import {
  AllObjectsResponse,
  BatchResponse,
  ClientProfile,
  ColumnMappingSuggestion,
  ExportFormat,
  ExportFormatResponse,
  LineCheckRequest,
  LineCheckResponse,
  MakeRuleRequest,
  ReferenceDataStatus,
  ReviewQuery,
  ReviewRow,
  ReviewTableResponse,
  RowReviewRequest,
  RuleResponse,
  UploadOptions,
} from './types';

export const API_BASE_URL = (
  process.env.REACT_APP_API_URL ?? 'http://127.0.0.1:8000'
).replace(/\/$/, '');

/** The envelope every endpoint returns — `cbh/core/wrappers.py`. */
interface CbhResponseWrapper<T> {
  data: T | null;
  successful: boolean;
  error: { message: string } | null;
}

export class ApiError extends Error {
  readonly status: number;

  constructor(message: string, status: number) {
    super(message);
    this.name = 'ApiError';
    this.status = status;
  }
}

const unreachable = () =>
  new ApiError(
    `Cannot reach the check service at ${API_BASE_URL}. Is the backend running?`,
    0
  );

async function send(path: string, init?: RequestInit): Promise<Response> {
  // A FormData body must set its own multipart boundary, so the JSON header is
  // only added for the string bodies that need it.
  const headers =
    typeof init?.body === 'string'
      ? { 'Content-Type': 'application/json', ...(init?.headers ?? {}) }
      : init?.headers;

  try {
    return await fetch(`${API_BASE_URL}${path}`, { ...init, headers });
  } catch {
    throw unreachable();
  }
}

async function request<T>(path: string, init?: RequestInit): Promise<T> {
  const response = await send(path, init);

  let body: CbhResponseWrapper<T> | null = null;
  try {
    body = (await response.json()) as CbhResponseWrapper<T>;
  } catch {
    body = null;
  }

  if (!response.ok || body?.successful === false) {
    throw new ApiError(
      body?.error?.message ?? `The check service returned status ${response.status}.`,
      response.status
    );
  }

  if (body === null || body.data === null || body.data === undefined) {
    throw new ApiError('The check service returned an empty response.', response.status);
  }

  return body.data;
}

export function checkLine(payload: LineCheckRequest): Promise<LineCheckResponse> {
  return request<LineCheckResponse>('/api/linecheck/line', {
    method: 'POST',
    body: JSON.stringify(payload),
  });
}

export function getReferenceStatus(): Promise<ReferenceDataStatus> {
  return request<ReferenceDataStatus>('/api/taric/status');
}

export function listClientProfiles(): Promise<AllObjectsResponse<ClientProfile>> {
  return request<AllObjectsResponse<ClientProfile>>('/api/client?pageSize=100');
}

/**
 * The header row is the profile's, not row 1. A Softpak pack carries five rows
 * of declaration metadata above its column headers, and reading row 1 reports
 * every required field as missing on a file that processes perfectly.
 */
export function suggestMapping(
  file: File,
  headerRow: number
): Promise<ColumnMappingSuggestion> {
  const form = new FormData();
  form.append('file', file);
  return request<ColumnMappingSuggestion>(
    `/api/client/suggest-mapping?headerRow=${headerRow}`,
    { method: 'POST', body: form }
  );
}

export function uploadBatch(options: UploadOptions): Promise<BatchResponse> {
  const form = new FormData();
  form.append('clientProfileId', options.clientProfileId);
  form.append('file', options.file);
  if (options.name) form.append('name', options.name);
  if (options.checkDate) form.append('checkDate', options.checkDate);
  if (options.destinationCountry) form.append('destinationCountry', options.destinationCountry);
  if (options.direction !== undefined) form.append('direction', String(options.direction));
  if (options.shipmentReference) form.append('shipmentReference', options.shipmentReference);

  return request<BatchResponse>('/api/batch/upload', { method: 'POST', body: form });
}

export function listBatches(): Promise<AllObjectsResponse<BatchResponse>> {
  return request<AllObjectsResponse<BatchResponse>>('/api/batch?pageSize=25');
}

export function getReviewTable(
  batchId: string,
  query: ReviewQuery = {}
): Promise<ReviewTableResponse> {
  const params = new URLSearchParams();
  if (query.needsReviewOnly) params.set('needsReviewOnly', 'true');
  if (query.confidence !== undefined) params.set('confidence', String(query.confidence));
  params.set('pageSize', String(query.pageSize ?? 100));
  params.set('pageIndex', String(query.pageIndex ?? 0));

  return request<ReviewTableResponse>(`/api/batch/${batchId}/review?${params}`);
}

export function reviewRow(
  batchId: string,
  rowIndex: number,
  payload: RowReviewRequest
): Promise<ReviewRow> {
  return request<ReviewRow>(`/api/batch/${batchId}/rows/${rowIndex}`, {
    method: 'PATCH',
    body: JSON.stringify(payload),
  });
}

export function makeRuleFromRow(
  batchId: string,
  rowIndex: number,
  payload: MakeRuleRequest
): Promise<RuleResponse> {
  return request<RuleResponse>(`/api/batch/${batchId}/rows/${rowIndex}/make-rule`, {
    method: 'POST',
    body: JSON.stringify(payload),
  });
}

export function recheckBatch(batchId: string): Promise<BatchResponse> {
  return request<BatchResponse>(`/api/batch/${batchId}/recheck`, { method: 'POST' });
}

export function startReview(batchId: string): Promise<BatchResponse> {
  return request<BatchResponse>(`/api/batch/${batchId}/review/start`, { method: 'POST' });
}

export function finishReview(batchId: string): Promise<BatchResponse> {
  return request<BatchResponse>(`/api/batch/${batchId}/review/finish`, { method: 'POST' });
}

export function listExportFormats(
  clientProfileId?: string
): Promise<ExportFormatResponse[]> {
  const query = clientProfileId
    ? `?clientProfileId=${encodeURIComponent(clientProfileId)}`
    : '';
  return request<ExportFormatResponse[]>(`/api/batch/export-formats${query}`);
}

/**
 * The export is a file, not an envelope — but a refused format still answers
 * with one (501 plus the reason the layout was not guessed at), so a failure
 * is read as JSON and surfaced as its own message.
 */
export async function downloadExport(
  batchId: string,
  format: ExportFormat
): Promise<{ blob: Blob; fileName: string }> {
  const response = await send(`/api/batch/${batchId}/export?format=${format}`);

  if (!response.ok) {
    let message = `The export failed with status ${response.status}.`;
    try {
      const body = (await response.json()) as CbhResponseWrapper<unknown>;
      if (body?.error?.message) message = body.error.message;
    } catch {
      /* the body was not an envelope; the status message stands */
    }
    throw new ApiError(message, response.status);
  }

  const disposition = response.headers.get('content-disposition') ?? '';
  const match = /filename\*?=(?:UTF-8'')?"?([^";]+)"?/i.exec(disposition);

  return {
    blob: await response.blob(),
    fileName: match ? decodeURIComponent(match[1]) : `shipment_${batchId}.xlsx`,
  };
}