import { WORKS_SQUARE_CONFIG } from '../api/works-config';
import { proxyAwareFetch } from '../utils/proxy-fetch';
import { getValidWorksSquareAccessToken } from './works-square-session';
import {
  LEARNING_MATERIAL_MAX_FILE_BYTES,
  LEARNING_MATERIAL_MAX_FILES,
  LEARNING_MATERIAL_MAX_TOTAL_BYTES,
  type LearningGeneration,
  type LearningGenerationMaterialUpload,
  type LearningGenerationOptions,
  type LearningGenerationUploadRequest,
} from '../../shared/learning';

type Dependencies = {
  fetchImpl?: typeof fetch;
  getAccessToken?: typeof getValidWorksSquareAccessToken;
  apiBaseUrl?: string;
};

function record(value: unknown): Record<string, unknown> {
  return value && typeof value === 'object' && !Array.isArray(value)
    ? value as Record<string, unknown>
    : {};
}

function errorMessage(payload: unknown, fallback: string): string {
  const root = record(payload);
  const detail = root.detail;
  if (typeof detail === 'string' && detail.trim()) return detail;
  const detailRecord = record(detail);
  if (typeof detailRecord.message === 'string' && detailRecord.message.trim()) {
    return detailRecord.message;
  }
  if (typeof root.error === 'string' && root.error.trim()) return root.error;
  return fallback;
}

function validateOptions(value: LearningGenerationOptions): LearningGenerationOptions {
  const requirement = typeof value?.requirement === 'string' ? value.requirement.trim() : '';
  if (!requirement) throw new Error('请填写课程需求');
  const booleanKeys = [
    'enableWebSearch',
    'enableImageGeneration',
    'enableVideoGeneration',
    'enableTTS',
    'interactiveMode',
    'taskEngineMode',
  ] as const;
  for (const key of booleanKeys) {
    if (typeof value[key] !== 'boolean') throw new Error('课程生成选项无效');
  }
  return {
    requirement,
    enableWebSearch: value.enableWebSearch,
    enableImageGeneration: value.enableImageGeneration,
    enableVideoGeneration: value.enableVideoGeneration,
    enableTTS: value.enableTTS,
    interactiveMode: value.interactiveMode,
    taskEngineMode: value.taskEngineMode,
  };
}

function safeFileName(value: string): string {
  const normalized = value.replace(/[\\/\0\r\n]/g, '_').trim().slice(0, 255);
  return normalized || 'material';
}

function materialBytes(material: LearningGenerationMaterialUpload): Uint8Array {
  return material.bytes instanceof Uint8Array
    ? new Uint8Array(material.bytes)
    : new Uint8Array(material.bytes as ArrayBuffer);
}

function validateMaterials(materials: LearningGenerationMaterialUpload[]): Array<{
  material: LearningGenerationMaterialUpload;
  bytes: Uint8Array;
}> {
  if (!Array.isArray(materials)) throw new Error('课程材料格式无效');
  if (materials.length > LEARNING_MATERIAL_MAX_FILES) {
    throw new Error(`课程材料最多 ${LEARNING_MATERIAL_MAX_FILES} 个`);
  }
  let totalBytes = 0;
  const validated = materials
    .map((material) => ({ material, bytes: materialBytes(material) }))
    .sort((left, right) => left.material.order - right.material.order);
  for (const { material, bytes } of validated) {
    if (!bytes.byteLength || bytes.byteLength !== material.size) throw new Error('课程材料内容不完整');
    if (bytes.byteLength > LEARNING_MATERIAL_MAX_FILE_BYTES) throw new Error('单个课程材料不能超过 50 MiB');
    totalBytes += bytes.byteLength;
  }
  if (totalBytes > LEARNING_MATERIAL_MAX_TOTAL_BYTES) throw new Error('课程材料总计不能超过 150 MiB');
  return validated;
}

export function createLearningGenerationClient(dependencies: Dependencies = {}) {
  const fetchImpl = dependencies.fetchImpl ?? proxyAwareFetch;
  const getAccessToken = dependencies.getAccessToken ?? getValidWorksSquareAccessToken;
  const apiBaseUrl = (dependencies.apiBaseUrl ?? WORKS_SQUARE_CONFIG.apiBaseUrl).replace(/\/+$/, '');

  async function start(input: LearningGenerationUploadRequest): Promise<LearningGeneration> {
    const options = validateOptions(input.options);
    const materials = validateMaterials(input.materials);
    const token = await getAccessToken({ fetchImpl });
    if (!token) throw new Error('请先登录');

    const form = materials.length > 0 ? new FormData() : null;
    if (form) {
      form.set('options', JSON.stringify(options));
      for (const { material, bytes } of materials) {
        const blobBytes = new Uint8Array(bytes.byteLength);
        blobBytes.set(bytes);
        form.append(
          'materials',
          new Blob([blobBytes.buffer], { type: material.mimeType || 'application/octet-stream' }),
          safeFileName(material.name),
        );
      }
    }
    const request = (accessToken: string) => fetchImpl(`${apiBaseUrl}/api/learning/generations`, {
      method: 'POST',
      headers: {
        Accept: 'application/json',
        Authorization: `Bearer ${accessToken}`,
        ...(form ? {} : { 'Content-Type': 'application/json' }),
      },
      body: form ?? JSON.stringify(options),
      redirect: 'manual',
    });
    let response = await request(token);
    if (response.status === 401) {
      await response.body?.cancel().catch(() => undefined);
      const refreshed = await getAccessToken({ fetchImpl, forceRefresh: true });
      if (refreshed) response = await request(refreshed);
    }
    const payload = await response.json().catch(() => null);
    if (!response.ok || !payload) {
      throw new Error(errorMessage(payload, `课程任务创建失败（HTTP ${response.status || 502}）`));
    }
    const generation = record(payload);
    if (typeof generation.jobId !== 'string' || !generation.jobId) {
      throw new Error('学习服务没有返回任务编号');
    }
    return generation as LearningGeneration;
  }

  return { start };
}