behavior.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""A behavior contains the logic of an entity, which takes place when that entity takes its turn in the game.

Behaviors are functions which always have two arguments: the caller, which is the entity that takes the turn,
and the target, which is some other object that the caller uses for its logic. The target could also be None.

A behavior could define, for example, the AI of an Actor, or other types of logic like the spreading of fire.
"""


def basic_monster(caller, target):
    """
    Follow a target if visible and attack when in melee range.

    Args:
        caller (Actor): Actor that performs the action.
        target (Actor): Actor that the caller will follow and attack.
    """
    # Check if the monster can see the target
    # TODO: For now, we just check if the player can see the monster and
    # assume the monster can see it too. If we make entities with different
    # visibility radius, this will have to change
    # TODO: Add patrol mode if the player is not visible
    assert caller.game_map is not None and caller.game_map == target.game_map
    game_map = caller.game_map
    if game_map.fov[caller.pos]:
        if caller.distance_to(target.pos) >= 2:
            # Target is too far to attack, try moving towards it
            path = game_map.compute_path(caller.pos, target.pos)
            if not path:
                # Can't reach the target, don't do anything
                return
            # Only try to move closer to the target if the monster doesn't have to lose vision of the target to do
            # so. In this case, don't do anything
            for tile in path:
                if not game_map.fov[tile]:
                    # Try to move closer taking one step in the direction of the target
                    direction = (target.pos - caller.pos).snap_to_grid()
                    if game_map.walkable[caller.pos + direction]:
                        caller.move(direction)
                        return
            # The path is clear and the monster doesn't have to lose sight of the target, so follow the path
            direction = path[0] - caller.pos
            caller.move(direction)
        else:
            # Attack the target
            if target.type == 'actor':
                caller.attack(target)