Order.hs

module Order where 


import Product
import Command
import Shipping
import Syntax
import Inventory

--
-- * Concrete command for place order on product 
-- 
data PlaceOrderCmd = PlaceOrderCmd

-- | concrete command implementation of placing user order
instance Command PlaceOrderCmd where
    placeOrder' PlaceOrderCmd m ps = let plist = getSingleCost ps
                                         get3rd = \(_,_,c) -> c 
                                         final = getFinalCost $ map get3rd plist 
                                         shippingcost = getFinalCost $ map (getShippingCost m) $ map snd ps
                                     in Just (plist,shippingcost,final + shippingcost)  

-- | helper functions for placeOrder 
getCurPriceList :: [(Product, Qty)] ->  [(Product, Price)]
getCurPriceList ps = let pidQtyList = map (\(p,qty) -> (productId p, qty)) ps
                         pidPriceList = checkFromInventory pidQtyList
                         productList = map fst ps 
                         priceList = map snd pidPriceList
                     in zip productList priceList

getSingleCost :: [(Product,Qty)] -> [(Product, Qty , Price)]
getSingleCost ps =  map (\(pro,i) -> (pro,i, (getCurPrice pro) * i)) ps 
    where   productPriceList = getCurPriceList ps 
            getCurPrice p = case lookup p productPriceList of 
                                Nothing -> error "Didn't find the price in invenrory"
                                Just curPrice -> curPrice

getShippingCost :: Shipping' m => m -> Int -> Int
getShippingCost m w = calculateShippingCost m w 

getFinalCost :: [Int] -> Int 
getFinalCost ps = Prelude.foldl (+) 0 ps

orderListEx :: [(Product, Int)]
orderListEx = [(Product Item1, 1), (Product Item2, 5)]

prettyFinalOrder :: Maybe ([(Product,Qty,Price)],Int,Int)  -> String 
prettyFinalOrder (Just (plist, shipping, final)) = unlines (map prettyInvoice plist) ++ "Shipping Cost:$" ++ show shipping ++ "\n" ++ "Final cost:$" ++ show final  
prettyFinalOrder _ = "Error: Order can't be placed."

prettyInvoice :: (Product,Qty,Price) -> String 
prettyInvoice (p, qty, price) = let curP = currentPrice p in
                                case curP == price `div` qty of 
                                    True ->  getProduct Cmd1 p ++ "| Qty:"  ++ show qty ++ "| cost:$" ++ show price
                                    False ->  getProduct Cmd1 p ++ "| Qty:"  ++ show qty ++ "| cost:$" ++ show price ++ "\n" ++ "Comments:" ++ "(Price changed to $" ++ show (price `div` qty )++ " due to product is not available in inventory and purchase from external vendor)"

--
--  * invoker instance for placeOrder
-- 
instance Invoker PlaceOrderCmd where
    executeOrder PlaceOrderCmd m ps = prettyFinalOrder $ placeOrder' PlaceOrderCmd m ps