-- Header structure:
-----------------------------------------------------------------------------------------------------
--|              |               |  2bit |  2bit | 2bit  |   2bit |   2bit |   2bit |               |
--| Flit_padding |   Packet_id   | Z_src | Y_src | X_src | Z_dest | Y_dest | X_dest | Packet_length |
--|31  3bits   29|28  12 bits  17|16      6bits        11|10        6bits          5|4    5bits    0|
-----------------------------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

----------------------NoC Interface Entity---------------------------
entity Noc_Interface is
    generic (
        SOURCE_ID : std_logic_vector(5 downto 0) := "000000"; -- Default source ID should be changed
        DEST_ID   : std_logic_vector(5 downto 0) := "000001"  -- Default destination ID should be changed
    );
    port(
        clk                  : in  std_logic; 
        rst                  : in  std_logic;
        Sent_valid_from_DMA  : in  std_logic;                            --From DMA
        Data_bus_noc_in      : in  std_logic_vector(7 downto 0);         --From RAM
        tx_packet_length_noc : in  std_logic_vector(4 downto 0);         --From DMA
        local_noc_rx         : in  std_logic_vector(31 downto 0);---     --From Noc 
        local_vc_write_tx_noc: in  std_logic; ---_vector(192-1 downto 0);--From NoC
        rx_packet_length_noc : out std_logic_vector(4 downto 0);         --To DMA
        local_noc_tx         : out std_logic_vector(31 downto 0);---     --To NoC
        local_vc_write_rx_noc: out std_logic; ---_vector(192-1 downto 0);--To NoC
        Receive_valid_to_DMA : out std_logic;                            --To DMA 
        Sent_Ack_to_DMA      : out std_logic_vector(4 downto 0);-----------To DMA
        Data_bus_noc_out     : out std_logic_vector(7 downto 0)          --To RAM
        );
end entity;

----------------------NoC Interface Behaviour------------------------

architecture Noc_Interface_Arch of Noc_Interface is
    Signal packet_id     : std_logic_vector(11 downto 0);
    signal count         : std_logic_vector(4 downto 0);
    signal Sent_packet   : std_logic_vector(4 downto 0);

    --signal packet_length : std_logic_vector(4 downto 0);

begin
    rxprocess : process(clk, rst)
    begin
        if rst = '0' then
            rx_packet_length_noc   <= (others => '0');
            local_noc_tx           <= (others => '0');
            local_vc_write_rx_noc  <= (others => '0');
            Receive_valid_to_DMA   <= (others => '0');
            Sent_Ack_to_DMA        <= (others => '0');
            Data_bus_noc_out       <= (others => '0'); 
            count                  <= (others => '0'); 
            Sent_packet            <= (others => '0');
            packet_id              <= (others => '0');
        
        elsif rising_edge(clk) then

--------------------Reading from NoC--------------------------------

            if (local_vc_write_tx_noc = '1') then
                if (local_vc_write_tx_noc(31 downto 29) = "100") then
                    rx_packet_length_noc <= local_vc_write_tx_noc(4 downto 0 );   --packet length                      
                    count                <= (others => '0');                      --counter reset
                    packet_id            <= local_vc_write_tx_noc(28 downto 17);  --current packetid 
                elsif(count < local_vc_write_tx_noc(4 downto 0 )) then 
                    Receive_valid_to_DMA <= '1';                                  --valid to DMA
                    count                <= count + 1;                            --counter update
                    Data_bus_noc_out     <= local_vc_write_tx_noc(7 downto 0 );   --NoC is given to RAM
                else 
                    Receive_valid_to_DMA <= '0';
                    Data_bus_noc_out     <= (others=>'0');
                    count                <= (others=>'0');
                end if;

--------------------Writing to NoC----------------------------------

            elsif (Sent_valid_from_DMA = '1' and tx_packet_length_noc > 0) then
               if(Sent_packet = "00000") then
                    Sent_Ack_to_DMA       <= Sent_packet + 1; --to DMA updated value
                    Sent_packet           <= Sent_packet + 1;
                    --updating packet id
                    local_noc_tx          <= "100" & packet_id & SOURCE_ID & DEST_ID & tx_packet_length_noc;
                    local_vc_write_rx_noc <= '1';
                else
                    Sent_Ack_to_DMA       <= Sent_packet + 1; --to DMA updated value                   
                    Sent_packet           <= Sent_packet + 1;
                    local_noc_tx          <= (others => '0') & Data_bus_noc_in;; --24bit zeros in msb and 8 bit data
                    local_vc_write_rx_noc <= '1';
                end if;
            else
                rx_packet_length_noc   <= (others => '0');
                local_noc_tx           <= (others => '0');
                local_vc_write_rx_noc  <= (others => '0');
                Receive_valid_to_DMA   <= (others => '0');
                Sent_Ack_to_DMA        <= (others => '0');
                Data_bus_noc_out       <= (others => '0'); 
                count                  <= (others => '0'); 
                Sent_packet            <= (others => '0');
            end if;
        end if; 
    end process;
end architecture;