import crypto from 'node:crypto';

export const FEEDBACK_TYPES = new Set(['bug', 'feature', 'other']);
export const FEEDBACK_STATUSES = new Set(['pending', 'reviewing', 'resolved', 'closed']);
export const FEEDBACK_MAX_IMAGES = 5;
export const FEEDBACK_MAX_TITLE = 120;
export const FEEDBACK_MAX_DESCRIPTION = 5000;
export const FEEDBACK_MAX_CONTACT = 120;
export const FEEDBACK_MAX_IMAGE_BYTES = Math.floor(1.5 * 1024 * 1024);

function feedbackError(message, code = 'invalid_input') {
  const err = new Error(message);
  err.code = code;
  return err;
}

function normalizeType(value) {
  const type = String(value ?? '').trim().toLowerCase();
  if (!FEEDBACK_TYPES.has(type)) {
    throw feedbackError('请选择反馈类型');
  }
  return type;
}

function normalizeImages(images) {
  if (!Array.isArray(images)) return [];
  if (images.length > FEEDBACK_MAX_IMAGES) {
    throw feedbackError(`最多上传 ${FEEDBACK_MAX_IMAGES} 张图片`);
  }

  return images.map((item, index) => {
    const mimeType = String(item?.mimeType ?? item?.mime_type ?? '').trim().toLowerCase();
    const dataBase64 = String(item?.dataBase64 ?? item?.data_base64 ?? '').trim();
    const filename = String(item?.filename ?? item?.name ?? `screenshot-${index + 1}.jpg`).trim();

    if (!mimeType.startsWith('image/')) {
      throw feedbackError('仅支持图片附件');
    }
    if (!dataBase64) {
      throw feedbackError('图片数据无效');
    }

    let buffer;
    try {
      buffer = Buffer.from(dataBase64, 'base64');
    } catch {
      throw feedbackError('图片数据无效');
    }
    if (!buffer.length) {
      throw feedbackError('图片数据无效');
    }
    if (buffer.length > FEEDBACK_MAX_IMAGE_BYTES) {
      throw feedbackError('单张图片不能超过 1.5MB');
    }

    return {
      filename: filename.slice(0, 120),
      mimeType,
      sizeBytes: buffer.length,
      dataBase64,
    };
  });
}

function normalizeContext(context) {
  if (!context || typeof context !== 'object') return {};
  const pageUrl = String(context.pageUrl ?? context.page_url ?? '').trim().slice(0, 500);
  const pagePath = String(context.pagePath ?? context.page_path ?? '').trim().slice(0, 300);
  const userAgent = String(context.userAgent ?? context.user_agent ?? '').trim().slice(0, 500);
  const viewport = String(context.viewport ?? '').trim().slice(0, 64);
  const sessionId = String(context.sessionId ?? context.session_id ?? '').trim().slice(0, 128);
  const appVersion = String(context.appVersion ?? context.app_version ?? '').trim().slice(0, 64);

  const normalized = {};
  if (pageUrl) normalized.pageUrl = pageUrl;
  if (pagePath) normalized.pagePath = pagePath;
  if (userAgent) normalized.userAgent = userAgent;
  if (viewport) normalized.viewport = viewport;
  if (sessionId) normalized.sessionId = sessionId;
  if (appVersion) normalized.appVersion = appVersion;
  return normalized;
}

function rowToFeedback(row, { includeImages = true, includeContact = true } = {}) {
  if (!row) return null;
  let images = [];
  let context = {};
  try {
    images = row.images_json ? JSON.parse(row.images_json) : [];
  } catch {
    images = [];
  }
  try {
    context = row.context_json ? JSON.parse(row.context_json) : {};
  } catch {
    context = {};
  }
  const item = {
    id: row.id,
    userId: row.user_id,
    type: row.type,
    title: row.title,
    description: row.description,
    status: row.status,
    context,
    createdAt: Number(row.created_at),
    updatedAt: Number(row.updated_at),
    submitterDisplayName: row.submitter_display_name ?? null,
    imageCount: images.length,
  };
  if (includeContact) {
    item.contact = row.contact ?? null;
  }
  if (includeImages) {
    item.images = images;
  }
  return item;
}

export function createFeedbackService(pool) {
  return {
    async submit(userId, input = {}) {
      const type = normalizeType(input.type);
      const title = String(input.title ?? '').trim();
      const description = String(input.description ?? '').trim();
      const contact = String(input.contact ?? '').trim().slice(0, FEEDBACK_MAX_CONTACT);

      if (!title) throw feedbackError('请填写标题');
      if (title.length > FEEDBACK_MAX_TITLE) throw feedbackError(`标题不能超过 ${FEEDBACK_MAX_TITLE} 字`);
      if (!description) throw feedbackError('请填写详细描述');
      if (description.length > FEEDBACK_MAX_DESCRIPTION) {
        throw feedbackError(`描述不能超过 ${FEEDBACK_MAX_DESCRIPTION} 字`);
      }

      const images = normalizeImages(input.images);
      const context = normalizeContext(input.context);
      const now = Date.now();
      const id = crypto.randomUUID();

      await pool.query(
        `INSERT INTO h5_user_feedback
         (id, user_id, type, title, description, contact, status, images_json, context_json, created_at, updated_at)
         VALUES (?, ?, ?, ?, ?, ?, 'pending', ?, ?, ?, ?)`,
        [
          id,
          userId,
          type,
          title,
          description,
          contact || null,
          JSON.stringify(images),
          JSON.stringify(context),
          now,
          now,
        ],
      );

      return {
        id,
        type,
        title,
        status: 'pending',
        createdAt: now,
      };
    },

    async listForUser(userId, { limit = 20 } = {}) {
      const safeLimit = Math.min(Math.max(Number(limit) || 20, 1), 50);
      const [rows] = await pool.query(
        `SELECT f.id, f.user_id, f.type, f.title, f.description, f.contact, f.status,
                f.images_json, f.context_json, f.created_at, f.updated_at,
                u.display_name AS submitter_display_name
         FROM h5_user_feedback f
         JOIN h5_users u ON u.id = f.user_id
         WHERE f.user_id = ?
         ORDER BY f.created_at DESC
         LIMIT ?`,
        [userId, safeLimit],
      );
      return rows.map((row) => rowToFeedback(row));
    },

    async listAll({ page = 1, limit = 10 } = {}) {
      const safeLimit = Math.min(Math.max(Number(limit) || 10, 1), 10);
      const safePage = Math.max(Number(page) || 1, 1);
      const offset = (safePage - 1) * safeLimit;

      const [[countRow]] = await pool.query(`SELECT COUNT(*) AS total FROM h5_user_feedback`);
      const total = Number(countRow?.total ?? 0);
      const totalPages = total === 0 ? 0 : Math.ceil(total / safeLimit);

      const [rows] = await pool.query(
        `SELECT f.id, f.user_id, f.type, f.title, f.description, f.status,
                f.images_json, f.context_json, f.created_at, f.updated_at,
                u.display_name AS submitter_display_name
         FROM h5_user_feedback f
         JOIN h5_users u ON u.id = f.user_id
         ORDER BY f.created_at DESC
         LIMIT ? OFFSET ?`,
        [safeLimit, offset],
      );

      return {
        items: rows.map((row) =>
          rowToFeedback(row, { includeImages: false, includeContact: false }),
        ),
        page: safePage,
        pageSize: safeLimit,
        total,
        totalPages,
      };
    },

    async getById(feedbackId, viewerUserId) {
      const id = String(feedbackId ?? '').trim();
      if (!id) throw feedbackError('反馈不存在', 'feedback_not_found');

      const [rows] = await pool.query(
        `SELECT f.id, f.user_id, f.type, f.title, f.description, f.contact, f.status,
                f.images_json, f.context_json, f.created_at, f.updated_at,
                u.display_name AS submitter_display_name
         FROM h5_user_feedback f
         JOIN h5_users u ON u.id = f.user_id
         WHERE f.id = ?
         LIMIT 1`,
        [id],
      );
      const row = rows[0];
      if (!row) throw feedbackError('反馈不存在', 'feedback_not_found');

      const isOwner = viewerUserId && row.user_id === viewerUserId;
      return rowToFeedback(row, { includeImages: true, includeContact: isOwner });
    },
  };
}