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#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

#include "wav.h"

int check_format(WAVHEADER header);
int get_block_size(WAVHEADER header);

int main(int argc, char *argv[])
{
    // Ensure proper usage
    if (argc != 3)
    {
        printf("Usage: ./reverse input.wav output.wav\n");
        return 1;
    }

    // Open input file for reading
    FILE *input = fopen(argv[1], "r");
    if (input == NULL)
    {
        printf("Could not open %s.\n", argv[1]);
        return 1;
    }

    // Read header
    WAVHEADER header;
    fread(&header, sizeof(WAVHEADER), 1, input);

    // Use check_format to ensure WAV format
    if (check_format(header) != 1)
    {
        printf("Incorrect file format");
        return 1;
    }

    // Open output file for writing
    FILE *output = fopen(argv[2], "w");
    if (output == NULL)
    {
        printf("Could not open %s.\n", argv[2]);
        return 1;
    }

    // Write header to file
    fwrite(&header, sizeof(WAVHEADER), 1, output);

    // Use get_block_size to calculate size of block
    int blockSize = get_block_size(header);

    // Write reversed audio to file
    BYTE buffer[blockSize];
    fseek(input, 0, SEEK_END);
    long audioLength = ftell(input) - sizeof(WAVHEADER);
    int audioBlock = audioLength / blockSize;

    for (int i = audioBlock - 1; i >= 0; i--)
    {
        fseek(input, sizeof(WAVHEADER) + i * blockSize, SEEK_SET);
        fread(buffer, blockSize, 1, input);
        fwrite(buffer, blockSize, 1, output);
    }

    fclose(input);
    fclose(output);
}

int check_format(WAVHEADER header)
{
    if (header.format[0] == 'W' && header.format[1] == 'A'
    && header.format[2] == 'V' && header.format[3] == 'E')
    {
        return 1;
    }
    return 0;
}

int get_block_size(WAVHEADER header)
{
    int blockSize = header.numChannels * (header.bitsPerSample / 8);
    return blockSize;
}