/*
A simple sound library for CSE 20211 by Douglas Thain
For course assignments, you should not change this file.
For complete documentation, see:
http://www.nd.edu/~dthain/courses/cse20211/fall2013/wavfile
*/

#include "wavfile.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef __cplusplus
extern "C" {
#endif

	FILE* wavfile_write_open(const char* filename)
	{
		struct wavfile_header header;

		int samples_per_second = WAVFILE_SAMPLES_PER_SECOND;
		int bits_per_sample = 16;

		strncpy(header.riff_tag, "RIFF", 4);
		strncpy(header.wave_tag, "WAVE", 4);
		strncpy(header.fmt_tag, "fmt ", 4);
		strncpy(header.data_tag, "data", 4);

		header.riff_length = 0;
		header.fmt_length = 16;
		header.audio_format = 1;
		header.num_channels = 1;
		header.sample_rate = samples_per_second;
		header.byte_rate = samples_per_second * (bits_per_sample / 8);
		header.block_align = bits_per_sample / 8;
		header.bits_per_sample = bits_per_sample;
		header.data_length = 0;

		FILE* file = fopen(filename, "w+");
		if (!file) return 0;

		fwrite(&header, sizeof(header), 1, file);

		fflush(file);

		return file;
	}

	FILE* wavfile_read_open(const char* filename, struct wavfile_header* header)
	{

		FILE* file = 0;
		if (header != NULL)
		{
			file = fopen(filename, "rb");

			if (!file)
				return 0;

			int r = fread(header, sizeof(struct wavfile_header), 1, file);
			r = sizeof(struct wavfile_header);
			printf("%d\n", r);
		}
		else
		{
			return 0;
		}

		return file;
	}

	long wavfile_read(FILE* file, short data[], int length)
	{
		return fread(data, sizeof(short), length, file);
	}

	void wavfile_write(FILE* file, short data[], int length)
	{
		fwrite(data, sizeof(short), length, file);
	}

	void wavfile_write_close(FILE* file)
	{
		int file_length = ftell(file);

		int data_length = file_length - sizeof(struct wavfile_header);

		fseek(file, sizeof(struct wavfile_header) - sizeof(int), SEEK_SET);

		fwrite(&data_length, sizeof(data_length), 1, file);

		int riff_length = file_length - 8;

		fseek(file, 4, SEEK_SET);

		fwrite(&riff_length, sizeof(riff_length), 1, file);
		fflush(file);
		fclose(file);
	}

	/*read the data from specified postion and channel*/
	static short wavfile_read_pos(FILE* file, int channel_num, int channel_index, int pos)
	{
		short value;


		long index = 44 + (pos * channel_num + channel_index) * sizeof(short);
		fseek(file, index, SEEK_SET);

		fread(&value, sizeof(short), 1, file);
		return value;
	}

	void wavfile_read_channel(FILE* file, short data[], int channel_num, int channel_index, int start_pos, int length)
	{
		int i;
		for (i = 0; i < length; ++i)
		{
			data[i] = wavfile_read_pos(file, channel_num, channel_index, start_pos + i);
		}
	}


#ifdef __cplusplus
}
#endif