/// <reference types="npm:@types/node" />

import {
  GetObjectCommand,
  ListObjectsV2Command,
  S3Client,
} from "@aws-sdk/client-s3";

import { AwsContext, s3MoveObject } from "./context.ts";
import { getLogger } from "../logger.ts";
import { getConfig } from "../config.ts";
import { Mail } from "../mail.ts";

export class AwsMailRetriever {
  readonly liveMailPrefix = "mail/live/";
  readonly archiveMailPrefix = "mail/archive/";
  readonly mailBucket = getConfig().getValue("awsMailBucket");

  private readonly s3Client;

  constructor(
    aws: AwsContext,
    private readonly callback: (mail: Mail) => Promise<void>,
  ) {
    const { region, credentials } = aws;
    this.s3Client = new S3Client({ region, credentials });
  }

  async listLiveMails(): Promise<string[]> {
    const listCommand = new ListObjectsV2Command({
      Bucket: this.mailBucket,
      Prefix: this.liveMailPrefix,
    });
    const res = await this.s3Client.send(listCommand);

    if (res.Contents == null) {
      getLogger().warn("Listing live mails in S3 returns null Content.");
      return [];
    }

    const result: string[] = [];
    for (const object of res.Contents) {
      if (object.Key != null) {
        // TODO: check prefix consistence here.
        result.push(object.Key.slice(this.liveMailPrefix.length));
      } else {
        getLogger().warn(
          "Listing live mails in S3 returns an object with no Key.",
        );
      }
    }
    return result;
  }

  async deliverS3MailObject(messageId: string) {
    const mailPath = `${this.liveMailPrefix}${messageId}`;
    const command = new GetObjectCommand({
      Bucket: this.mailBucket,
      Key: mailPath,
    });
    const res = await this.s3Client.send(command);

    if (res.Body == null) {
      // TODO: Better error.
      throw new Error();
    }

    const rawMail = await res.Body.transformToString();
    const mail = new Mail(rawMail);
    mail.awsMessageId = messageId;
    await this.callback(mail);

    // TODO: Continue here.
    await s3MoveObject(
      this.s3Client,
      this.mailBucket,
      mailPath,
      `${this.archiveMailPrefix}${
        mail.simpleGetDateString("invalid-date")
      }/${messageId}`,
    );
  }

  async recycleLiveMails() {
    const mails = await this.listLiveMails();
    for (const messageId of mails) {
      await this.deliverS3MailObject(messageId);
    }
  }
}