server/packages/media-manager/media-converter.ts

/**
 * @packageDocumentation
 * @module MediaManager
 * @description Handles media conversion between formats
 */
import sharp from "sharp";

export enum ConvertableMediaFormats {
    PNG = "png",
    WEBP = "webp",
    JPEG = "jpeg",
    JPG = "jpg",
    AVIF = "avif",
    JXL = "jxl",
    HEIF = "heif",
}

/**
 * Handles media conversion between formats
 */
export class MediaConverter {
    constructor(
        public fromFormat: ConvertableMediaFormats,
        public toFormat: ConvertableMediaFormats,
    ) {}

    /**
     * Returns whether the media is convertable
     * @returns Whether the media is convertable
     */
    public isConvertable() {
        return (
            this.fromFormat !== this.toFormat &&
            Object.values(ConvertableMediaFormats).includes(this.fromFormat)
        );
    }

    /**
     * Returns the file name with the extension replaced
     * @param fileName File name to replace
     * @returns File name with extension replaced
     */
    private getReplacedFileName(fileName: string) {
        return this.extractFilenameFromPath(fileName).replace(
            new RegExp(`\\.${this.fromFormat}$`),
            `.${this.toFormat}`,
        );
    }

    /**
     * Extracts the filename from a path
     * @param path Path to extract filename from
     * @returns Extracted filename
     */
    private extractFilenameFromPath(path: string) {
        // Don't count escaped slashes as path separators
        const pathParts = path.split(/(?<!\\)\//);
        return pathParts[pathParts.length - 1];
    }

    /**
     * Converts media to the specified format
     * @param media Media to convert
     * @returns Converted media
     */
    public async convert(media: File) {
        if (!this.isConvertable()) {
            return media;
        }

        const sharpCommand = sharp(await media.arrayBuffer());

        // Calculate newFilename before changing formats to prevent errors with jpg files
        const newFilename = this.getReplacedFileName(media.name);

        if (this.fromFormat === ConvertableMediaFormats.JPG) {
            this.fromFormat = ConvertableMediaFormats.JPEG;
        }

        if (this.toFormat === ConvertableMediaFormats.JPG) {
            this.toFormat = ConvertableMediaFormats.JPEG;
        }

        const convertedBuffer = await sharpCommand[this.toFormat]().toBuffer();

        // Convert the buffer to a BlobPart
        const buffer = new Blob([convertedBuffer]);

        return new File([buffer], newFilename, {
            type: `image/${this.toFormat}`,
            lastModified: Date.now(),
        });
    }
}