`timescale 1ns/1ps

module tb_out_axis_fifo;

    localparam int ACCUM_WIDTH = 32;
    localparam int WINDOW_SIZE = 65;
    localparam int PACKET_SIZE = 1024;
    localparam int BYTES_PER_WORD = ACCUM_WIDTH / 8;
    localparam int WORDS_PER_BATCH = PACKET_SIZE / BYTES_PER_WORD; // 1024 / 4 = 256 слов

    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 send_req;
    logic req_ready;

    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),

        .req_ready     (req_ready),
        .send_req      (send_req),

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

    // clocks
    initial begin
        eth_clk_in = 0;
        forever #6 eth_clk_in = ~eth_clk_in;   // 125
    end

    initial begin
        acc_clk_in = 0;
        forever #7.692307692 acc_clk_in = ~acc_clk_in;   // 65
    end

    // scoreboard
    byte expected_bytes[$];
    int unsigned compared_bytes;
    int unsigned mismatch_count;
    int unsigned total_pushed_words;

    task automatic scoreboard_reset();
        begin
            expected_bytes.delete();
            compared_bytes   = 0;
            mismatch_count   = 0;
            total_pushed_words = 0;
        end
    endtask

    task automatic push_expected_word(input logic [ACCUM_WIDTH-1:0] word);
        begin
            // queue push
            expected_bytes.push_back(word[7:0]);
            expected_bytes.push_back(word[15:8]);
            expected_bytes.push_back(word[23:16]);
            expected_bytes.push_back(word[31:24]);
            total_pushed_words++;
        end
    endtask

    task automatic check_expected_empty(string case_name);
        begin
            if (expected_bytes.size() != 0) begin
                $error("[%0t] %s: expected_bytes is not empty, remaining=%0d",
                       $time, case_name, expected_bytes.size());
            end else begin
                $display("[%0t] %s: scoreboard queue empty, all expected bytes were transmitted",
                         $time, case_name);
            end
        end
    endtask

    // axis check
    always_ff @(posedge eth_clk_in or posedge rst) begin
        byte exp_byte;
        if (rst) begin
            compared_bytes <= 0;
            mismatch_count <= 0;
        end else begin
            if (s_axis_tvalid && s_axis_tready) begin
                if (expected_bytes.size() == 0) begin
                    $error("[%0t] AXIS produced unexpected byte 0x%02x: expected queue is empty",
                           $time, s_axis_tdata);
                    mismatch_count <= mismatch_count + 1;
                end else begin
                    exp_byte = expected_bytes.pop_front();
                    compared_bytes <= compared_bytes + 1;

                    if (s_axis_tdata !== exp_byte) begin
                        $error("[%0t] AXIS mismatch at byte #%0d: got=0x%02x expected=0x%02x",
                               $time, compared_bytes, s_axis_tdata, exp_byte);
                        mismatch_count <= mismatch_count + 1;
                    end
                end
            end
        end
    end

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

            scoreboard_reset();

            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;
        logic [ACCUM_WIDTH-1:0] rand_word;
        begin
            for (i = 0; i < n_words; i++) begin
                rand_word = $urandom;

                @(posedge acc_clk_in);
                din_valid <= 1'b1;
                acc_din   <= rand_word;

                // expected result
                push_expected_word(rand_word);
            end

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


    // 1. set smp_num
    // 2. pulse readout_begon
    // 3. send 1KB (PACKET_SIZE) after each batch_req pulse
    // 4. wait for finish
    // 5. compare axis result
    task automatic run_case(input logic [31:0] smp_num_i);
        int batch_count;
        string case_name;
        begin
            batch_count = 0;
            case_name = $sformatf("run_case(smp_num=%0d)", smp_num_i);

            $display("[%0t] %s start", $time, case_name);

            pulse_readout_begin(smp_num_i);

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

                if (batch_req) begin
                    batch_count++;
                    $display("[%0t] %s: batch_req #%0d -> send %0d words",
                             $time, case_name, batch_count, WORDS_PER_BATCH);

                    send_random_words(WORDS_PER_BATCH);
                end
            end


            repeat (200) @(posedge eth_clk_in);

            $display("[%0t] %s done: batches=%0d, pushed_words=%0d, compared_bytes=%0d, mismatches=%0d, wr_cnt=%0d, wr_total=%0d",
                     $time, case_name, batch_count, total_pushed_words, compared_bytes, mismatch_count,
                     dut.wr_cnt, dut.wr_total);

            check_expected_empty(case_name);

            if (mismatch_count != 0) begin
                $fatal(1, "[%0t] %s FAILED: mismatches=%0d", $time, case_name, mismatch_count);
            end else begin
                $display("[%0t] %s PASSED", $time, case_name);
            end

            @(posedge acc_clk_in);
        end
    endtask

    // eth beh simulator
    int axis_byte_count;

    always_ff @(posedge eth_clk_in or posedge rst) begin
        if (rst) begin
            axis_byte_count <= 0;
            req_ready       <= 0;
            s_axis_tready   <= 1'b0;
        end else begin
            req_ready <= 1;

            // request send
            if (send_req) begin
                s_axis_tready <= 1'b1;
                req_ready <= 0;
            end

            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;

        repeat (500) @(posedge acc_clk_in);

        // 1
        do_reset();
        repeat (500) @(posedge acc_clk_in);
        run_case(32'd17);
        repeat (20) @(posedge acc_clk_in);

        // 2
        do_reset();
        run_case(32'd1024);
        repeat (20) @(posedge acc_clk_in);

        // 3
        do_reset();
        run_case(32'd77777);
        repeat (20) @(posedge acc_clk_in);

        do_reset();
        repeat (20) @(posedge acc_clk_in);

        $display("[%0t] ALL TESTS DONE", $time);
        $finish;
    end

endmodule