#include <stdio.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <sys/mman.h>

#include <fcntl.h>

#include "dictre.h"

const static char indexext[] = ".index";

const static char dictext[] = ".dict";

int get_filesize(const char *fname)

{

    struct stat st;

    int res;

    res = stat(fname, &st);

    if (res == -1)

    {

        fprintf(stderr, "Problem stating the file %s\n", fname);

        perror("Error:");

        exit(-1);

    }

    return st.st_size;

}

void init_dictionary(struct Dict *d, const char *base)

{

    char *filename;

    filename = (char *) malloc(strlen(base) + 10);

    /* Prepare .index filename and open it*/

    strcpy(filename, base);

    strcat(filename, indexext);

    d->indexsize = get_filesize(filename);

    d->indexfd = open(filename, O_RDONLY);

    if (d->indexfd == -1)

    {

        fprintf(stderr, "Problem opening the file %s\n", filename);

        perror("Error:");

        exit(-1);

    }

    d->index = (unsigned char *) mmap(0, d->indexsize, PROT_READ, MAP_SHARED,

            d->indexfd, 0);

    /* Prepare .dict filename and open it*/

    strcpy(filename, base);

    strcat(filename, dictext);

    d->defs = fopen(filename, "r");

    if (d->defs == 0)

    {

        fprintf(stderr, "Problem opening the file %s\n", filename);

        perror("Error:");

        exit(-1);

    }

    free(filename);

}

void end_dictionary(struct Dict *d)

{

    munmap(d->index, d->indexsize);

    close(d->indexfd);

    fclose(d->defs);

}

static void fill_def(struct Dict *d, int offset, int length, char * def)

{

    fseek(d->defs, offset, SEEK_SET);

    fread(def, 1, length, d->defs);

}

static int pointer_at_end(struct Dict *d, unsigned char *ptr)

{

    if (ptr >= (d->index + d->indexsize))

        return 1;

    return 0;

}

static char * skip_until_newline(struct Dict *d, char *from)

{

    if (pointer_at_end(d, from))

        return 0;

    while(*from != '\n' && *from != 0)

    {

        ++from;

        if(pointer_at_end(d, from))

            return 0;

    }

    return from;

}

static int compare(const unsigned char *word, const unsigned char *test)

{

    int i;

    /*printf("Comparing %s to %.20s\n", word, test);*/

    for(i=0; word[i] != 0 && test[i] != 0; ++i)

    {

        if (word[i] != test[i])

        {

            break;

        }

    }

    if (word[i] == 0 && test[i] == '\t')

        return 0;

    else if (word[i] == 0)

        return -1;

    else if (test[i] == '\t')

        return 1;

    else if (word[i] > test[i])

        return 1;

    else if (word[i] < test[i])

        return -1;

    /* It should never reach this. */

    return -1;

}

static char * bin_search(struct Dict *d, const char *word)

{

    int step, pivot;

    pivot = d->indexsize / 2;

    step = d->indexsize / 2;

    do

    {

        char *test;

        int comparision;

        test = d->index + pivot;

        test = skip_until_newline(d, test);

        if (test == 0)

            return 0;

        test += 1; /* skip exactly the new line */

        comparision = compare(word, test);

        if (comparision == 0)

        {

            return test + strlen(word) + 1; /* skip word and \n */

        } else if (comparision < 0)

        {

            step = step / 2;

            pivot = pivot - step;

        } else if (comparision > 0)

        {

            step = step / 2;

            pivot = pivot + step;

        }

    } while(step > 0);

    return 0;

}

static int my_get_int(char **pos)

{

    int i;

    char *start;

    int val;

    start = *pos;

    for(i=0; start[i] != '\t' && start[i] != '\n'; ++i)

        ;

    val = str2int_len(start, i);

    *pos += i + 1;

    return val;

}

void find_def(struct Dict *d, const char *word, char * def)

{

    int offset, len;

    char *pos;

    pos = bin_search(d, word); /* pos points to the offset already. */

    if (pos == 0)

    {

        def[0] = 0;

        /*fprintf(stderr, "Cannot find %s\n", word);*/

        return;

    }

    offset = my_get_int(&pos); /* increments pos */

    len = my_get_int(&pos); /* increments pos */

    fill_def(d, offset, len, def);

}