`timescale 1ns/1ps

// ================================================================
// V3 -- Neural Director, GROUPED variant (EXP-0089/EXP-0090), forked
// from neural_director_packed.v for dispatching to systolic_group.v
// instances instead of flat packed_slot.v instances.
//
// REAL, DIRECT EXTENSION of neural_director_packed.v's own already-
// proven pairing discipline -- NOT a redesign. That module dispatches
// the 2 OLDEST queue entries together, requiring them to share
// w_base/n_tiles (one packed core = 2 positions sharing one weight
// stream). This module dispatches the 8 OLDEST queue entries together
// (GROUP_SIZE=8, matching systolic_group.v's own real, fixed 4 PEs x
// 2 lanes each), requiring ALL EIGHT to share w_base/n_tiles -- same
// real reasoning, same real failure mode if violated (the queue simply
// stops draining, a visible, diagnosable symptom, never a silent
// mis-pair), just a wider match window.
//
// REAL, DELIBERATE NON-CHANGE: the host-facing job_in_* submission
// interface is BYTE-FOR-BYTE IDENTICAL to neural_director_packed.v's
// own -- one job descriptor (x_base/w_base/n_tiles/result_addr/
// node_id) per push, exactly like today. The ESP32/SPI protocol
// (spi_host_bridge_v3.v's own WRITE_JOB opcode) needs ZERO real
// changes to use this Director -- the host just submits 8 individual
// jobs sharing the same w_base/n_tiles instead of 2, exactly the same
// real submission pattern already required today, just a wider batch.
// This was a deliberate design goal, not an accident: keeping the
// host-facing contract unchanged means this Director can be swapped
// in without touching any already-verified host-side firmware
// contract or SPI opcode.
// ================================================================

module neural_director_grouped #(
    parameter ADDR_WIDTH   = 26,
    parameter N_GROUPS     = 4,
    parameter QUEUE_DEPTH  = 16,
    // real fix (found via real synthesis, N_GROUPS=1 real N=4 scaling
    // test): bare `$clog2(N_GROUPS)` is 0 for N_GROUPS=1, producing an
    // invalid `[-1:0]` part-select everywhere below -- same real edge
    // case sdram_arbiter_n.v's own `SELW` localparam already guards
    // against, applied here too.
    localparam GROUP_IDX_WIDTH = (N_GROUPS <= 1) ? 1 : $clog2(N_GROUPS)
)(
    input  wire clk,
    input  wire rst,

    // ---- job submission: identical single-job-descriptor interface
    // to neural_director_packed.v -- see header ----
    input  wire                     job_in_valid,
    output wire                     job_in_ready,
    input  wire [ADDR_WIDTH-1:0]    job_in_x_base,
    input  wire [ADDR_WIDTH-1:0]    job_in_w_base,
    input  wire [15:0]              job_in_n_tiles,
    input  wire [ADDR_WIDTH-1:0]    job_in_result_addr,
    input  wire [15:0]              job_in_node_id,

    // ---- per-group job control (arrayed, N_GROUPS wide). Each group
    // gets ONE shared w_base/n_tiles and 4 PEs' worth of x_base_a/b +
    // result_addr_a/b + node_id_a/b (8 positions total) -- flattened
    // as 4*ADDR_WIDTH / 4*16 buses, matching systolic_group.v's own
    // real pe_x_base_a/pe_x_base_b/etc port shapes exactly. ----
    output wire [N_GROUPS-1:0]                  group_job_start,
    output wire [ADDR_WIDTH*N_GROUPS-1:0]       group_w_base,
    output wire [16*N_GROUPS-1:0]               group_n_tiles,
    output wire [4*ADDR_WIDTH*N_GROUPS-1:0]     group_pe_x_base_a,
    output wire [4*ADDR_WIDTH*N_GROUPS-1:0]     group_pe_x_base_b,
    output wire [4*ADDR_WIDTH*N_GROUPS-1:0]     group_pe_result_addr_a,
    output wire [4*ADDR_WIDTH*N_GROUPS-1:0]     group_pe_result_addr_b,
    output wire [4*16*N_GROUPS-1:0]             group_pe_node_id_a,
    output wire [4*16*N_GROUPS-1:0]             group_pe_node_id_b,
    input  wire [N_GROUPS-1:0]                  group_job_done,

    output reg                       job_out_done,  // one-cycle pulse
    output reg  [GROUP_IDX_WIDTH-1:0] job_out_group,

    output reg [3:0] dir_state,
    output reg       dir_error,

    output wire      queue_empty
);
    localparam GROUP_SIZE = 8; // 4 PEs x 2 lanes each, matches systolic_group.v's own fixed shape

    localparam DIR_IDLE       = 4'd0;
    localparam DIR_SCAN_READY = 4'd1;
    localparam DIR_ALLOCATE   = 4'd2;
    localparam DIR_ERROR      = 4'd3;

    localparam Q_ADDR_WIDTH = $clog2(QUEUE_DEPTH);

    reg [ADDR_WIDTH-1:0] q_x_base      [0:QUEUE_DEPTH-1];
    reg [ADDR_WIDTH-1:0] q_w_base      [0:QUEUE_DEPTH-1];
    reg [15:0]           q_n_tiles     [0:QUEUE_DEPTH-1];
    reg [ADDR_WIDTH-1:0] q_result_addr [0:QUEUE_DEPTH-1];
    reg [15:0]           q_node_id     [0:QUEUE_DEPTH-1];

    reg [Q_ADDR_WIDTH-1:0] q_head, q_tail;
    reg [Q_ADDR_WIDTH:0]   q_count;

    wire q_empty = (q_count == 0);
    assign queue_empty = q_empty;
    wire q_full  = (q_count == QUEUE_DEPTH[Q_ADDR_WIDTH:0]);
    wire q_has_octet = (q_count >= GROUP_SIZE[Q_ADDR_WIDTH:0]);

    assign job_in_ready = !q_full;

    // real wrapping index for the k-th oldest entry (k=0..7), same
    // wrap-around style neural_director_packed.v's own q_head_plus1
    // already established, generalized to an 8-wide offset table.
    wire [Q_ADDR_WIDTH-1:0] q_idx [0:7];
    genvar qk;
    generate
        for (qk = 0; qk < 8; qk = qk + 1) begin : GEN_QIDX
            // real, deliberate width widening BEFORE the wrap compare --
            // computing q_head+qk at only Q_ADDR_WIDTH bits could
            // silently overflow/wrap in the addition itself (e.g.
            // q_head=14, qk=7, QUEUE_DEPTH=16 needs 5 bits to represent
            // 21 correctly before reducing mod 16), giving a WRONG
            // index rather than an out-of-range one -- a real, silent
            // correctness bug, not just a corner case to assume away.
            wire [Q_ADDR_WIDTH:0] q_sum = {1'b0, q_head} + qk[Q_ADDR_WIDTH:0];
            assign q_idx[qk] = (q_sum >= QUEUE_DEPTH[Q_ADDR_WIDTH:0])
                                    ? (q_sum - QUEUE_DEPTH[Q_ADDR_WIDTH:0])
                                    : q_sum[Q_ADDR_WIDTH-1:0];
        end
    endgenerate

    // the 8 oldest entries share a resident weight iff w_base AND
    // n_tiles ALL match (checked pairwise against entry 0, same real
    // reasoning as neural_director_packed.v's own pair_ready -- a
    // coincidentally-equal w_base with mismatched n_tiles must not be
    // wrongly accepted).
    wire octet_match =
        (q_w_base[q_idx[1]]  == q_w_base[q_idx[0]]) && (q_n_tiles[q_idx[1]]  == q_n_tiles[q_idx[0]]) &&
        (q_w_base[q_idx[2]]  == q_w_base[q_idx[0]]) && (q_n_tiles[q_idx[2]]  == q_n_tiles[q_idx[0]]) &&
        (q_w_base[q_idx[3]]  == q_w_base[q_idx[0]]) && (q_n_tiles[q_idx[3]]  == q_n_tiles[q_idx[0]]) &&
        (q_w_base[q_idx[4]]  == q_w_base[q_idx[0]]) && (q_n_tiles[q_idx[4]]  == q_n_tiles[q_idx[0]]) &&
        (q_w_base[q_idx[5]]  == q_w_base[q_idx[0]]) && (q_n_tiles[q_idx[5]]  == q_n_tiles[q_idx[0]]) &&
        (q_w_base[q_idx[6]]  == q_w_base[q_idx[0]]) && (q_n_tiles[q_idx[6]]  == q_n_tiles[q_idx[0]]) &&
        (q_w_base[q_idx[7]]  == q_w_base[q_idx[0]]) && (q_n_tiles[q_idx[7]]  == q_n_tiles[q_idx[0]]);
    wire group_ready = q_has_octet && octet_match;

    reg [N_GROUPS-1:0] group_busy;
    wire [N_GROUPS-1:0] group_free = ~group_busy;
    wire                 any_group_free = |group_free;

    reg [GROUP_IDX_WIDTH-1:0] free_group_idx;
    integer fi;
    always @(*) begin
        free_group_idx = {GROUP_IDX_WIDTH{1'b0}};
        for (fi = N_GROUPS-1; fi >= 0; fi = fi - 1) begin
            if (group_free[fi]) free_group_idx = fi[GROUP_IDX_WIDTH-1:0];
        end
    end

    // per-group output storage -- N_GROUPS parallel constant-indexed
    // writes (same anti-runtime-indexed-part-select discipline
    // neural_director_packed.v's own slot_x_base_r already established).
    reg                  group_job_start_r        [0:N_GROUPS-1];
    reg [ADDR_WIDTH-1:0] group_w_base_r           [0:N_GROUPS-1];
    reg [15:0]           group_n_tiles_r          [0:N_GROUPS-1];
    reg [ADDR_WIDTH-1:0] group_pe_x_base_a_r      [0:N_GROUPS-1][0:3];
    reg [ADDR_WIDTH-1:0] group_pe_x_base_b_r      [0:N_GROUPS-1][0:3];
    reg [ADDR_WIDTH-1:0] group_pe_result_addr_a_r [0:N_GROUPS-1][0:3];
    reg [ADDR_WIDTH-1:0] group_pe_result_addr_b_r [0:N_GROUPS-1][0:3];
    reg [15:0]           group_pe_node_id_a_r     [0:N_GROUPS-1][0:3];
    reg [15:0]           group_pe_node_id_b_r     [0:N_GROUPS-1][0:3];

    genvar gg, gp;
    generate
        for (gg = 0; gg < N_GROUPS; gg = gg + 1) begin : GEN_GROUP_OUT
            assign group_job_start[gg]                           = group_job_start_r[gg];
            assign group_w_base[gg*ADDR_WIDTH +: ADDR_WIDTH]      = group_w_base_r[gg];
            assign group_n_tiles[gg*16 +: 16]                     = group_n_tiles_r[gg];
            for (gp = 0; gp < 4; gp = gp + 1) begin : GEN_PE_OUT
                assign group_pe_x_base_a[(gg*4+gp)*ADDR_WIDTH +: ADDR_WIDTH]      = group_pe_x_base_a_r[gg][gp];
                assign group_pe_x_base_b[(gg*4+gp)*ADDR_WIDTH +: ADDR_WIDTH]      = group_pe_x_base_b_r[gg][gp];
                assign group_pe_result_addr_a[(gg*4+gp)*ADDR_WIDTH +: ADDR_WIDTH] = group_pe_result_addr_a_r[gg][gp];
                assign group_pe_result_addr_b[(gg*4+gp)*ADDR_WIDTH +: ADDR_WIDTH] = group_pe_result_addr_b_r[gg][gp];
                assign group_pe_node_id_a[(gg*4+gp)*16 +: 16]     = group_pe_node_id_a_r[gg][gp];
                assign group_pe_node_id_b[(gg*4+gp)*16 +: 16]     = group_pe_node_id_b_r[gg][gp];
            end
        end
    endgenerate

    reg [GROUP_IDX_WIDTH-1:0] done_group_idx;
    integer di;
    always @(*) begin
        done_group_idx = {GROUP_IDX_WIDTH{1'b0}};
        for (di = N_GROUPS-1; di >= 0; di = di - 1) begin
            if (group_job_done[di]) done_group_idx = di[GROUP_IDX_WIDTH-1:0];
        end
    end

    integer pi;
    always @(posedge clk) begin
        if (rst) begin
            dir_state  <= DIR_IDLE;
            dir_error  <= 1'b0;
            q_head     <= {Q_ADDR_WIDTH{1'b0}};
            q_tail     <= {Q_ADDR_WIDTH{1'b0}};
            q_count    <= {(Q_ADDR_WIDTH+1){1'b0}};
            group_busy <= {N_GROUPS{1'b0}};
            for (fi = 0; fi < N_GROUPS; fi = fi + 1) begin
                group_job_start_r[fi]  <= 1'b0;
                group_w_base_r[fi]     <= {ADDR_WIDTH{1'b0}};
                group_n_tiles_r[fi]    <= 16'b0;
                for (pi = 0; pi < 4; pi = pi + 1) begin
                    group_pe_x_base_a_r[fi][pi]      <= {ADDR_WIDTH{1'b0}};
                    group_pe_x_base_b_r[fi][pi]      <= {ADDR_WIDTH{1'b0}};
                    group_pe_result_addr_a_r[fi][pi] <= {ADDR_WIDTH{1'b0}};
                    group_pe_result_addr_b_r[fi][pi] <= {ADDR_WIDTH{1'b0}};
                    group_pe_node_id_a_r[fi][pi]      <= 16'b0;
                    group_pe_node_id_b_r[fi][pi]      <= 16'b0;
                end
            end
            job_out_done  <= 1'b0;
            job_out_group <= {GROUP_IDX_WIDTH{1'b0}};
        end else begin
            for (fi = 0; fi < N_GROUPS; fi = fi + 1) group_job_start_r[fi] <= 1'b0;
            job_out_done <= 1'b0;

            if (job_in_valid && job_in_ready) begin
                q_x_base[q_tail]      <= job_in_x_base;
                q_w_base[q_tail]      <= job_in_w_base;
                q_n_tiles[q_tail]     <= job_in_n_tiles;
                q_result_addr[q_tail] <= job_in_result_addr;
                q_node_id[q_tail]     <= job_in_node_id;
                q_tail <= (q_tail == QUEUE_DEPTH[Q_ADDR_WIDTH-1:0]-1'b1) ? {Q_ADDR_WIDTH{1'b0}} : q_tail + 1'b1;
            end

            group_busy <= group_busy & ~group_job_done;
            if (|group_job_done) begin
                job_out_done  <= 1'b1;
                job_out_group <= done_group_idx;
            end

            case (dir_state)

                DIR_IDLE: begin
                    dir_state <= DIR_SCAN_READY;
                end

                DIR_SCAN_READY: begin
                    if (group_ready && any_group_free) begin
                        dir_state <= DIR_ALLOCATE;
                    end
                end

                DIR_ALLOCATE: begin
                    for (fi = 0; fi < N_GROUPS; fi = fi + 1) begin
                        if (fi[GROUP_IDX_WIDTH-1:0] == free_group_idx) begin
                            group_job_start_r[fi] <= 1'b1;
                            group_w_base_r[fi]    <= q_w_base[q_idx[0]];  // all 8 match, checked by group_ready
                            group_n_tiles_r[fi]   <= q_n_tiles[q_idx[0]];
                            for (pi = 0; pi < 4; pi = pi + 1) begin
                                group_pe_x_base_a_r[fi][pi]      <= q_x_base[q_idx[pi*2]];
                                group_pe_x_base_b_r[fi][pi]      <= q_x_base[q_idx[pi*2+1]];
                                group_pe_result_addr_a_r[fi][pi] <= q_result_addr[q_idx[pi*2]];
                                group_pe_result_addr_b_r[fi][pi] <= q_result_addr[q_idx[pi*2+1]];
                                group_pe_node_id_a_r[fi][pi]     <= q_node_id[q_idx[pi*2]];
                                group_pe_node_id_b_r[fi][pi]     <= q_node_id[q_idx[pi*2+1]];
                            end
                        end
                    end
                    group_busy[free_group_idx] <= 1'b1;
                    q_head <= q_idx[7] + 1'b1 == QUEUE_DEPTH[Q_ADDR_WIDTH-1:0]
                                  ? {Q_ADDR_WIDTH{1'b0}} : q_idx[7] + 1'b1;
                    dir_state <= DIR_SCAN_READY;
                end

                DIR_ERROR: begin
                end

                default: dir_state <= DIR_ERROR;

            endcase

            // q_count: +1 per accepted push, -8 per dispatched OCTET
            case ({job_in_valid && job_in_ready,
                   (dir_state == DIR_SCAN_READY) && group_ready && any_group_free})
                2'b10: q_count <= q_count + 1'b1;
                2'b01: q_count <= q_count - GROUP_SIZE[Q_ADDR_WIDTH:0];
                2'b11: q_count <= q_count - GROUP_SIZE[Q_ADDR_WIDTH:0] + 1'b1;
                2'b00: q_count <= q_count;
            endcase
        end
    end

endmodule