#!/usr/bin/env python3
# Eryn Wells <eryn@erynwells.me>

'''
This module defines all of the actions that can be performed by the game. These actions can come from the player (e.g.
via keyboard input), or from non-player entities (e.g. AI deciboard input), or from non-player entities (e.g. AI
decisions).

Class Hierarchy
---------------

Action : Base class of all actions
    MoveAction : Base class for all actions that are performed with a direction
        BumpAction
        WalkAction
        MeleeAction
    ExitAction
    WaitAction
'''

import logging
from typing import Optional, TYPE_CHECKING

from . import items
from .geometry import Direction
from .object import Actor, Item

if TYPE_CHECKING:
    from .engine import Engine

LOG = logging.getLogger(__name__)

class ActionResult:
    '''The result of an Action.

    `Action.perform()` returns an instance of this class to inform the caller of the result

    Attributes
    ----------
    action : Action
        The Action that was performed
    success : bool, optional
        True if the action succeeded
    done : bool, optional
        True if the action is complete, and no follow-up action is needed
    alternate : Action, optional
        An alternate action to perform if this action failed
    '''

    def __init__(self, action: 'Action', *,
                 success: Optional[bool] = None,
                 done: Optional[bool] = None,
                 alternate: Optional['Action'] = None):
        self.action = action
        self.alternate = alternate

        if success is not None:
            self.success = success
        elif alternate:
            self.success = False
        else:
            self.success = True

        if done is not None:
            self.done = done
        elif self.success:
            self.done = True
        else:
            self.done = not alternate

    def __repr__(self):
        return f'{self.__class__.__name__}({self.action!r}, success={self.success}, done={self.done}, alternate={self.alternate!r})'

class Action:
    '''An action that an Entity should perform.'''

    def __init__(self, actor: Optional[Actor]):
        self.actor = actor

    def perform(self, engine: 'Engine') -> ActionResult:
        '''Perform this action.

        Parameters
        ----------
        engine : Engine
            The game engine

        Returns
        -------
        ActionResult
            A result object reflecting how the action was handled, and what follow-up actions, if any, are needed to
            complete the action.
        '''
        raise NotImplementedError()

    def failure(self) -> ActionResult:
        '''Create an ActionResult indicating failure with no follow-up'''
        return ActionResult(self, success=False)

    def success(self) -> ActionResult:
        '''Create an ActionResult indicating success with no follow-up'''
        return ActionResult(self, success=True)

    def __repr__(self):
        return f'{self.__class__.__name__}({self.actor!r})'

class ExitAction(Action):
    '''Exit the game.'''

    def perform(self, engine: 'Engine') -> ActionResult:
        raise SystemExit()

class RegenerateRoomsAction(Action):
    '''Regenerate the dungeon map'''

    def perform(self, engine: 'Engine') -> ActionResult:
        return ActionResult(self, success=False)

# pylint: disable=abstract-method
class MoveAction(Action):
    '''An abstract Action that requires a direction to complete.'''

    def __init__(self, actor: Actor, direction: Direction):
        super().__init__(actor)
        self.direction = direction

    def __repr__(self):
        return f'{self.__class__.__name__}({self.actor!r}, {self.direction!r})'

class BumpAction(MoveAction):
    '''Attempt to perform a movement action in a direction.

    This action tests if an action in the direction is possible and returns the action that can be completed.

    Attributes
    ----------
    direction : Direction
        The direction to test
    '''

    def perform(self, engine: 'Engine') -> ActionResult:
        new_position = self.actor.position + self.direction

        position_is_in_bounds = engine.map.tile_is_in_bounds(new_position)
        position_is_walkable = engine.map.tile_is_walkable(new_position)

        for ent in engine.entities:
            if new_position != ent.position:
                continue
            entity_occupying_position = ent
            break
        else:
            entity_occupying_position = None

        LOG.info('Bumping %s into %s (in_bounds:%s walkable:%s overlaps:%s)',
                 self.actor,
                 new_position,
                 position_is_in_bounds,
                 position_is_walkable,
                 entity_occupying_position)

        if not position_is_in_bounds or not position_is_walkable:
            return self.failure()

        if entity_occupying_position and entity_occupying_position.blocks_movement:
            return ActionResult(self, alternate=MeleeAction(self.actor, self.direction, entity_occupying_position))

        return ActionResult(self, alternate=WalkAction(self.actor, self.direction))


class WalkAction(MoveAction):
    '''Walk one step in the given direction.'''

    def perform(self, engine: 'Engine') -> ActionResult:
        new_position = self.actor.position + self.direction

        LOG.info('Moving %s to %s', self.actor, new_position)
        self.actor.position = new_position

        return self.success()

class MeleeAction(MoveAction):
    '''Perform a melee attack on another Actor'''

    def __init__(self, actor: Actor, direction: Direction, target: Actor):
        super().__init__(actor, direction)
        self.target = target

    def perform(self, engine: 'Engine') -> ActionResult:
        if not self.target:
            return self.failure()

        if not self.actor.fighter or not self.target.fighter:
            return self.failure()

        damage = self.actor.fighter.attack_power - self.target.fighter.defense
        if damage > 0:
            LOG.info('%s attacks %s for %d damage!', self.actor, self.target, damage)
            self.target.fighter.hit_points -= damage
        else:
            LOG.info('%s attacks %s but does no damage!', self.actor, self.target)

        if self.target.fighter.is_dead:
            LOG.info('%s is dead!', self.target)
            return ActionResult(self, alternate=DieAction(self.target))

        return self.success()

class WaitAction(Action):
    '''Wait a turn'''

    def perform(self, engine: 'Engine') -> ActionResult:
        LOG.info('%s is waiting a turn', self.actor)
        return self.success()

class DieAction(Action):
    '''Kill an Actor'''

    def perform(self, engine: 'Engine') -> ActionResult:
        LOG.info('%s dies', self.actor)
        engine.entities.remove(self.actor)

        if self.actor.yields_corpse_on_death:
            LOG.info('%s leaves a corpse behind', self.actor)
            corpse = Item(kind=items.Corpse, name=f'{self.actor.name} Corpse', position=self.actor.position)
            return ActionResult(self, alternate=DropItemAction(self.actor, corpse))

        return self.success()

class DropItemAction(Action):
    '''Drop an item'''

    def __init__(self, actor: 'Actor', item: 'Item'):
        super().__init__(actor)
        self.item = item

    def perform(self, engine: 'Engine') -> ActionResult:
        engine.entities.add(self.item)
        return self.success()