/* tslint:disable:no-console */
import IPC from 'ipc';

// Mostly based on the example from MDN,
// https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Native_messaging
export default class NativeMessage {
    ipc: IPC;

    constructor(ipc: IPC) {
        this.ipc = ipc;
    }

    send(message: object) {
        const messageBuffer = Buffer.from(JSON.stringify(message));

        const headerBuffer = Buffer.alloc(4);
        headerBuffer.writeUInt32LE(messageBuffer.length, 0);

        process.stdout.write(Buffer.concat([headerBuffer, messageBuffer]));
    }

    listen() {
        let payloadSize: number = null;

        // A queue to store the chunks as we read them from stdin.
        // This queue can be flushed when `payloadSize` data has been read
        const chunks: any = [];

        // Only read the size once for each payload
        const sizeHasBeenRead = () => Boolean(payloadSize);

        // All the data has been read, reset everything for the next message
        const flushChunksQueue = () => {
            payloadSize = null;
            chunks.splice(0);
        };

        const processData = () => {
            // Create one big buffer with all all the chunks
            const stringData = Buffer.concat(chunks);
            console.error(stringData);

            // The browser will emit the size as a header of the payload,
            // if it hasn't been read yet, do it.
            // The next time we'll need to read the payload size is when all of the data
            // of the current payload has been read (ie. data.length >= payloadSize + 4)
            if (!sizeHasBeenRead()) {
                payloadSize = stringData.readUInt32LE(0);
            }

            // If the data we have read so far is >= to the size advertised in the header,
            // it means we have all of the data sent.
            // We add 4 here because that's the size of the bytes that old the payloadSize
            if (stringData.length >= payloadSize + 4) {
                // Remove the header
                const contentWithoutSize = stringData
                    .slice(4, payloadSize + 4)
                    .toString();

                // Reset the read size and the queued chunks
                flushChunksQueue();

                const json = JSON.parse(contentWithoutSize);

                // Forward to desktop application
                this.ipc.send(json);
            }
        };

        process.stdin.on('readable', () => {
            // A temporary variable holding the nodejs.Buffer of each
            // chunk of data read off stdin
            let chunk = null;

            // Read all of the available data
            // tslint:disable-next-line:no-conditional-assignment
            while ((chunk = process.stdin.read()) !== null) {
                chunks.push(chunk);
            }

            processData();
        });
    }
}