class sequencer_reset extends uvm_sequencer;
    `uvm_component_utils(sequencer_reset)

    function new(string name, uvm_component parent);
        super.new(name, parent);
    endfunction
endclass

class driver_reset extends uvm_driver;
    virtual testbench_if tb_if;

    `uvm_component_utils(driver_reset)

    function new(string name, uvm_component parent);
        super.new(name, parent);
    endfunction

    function void build_phase(uvm_phase phase);
        super.build_phase(phase);

        if (!uvm_config_db#(virtual testbench_if)::get(this, "", "tb_vif", tb_if)) begin
            `uvm_fatal("CFG_DB_FAIL", $sformatf("Failed to fetch interface for %0s", get_full_name()))
        end
    endfunction

    virtual task run_phase(uvm_phase phase);
        forever begin
            @(posedge tb_if.rst_n);
            while (tb_if.rst_n != 0) begin
                seq_item_port.get_next_item(req);
                drive_item(req);
                seq_item_port.item_done();
            end
        end
    endtask

    task drive_item(uvm_sequence_item req);
        `uvm_info("drive_item", $sformatf("Initiating reset..."), UVM_LOW)
        tb_if.rst_n = 0;
        repeat(10) @(posedge tb_if.clk);
        tb_if.rst_n = 1;
        `uvm_info("drive_item", $sformatf("Reset done."), UVM_LOW)
    endtask
endclass

class monitor_reset extends uvm_monitor;
    virtual testbench_if tb_if;

    `uvm_component_utils(monitor_reset)

    function new(string name, uvm_component parent);
        super.new(name, parent);
    endfunction

    function void build_phase(uvm_phase phase);
        super.build_phase(phase);

        if (!uvm_config_db#(virtual testbench_if)::get(this, "", "tb_vif", tb_if)) begin
            `uvm_fatal("CFG_DB_FAIL", $sformatf("Failed to fetch interface for %0s", get_full_name()))
        end
    endfunction

    virtual task run_phase(uvm_phase phase);
        fork
            do_monitor();
        join
    endtask

    task do_monitor();
        bit prev_val;

        if (tb_if.rst_n === 1'b0) begin
            `uvm_info("do_monitor", $sformatf("Starting with reset asserted"), UVM_LOW)
        end else if (tb_if.rst_n === 1'b1) begin
            `uvm_info("do_monitor", $sformatf("Starting with reset de-asserted"), UVM_LOW)
        end else begin
            `uvm_info("do_monitor", $sformatf("Starting with reset unknown"), UVM_LOW)
        end

        forever begin
            prev_val = tb_if.rst_n;

            @(tb_if.rst_n);
            if ((prev_val !== 1'b1) && (tb_if.rst_n !== 1'b1)) begin
                `uvm_info("drive_item", $sformatf("Reset de-asserted"), UVM_LOW)
            end
            if ((prev_val !== 1'b0) && (tb_if.rst_n !== 1'b0)) begin
                `uvm_info("drive_item", $sformatf("Reset asserted"), UVM_LOW)
            end
        end
    endtask
endclass

class agent_reset extends uvm_agent;
    sequencer_reset sequencer;
    driver_reset    driver;
    monitor_reset   monitor;

    `uvm_component_utils(agent_reset)

    function new(string name, uvm_component parent);
        super.new(name, parent);
    endfunction

    function void build_phase(uvm_phase phase);
        super.build_phase(phase);

        sequencer = sequencer_reset::type_id::create("sequencer", this);
        driver = driver_reset::type_id::create("driver", this);
        monitor = monitor_reset::type_id::create("monitor", this);

        `uvm_info("build_phase", $sformatf("Building done"), UVM_LOW)
    endfunction

    function void connect_phase(uvm_phase phase);
        super.connect_phase(phase);

        driver.seq_item_port.connect(sequencer.seq_item_export);

        `uvm_info("connect_phase", $sformatf("Connecting done"), UVM_LOW)
    endfunction

endclass