import type { ImportStatementResponse } from '@family-budget/shared';
import { api } from './client';

export async function importStatement(
  file: File,
): Promise<ImportStatementResponse> {
  const formData = new FormData();
  formData.append('file', file);
  return api.postFormData<ImportStatementResponse>(
    '/api/import/statement',
    formData,
  );
}

export interface SseProgressEvent {
  stage: 'pdf' | 'llm' | 'import';
  progress: number;
  message: string;
}

export interface SseDoneEvent {
  stage: 'done';
  progress: 100;
  result: ImportStatementResponse;
}

export interface SseErrorEvent {
  stage: 'error';
  message: string;
}

export type SseEvent = SseProgressEvent | SseDoneEvent | SseErrorEvent;

export async function importStatementStream(
  file: File,
  onEvent: (event: SseEvent) => void,
): Promise<void> {
  const formData = new FormData();
  formData.append('file', file);

  const res = await fetch('/api/import/statement', {
    method: 'POST',
    body: formData,
    credentials: 'include',
  });

  if (!res.ok) {
    let msg = 'Ошибка импорта';
    try {
      const body = await res.json();
      if (body.message) msg = body.message;
    } catch { /* use default */ }
    onEvent({ stage: 'error', message: msg });
    return;
  }

  const reader = res.body?.getReader();
  if (!reader) {
    onEvent({ stage: 'error', message: 'Streaming не поддерживается' });
    return;
  }

  const decoder = new TextDecoder();
  let buffer = '';

  while (true) {
    const { done, value } = await reader.read();
    if (done) break;

    buffer += decoder.decode(value, { stream: true });

    const lines = buffer.split('\n');
    buffer = lines.pop() ?? '';

    for (const line of lines) {
      const trimmed = line.trim();
      if (!trimmed.startsWith('data: ')) continue;
      try {
        const parsed = JSON.parse(trimmed.slice(6)) as SseEvent;
        onEvent(parsed);
      } catch { /* skip malformed lines */ }
    }
  }
}