import {z} from 'zod'

export type GetApiApiAnalyticsChurnCohortsArgs = {months?: number | undefined};

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

export const cohortRow = z.object({month: z.string(), totalCustomers: z.number(), retentionPercentages: z.array(z.number())});

export const churnCohortsResponse = z.object({months: z.array(z.string()), cohorts: z.array(cohortRow)});

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
};

/**
 * Get churn cohort analysis
 * 
 * GET /api/analytics/churn-cohorts
 */
export const getApiApiAnalyticsChurnCohorts = async (args: GetApiApiAnalyticsChurnCohortsArgs, options?: GetApiApiAnalyticsChurnCohortsOptions) => {
const {baseUrl = "https://api.novabilling.one", fetch: fetchFn = fetch, apiKey} = options ?? {}

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

if (args.months != null) query.append("months", String(args.months))
if (apiKey !== undefined) headers.set("Authorization", apiKey)

const url = `${baseUrl.replace(/\/+$/, '')}/api/analytics/churn-cohorts${query.size > 0 ? `?${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(churnCohortsResponse, await res.json())
};