-- ============================================================================
-- P4 T=SQL Settler — VHDL RTL
-- Strict Settlement ID Sequencing for Worm Chain Index Ordering
-- Authors: Ahmad Ali Parr, Jessica L. Williams (SNAPKITTYWEST)
-- ============================================================================
--
-- Resolves T=SQL index collisions via monotone sequence counter.
-- Each valid (q_seed_valid) input triggers one settlement output
-- with a unique, strictly increasing settle_id.
--
-- Evidence boundary:
--   Pigeonhole guarantees collisions exist in the T=SQL hash.
--   This module does NOT prevent them — it orders them deterministically.
-- ============================================================================

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity p4_tsql_settler is
    port (
        clk          : in  std_logic;
        rst_n        : in  std_logic;
        -- Inputs from ANu
        t_sql_index  : in  std_logic_vector(31 downto 0);
        q_seed_valid : in  std_logic;
        -- P4 Settlement Outputs
        settle_valid : out std_logic;
        settle_id    : out std_logic_vector(63 downto 0);
        settle_index : out std_logic_vector(31 downto 0)
    );
end entity p4_tsql_settler;

architecture rtl of p4_tsql_settler is
    signal sequence_cnt : unsigned(63 downto 0) := (others => '0');
begin

    process(clk, rst_n)
    begin
        if rst_n = '0' then
            sequence_cnt <= (others => '0');
            settle_valid <= '0';
        elsif rising_edge(clk) then
            settle_valid <= '0';

            if q_seed_valid = '1' then
                -- Monotone increment guarantees strict ordering
                -- even when t_sql_index values collide
                sequence_cnt <= sequence_cnt + 1;

                settle_id    <= std_logic_vector(sequence_cnt + 1);
                settle_index <= t_sql_index;
                settle_valid <= '1';
            end if;
        end if;
    end process;

end architecture rtl;