`timescale 1ns / 1ps

module sampler_tb;

    localparam DATA_WIDTH   = 12;
    localparam PACK_FACTOR  = 1;
    localparam PROCESS_MODE = 0;
    localparam CLK_PERIOD   = 15.3846;

    logic clk;
    logic rst;

    logic [DATA_WIDTH-1:0] data_in;
    logic out_of_range;

    logic [31:0] smp_num;

    logic done;
    logic request;

    logic [DATA_WIDTH*PACK_FACTOR-1:0] m_axis_tdata;
    logic m_axis_tvalid;

    int received_count;

    sampler #(
        .DATA_WIDTH  (DATA_WIDTH),
        .PACK_FACTOR (PACK_FACTOR),
        .PROCESS_MODE(PROCESS_MODE)
    ) dut (
        .clk_in       (clk),
        .rst          (rst),

        .data_in      (data_in),
        .out_of_range (out_of_range),

        .smp_num      (smp_num),
        .done         (done),

        .m_axis_tdata (m_axis_tdata),
        .m_axis_tvalid(m_axis_tvalid),

        .request      (request)
    );

    // =====================================================
    // CLOCK
    // =====================================================
    initial begin
        clk = 0;
        forever #(CLK_PERIOD/2) clk = ~clk;
    end

    // =====================================================
    // RESET
    // =====================================================
    initial begin
        rst = 1;
        data_in = 0;
        out_of_range = 0;
        done = 0;
        smp_num = 0;

        repeat(5) @(posedge clk);
        rst = 0;
    end

    // =====================================================
    // OUTPUT COUNTER
    // =====================================================
    always @(posedge clk) begin
        if (m_axis_tvalid)
            received_count++;
    end

    // =====================================================
    // FEED DATA
    // =====================================================
    task automatic feed_data_stream(
        input int num_words,
        input bit random_data,
        input bit random_out_of_range
    );
        logic [DATA_WIDTH-1:0] value;
        bit oor;
    begin
        value = 1;

        for (int i = 0; i < num_words; i++) begin

            if (random_data)
                value = $urandom_range(1, (1<<DATA_WIDTH)-1);
            else
                value = value + 1;

            if (random_out_of_range)
                oor = ($urandom_range(0,3) == 0);
            else
                oor = 0;

            data_in      = value;
            out_of_range = oor;

            @(posedge clk);
        end

        out_of_range = 0;
    end
    endtask

    // =====================================================
    // TEST CASE
    // =====================================================
    task automatic run_test_case(
        input int n,
        input bit random_data,
        input bit random_out_of_range
    );
    begin
        received_count = 0;

        data_in = 0;
        out_of_range = 0;
        done = 0;

        smp_num = n;

        // handshake
        @(posedge clk);
        done <= 1'b1;
        wait(request == 1'b1);
        @(posedge clk);
        done <= 1'b0;

        // wait enable
        wait(dut.enable == 1'b1);

        // feed data
        feed_data_stream(n + 10, random_data, random_out_of_range);

        // wait completion
        wait(dut.enable == 1'b0);

        $display("Expected smp_num=%0d Received=%0d", smp_num, received_count);

        if (received_count == smp_num)
            $display("[OK]");
        else
            $display("[ERROR]");

        repeat(10) @(posedge clk);
    end
    endtask

    // =====================================================
    // RANDOM TESTS
    // =====================================================
    task automatic random_stress_test;
        int n;
    begin
        for (int i = 0; i < 20; i++) begin
            n = $urandom_range(5,20);

            $display("\n--- TEST %0d --- n=%0d", i, n);

            run_test_case(
                n,
                1,
                1
            );
        end
    end
    endtask

    // =====================================================
    // MAIN
    // =====================================================
    initial begin

        $display("\n=== BASIC TEST ===");
        run_test_case(10, 0, 0);

        $display("\n=== OUT_OF_RANGE TEST ===");
        run_test_case(20, 1, 1);

        $display("\n=== RANDOM STRESS TEST ===");
        random_stress_test();

        $display("\n=== TEST FINISHED ===");
        $finish;

    end

endmodule