fe-middleware/src/services/ImageService.ts

import GelbooruServiceResponse from "../types/GelbooruServiceResponse";
import Image from "../types/Image";
import BotApiService from "./BotApiService";
import GelbooruApiService from "./GelbooruApiService";

class ImageService {
    postsQueue: Image[] = [];

    async get(): Promise<Image> {
        while (this.postsQueue.length === 0) {
            const validPosts = await this.getNewValidImages();
            this.postsQueue = validPosts;
        }
        return this.postsQueue.pop() as Image;
    }

    private async getNewValidImages(): Promise<Image[]> {
        const gelbooruResponse: GelbooruServiceResponse = await GelbooruApiService.get();
        const posts = gelbooruResponse.posts;

        const botResponse = await BotApiService.getAll();
        const imagesUrls = botResponse.images.map(image => image.url);

        const validPosts = Promise.all(posts
            .filter(post => !imagesUrls.some(url => url === post.url))
            .map(async (post): Promise<Image> => {
                const imageData = await this.urlToImageData(post.url);
                const encodedImage = this.imageToBase64(imageData);
                return { url: post.url, tags: post.tags, content: encodedImage };
            }));
        
        return validPosts;
    }

    private async urlToImageData(url: string): Promise<string> {
        return await (await fetch(url)).text();
    }

    private imageToBase64(imageData: string): string {
        return Buffer.from(imageData, "binary").toString("base64");
    }
}

export default new ImageService();