// Wavefront Emitter - Implements wavefront emission theory from Signal Theory Compendium
// Based on Semantics/WavefrontEmitter.lean
//
// Core concepts:
// - Wavefront structure: amplitude, frequency, phase, position
// - Wavefront parameters: default amplitude=1.0, frequency=0.1, speed=1.0, decay=0.01
// - Wavefront computation with decay and oscillation
// - Wavefront injection into resonant field

/* verilator lint_off UNUSEDSIGNAL */
/* verilator lint_off UNUSEDPARAM */
/* verilator lint_off WIDTHTRUNC */

module wavefront_emitter (
    input wire clk,
    input wire rst_n,
    input wire [15:0] amplitude_in,      // Q16.16 amplitude
    input wire [15:0] frequency_in,      // Q16.16 frequency
    input wire [15:0] phase_in,         // Q16.16 phase
    input wire [15:0] position_x,       // Q16.16 x position
    input wire [15:0] position_y,       // Q16.16 y position
    input wire        emit_trigger,     // Trigger wavefront emission
    input wire [15:0] emitter_id,       // Emitter identifier
    output reg [15:0] wavefront_value,   // Computed wavefront value
    output reg        wavefront_valid
);

    // Wavefront parameters (Q16.16 fixed-point)
    localparam DEFAULT_AMPLITUDE = 16'h7FFF;  // 1.0
    localparam DEFAULT_FREQUENCY = 16'h0CCC;  // 0.1
    localparam WAVE_SPEED = 16'h7FFF;         // 1.0
    localparam DECAY_RATE = 16'h028F;         // 0.01
    localparam WAVE_DISTANCE = 16'h000A;      // 10.0 units

    // Wavefront state
    reg [15:0] current_amplitude;
    reg [15:0] current_frequency;
    reg [15:0] current_phase;
    reg [15:0] current_position_x;
    reg [15:0] current_position_y;
    reg [15:0] emitter_position_x;
    reg [15:0] emitter_position_y;
    reg [15:0] emission_time;

    // Distance calculation (simplified Manhattan distance for Q16.16)
    function [15:0] calculate_distance;
        input [15:0] x1, y1, x2, y2;
        reg [15:0] dx, dy;
        begin
            if (x1 > x2)
                dx = x1 - x2;
            else
                dx = x2 - x1;

            if (y1 > y2)
                dy = y1 - y2;
            else
                dy = y2 - y1;

            calculate_distance = dx + dy;  // Manhattan distance
        end
    endfunction

    // Wavefront computation: value = decayed_amplitude * oscillation
    function [15:0] compute_wavefront;
        input [15:0] amplitude;
        input [15:0] distance;
        input [15:0] frequency;
        input [15:0] phase;
        reg [31:0] decay_product;
        reg [15:0] decayed_amplitude;
        reg [15:0] phase_shift;
        reg oscillation;
        begin
            // decay = distance * decay_rate
            decay_product = (distance * DECAY_RATE) >>> 16;

            // decayed_amplitude = amplitude - decay (with saturation at 0)
            if (decay_product >= amplitude)
                decayed_amplitude = 16'h0000;
            else
                decayed_amplitude = amplitude - decay_product[15:0];

            // phase_shift = frequency * distance
            phase_shift = ((frequency * distance) >>> 16) & 16'h0001;  // Parity only

            // oscillation = +1 if phase_shift even, -1 if odd
            oscillation = ~phase_shift;  // Toggle based on parity

            // value = decayed_amplitude * oscillation
            if (oscillation)
                compute_wavefront = decayed_amplitude;
            else
                compute_wavefront = ~decayed_amplitude + 1'b1;  // Negate
        end
    endfunction

    // State change trigger: emit wavefront when triggered
    always @(posedge clk or negedge rst_n) begin
        if (!rst_n) begin
            current_amplitude <= DEFAULT_AMPLITUDE;
            current_frequency <= DEFAULT_FREQUENCY;
            current_phase <= 16'h0000;
            current_position_x <= 16'h0000;
            current_position_y <= 16'h0000;
            emitter_position_x <= 16'h0000;
            emitter_position_y <= 16'h0000;
            emission_time <= 16'h0000;
            wavefront_value <= 16'h0000;
            wavefront_valid <= 1'b0;
        end else begin
            if (emit_trigger) begin
                // Capture wavefront parameters
                current_amplitude <= amplitude_in;
                current_frequency <= frequency_in;
                current_phase <= phase_in;
                current_position_x <= position_x;
                current_position_y <= position_y;
                emitter_position_x <= 16'h0000;  // Assume emitter at origin
                emitter_position_y <= 16'h0000;
                emission_time <= emission_time + 16'h0001;

                // Compute wavefront value
                wavefront_value <= compute_wavefront(
                    amplitude_in,
                    calculate_distance(position_x, position_y, 16'h0000, 16'h0000),
                    frequency_in,
                    phase_in
                );
                wavefront_valid <= 1'b1;
            end else begin
                wavefront_valid <= 1'b0;
            end
        end
    end

endmodule