// tb_sha3_xsim_simple.v - Self-checking testbench for sha3_top (G/H/J modes)
//
// Drives sha3_top in all three modes and checks hash_o against expected
// values computed by the verified Python reference (server_code SHA_3,
// KAT-validated). Vectors are deterministic (gen_vectors seed=20260627).
//
//   G (mode=00, SHA3-512): data_i[263:0] = d||k, output 512 bits
//   H (mode=01, SHA3-256): data_i[255:0] = ek,   output low 256 bits
//   J (mode=10, SHAKE-256): data_i[511:0] = z||c, output low 256 bits
//
// data_i / hash_o use MSB-first hex packing (hex[511:0] literal == data_i).
//
// Usage:
//   xvlog -sv sha3_top.v tb_sha3_xsim_simple.v
//   xelab tb_sha3_xsim_simple -s sha3_sim
//   xsim sha3_sim -R

`timescale 1ns / 1ps

module tb_sha3_xsim_simple;

    // ================================================================
    // DUT signals
    // ================================================================
    reg              clk;
    reg              rst_n;
    reg  [1:0]       mode;
    reg  [511:0]     data_i;
    reg              valid_i;
    wire             ready_o;
    wire [511:0]     hash_o;
    wire             valid_o;
    reg              ready_i;

    // ================================================================
    // DUT instantiation
    // ================================================================
    sha3_top u_dut (
        .clk      (clk),
        .rst_n    (rst_n),
        .mode     (mode),
        .data_i   (data_i),
        .valid_i  (valid_i),
        .ready_o  (ready_o),
        .hash_o   (hash_o),
        .valid_o  (valid_o),
        .ready_i  (ready_i)
    );

    // ================================================================
    // Clock generation: 100 MHz (10 ns period)
    // ================================================================
    initial clk = 1'b0;
    always #5 clk = ~clk;

    // ================================================================
    // Expected vectors (verified Python reference, seed=20260627)
    // ================================================================
    // G: data_i[263:0] = {k=2, d}; output 512-bit SHA3-512
    localparam [511:0] G_DATA = 512'h000000000000000000000000000000000000000000000000000000000000007DBC2AC0D13D719B37B4E2D4691951FF890A97854EF5D3A8957EF67A54978E26C9;
    localparam [511:0] G_EXP  = 512'h615E530C77D5D834311E922DB99D5B7F1D57C7B08F029FD829914D3F4035FB730350FD00A852A5CCE9CFC79CF8C61384FEA115030E41750A6AE2CFE055D7976D;

    // H: data_i[255:0] = ek; output 256-bit SHA3-256 (in hash_o[255:0])
    localparam [511:0] H_DATA = 512'h000000000000000000000000000000000000000000000000000000000000000047885BF4E257CF39645D34C593047B7570D6ABBA300599D96171A950BB5027D5;
    localparam [255:0] H_EXP  = 256'h6B44867E24B29A9231570DF5E1D6D14DB0C29EBD7A40AE98606EF66B8244C308;

    // J: data_i[511:0] = {c, z}; output 256-bit SHAKE-256 (in hash_o[255:0])
    localparam [511:0] J_DATA = 512'hB73DCA0F437D2334320494E5D0F728D73F5275E342572FF9B0219DC338CB3C2F0F7398474A3D68C4C90B777F42FA4C12B1FC8F70E1DAADF20755473CC2653D3C;
    localparam [255:0] J_EXP  = 256'hECEC4DAD11DFF42D911925DB83F13D119209AB4EE182E9E9BA0F29F5524B240E;

    integer     error_count;
    integer     cycle_count;
    parameter   TIMEOUT = 200;

    // ================================================================
    // Drive one mode and self-check against expected output
    // ================================================================
    task run_mode(input [1:0] m, input [511:0] din,
                  input [511:0] exp, input integer out_bits,
                  input [127:0] label);
        reg [511:0] got;
        begin
            @(posedge clk);
            mode    <= m;
            data_i  <= din;
            valid_i <= 1'b1;
            @(posedge clk);
            valid_i <= 1'b0;

            cycle_count = 0;
            while (!valid_o && cycle_count < TIMEOUT) begin
                @(posedge clk);
                cycle_count = cycle_count + 1;
            end

            if (cycle_count >= TIMEOUT) begin
                $display("FAIL [%0s]: TIMEOUT, valid_o not asserted", label);
                error_count = error_count + 1;
            end else begin
                got = hash_o;
                if (out_bits == 512) begin
                    if (got !== exp) begin
                        $display("FAIL [%0s]: hash mismatch", label);
                        $display("  got = 512'h%0h", got);
                        $display("  exp = 512'h%0h", exp);
                        error_count = error_count + 1;
                    end else begin
                        $display("PASS [%0s]: hash_o = 512'h%0h", label, got);
                    end
                end else begin
                    // Compare low 256 bits only
                    if (got[255:0] !== exp[255:0]) begin
                        $display("FAIL [%0s]: hash mismatch", label);
                        $display("  got = 256'h%0h", got[255:0]);
                        $display("  exp = 256'h%0h", exp[255:0]);
                        error_count = error_count + 1;
                    end else begin
                        $display("PASS [%0s]: hash_o = 256'h%0h", label, got[255:0]);
                    end
                end
            end

            // Wait for DUT to return to IDLE
            @(posedge clk);
            while (!ready_o) @(posedge clk);
        end
    endtask

    // ================================================================
    // Test sequence
    // ================================================================
    initial begin
        error_count = 0;

        $display("========================================");
        $display(" SHA3 Top Testbench (G / H / J modes)");
        $display("========================================");

        mode    <= 2'd0;
        data_i  <= 512'd0;
        valid_i <= 1'b0;
        ready_i <= 1'b1;

        rst_n <= 1'b0;
        repeat (3) @(posedge clk);
        rst_n <= 1'b1;
        @(posedge clk);

        $display("INFO: Reset complete. Running G/H/J...");

        run_mode(2'd0, G_DATA, G_EXP,         512, "G SHA3-512");
        run_mode(2'd1, H_DATA, {256'd0,H_EXP},256, "H SHA3-256");
        run_mode(2'd2, J_DATA, {256'd0,J_EXP},256, "J SHAKE-256");

        $display("========================================");
        if (error_count == 0)
            $display("ALL TESTS PASSED (3/3 modes)");
        else
            $display("TESTS FAILED: %0d error(s)", error_count);
        $display("========================================");

        $finish;
    end

    // ================================================================
    // Timeout watchdog
    // ================================================================
    initial begin
        #(TIMEOUT * 10 * 100);
        $display("FATAL: Global simulation timeout");
        $finish;
    end

endmodule