lib/RPGEngine/Data/Level.hs

@@ -92,3 +92,9 @@ isInventoryFull p = inventorySize <= length (inventory p)
 -- Check if the inventory of the player contains an item.
 inventoryContains :: ItemId -> Player -> Bool
 inventoryContains id p = any ((== id) . itemId) $ inventory p
+
+-- Retrieve an item from inventory
+itemFromInventory :: ItemId -> [Item] -> (Maybe Item, [Item])
+itemFromInventory iid list = (match, filteredList)
+    where match = find ((== iid) . itemId) list
+          filteredList = filter ((/= iid) . itemId) list

lib/RPGEngine/Input/ActionSelection.hs

@@ -4,11 +4,11 @@ module RPGEngine.Input.ActionSelection
 
 import RPGEngine.Input.Core (InputHandler, handleKey, composeInputHandlers, ListSelector (selection))
 
-import RPGEngine.Data (Game (..), State (..), Direction (..), Action (..), ItemId, EntityId, Level (..), Player (inventory, playerHp, Player), Item (..), HP)
+import RPGEngine.Data (Game (..), State (..), Direction (..), Action (..), ItemId, EntityId, Level (..), Player (inventory, playerHp, Player), Item (..), HP, Entity (..))
 import Graphics.Gloss.Interface.IO.Game (Key(SpecialKey), SpecialKey (KeyUp, KeyDown))
 import Graphics.Gloss.Interface.IO.Interact
     ( SpecialKey(..), KeyState(..) )
-import RPGEngine.Data.Level (getWithId)
+import RPGEngine.Data.Level (getWithId, itemFromInventory)
 import Data.Foldable (find)
 
 ------------------------------ Exported ------------------------------
@@ -72,13 +72,30 @@ useItem :: ItemId -> State -> State -- TODO
 useItem _ s = s -- TODO
 
 -- Attack an entity using an item
+-- Should receive a Playing state
 decreaseHp :: EntityId -> ItemId -> State -> State
-decreaseHp _ _ s = s
+decreaseHp eid iid s@Playing{ level = level, player = player } = newState
--- TODO DecreaseHp of monster
+    where newState = s{ level = newLevel, player = newPlayer }
--- TODO Check if monster is dead
+          -- Change player
--- TODO Entity attack player
+          (Just usingItem) = find ((== iid) . itemId) (inventory player)
--- TODO Decrease durability of item
+          usedItem         = decreaseDurability usingItem
--- TODO Break item if durability below zero
+          newInventory     = filter (/= usingItem) $ inventory player
+          newPlayer = player{ inventory = putItemBack usedItem newInventory, playerHp = newHp }
+          putItemBack Nothing inv     = inv
+          putItemBack (Just item) inv = item:inv
+          newHp                       = changeHealth (playerHp player) damageGetAmount -- Damage dealt by entity
+          damageDealAmount = itemValue usingItem
+          -- Change entity
+          (Just (Right attackedEntity)) = getWithId eid level
+          newLevel = level{ entities = putEntityBack dealtWithEntity newEntities }
+          newEntities = filter ((/= eid) . entityId) $ entities level
+          dealtWithEntity = decreaseHealth attackedEntity damageDealAmount 
+          putEntityBack Nothing    list = list
+          putEntityBack (Just ent) list = ent:list
+          damageGetAmount = inverse (entityValue attackedEntity)
+          inverse (Just val) = Just (-val)
+          inverse Nothing    = Nothing
+decreaseHp _ _ _ = Error "something went wrong while attacking"
 
 -- Heal a bit
 -- Should receive a Player
@@ -97,6 +114,12 @@ decreaseDurability item@Item{ useTimes = Nothing  } = Just item -- Infinite uses
 decreaseDurability item@Item{ useTimes = Just val } | 0 < val - 1 = Just item{ useTimes = Just (val - 1) }
                                                     | otherwise = Nothing -- Broken
 
+decreaseHealth :: Entity -> Maybe Int -> Maybe Entity
+decreaseHealth entity@Entity{ entityHp = Nothing  } _ = Just entity
+decreaseHealth entity@Entity{ entityHp = Just val } (Just i) | 0 < val - i = Just entity{ entityHp = Just (val - i) }
+                                                             | otherwise   = Nothing
+decreaseHealth entity _ = Just entity
+
 -- Change given health by a given amount
 changeHealth :: HP -> HP -> HP
 changeHealth (Just health) (Just difference) = Just (health + difference)

lib/RPGEngine/Parse/TextToStructure.hs

@@ -139,7 +139,7 @@ action = try $ do
     let answer | script == "leave"            = Leave
                | script == "retrieveItem"     = RetrieveItem arg
                | script == "useItem"          = UseItem arg
-               | script == "decreaseHp"       = DecreaseHp first second
+               | script == "decreaseHp"       = DecreaseHp first (filter (/= ' ') second) -- TODO Work this hack away
                | script == "increasePlayerHp" = IncreasePlayerHp arg
                | otherwise                    = DoNothing
         (first, ',':second) = break (== ',') arg

src/Main.hs

@@ -1,4 +1,4 @@
-import RPGEngine
+import RPGEngine ( playRPGEngine )
 
 ----------------------------- Constants ------------------------------
 

test/Parser/GameSpec.hs

@@ -6,7 +6,6 @@ import RPGEngine.Data
 import RPGEngine.Parse.Core
 import RPGEngine.Parse.TextToStructure
 import RPGEngine.Parse.StructureToGame
-import RPGEngine.Parse.TextToStructure (gameFile)
 
 spec :: Spec
 spec = do
@@ -142,6 +141,12 @@ spec = do
                 Right struct = parseWith structure input
             structureToActions struct `shouldBe` correct
         
+        it "DecreaseHp(entityid, itemid)" $ do
+            let input   = "{ [] decreaseHp(devil, sword) }"
+                correct = [([], DecreaseHp "devil" "sword")]
+                Right struct = parseWith structure input
+            structureToActions struct `shouldBe` correct
+
     describe "Entities" $ do
         it "Simple entity" $ do
             pendingWith "still need to write this"

test/Parser/StructureSpec.hs

@@ -146,6 +146,10 @@ spec = do
                 correct = Right $ Regular $ Action $ UseItem "secondId"
             parseWith regular input `shouldBe` correct
 
+            let input   = "decreaseHp(entityId, objectId)"
+                correct = Right $ Regular $ Action $ DecreaseHp "entityId" "objectId"
+            parseWith regular input `shouldBe` correct
+
             let input   = "decreaseHp(entityId,objectId)"
                 correct = Right $ Regular $ Action $ DecreaseHp "entityId" "objectId"
             parseWith regular input `shouldBe` correct