#include "chunk_array.h"
#include "stdbool.h"
#include "stdlib.h"

#define MAX_CHUNK_SIZE 2048*2048

int get_mod(chunk_array_t* chunk_array,int init_pos) {
    int mod;
    if (chunk_array->total_size - init_pos > chunk_array->chunk_size ) {
        mod = chunk_array->chunk_size;
    } else {
        mod = chunk_array->total_size - init_pos;
    }
    return mod;
}

bool inside_buffer(chunk_array_t* chunk_array,int init_pos, size_t pos) {
    if (pos<init_pos || pos>init_pos + chunk_array->chunk_size-1) {
        return false;
    }
    return true;
}

void chunk_array_free(chunk_array_t* chunk_array) {
  	fclose(chunk_array->fp);
    buffer_free(chunk_array->buffer1);
    buffer_free(chunk_array->buffer2);
	free(chunk_array);  
}

void chunk_array_flush(chunk_array_t* chunk_array) {
    buffer_flush(chunk_array, chunk_array->buffer1);
    buffer_flush(chunk_array, chunk_array->buffer2);
}

void buffer_flush(chunk_array_t* chunk_array, buffer_t* buffer) {
    if (buffer->dirty) {
        int mod = get_mod(chunk_array, buffer->init_pos);
        fseek(chunk_array->fp, buffer->init_pos * sizeof(double), SEEK_SET);
        fwrite(buffer->data, sizeof(double), mod, chunk_array->fp);
        buffer->dirty = false;
    }
}


void buffer_update(chunk_array_t* chunk_array, buffer_t* buffer, size_t pos) {
    buffer_flush(chunk_array, buffer);

    int new_init = pos/chunk_array->chunk_size;
    buffer->init_pos = new_init * chunk_array->chunk_size;

    fseek(chunk_array->fp, buffer->init_pos * sizeof(double), SEEK_SET);
    fread(buffer->data, sizeof(double), chunk_array->chunk_size, chunk_array->fp);
}

buffer_t* buffer_create() {
    buffer_t * buffer = (buffer_t*)malloc(sizeof(buffer_t));

    if (buffer == NULL) return NULL;

    buffer->data = malloc(MAX_CHUNK_SIZE * sizeof(double));

    if (buffer->data == NULL) {
        free(buffer);
        return NULL;
    }

    buffer->init_pos = 0;
    buffer->dirty = false;

    return buffer;
}

void buffer_free(buffer_t* buffer) {
    free(buffer->data);
    free(buffer);
}

chunk_array_t* chunk_array_create(char* filename, size_t total_size) {
    chunk_array_t* chunk_array = (chunk_array_t*)malloc(sizeof(chunk_array_t));
    chunk_array->fp = fopen(filename, "r+");

    if (chunk_array == NULL || chunk_array->fp == NULL) {
        chunk_array->fp = fopen(filename, "w+");

        if (chunk_array->fp == NULL) {
            return NULL;
        }
    }

    chunk_array->buffer1 = buffer_create();

    if (chunk_array->buffer1 == NULL) {
        fclose(chunk_array->fp);
        free(chunk_array);
        return NULL;
    }

    chunk_array->buffer2 = buffer_create();

    if (chunk_array->buffer2 == NULL) {
        fclose(chunk_array->fp);
        buffer_free(chunk_array->buffer1);
        free(chunk_array);
        return NULL;
    }

    fread(chunk_array->buffer1->data, sizeof(double), MAX_CHUNK_SIZE, chunk_array->fp);
    chunk_array->buffer1->init_pos = 0;
    fread(chunk_array->buffer2->data, sizeof(double), MAX_CHUNK_SIZE, chunk_array->fp);
    chunk_array->buffer2->init_pos = MAX_CHUNK_SIZE;
    
    chunk_array->filename = filename;
    chunk_array->chunk_size = MAX_CHUNK_SIZE;
    chunk_array->total_size = total_size;
    return chunk_array;
}

buffer_t* chunk_array_update(chunk_array_t* chunk_array, size_t pos) {
    int distance_to_1 = abs(chunk_array->buffer1->init_pos - pos);
    int distance_to_2 = abs(chunk_array->buffer2->init_pos - pos);

    if (distance_to_1 < distance_to_2) {
        buffer_update(chunk_array, chunk_array->buffer1, pos);
        return chunk_array->buffer1;
    }
    buffer_update(chunk_array, chunk_array->buffer2, pos);
    return chunk_array->buffer2;
}

bool chunk_array_get(chunk_array_t* chunk_array, size_t pos, double *valor) {
    buffer_t* buffer;
    if (inside_buffer(chunk_array, chunk_array->buffer1->init_pos, pos)) {
        buffer = chunk_array->buffer1;
    }
    else if (inside_buffer(chunk_array, chunk_array->buffer2->init_pos, pos)) {
        buffer = chunk_array->buffer2;
    }
    else {
        // need to update one buffer
        buffer = chunk_array_update(chunk_array, pos);
    }

    int real_pos = pos%get_mod(chunk_array, buffer->init_pos);
    *valor=buffer->data[real_pos];
    return true;
}


bool chunk_array_save(chunk_array_t* chunk_array, size_t pos, double valor) {
	buffer_t* buffer;
    if (inside_buffer(chunk_array, chunk_array->buffer1->init_pos, pos)) {
        buffer = chunk_array->buffer1;
    }
    else if (inside_buffer(chunk_array, chunk_array->buffer2->init_pos, pos)) {
        buffer = chunk_array->buffer2;
    }
    else {
        // need to update one buffer
        buffer = chunk_array_update(chunk_array, pos);
    }
    int real_pos = pos%get_mod(chunk_array, buffer->init_pos);
	buffer->data[real_pos]=valor;
    buffer->dirty = true;
	return true;
}