import { Injectable, InternalServerErrorException } from '@nestjs/common';
import type {
  IOssProvider,
  OssPutObjectInput,
  OssPutObjectResult,
  OssUploadTokenInput,
  OssUploadTokenResult,
} from './oss.interface';
import { buildOssObjectKey, resolveOssUploadDir } from './oss.key.util';
import { createAliyunOssClient, resolveOssUploadHost } from './oss.aliyun.client';

const DEFAULT_EXPIRE_SECONDS = 15 * 60;
const DEFAULT_MAX_BYTES = 10 * 1024 * 1024;

@Injectable()
export class OssAliyunProvider implements IOssProvider {
  private readonly accessKeyId = process.env.OSS_ACCESS_KEY_ID ?? '';
  private readonly accessKeySecret = process.env.OSS_ACCESS_KEY_SECRET ?? '';
  private readonly bucket = process.env.OSS_BUCKET ?? '';
  private readonly region = process.env.OSS_REGION ?? 'oss-cn-hangzhou';
  private readonly cdnBase = process.env.OSS_CDN_BASE ?? '';
  private readonly endpoint = process.env.OSS_ENDPOINT ?? '';
  private readonly uploadPrefix = (process.env.OSS_UPLOAD_PREFIX ?? 'uploads').replace(/\/$/, '');
  private readonly expireSeconds = Number(process.env.OSS_UPLOAD_EXPIRE_SECONDS ?? DEFAULT_EXPIRE_SECONDS);
  private readonly maxUploadBytes = Number(process.env.OSS_MAX_UPLOAD_BYTES ?? DEFAULT_MAX_BYTES);
  private readonly authorizationV4 = process.env.OSS_AUTHORIZATION_V4 === 'true';
  private client: ReturnType<typeof createAliyunOssClient> | null = null;

  isEnabled() {
    return !!(this.accessKeyId && this.accessKeySecret && this.bucket);
  }

  private assertConfigured() {
    if (this.isEnabled()) return;
    throw new InternalServerErrorException(
      'OSS 未配置：请设置 OSS_ACCESS_KEY_ID、OSS_ACCESS_KEY_SECRET、OSS_BUCKET（及 OSS_REGION）',
    );
  }

  private getClient() {
    this.assertConfigured();
    if (!this.client) {
      this.client = createAliyunOssClient({
        accessKeyId: this.accessKeyId,
        accessKeySecret: this.accessKeySecret,
        bucket: this.bucket,
        region: this.region,
        endpoint: this.endpoint || undefined,
        authorizationV4: this.authorizationV4,
      });
    }
    return this.client;
  }

  buildPublicUrl(ossKey: string) {
    const key = ossKey.replace(/^\//, '');
    const client = this.getClient();
    return client.generateObjectUrl(key, this.cdnBase || undefined);
  }

  getUploadToken(dto: OssUploadTokenInput): OssUploadTokenResult {
    const client = this.getClient();
    const ossKey = buildOssObjectKey(this.uploadPrefix, dto.bizType, dto.fileName);
    const expireAt = new Date(Date.now() + this.expireSeconds * 1000);
    const host = resolveOssUploadHost(this.bucket, this.region);
    const keyPrefix = resolveOssUploadDir(this.uploadPrefix, dto.bizType);

    const policy = {
      expiration: expireAt.toISOString(),
      conditions: [
        ['content-length-range', 0, this.maxUploadBytes],
        ['eq', '$bucket', this.bucket],
        ['starts-with', '$key', keyPrefix],
      ],
    };

    const signed = client.calculatePostSignature(policy);

    return {
      bucket: this.bucket,
      region: this.region,
      ossKey,
      url: this.buildPublicUrl(ossKey),
      mock: false,
      expireAt: expireAt.toISOString(),
      mediaType: dto.mediaType,
      bizType: dto.bizType,
      host,
      policy: signed.policy,
      signature: signed.Signature,
      accessKeyId: signed.OSSAccessKeyId,
    };
  }

  async putObject(input: OssPutObjectInput): Promise<OssPutObjectResult> {
    const client = this.getClient();
    const ossKey = buildOssObjectKey(this.uploadPrefix, input.bizType, input.fileName);
    await client.put(ossKey, input.buffer, {
      mime: input.mimeType || 'application/octet-stream',
      headers: {
        'Content-Disposition': 'inline',
      },
    });
    return {
      bucket: this.bucket,
      region: this.region,
      ossKey,
      url: this.buildPublicUrl(ossKey),
      mock: false,
    };
  }
}