`timescale 1ns/1ps

module tb_out_axis_fifo;

    localparam int ACCUM_WIDTH = 32;
    localparam int WINDOW_SIZE = 65;
    localparam int PACKET_SIZE = 1024;

    logic eth_clk_in;
    logic acc_clk_in;
    logic rst;

    logic [31:0] smp_num;

    logic [7:0]  s_axis_tdata;
    logic        s_axis_tvalid;
    logic        s_axis_tready;
    logic        s_axis_tlast;

    logic [ACCUM_WIDTH-1:0] acc_din;
    logic                   din_valid;

    logic readout_begin;

    logic batch_req;
    logic finish;

    out_axis_fifo #(
        .ACCUM_WIDTH(ACCUM_WIDTH),
        .WINDOW_SIZE(WINDOW_SIZE),
        .PACKET_SIZE(PACKET_SIZE)
    ) dut (
        .eth_clk_in    (eth_clk_in),
        .acc_clk_in    (acc_clk_in),
        .rst           (rst),
        .smp_num       (smp_num),

        .s_axis_tdata  (s_axis_tdata),
        .s_axis_tvalid (s_axis_tvalid),
        .s_axis_tready (s_axis_tready),
        .s_axis_tlast  (s_axis_tlast),

        .acc_din       (acc_din),
        .din_valid     (din_valid),

        .readout_begin (readout_begin),

        .batch_req     (batch_req),
        .finish        (finish)
    );

    // -----------------------------
    // clocks
    // -----------------------------
    initial begin
        eth_clk_in = 0;
        forever #4 eth_clk_in = ~eth_clk_in;   // 125 MHz
    end

    initial begin
        acc_clk_in = 0;
        forever #3 acc_clk_in = ~acc_clk_in;   // ~166.7 MHz
    end

    // -----------------------------
    // simple AXIS sink
    // -----------------------------
    initial begin
        s_axis_tready = 1'b1;
    end

    // У DUT нет своей логики rd_en, поэтому для теста подадим её force-ом.
    initial begin
        force dut.rd_en = dut.s_axis_tvalid && s_axis_tready;
    end

    // -----------------------------
    // helpers
    // -----------------------------
    task automatic do_reset();
        begin
            rst          = 1'b1;
            readout_begin = 1'b0;
            din_valid    = 1'b0;
            acc_din      = '0;
            smp_num      = '0;

            repeat (10) @(posedge acc_clk_in);
            rst = 1'b0;

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

    task automatic pulse_readout_begin(input logic [31:0] smp_num_i);
        begin
            smp_num = smp_num_i;
            @(posedge acc_clk_in);
            readout_begin <= 1'b1;
            @(posedge acc_clk_in);
            readout_begin <= 1'b0;
        end
    endtask

    task automatic send_random_words(input int unsigned n_words);
        int unsigned i;
        begin
            for (i = 0; i < n_words; i++) begin
                @(posedge acc_clk_in);
                din_valid <= 1'b1;
                acc_din   <= $urandom;
            end

            @(posedge acc_clk_in);
            din_valid <= 1'b0;
            acc_din   <= '0;
        end
    endtask

    // Один запуск:
    // 1) задаём smp_num
    // 2) даём readout_begin
    // 3) каждый раз, когда DUT просит batch_req, отправляем PACKET_SIZE слов
    // 4) ждём finish
    task automatic run_case(input logic [31:0] smp_num_i);
        int batch_count;
        begin
            batch_count = 0;

            $display("[%0t] run_case start, smp_num=%0d", $time, smp_num_i);

            pulse_readout_begin(smp_num_i);

            while (finish !== 1'b1) begin
                @(posedge acc_clk_in);

                if (batch_req) begin
                    batch_count++;
                    $display("[%0t] batch_req #%0d -> send %0d words",
                             $time, batch_count, PACKET_SIZE / ACCUM_WIDTH * 8);
                    
                    // send packets to accomplish 1kb packet.
                    send_random_words(PACKET_SIZE / ACCUM_WIDTH * 8);
                end
            end

            $display("[%0t] run_case done, smp_num=%0d, batches=%0d, wr_cnt=%0d, wr_total=%0d",
                     $time, smp_num_i, batch_count, dut.wr_cnt, dut.wr_total);

            @(posedge acc_clk_in);
        end
    endtask

    // -----------------------------
    // monitor
    // -----------------------------
    int axis_byte_count;

    always_ff @(posedge eth_clk_in or posedge rst) begin
        if (rst) begin
            axis_byte_count <= 0;
        end else begin
            if (s_axis_tvalid && s_axis_tready) begin
                axis_byte_count <= axis_byte_count + 1;
            end
        end
    end

    // -----------------------------
    // main
    // -----------------------------
    initial begin
        // init
        rst           = 1'b0;
        readout_begin = 1'b0;
        din_valid     = 1'b0;
        acc_din       = '0;
        smp_num       = '0;

        // 1-й запуск
        do_reset();
        run_case(32'd17);

        // 2-й запуск
        do_reset();
        run_case(32'd1024);

        // 3-й запуск
        do_reset();
        run_case(32'd77777);
        
        do_reset();
        repeat (50) @(posedge acc_clk_in);
        $display("[%0t] ALL TESTS DONE", $time);
        $finish;
    end

endmodule