#ifndef MARKOV_H
#define MARKOV_H

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include <time.h>

extern int ITEMS;
extern double chain[][ITEM_CAP];
extern char item_names[][64];

void generate_chain(char *file_path)
{
    FILE *fp = fopen(file_path, "r");
    if(!fp) {
        fprintf(stderr, "ERROR: Could not open file %s\n", file_path);
        exit(EXIT_FAILURE);
    }

    int items_seen[ITEM_CAP][ITEM_CAP] = {0};
    int cur_item = -1;

    char line[256] = {0};
    while((fgets(line, sizeof(line), fp)) != NULL)
    {
        if(line[strlen(line)-1] == '\n')
            line[strlen(line)-1] = '\0';

        int item = ITEMS;

        for(int i = 0; i < ITEMS; i++)
        {
            if(strcmp(line, item_names[i]) == 0)
                item = i;
        }

        if(item == ITEMS) {
            ITEMS++;
            strcpy(item_names[item], line);
        }

        if(cur_item != -1)
            items_seen[cur_item][item]++;

        cur_item = item;
    }

    fclose(fp);

    for(int i = 0; i < ITEMS; i++)
    {
        int all = 0;
        for(int j = 0; j < ITEMS; j++)
            all += items_seen[i][j];

        for(int j = 0; j < ITEMS; j++)
            chain[i][j] = (double)items_seen[i][j]/all;
    }
}

int walk_step(int item)
{
    int item_lim = 0;
    int r = rand();

    for(int i = 0; i < ITEMS; i++)
    {
        item_lim += RAND_MAX * chain[item][i];
        if(r <= item_lim) return i;
    }

    return -1;
}

void take_walk()
{
#ifdef SAVE_TO_FILE_ON_WALK
    FILE *fp = fopen(SAVE_TO_FILE_ON_WALK, "w");
    if(!fp) {
        fprintf(stderr, "ERROR: Could not open file %s\n", SAVE_TO_FILE_ON_WALK);
        exit(EXIT_FAILURE);
    }
#endif

    int items_seen[ITEM_CAP] = {0};
    int cur_item = rand() % ITEMS;

    for(size_t i = 0; i < WALK_LEN; i++)
    {
    #ifdef PRINT_ON_WALK
        puts(item_names[cur_item]);
    #endif
    #ifdef SAVE_TO_FILE_ON_WALK
        fprintf(fp, "%s\n", item_names[cur_item]);
    #endif
        items_seen[cur_item]++;
        int ni = walk_step(cur_item);
        assert(ni != -1);
        cur_item = ni;
    }

#ifdef SAVE_TO_FILE_ON_WALK
    fclose(fp);
    printf("Saved file with %d items at %s\n", WALK_LEN, SAVE_TO_FILE_ON_WALK);
#endif

#ifdef PRINT_ITEM_FREQUENCY
    puts("Item Frequency:");
    for(int i = 0; i < ITEMS; i++)
        printf("%f %s\n", (double)items_seen[i]/WALK_LEN, item_names[i]);
    puts("");
#endif
}

void print_chain()
{
    puts("Chain Matrix:");
    for(int i = 0; i < ITEMS; i++)
    {
        printf("{");
        for(int j = 0; j < ITEMS; j++)
            printf(" %f,", chain[i][j]);
        printf("}\n");
    }
    puts("");
}

#endif