/**
 * 频响文件 S3 存储服务
 * 本地开发环境：使用 AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY
 * 正式环境：通过 IAM 角色访问 S3（无需配置密钥）
 */
const { S3Client, PutObjectCommand, GetObjectCommand } = require('@aws-sdk/client-s3');
const logger = require('../config/logger');

const AWS_REGION = process.env.AWS_REGION || 'eu-central-1';
const AWS_ACCESS_KEY_ID = process.env.AWS_ACCESS_KEY_ID || '';
const AWS_SECRET_ACCESS_KEY = process.env.AWS_SECRET_ACCESS_KEY || '';
const S3_BUCKET = process.env.AWS_S3_MEASUREMENT_BUCKET || process.env.AWS_S3_OTA_BUCKET || 'luxsin-app-bucket';

/**
 * 获取 S3 客户端
 * 有显式凭证则用凭证，否则走 IAM 角色
 */
function getS3Client() {
  const options = { region: AWS_REGION };
  if (AWS_ACCESS_KEY_ID && AWS_SECRET_ACCESS_KEY) {
    options.credentials = {
      accessKeyId: AWS_ACCESS_KEY_ID,
      secretAccessKey: AWS_SECRET_ACCESS_KEY,
    };
  }
  return new S3Client(options);
}

/**
 * 获取品牌首字符（字母则转大写）
 */
function getBrandFirstChar(brandName) {
  if (!brandName || !brandName.length) return '_';
  const first = brandName[0];
  return /[a-zA-Z]/.test(first) ? first.toUpperCase() : first;
}

/**
 * 构建 S3 Key
 * 路径：autoeq/measurements/{source}/data/{form}/{brandFirstChar}/{brand model}.csv
 * @param {object} params
 * @param {string} params.source - 来源，默认 Eafonyoung
 * @param {string} params.form - 佩戴方式 (in-ear / over-ear / earbud)
 * @param {string} params.brandName - 品牌名称
 * @param {string} params.modelName - 型号名称
 * @returns {string} S3 Key
 */
function buildMeasurementKey({ source, form, brandName, modelName }) {
  const src = source || 'Eafonyoung';
  const brandChar = getBrandFirstChar(brandName);
  const fileName = `${brandName} ${modelName}.csv`;
  return `autoeq/measurements/${src}/data/${form}/${brandChar}/${fileName}`;
}

/**
 * 上传频响文件到 S3
 * @param {Buffer} buffer - 文件内容（已转换为 CSV）
 * @param {object} params - 路径参数
 * @returns {Promise<string>} S3 Key
 */
async function uploadMeasurementToS3(buffer, params) {
  const key = buildMeasurementKey(params);
  const client = getS3Client();

  try {
    await client.send(
      new PutObjectCommand({
        Bucket: S3_BUCKET,
        Key: key,
        Body: buffer,
        ContentType: 'text/csv',
      })
    );
    logger.info(`Measurement uploaded to s3://${S3_BUCKET}/${key}`);
    return key;
  } catch (e) {
    logger.error(`S3 measurement upload failed: ${e.message}`);
    throw new Error(`S3 上传失败：${e.message}`);
  }
}

/**
 * 从 S3 读取频响 CSV 文件
 * @param {object} params - 路径参数（同 buildMeasurementKey）
 * @returns {Promise<{ key: string, content: string }>}
 */
async function getMeasurementFromS3(params) {
  const key = buildMeasurementKey(params);
  const client = getS3Client();

  try {
    const response = await client.send(
      new GetObjectCommand({
        Bucket: S3_BUCKET,
        Key: key,
      })
    );
    const content = await response.Body.transformToString('utf-8');
    logger.info(`Measurement read from s3://${S3_BUCKET}/${key}`);
    return { key, content };
  } catch (e) {
    if (e.name === 'NoSuchKey' || e.$metadata?.httpStatusCode === 404) {
      throw new Error('S3 上未找到该型号的频响文件');
    }
    logger.error(`S3 measurement read failed: ${e.message}`);
    throw new Error(`S3 读取失败：${e.message}`);
  }
}

module.exports = {
  uploadMeasurementToS3,
  getMeasurementFromS3,
  buildMeasurementKey,
};