spessasynth_lib/external_midi/midi_handler.js

import { Synthetizer } from "../synthetizer/synthetizer.js";
import { consoleColors } from "../utils/other.js";
import { SpessaSynthInfo, SpessaSynthWarn } from "../utils/loggin.js";

/**
 * midi_handler.js
 * purpose: handles the connection between MIDI devices and synthesizer/sequencer via Web MIDI API
 */

const NO_INPUT = null;

export class MIDIDeviceHandler
{
    constructor()
    {
    }
    
    /**
     * @returns {Promise<boolean>} if succeded
     */
    async createMIDIDeviceHandler()
    {
        /**
         * @type {MIDIInput}
         */
        this.selectedInput = NO_INPUT;
        /**
         * @type {MIDIOutput}
         */
        this.selectedOutput = NO_INPUT;
        if (navigator.requestMIDIAccess)
        {
            // prepare the midi access
            try
            {
                const response = await navigator.requestMIDIAccess({ sysex: true, software: true });
                this.inputs = response.inputs;
                this.outputs = response.outputs;
                SpessaSynthInfo("%cMIDI handler created!", consoleColors.recognized);
                return true;
            }
            catch (e)
            {
                SpessaSynthWarn(`Could not get MIDI Devices:`, e);
                this.inputs = [];
                this.outputs = [];
                return false;
            }
        }
        else
        {
            SpessaSynthWarn("Web MIDI Api not supported!", consoleColors.unrecognized);
            this.inputs = [];
            this.outputs = [];
            return false;
        }
    }
    
    /**
     * Connects the sequencer to a given MIDI output port
     * @param output {MIDIOutput}
     * @param seq {Sequencer}
     */
    connectMIDIOutputToSeq(output, seq)
    {
        this.selectedOutput = output;
        seq.connectMidiOutput(output);
        SpessaSynthInfo(
            `%cPlaying MIDI to %c${output.name}`,
            consoleColors.info,
            consoleColors.recognized
        );
    }
    
    /**
     * Disconnects a midi output port from the sequencer
     * @param seq {Sequencer}
     */
    disconnectSeqFromMIDI(seq)
    {
        this.selectedOutput = NO_INPUT;
        seq.connectMidiOutput(undefined);
        SpessaSynthInfo(
            "%cDisconnected from MIDI out.",
            consoleColors.info
        );
    }
    
    /**
     * Connects a MIDI input to the synthesizer
     * @param input {MIDIInput}
     * @param synth {Synthetizer}
     */
    connectDeviceToSynth(input, synth)
    {
        this.selectedInput = input;
        input.onmidimessage = event =>
        {
            synth.sendMessage(event.data);
        };
        SpessaSynthInfo(
            `%cListening for messages on %c${input.name}`,
            consoleColors.info,
            consoleColors.recognized
        );
    }
    
    /**
     * @param input {MIDIInput}
     */
    disconnectDeviceFromSynth(input)
    {
        this.selectedInput = NO_INPUT;
        input.onmidimessage = undefined;
        SpessaSynthInfo(
            `%cDisconnected from %c${input.name}`,
            consoleColors.info,
            consoleColors.recognized
        );
    }
    
    disconnectAllDevicesFromSynth()
    {
        this.selectedInput = NO_INPUT;
        for (const i of this.inputs)
        {
            i[1].onmidimessage = undefined;
        }
    }
}