261 lines
8.0 KiB
Standard ML
261 lines
8.0 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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(* same function takes either wallTree or platformTree and returns true
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* if standing on tree.
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* Function is monomorphic in the sense that wallTree and platformTree
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* are both same type (no generics/parametric polymorphism).
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* *)
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fun standingOnArea (enemy: enemy, tree) =
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let
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val {x = ex, y = ey, ...} = enemy
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val ey = ey + Constants.enemySize - 1
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val width = Constants.enemySize
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val height = Platform.platHeight
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val ww = Constants.worldWidth
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val wh = Constants.worldHeight
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in
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QuadTree.hasCollisionAt (ex, ey, width, height, 0, 0, ww, wh, ~1, tree)
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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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(* pathfinding *)
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fun isBetween (p1, check, p2) = check >= p1 andalso check <= p2
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fun getHighestPlatform (collisions, platforms, highestY, highestID) =
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case collisions of
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id :: tl =>
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let
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val {y = platY, ...} = Platform.find (id, platforms)
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in
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(* platY < highestY is correct because lowest number = highest
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* in * this case *)
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if platY < highestY then getHighestPlatform (tl, platforms, platY, id)
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else getHighestPlatform (tl, platforms, highestY, highestID)
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end
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| [] => highestID
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fun getPlatformBelowPlayer (player, platformTree, platforms) =
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let
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val {x, y, ...} = player
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val searchWidth = Constants.playerSize
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val searchHeight = Constants.worldHeight - y
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val ww = Constants.worldWidth
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val wh = Constants.worldHeight
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val collisions = QuadTree.getCollisions
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(x, y, searchWidth, searchHeight, 0, 0, ww, wh, ~1, platformTree)
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in
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getHighestPlatform (collisions, platforms, wh, ~1)
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end
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fun getPlatformBelowEnemy (enemy: enemy, platformTree, platforms) =
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let
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val {x, y, ...} = enemy
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val searchWidth = Constants.enemySize
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val searchHeight = Constants.worldHeight - y
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val y = y + Constants.enemySize
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val ww = Constants.worldWidth
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val wh = Constants.worldHeight
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val collisions = QuadTree.getCollisions
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(x, y, searchWidth, searchHeight, 0, 0, ww, wh, ~1, platformTree)
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in
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getHighestPlatform (collisions, platforms, wh, ~1)
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end
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fun canJump (nextPlatform, platformTree, enemy) =
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let
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val {x = platX, y = platY, width = platW, ...} = nextPlatform
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val platFinishX = platX + platW
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val {x = eX, y = ey, yAxis = eyAxis, ...} = enemy
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val standingOnPlat = standingOnArea (enemy, platformTree)
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in
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isBetween (platX, eX, platFinishX) andalso standingOnPlat
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andalso (ey > platY andalso ey + Constants.jumpLimit >= platY)
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end
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(* get patches to help enemy move to nextPlatformID *)
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fun getPathToNextPlatform
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(nextPlatformID, platforms, platformTree, enemy, eID, pID, acc) =
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let
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val nextPlatform = Platform.find (nextPlatformID, platforms)
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val {x = eX, y = ey, yAxis = eyAxis, ...} = enemy
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val canJump = canJump (nextPlatform, platformTree, enemy)
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in
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if canJump then
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case eyAxis of
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ON_GROUND => EnemyPatch.W_Y_AXIS (JUMPING 0) :: acc
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| FALLING => EnemyPatch.W_Y_AXIS (JUMPING 0) :: acc
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| _ => acc
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else
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acc
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end
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fun canJumpOnPlatform (player, platforms, enemy: enemy, platformTree, acc) =
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let
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(* todo: possibly get pID and eID of player/enemy in a different way *)
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val pID = getPlatformBelowPlayer (player, platformTree, platforms)
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val eID = getPlatformBelowEnemy (enemy, platformTree, platforms)
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val bestPath = PathFinding.start (pID, eID, platforms, platformTree)
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in
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if eID = pID then
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EnemyPatch.W_Y_AXIS FALLING :: acc
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else
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case bestPath of
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nextPlatformID :: _ =>
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getPathToNextPlatform
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(nextPlatformID, platforms, platformTree, enemy, eID, pID, acc)
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| [] => acc
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end
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fun getFollowPatches
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(player: player, enemy, wallTree, platformTree, platforms, acc) =
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let
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val {x = px, y = py, ...} = player
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val {x = ex, y = ey, yAxis = eyAxis, ...} = enemy
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val xAxis = if px < ex then MOVE_LEFT else MOVE_RIGHT
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val acc = canJumpOnPlatform (player, platforms, enemy, platformTree, acc)
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in
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EnemyPatch.W_X_AXIS 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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| FOLLOW_SIME =>
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getFollowPatches
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(player, enemy, wallTree, platformTree, platforms, acc)
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end
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end
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