// CMYK Adaptive Router
// Derived from docs/semantics/ADAPTIVE_1BIT_CMYK_MERGED.md
// Implements stress-based routing state machine

`timescale 1ns / 1ps

module cmyk_adaptive_router (
    input  wire        clk,
    input  wire        rst_n,
    input  wire [31:0] v_t,        // Q16.16 input signal
    input  wire [31:0] m_t,        // Q16.16 metaprobe stress
    input  wire [31:0] delta_t,    // Q16.16 delta stress
    output reg  [1:0]  state,      // 00=K, 01=C, 10=M, 11=Y
    output reg  [31:0] residual,   // e_t: Error residual
    output reg         gate_open   // Control signal for data emission
);

    // ═══════════════════════════════════════════════════════════════════════════
    // Parameters (Match Lean FabricConfig)
    // ═══════════════════════════════════════════════════════════════════════════
    parameter DELTA_PHI = 32'h12345678;
    parameter PHI_SHIFT = 5'd24;
    parameter MASK      = 32'h000000AA;
    parameter SLUQ_SHIFT = 5'd4;
    parameter LAMBDA1   = 32'h00008000; // 0.5
    parameter LAMBDA2   = 32'h00004000; // 0.25
    parameter LAMBDA3   = 32'h00004000; // 0.25

    // ═══════════════════════════════════════════════════════════════════════════
    // Internal Registers
    // ═══════════════════════════════════════════════════════════════════════════
    reg [31:0] phi;
    reg [31:0] sluq_acc;
    
    // LUT for Threshold (Simplified 256-entry uniform for PoC)
    wire [31:0] theta_t = 32'h00008000; // 0.5

    // ═══════════════════════════════════════════════════════════════════════════
    // Adaptive Update Loop (Match Lean step function)
    // ═══════════════════════════════════════════════════════════════════════════
    
    wire [31:0] abs_residual = residual[31] ? (~residual + 1) : residual;
    
    // Fixed-point multiply helper (Q16.16)
    function [31:0] q_mul;
        input [31:0] a, b;
        reg [63:0] prod;
        begin
            prod = {{32{a[31]}}, a} * {{32{b[31]}}, b};
            q_mul = prod[47:16];
        end
    endfunction

    always @(posedge clk or negedge rst_n) begin
        if (!rst_n) begin
            phi <= 0;
            residual <= 0;
            sluq_acc <= 0;
            state <= 2'b00;
            gate_open <= 1'b1;
        end else begin
            // 1. φ-Accumulator
            phi <= phi + DELTA_PHI;
            
            // 2. 1-Bit Noise-Shaped Encoder
            // b_t = 1 if v_t + e_{t-1} > θ_t else 0
            if ((v_t + residual) > theta_t) begin
                residual <= (v_t + residual) - 32'h00010000; // b_t = 1.0
            end else begin
                residual <= (v_t + residual);                // b_t = 0.0
            end

            // 3. SLUQ Routing Accumulator
            // a_{t+1} = a_t - (a_t >> r) + λ_1 |e_t| + λ_2 Δ_t + λ_3 m_t
            sluq_acc <= sluq_acc - (sluq_acc >> SLUQ_SHIFT) + 
                        q_mul(LAMBDA1, abs_residual) + 
                        q_mul(LAMBDA2, delta_t) + 
                        q_mul(LAMBDA3, m_t);

            // 4. CMYK State Classification
            // s_t = a_t >> 14
            state <= sluq_acc[15:14]; // Taking the relevant bits for state
            
            // Gate Control
            gate_open <= (sluq_acc[15:14] < 2'b10); // K and C are open, M and Y are closed
        end
    end

endmodule