feat(frontend): add PWA support with manifest, service worker, and audio processing features

meshchatx/src/frontend/public/assets/js/codec2-emscripten/wav-encoder.js

@@ -0,0 +1,47 @@
+class WavEncoder {
+
+    static encodeWAV(samples, sampleRate = 8000, numChannels = 1) {
+
+        const buffer = new ArrayBuffer(44 + samples.length * 2);
+        const view = new DataView(buffer);
+
+        // RIFF chunk descriptor
+        this.writeString(view, 0, 'RIFF');
+        view.setUint32(4, 36 + samples.length * 2, true); // file length
+        this.writeString(view, 8, 'WAVE');
+
+        // fmt sub-chunk
+        this.writeString(view, 12, 'fmt ');
+        view.setUint32(16, 16, true); // sub-chunk size
+        view.setUint16(20, 1, true); // audio format (1 = PCM)
+        view.setUint16(22, numChannels, true); // number of channels
+        view.setUint32(24, sampleRate, true); // sample rate
+        view.setUint32(28, sampleRate * numChannels * 2, true); // byte rate
+        view.setUint16(32, numChannels * 2, true); // block align
+        view.setUint16(34, 16, true); // bits per sample
+
+        // data sub-chunk
+        this.writeString(view, 36, 'data');
+        view.setUint32(40, samples.length * 2, true); // data chunk length
+
+        // write the PCM samples
+        this.floatTo16BitPCM(view, 44, samples);
+
+        return buffer;
+
+    }
+
+    static writeString(view, offset, string) {
+        for(let i = 0; i < string.length; i++){
+            view.setUint8(offset + i, string.charCodeAt(i));
+        }
+    }
+
+    static floatTo16BitPCM(output, offset, input) {
+        for(let i = 0; i < input.length; i++, offset += 2){
+            const s = Math.max(-1, Math.min(1, input[i]));
+            output.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7FFF, true);
+        }
+    }
+
+}