124 lines
3.7 KiB
Standard ML
124 lines
3.7 KiB
Standard ML
structure EnemyBehaviour =
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struct
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open GameType
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fun canWalkAhead (x, y, wallTree, platformTree) =
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let
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val ww = Constants.worldWidth
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val wh = Constants.worldHeight
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val searchWidth = Constants.enemySize
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val y = y + Constants.enemySize - 5
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val searchHeight = 10
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in
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QuadTree.hasCollisionAt
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(x, y, searchWidth, searchHeight, 0, 0, ww, wh, ~1, wallTree)
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orelse
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QuadTree.hasCollisionAt
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(x, y, searchWidth, searchHeight, 0, 0, ww, wh, ~1, platformTree)
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end
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fun getPatrollPatches (enemy: enemy, wallTree, platformTree, acc) =
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let
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(* This function is meant to check
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* if enemy should switch the horizontal direction
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* if the enemy is patrolling.
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*
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* Algorithm:
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* 1. Check if enemy there is a wall ahead of the enemy
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* in the direction the enemy is walking.
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* 1.1. If there is a wall, then invert the direction.
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*
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* 2. If there is no wall, check if there is space to
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* walk ahead on, such that enemy will not fall
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* if enemy continues to walk.
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* 2.1. If continuing to walk will cause the enemy to fall,
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* then invert the direction.
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*
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* 3. Else, do not invert direction and simply return given list.
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* *)
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val {x, y, xAxis, ...} = enemy
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in
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case xAxis of
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MOVE_LEFT =>
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let
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(* search to see if there is wall on left side *)
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val searchStartX = x - Constants.moveEnemyBy
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val searchWidth = Constants.enemySize
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val searchHeight = Constants.enemySize - 5
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val ww = Constants.worldWidth
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val wh = Constants.worldHeight
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val hasWallAhead = QuadTree.hasCollisionAt
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( searchStartX
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, y
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, searchWidth
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, searchHeight
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, 0
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, 0
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, ww
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, wh
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, ~1
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, wallTree
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)
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in
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if
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hasWallAhead
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then EnemyPatch.W_X_AXIS MOVE_RIGHT :: acc
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else (* invert direction if moving further left
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* will result in falling down *) if
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canWalkAhead (searchStartX, y, wallTree, platformTree)
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then acc
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else EnemyPatch.W_X_AXIS MOVE_RIGHT :: acc
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end
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| MOVE_RIGHT =>
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let
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(* enemy's x field is top left coordinate
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* but we want to check top * right coordinate,
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* so add enemySize *)
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val searchStartX = x + Constants.enemySize + Constants.moveEnemyBy
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val searchWidth = Constants.enemySize
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val searchHeight = Constants.enemySize - 5
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val ww = Constants.worldWidth
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val wh = Constants.worldHeight
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val hasWallAhead = QuadTree.hasCollisionAt
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( searchStartX
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, y
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, searchWidth
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, searchHeight
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, 0
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, 0
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, ww
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, wh
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, ~1
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, wallTree
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)
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in
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if
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hasWallAhead
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then EnemyPatch.W_X_AXIS MOVE_LEFT :: acc
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else (* invert direction if moving further right
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* will result in falling down *) if
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canWalkAhead (searchStartX, y, wallTree, platformTree)
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then acc
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else EnemyPatch.W_X_AXIS MOVE_LEFT :: acc
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end
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| STAY_STILL => acc
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end
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fun getVariantPatches
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(enemy, walls, wallTree, platforms, platformTree, player, acc) =
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let
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open EnemyVariants
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in
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case #variant enemy of
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PATROL_SLIME => getPatrollPatches (enemy, wallTree, platformTree, acc)
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end
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end
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