/* ------------------------------------------------------------------
 * Copyright (C) 2009 Martin Storsjo
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 * -------------------------------------------------------------------
 */

#include "wavfile.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#define TAG(a, b, c, d) (((a) << 24) | ((b) << 16) | ((c) << 8) | (d))

struct wav_reader {
    FILE *wav;
    uint32_t data_length;

    int format;
    int sample_rate;
    int bits_per_sample;
    int channels;
    int byte_rate;
    int block_align;

    int streamed;
};

static uint32_t read_tag(struct wav_reader* wr) {
    uint32_t tag = 0;
    tag = (tag << 8) | fgetc(wr->wav);
    tag = (tag << 8) | fgetc(wr->wav);
    tag = (tag << 8) | fgetc(wr->wav);
    tag = (tag << 8) | fgetc(wr->wav);
    return tag;
}

static uint32_t read_int32(struct wav_reader* wr) {
    uint32_t value = 0;
    value |= fgetc(wr->wav) <<  0;
    value |= fgetc(wr->wav) <<  8;
    value |= fgetc(wr->wav) << 16;
    value |= fgetc(wr->wav) << 24;
    return value;
}

static uint16_t read_int16(struct wav_reader* wr) {
    uint16_t value = 0;
    value |= fgetc(wr->wav) << 0;
    value |= fgetc(wr->wav) << 8;
    return value;
}

static void skip(FILE *f, int n) {
    int i;
    for (i = 0; i < n; i++)
        fgetc(f);
}

void* wav_read_open(const char *filename) {
    struct wav_reader* wr = (struct wav_reader*) malloc(sizeof(*wr));
    long data_pos = 0;
    memset(wr, 0, sizeof(*wr));

    if (!strcmp(filename, "-"))
        wr->wav = stdin;
    else
        wr->wav = fopen(filename, "rb");
    if (wr->wav == NULL) {
        free(wr);
        return NULL;
    }

    while (1) {
        uint32_t tag, tag2, length;
        tag = read_tag(wr);
        if (feof(wr->wav))
            break;
        length = read_int32(wr);
        if (!length || length >= 0x7fff0000) {
            wr->streamed = 1;
            length = ~0;
        }
        if (tag != TAG('R', 'I', 'F', 'F') || length < 4) {
            fseek(wr->wav, length, SEEK_CUR);
            continue;
        }
        tag2 = read_tag(wr);
        length -= 4;
        if (tag2 != TAG('W', 'A', 'V', 'E')) {
            fseek(wr->wav, length, SEEK_CUR);
            continue;
        }
        // RIFF chunk found, iterate through it
        while (length >= 8) {
            uint32_t subtag, sublength;
            subtag = read_tag(wr);
            if (feof(wr->wav))
                break;
            sublength = read_int32(wr);
            length -= 8;
            if (length < sublength)
                break;
            if (subtag == TAG('f', 'm', 't', ' ')) {
                if (sublength < 16) {
                    // Insufficient data for 'fmt '
                    break;
                }
                wr->format          = read_int16(wr);
                wr->channels        = read_int16(wr);
                wr->sample_rate     = read_int32(wr);
                wr->byte_rate       = read_int32(wr);
                wr->block_align     = read_int16(wr);
                wr->bits_per_sample = read_int16(wr);
                if (wr->format == 0xfffe) {
                    if (sublength < 28) {
                        // Insufficient data for waveformatex
                        break;
                    }
                    skip(wr->wav, 8);
                    wr->format = read_int32(wr);
                    skip(wr->wav, sublength - 28);
                } else {
                    skip(wr->wav, sublength - 16);
                }
            } else if (subtag == TAG('d', 'a', 't', 'a')) {
                data_pos = ftell(wr->wav);
                wr->data_length = sublength;
                if (!wr->data_length || wr->streamed) {
                    wr->streamed = 1;
                    return wr;
                }
                fseek(wr->wav, sublength, SEEK_CUR);
            } else {
                skip(wr->wav, sublength);
            }
            length -= sublength;
        }
        if (length > 0) {
            // Bad chunk?
            fseek(wr->wav, length, SEEK_CUR);
        }
    }
    fseek(wr->wav, data_pos, SEEK_SET);
    return wr;
}

void wav_read_close(void* obj) {
    struct wav_reader* wr = (struct wav_reader*) obj;
    if (wr->wav != stdin)
        fclose(wr->wav);
    free(wr);
}

int wav_get_header(void* obj, int* format, int* channels, int* sample_rate, int* bits_per_sample, unsigned int* data_length) {
    struct wav_reader* wr = (struct wav_reader*) obj;
    if (format)
        *format = wr->format;
    if (channels)
        *channels = wr->channels;
    if (sample_rate)
        *sample_rate = wr->sample_rate;
    if (bits_per_sample)
        *bits_per_sample = wr->bits_per_sample;
    if (data_length)
        *data_length = wr->data_length;
    return wr->format && wr->sample_rate;
}

int wav_read_data(void* obj, unsigned char* data, unsigned int length) {
    struct wav_reader* wr = (struct wav_reader*) obj;
    int n;
    if (wr->wav == NULL)
        return -1;
    if (length > wr->data_length && !wr->streamed)
        length = wr->data_length;
    n = fread(data, 1, length, wr->wav);
    wr->data_length -= length;
    return n;
}