#include <iostream>
#include <cstdlib>   // for the exit function
#include "wolf.h"
using namespace std;

wolf::wolf(const terminal& init_t, unsigned init_x, unsigned init_y):
    t {&init_t}, x {init_x}, y {init_y}, c {'W'}
{
    if (!t->in_range(x, y)) {
        cerr << "Initial wolf position (" << x << ", " << y
             << ") off " << t->xmax() << " by " << t->ymax()
             << " terminal.\n";
        exit(EXIT_FAILURE);
    }

    const char other {t->get(x, y)};
    const char background {t->background()};

    if (other != background) {
        cerr << "Initial wolf position (" << x << ", " << y
             << ") already occupied by '" << other << "'.\n";
        exit(EXIT_FAILURE);
    }

    if (c == background) {
        cerr << "Wolf character '" << c << "' can't be the same as "
             << "the terminal's background character.\n";
        exit(EXIT_FAILURE);
    }

    t->put(x, y, c);
}

// Return false if this wolf ate another animal, true otherwise.
bool wolf::move()
{
    struct keystroke {
        char c;
        int dx;   // horizontal motion
        int dy;   // vertical motion
    };

    static const keystroke a[] = {
        {'h', -1, 0},   // left
        {'j', 0, 1},    // down
        {'k', 0, -1},   // up
        {'l', 1, 0}     // right
    };

    if (const char k {t->key()}) {  // If a key was pressed,
        for (const auto& stroke : a) {
            if (k == stroke.c) {
                const unsigned newx {x + stroke.dx};
                const unsigned newy {y + stroke.dy};

                if (!t->in_range(newx, newy)) {
                    break;  // Can't move off the screen.
                }

                const bool I_ate_him
                    {t->get(newx, newy) != t->background()};

                t->put(x, y); // Erase wolf from its old location
                x = newx;
                y = newy;
                t->put(x, y, c);  // Redraw wolf at new location.

                return !I_ate_him;
            }
        }

        // Arrive here to punish user who pressed an illegal key
        // or tried to move off the screen.
        t->beep();
    }

    return true;  // Keep the game going if wolf didn't move.
}