lru

`timescale 1ns/1ps

module lru (
    input clk,
    input reset,
    input enable,
    input [31:0] data,
    output reg[31:0] out1,
    output reg[31:0] out2,
    output reg[31:0] out3,
    output reg[31:0] out4,
    output reg[31:0] out5,
    output reg[31:0] out6,
    output reg[31:0] out7,
    output reg[31:0] out8
);

reg[2:0] state = 0;
reg[3:0] ages[0:7];
reg[3:0] max_age = 0, preempted_index = 8;
reg[3:0] amount_empty_spaces = 8;
reg[3:0] hit_cache_index = 8;
reg is_value_in_cache = 0;
reg is_value_setted_to_cache = 0;


parameter INITIAL = 0, IDLE = 1, VALUE_IN_CACHE = 2, NO_VALUE_IN_CACHE_ENOUGH_SPACE = 3, NO_VALUE_IN_CACHE_NO_ENOUGH_SPACE = 4, DONE = 5;
integer i;

always @(posedge reset) begin
    if (reset) begin
        out1 <= 32'hffffffff;
        out2 <= 32'hffffffff;
        out3 <= 32'hffffffff;
        out4 <= 32'hffffffff;
        out5 <= 32'hffffffff;
        out6 <= 32'hffffffff;
        out7 <= 32'hffffffff;
        out8 <= 32'hffffffff;
        for (i = 0; i < 8; i = i + 1) begin
            ages[i] <= 8;
        end
        state <= IDLE;
    end
end

always @(posedge clk) begin
    case (state)
    INITIAL: begin
        out1 <= 32'hffffffff;
        out2 <= 32'hffffffff;
        out3 <= 32'hffffffff;
        out4 <= 32'hffffffff;
        out5 <= 32'hffffffff;
        out6 <= 32'hffffffff;
        out7 <= 32'hffffffff;
        out8 <= 32'hffffffff;
        for (i = 0; i < 8; i = i + 1) begin
            ages[i] <= 8;
        end
        state <= IDLE;
    end
    IDLE : begin
        if (enable) begin
            if (out1 == data) begin hit_cache_index = 0; state <= VALUE_IN_CACHE; is_value_in_cache = 1; end
            if (out2 == data) begin hit_cache_index = 1; state <= VALUE_IN_CACHE; is_value_in_cache = 1; end
            if (out3 == data) begin hit_cache_index = 2; state <= VALUE_IN_CACHE; is_value_in_cache = 1; end
            if (out4 == data) begin hit_cache_index = 3; state <= VALUE_IN_CACHE; is_value_in_cache = 1; end
            if (out5 == data) begin hit_cache_index = 4; state <= VALUE_IN_CACHE; is_value_in_cache = 1; end
            if (out6 == data) begin hit_cache_index = 5; state <= VALUE_IN_CACHE; is_value_in_cache = 1; end
            if (out7 == data) begin hit_cache_index = 6; state <= VALUE_IN_CACHE; is_value_in_cache = 1; end
            if (out8 == data) begin hit_cache_index = 7; state <= VALUE_IN_CACHE; is_value_in_cache = 1; end

            if (amount_empty_spaces && is_value_in_cache == 0) state <= NO_VALUE_IN_CACHE_ENOUGH_SPACE;
            else state <= NO_VALUE_IN_CACHE_NO_ENOUGH_SPACE;

            is_value_in_cache = 0;
        end
    end
    VALUE_IN_CACHE : begin
        for (i = 0; i < 8; i = i + 1) begin
            if (i == hit_cache_index) begin
                ages[i] <= 0;
            end else if (ages[i] != 8) begin
                ages[i] <= ages[i] + 1;
            end
        end
        hit_cache_index <= 8;
        state <= DONE;
    end
    NO_VALUE_IN_CACHE_ENOUGH_SPACE : begin
        for (i = 0; i < 8; i = i + 1) begin
            if (ages[i] != 8) begin
                ages[i] <= ages[i] + 1;
            end
        end
        for (i = 0; i < 8; i = i + 1) begin
            if (ages[i] >= 8 && is_value_setted_to_cache != 1) begin
                ages[i] <= 0;
                case (i)
                    0: begin out1 <= data; is_value_setted_to_cache = 1; end
                    1: begin out2 <= data; is_value_setted_to_cache = 1; end
                    2: begin out3 <= data; is_value_setted_to_cache = 1; end
                    3: begin out4 <= data; is_value_setted_to_cache = 1; end
                    4: begin out5 <= data; is_value_setted_to_cache = 1; end
                    5: begin out6 <= data; is_value_setted_to_cache = 1; end
                    6: begin out7 <= data; is_value_setted_to_cache = 1; end
                    7: begin out8 <= data; is_value_setted_to_cache = 1; end
                endcase
            end
        end
        is_value_setted_to_cache = 0;
        amount_empty_spaces <= amount_empty_spaces - 1;
        state <= DONE;
    end
    NO_VALUE_IN_CACHE_NO_ENOUGH_SPACE : begin
        for (i = 0; i < 8; i = i + 1) begin
            if (ages[i] != 8) begin
                ages[i] <= ages[i] + 1;
            end
        end
        $display("ages = [%d, %d, %d, %d, %d, %d, %d, %d]", ages[0], ages[1], ages[2], ages[3], ages[4], ages[5], ages[6], ages[7]);
        $display("max_age: %d", max_age);
        for (i = 0; i < 8; i = i + 1) begin
                if (ages[i] > max_age) begin
                    max_age = ages[i];
                    preempted_index = i;
                end
        end
        $display("max_age: %d", max_age);
        $display("preempted_index: %d", preempted_index);
        case (preempted_index)
            0: begin out1 <= data; end
            1: begin out2 <= data; end
            2: begin out3 <= data; end
            3: begin out4 <= data; end
            4: begin out5 <= data; end
            5: begin out6 <= data; end
            6: begin out7 <= data; end
            7: begin out8 <= data; end
        endcase
        ages[preempted_index] <= 0;
        preempted_index <= 8;
        max_age <= 0;
        state <= DONE;
    end
    DONE : begin
        state <= IDLE;
    end
    endcase
end

endmodule