#include "chunk_array.h"
#include "stdbool.h"
#include "stdlib.h"
#include <sys/mman.h>

#define MAX_CHUNK_SIZE 33554432*2
#define N_BUFFERS 8

int min(int value1, int value2) {
    if (value1 < value2) return value1;
    return value2;
}

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) {
    if (chunk_array->mmap_array) munmap(chunk_array->mmap_array, chunk_array->total_size * sizeof(double));
    for (int i = 0; i < chunk_array->n_buffers; i++) {
        buffer_free(chunk_array->buffers[i]);
    }
    free(chunk_array->buffers);
	free(chunk_array);  
}

void buffer_flush(chunk_array_t* chunk_array, buffer_t* buffer) {
    if (buffer->dirty && chunk_array->mmap_array) {
        int mod = get_mod(chunk_array, buffer->init_pos);
        memcpy(&chunk_array->mmap_array[buffer->init_pos], buffer->data, mod * sizeof(double));
        
        buffer->dirty = false;
    }
}


void buffer_update(chunk_array_t* chunk_array, buffer_t* buffer, size_t pos) {
    buffer_flush(chunk_array, buffer);
    
    if (chunk_array->mmap_array) {
        int new_init = pos/chunk_array->chunk_size;
        buffer->init_pos = new_init * chunk_array->chunk_size;
        int mod = get_mod(chunk_array, buffer->init_pos);
        memcpy(buffer->data, &chunk_array->mmap_array[buffer->init_pos], mod * sizeof(double));
    }
}

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

    if (buffer == NULL) return NULL;

    buffer->data = malloc(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));

    if (chunk_array == NULL) {
        return NULL;
    }

    chunk_array->chunk_size = min(MAX_CHUNK_SIZE, total_size);

    chunk_array->buffers = malloc(sizeof(buffer_t) * N_BUFFERS);

    chunk_array->buffers[0] = buffer_create(chunk_array->chunk_size);

    chunk_array->buffers[0]->init_pos = 0;

    chunk_array->n_buffers = 1;

    for (int i = 1; i<N_BUFFERS; i++) {
        if (total_size > i*chunk_array->chunk_size) {
            chunk_array->n_buffers++;
            chunk_array->buffers[i] = buffer_create(chunk_array->chunk_size);
            chunk_array->buffers[i]->init_pos = i*chunk_array->chunk_size;
        } else {
            break;
        }
    }

    if (chunk_array->chunk_size*chunk_array->n_buffers < total_size) {

        chunk_array->mmap_array = mmap ( NULL, total_size*sizeof(double), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0 );

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

    chunk_array->filename = filename;
    chunk_array->total_size = total_size;
    return chunk_array;
}

buffer_t* chunk_array_update(chunk_array_t* chunk_array, size_t pos) {
    buffer_t* buffer = chunk_array->buffers[0];
    int distance = abs(buffer->init_pos - pos);

    for(int i=1; i<chunk_array->n_buffers; i++) {
        int new_distance = abs(chunk_array->buffers[i]->init_pos - pos);
        if (new_distance < distance) {
            distance = new_distance;
            buffer = chunk_array->buffers[i];
        }
    }
    buffer_update(chunk_array, buffer, pos);
    return buffer;
}

bool chunk_array_get(chunk_array_t* chunk_array, size_t pos, double *valor) {
    // full memory
    if (chunk_array->total_size <= chunk_array->chunk_size) {
        *valor=chunk_array->buffers[0]->data[pos];
        return true;
    }

    // mmap
    buffer_t* buffer = NULL;
    for (int i = 0; i<chunk_array->n_buffers; i++) {
        if (inside_buffer(chunk_array, chunk_array->buffers[i]->init_pos, pos)) {
            buffer = chunk_array->buffers[i];
        }
    }

    if (!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) {
    // full memory
    if (chunk_array->total_size <= chunk_array->chunk_size) {
        chunk_array->buffers[0]->data[pos]=valor;
        chunk_array->buffers[0]->dirty = true;
        return true;
    }

    // mmap
	buffer_t* buffer = NULL;

    for (int i = 0; i<chunk_array->n_buffers; i++) {
        if (inside_buffer(chunk_array, chunk_array->buffers[i]->init_pos, pos)) {
            buffer = chunk_array->buffers[i];
        }
    }

    if (!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;
}