).optional(), kFactor: z.number().int().optional(), expectedScore: z.number().optional(), newRating: z.number().int().optional(), change: z.number().int().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
};

/**
 * Compute an Elo rating change for a single game
 * 
 * GET /elo-calculator
 */
export const getApiEloCalculator = async (args: GetApiEloCalculatorArgs, options?: GetApiEloCalculatorOptions) => {
const {baseUrl = "https://www.chessigma.com/public-api/v1", fetch: fetchFn = fetch} = options ?? {}

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

if (args.yourRating != null) query.append("yourRating", String(args.yourRating))
if (args.opponentRating != null) query.append("opponentRating", String(args.opponentRating))
if (args.result != null) query.append("result", String(args.result))
if (args.system != null) query.append("system", String(args.system))
if (args.kFactor != null) query.append("kFactor", String(args.kFactor))

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