#include <ctype.h>
#include <string.h>

#include "coordinate.h"

/*
 * Returns 0 if the coordinate is between a1 and h8.
 */
int coord_is_valid(char *s) {
    if (strnlen(s, 3) != 2)
        return 1;

    char col = tolower(s[0]);
    char row = tolower(s[1]);

    if (col >= 'a' && col <= 'h' && row >= '1' && row <= '8')
        return 0;

    return 2;
}

/*
 * Does not check if s is a valid string representing. If input is
 * untrusted, use coord_is_valid(char*) to check it.
 */
Coord coord_init(char* s) {
    Coord c;
    char col = tolower(s[0]);
    char row = tolower(s[1]);

    c.col = col;
    c.row = row;

    return c;
}

/*
 * Returns 0 if c is the null coordinate
 */
int coord_is_null(Coord c) {
    return (c.col == 0 && c.row == 0);
}

/*
 * Returns the null coordinate
 */
Coord coord_null() {
    Coord c;

    c.col = 0;
    c.row = 0;

    return c;
}

/*
 * Set Coord row
 */
Coord coord_set_row(Coord c, char row) {
    c.row = row;

    return c;
}

/*
 * Set Coord column
 */
Coord coord_set_col(Coord c, char col) {
    c.col = col;

    return c;
}

/*
 * Get Coord row
 */
char coord_get_row(Coord c) {
    return c.row;
}

/*
 * Get Coord column
 */
char coord_get_col(Coord c) {
    return c.col;
}

/*
 * Returns the next coordinate. Useful for traversing the board forwards.
 */
Coord coord_next(Coord c) {
    if (coord_is_null(c))
        c = coord_init("a8");
    else
        if (c.col == 'h')
            if (c.row == '1')
                c = coord_null();
            else {
                c.row -= 1;
                c.col = 'a';
            }
        else
            c.col += 1;

    return c;
}

/*
 * Returns the previous coordinate. Useful for traversing the board backwards.
 */
Coord coord_prev(Coord c) {
    if (coord_is_null(c))
        c = coord_init("h1");
    else
        if (c.col == 'a')
            if (c.row == '8')
                c = coord_null();
            else {
                c.row += 1;
                c.col = 'h';
            }
        else
            c.col -= 1;

    return c;
}