-- Book_Inventory.adb
-- Written by James Halvorsen (W00974148)

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
with Ada.Command_Line; use Ada.Command_Line;

-- I was thinking about using a linked list to store my inventory
-- With the Queue_Generic to store back orders as required
-- But then I realized you never said we couldn't use Ada's prefedined types.
-- So here's to laziness. Because with the time I could have used making my own
-- Storage system, I could have used it doing much more productive things, like
-- Writing this wonderfully useless comment.
with Ada.Containers.Vectors; use Ada.Containers;
with Queue_Generic;

procedure book_inventory is

    subtype ISBN_Type is String(1 .. 10);
    type Dollars is delta 0.01 digits 6 range 0.0 .. 9999.0;
    type Book is record
        ISBN : ISBN_Type;
        Price : Dollars;
        Amount : Natural;
    end record;
    type Back_Order is record
        Customer_Number : Natural;
        ISBN : ISBN_Type;
        Amount : Natural;
    end record;

    package BOQ is new Queue_Generic (Back_Order); -- Back order queue
    package Book_Storage is new Vectors (Positive, Book);
    package Dollar_IO is new Decimal_IO (Dollars); use Dollar_IO;

    Back_Order_Queue : BOQ.Queue_Type;
    Inventory_File : File_Type;
    Actions_File : File_Type;
    Wrong_Args : exception;
    Inventory : Book_Storage.Vector;
    Revenue : Dollars := 0.00;

    -- Reads the input file and fills Inventory with it
    procedure Inventory_From_File (Initial_Inventory : in File_Type) is
        Temp_Book : Book;
    begin
        while not End_Of_File (Initial_Inventory) loop
            -- Read fields for a Book Type
            Get(Initial_Inventory, Temp_Book.ISBN);
            Get(Initial_Inventory, Temp_Book.Price);
            Get(Initial_Inventory, Temp_Book.Amount);

            -- Attach to a vector and reset fields
            Inventory.Append(Temp_Book);
            Temp_Book.ISBN := "0000000000";
            Temp_Book.Price := 0.00;
            Temp_Book.Amount := 0;

        end loop;
    end Inventory_From_File;

    -- Handles STOCK and ORDER requests
    procedure Execute_Orders (Order_File : in File_Type) is
        Order_Type : String (1 .. 5);
        Ignore_Space : Character;
        ISBN : ISBN_Type;
        Num_Purchased : Natural;
        Customer_Number : Natural;

        Temp_Back_Order : Back_Order;
        Temp_Book : Book;
        Book_Found : Boolean := false;
        Book_Index : Positive;

    begin
        while not End_Of_File (Order_File) loop
            -- Read fields for the order
            Get(Order_File, Order_Type);
            Get(Order_File, Ignore_Space);
            Get(Order_File, ISBN);
            Get(Order_File, Num_Purchased);

            if (Order_Type = "ORDER") then
                Get(Order_File, Customer_Number);
            end if;

            if (Order_Type = "STOCK") then
                -- Check if back orders exist
                -- If back orders exist
                    -- Fill out as many as possible with
                    -- The new stock
                -- If no back orders exist
                    -- Add book to inventory
                    -- Be sure to check if similar books
                    -- Exist, or if books need to be pushed
                    -- Into the vector
                null;
            elsif (Order_Type = "ORDER") then
                -- Check to see if books are available
                for I in Inventory.First_Index .. Inventory.Last_Index loop
                    if Inventory.Element(Index => I).ISBN = ISBN then
                        Book_Found := true;
                        Book_Index := I;
                    end if;
                end loop;
                if Book_Found then
                    -- All books required are in inventory
                    if Inventory.Element(Index => Book_Index).Amount >= Num_Purchased then
                        Put("Order for customer ");
                        Put(Item => Customer_Number, Width => 0);
                        Put(" For "); Put(Item => Num_Purchased, Width => 0);
                        Put(" Copies of book "); Put(ISBN);
                        new_line;

                        Temp_Book := Inventory.Element(Index => Book_Index);
                        Revenue := Revenue + (Temp_Book.Price * Num_Purchased);
                        Temp_Book.Amount := Temp_Book.Amount - Num_Purchased;
                        Book_Storage.Replace_Element(Inventory, Book_Index, Temp_Book);
                    -- None in stock
                    elsif Inventory.Element(Index => Book_Index).Amount = 0 then
                        Temp_Back_Order.Customer_Number := Customer_Number;
                        Temp_Back_Order.ISBN := ISBN;
                        Temp_Back_Order.Amount := Num_Purchased;
                        BOQ.Enqueue(Back_Order_Queue, Temp_Back_Order);
                    -- Some in stock, not sufficient for all of order
                    else

                    end if;
                else
                    Temp_Back_Order.Customer_Number := Customer_Number;
                    Temp_Back_Order.ISBN := ISBN;
                    Temp_Back_Order.Amount := Num_Purchased;
                    BOQ.Enqueue(Back_Order_Queue, Temp_Back_Order);
                end if;
            else
                null;
                -- Throw an exception, nothing other than
                -- Stock or order should exist.
            end if;
            skip_line(Order_File);
        end loop;
    end Execute_Orders;

-- Main Procedure, handles command line arguments then passes them off
-- To Inventory_From_File and Execute_Orders
begin
    if Argument_Count /= 2 then
        raise Wrong_Args;
    end if;

    Open( File => Inventory_File, Mode => In_File, Name => Argument(1) );
    Inventory_From_File(Inventory_File);
    Close(Inventory_File);

    Open( File => Actions_File, Mode => In_File, Name => Argument(2) );
    Execute_Orders(Actions_File);
    Close(Actions_File);
exception
    when Wrong_Args =>
        Put("Usage: book_inventory InventoryFile TransactionsFile");
        new_line;
    when Name_Error =>
        Put("One or more files inputted does not exist");
        new_line;

end book_inventory;