import { createHash } from "node:crypto";
import { createReadStream } from "node:fs";
import { stat } from "node:fs/promises";
import type { Readable } from "node:stream";
import { S3Client, PutObjectCommand, GetObjectCommand, DeleteObjectCommand } from "@aws-sdk/client-s3";
import type { ObjectStorageProvider, PutObjectResult } from "./types";

export interface S3ProviderOptions {
  bucket: string;
  region?: string;
  /** Endpoint custom pra S3-compatible (MinIO, secao 92) — omitido usa
   * AWS S3 real. */
  endpoint?: string;
  accessKeyId?: string;
  secretAccessKey?: string;
  /** MinIO e a maioria dos S3-compatible precisam de path-style
   * (`endpoint/bucket/key`) em vez do virtual-hosted-style padrão da AWS. */
  forcePathStyle?: boolean;
}

/**
 * Backend S3-compatible (agente.md secao 92) — preparado pra AWS S3 e
 * MinIO. **Nunca exercitado nesta sessão**: não existe um servidor S3/MinIO
 * disponível neste laboratório pra testar contra. A implementação segue a
 * API padrão do `@aws-sdk/client-s3`; revisar com um MinIO real antes de
 * confiar em produção.
 */
export class S3ObjectStorageProvider implements ObjectStorageProvider {
  private readonly client: S3Client;
  private readonly bucket: string;

  constructor(options: S3ProviderOptions) {
    this.bucket = options.bucket;
    this.client = new S3Client({
      region: options.region ?? "us-east-1",
      endpoint: options.endpoint,
      forcePathStyle: options.forcePathStyle,
      credentials:
        options.accessKeyId && options.secretAccessKey
          ? { accessKeyId: options.accessKeyId, secretAccessKey: options.secretAccessKey }
          : undefined,
    });
  }

  async putObject(key: string, sourceFilePath: string): Promise<PutObjectResult> {
    const [{ size }, checksum] = await Promise.all([stat(sourceFilePath), sha256File(sourceFilePath)]);

    await this.client.send(
      new PutObjectCommand({
        Bucket: this.bucket,
        Key: key,
        Body: createReadStream(sourceFilePath),
        ContentLength: size,
      }),
    );

    return { sizeBytes: size, checksum };
  }

  async getObjectStream(key: string): Promise<Readable> {
    const result = await this.client.send(new GetObjectCommand({ Bucket: this.bucket, Key: key }));
    return result.Body as Readable;
  }

  async deleteObject(key: string): Promise<void> {
    await this.client.send(new DeleteObjectCommand({ Bucket: this.bucket, Key: key }));
  }
}

function sha256File(path: string): Promise<string> {
  return new Promise((resolve, reject) => {
    const hash = createHash("sha256");
    const stream = createReadStream(path);
    stream.on("data", (chunk) => hash.update(chunk));
    stream.on("end", () => resolve(hash.digest("hex")));
    stream.on("error", reject);
  });
}