#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
#include <time.h>
#include <stdint.h>
#include <sys/types.h>
#include <sys/stat.h>

#define SERIAL_PORT "/dev/ttyACM1"
#define BAUD_RATE B1500000
#define RATE 16000
#define CHANNELS 2
#define SAMPLE_WIDTH 2   // 16-bit
#define CHUNK_SIZE 256   // frames per block
#define DURATION 3       // seconds

// Write a simple WAV header
void write_wav_header(FILE *f, int data_size) {
    int byte_rate = RATE * CHANNELS * SAMPLE_WIDTH;
    int block_align = CHANNELS * SAMPLE_WIDTH;

    // RIFF header
    fwrite("RIFF", 1, 4, f);
    int chunk_size = 36 + data_size;
    fwrite(&chunk_size, 4, 1, f);
    fwrite("WAVE", 1, 4, f);

    // fmt subchunk
    fwrite("fmt ", 1, 4, f);
    int subchunk1_size = 16;
    fwrite(&subchunk1_size, 4, 1, f);
    short audio_format = 1; // PCM
    fwrite(&audio_format, 2, 1, f);
    short num_channels = CHANNELS;
    fwrite(&num_channels, 2, 1, f);
    int sample_rate = RATE;
    fwrite(&sample_rate, 4, 1, f);
    fwrite(&byte_rate, 4, 1, f);
    fwrite(&block_align, 2, 1, f);
    short bits_per_sample = SAMPLE_WIDTH * 8;
    fwrite(&bits_per_sample, 2, 1, f);

    // data subchunk
    fwrite("data", 1, 4, f);
    fwrite(&data_size, 4, 1, f);
}

int main() {
    // Open serial port
    int fd = open(SERIAL_PORT, O_RDONLY | O_NOCTTY);
    if (fd < 0) {
        perror("open");
        return 1;
    }

    // Configure serial
    struct termios tty;
    memset(&tty, 0, sizeof tty);
    if (tcgetattr(fd, &tty) != 0) {
        perror("tcgetattr");
        return 1;
    }
    cfsetospeed(&tty, BAUD_RATE);
    cfsetispeed(&tty, BAUD_RATE);
    tty.c_cflag |= (CLOCAL | CREAD);
    tty.c_cflag &= ~CSIZE;
    tty.c_cflag |= CS8;
    tty.c_cflag &= ~PARENB;
    tty.c_cflag &= ~CSTOPB;
    tcsetattr(fd, TCSANOW, &tty);

    FILE *out = fopen("capture.wav", "wb");
    if (!out) {
        perror("fopen");
        return 1;
    }

    // Reserve space for header
    fseek(out, 44, SEEK_SET);

    int total_bytes = 0;
    char buf[CHUNK_SIZE * CHANNELS * SAMPLE_WIDTH];
    time_t start = time(NULL);

    while (time(NULL) - start < DURATION) {
        int n = read(fd, buf, sizeof(buf));
        if (n > 0) {
            fwrite(buf, 1, n, out);
            total_bytes += n;
        }
    }

    // Write header at beginning
    fseek(out, 0, SEEK_SET);
    write_wav_header(out, total_bytes);

    fclose(out);
    close(fd);

    printf("Saved capture.wav (%d bytes of audio)\n", total_bytes);
    return 0;
}