"use strict";

const ShieldLowAlarmSound = (function(){

    return function(audio_ctx, output_node, volume_multiplier = 1.0){
        const now = audio_ctx.currentTime;
        const duration = 0.22; // Pulso de sirena industrial rápido

        const preset_bus = audio_ctx.createGain();
        preset_bus.gain.setValueAtTime(volume_multiplier * 0.45, now);

        // 1. REVERBERACIÓN CORTA DE MAMPARA (Eco de pasillo de nave)
        const room_delay = audio_ctx.createDelay();
        room_delay.delayTime.setValueAtTime(0.045, now);

        const room_feedback = audio_ctx.createGain();
        room_feedback.gain.setValueAtTime(0.35, now);

        const room_filter = audio_ctx.createBiquadFilter();
        room_filter.type = "lowpass";
        room_filter.frequency.setValueAtTime(1200, now);

        room_delay.connect(room_filter);
        room_filter.connect(room_feedback);
        room_feedback.connect(room_delay);
        room_filter.connect(preset_bus);

        // 2. ENVOLVENTE DINÁMICA DE BOCINA (Ataque percusivo + cuerpo)
        const env = audio_ctx.createGain();
        env.gain.setValueAtTime(0.001, now);
        // Ataque rápido simulando apertura de válvula
        env.gain.linearRampToValueAtTime(0.85, now + 0.02);
        env.gain.setValueAtTime(0.85, now + 0.14);
        env.gain.exponentialRampToValueAtTime(0.001, now + duration);

        // 3. GENERADOR DE SIRENA INDUSTRIAL (Síntesis FM limpia)
        // Transportadora principal: Tono puro de bocina (senoidal limpia)
        const carrier = audio_ctx.createOscillator();
        carrier.type = "sine";

        // Barrido característico de evacuación: empieza arriba y resbala hacia abajo
        carrier.frequency.setValueAtTime(740, now);
        carrier.frequency.exponentialRampToValueAtTime(460, now + duration);

        // Modulador FM: Añade el zumbido de vibración de la membrana metálica
        const modulator = audio_ctx.createOscillator();
        const mod_gain = audio_ctx.createGain();

        modulator.type = "sine";
        // Modulación a 45Hz para simular el traqueteo del motor de la sirena
        modulator.frequency.setValueAtTime(45, now);
        mod_gain.gain.setValueAtTime(140, now);
        mod_gain.gain.exponentialRampToValueAtTime(40, now + duration);

        modulator.connect(mod_gain);
        mod_gain.connect(carrier.frequency);

        // 4. SEGUNDO TONO ARMÓNICO (Cuerpo de resonador hueco)
        const sub_carrier = audio_ctx.createOscillator();
        const sub_gain = audio_ctx.createGain();
        sub_carrier.type = "triangle";
        sub_carrier.frequency.setValueAtTime(370, now);
        sub_carrier.frequency.exponentialRampToValueAtTime(230, now + duration);

        sub_gain.gain.setValueAtTime(0.3, now);
        sub_carrier.connect(sub_gain);
        sub_gain.connect(env);

        // 5. FILTRO PASO-BANDA (Emula el megáfono físico de cabina)
        const megaphone_filter = audio_ctx.createBiquadFilter();
        megaphone_filter.type = "bandpass";
        megaphone_filter.frequency.setValueAtTime(650, now);
        megaphone_filter.Q.setValueAtTime(1.8, now);

        carrier.connect(env);
        env.connect(megaphone_filter);

        // Enviamos al bus directo y una copia a la reverberación de mampara
        megaphone_filter.connect(preset_bus);
        megaphone_filter.connect(room_delay);

        preset_bus.connect(output_node);

        // Disparo coordinado
        modulator.start(now);
        carrier.start(now);
        sub_carrier.start(now);

        modulator.stop(now + duration);
        carrier.stop(now + duration);
        sub_carrier.stop(now + duration);
    };

})();