# Copyright (c) Microsoft Corporation.
# Licensed under the MIT License.
"""Multi-rank intranode functional validation for mscclpp_ep.

Launch with:
    torchrun --nproc_per_node=<N> test/python/ext/ep/test_intranode_multirank.py

Tests that Buffer::sync() succeeds across N GPUs on a single node and that
a round-trip dispatch + combine preserves data (sum of top-k weighted copies).

Set ``MSCCLPP_EP_BENCH=1`` to also run a post-correctness benchmark pass
that times dispatch and combine **separately** with CUDA events and
reports per-phase latency (max across ranks) plus aggregate effective
NVLink bandwidth (sum across ranks). Override iteration counts with
``MSCCLPP_EP_BENCH_WARMUP`` / ``MSCCLPP_EP_BENCH_ITERS`` and the bench
problem size with ``MSCCLPP_EP_BENCH_TOKENS`` / ``_HIDDEN``.

This is a minimal adaptation of DeepEP's tests/test_intranode.py stripped
to exercise only the code paths we've ported.
"""

from __future__ import annotations

import os
import sys

# Disable ProcessGroupNCCL's HeartbeatMonitor before importing torch.distributed.
# It runs in a background thread polling the TCPStore; under mpirun, rank 0
# (the store server) can exit before non-zero ranks finish teardown, producing
# noisy 'recvValue failed / Connection was likely closed' stack traces.
os.environ.setdefault("TORCH_NCCL_ENABLE_MONITORING", "0")

import torch
import torch.distributed as dist


def init_dist():
    rank = int(os.environ["RANK"])
    world_size = int(os.environ["WORLD_SIZE"])
    local_rank = int(os.environ.get("LOCAL_RANK", rank))
    torch.cuda.set_device(local_rank)
    dist.init_process_group(
        backend="nccl",
        init_method=f"tcp://{os.environ.get('MASTER_ADDR','127.0.0.1')}:{os.environ.get('MASTER_PORT','29500')}",
        world_size=world_size,
        rank=rank,
    )
    return rank, world_size, local_rank, dist.new_group(list(range(world_size)))


def inplace_unique(x: torch.Tensor, num_slots: int):
    assert x.dim() == 2
    mask = x < 0
    x_padded = x.masked_fill(mask, num_slots)
    bin_count = torch.zeros((x.size(0), num_slots + 1), dtype=x.dtype, device=x.device)
    bin_count.scatter_add_(1, x_padded, torch.ones_like(x_padded))
    bin_count = bin_count[:, :num_slots]
    sorted_bin_count, sorted_bin_idx = torch.sort(bin_count, dim=-1, descending=True)
    sorted_bin_idx.masked_fill_(sorted_bin_count == 0, -1)
    sorted_bin_idx = torch.sort(sorted_bin_idx, descending=True, dim=-1).values
    x[:, :].fill_(-1)
    valid_len = min(num_slots, x.size(1))
    x[:, :valid_len] = sorted_bin_idx[:, :valid_len]


def main():
    rank, num_ranks, local_rank, group = init_dist()
    from mscclpp.ext import ep

    # Small settings for functional check
    num_tokens = 128
    hidden = 1024
    num_topk = min(4, num_ranks)
    num_experts = num_ranks * 4

    torch.manual_seed(0xA1B2 + rank)

    # Build topk layout that maps each token to num_topk distinct ranks/experts
    scores = torch.randn((num_tokens, num_experts), device="cuda", dtype=torch.float32).abs() + 1
    topk_idx = torch.topk(scores, num_topk, dim=-1, sorted=False).indices
    topk_weights = torch.ones((num_tokens, num_topk), dtype=torch.float32, device="cuda")

    rank_idx = topk_idx // (num_experts // num_ranks)
    rank_idx.masked_fill_(topk_idx == -1, -1)
    inplace_unique(rank_idx, num_ranks)

    # Expert / rank meta
    num_tokens_per_expert = torch.zeros((num_experts,), dtype=torch.int, device="cuda")
    for i in range(num_experts):
        num_tokens_per_expert[i] = (topk_idx == i).sum()

    num_tokens_per_rank = torch.empty((num_ranks,), dtype=torch.int, device="cuda")
    token_idx_in_rank = torch.full((num_ranks, num_tokens), -1, dtype=torch.long, device="cuda")
    for i in range(num_ranks):
        num_tokens_per_rank[i] = (rank_idx == i).sum()
        token_sel = (rank_idx == i).max(dim=-1).values
        cnt = token_sel.sum().item()
        tokens = torch.sort(token_sel.to(torch.int), descending=True).indices
        tokens[:cnt] = torch.sort(tokens[:cnt]).values
        token_idx_in_rank[i][tokens[:cnt]] = torch.arange(cnt, dtype=torch.long, device="cuda")
    token_idx_in_rank = token_idx_in_rank.T.contiguous().to(torch.int)
    is_token_in_rank = token_idx_in_rank >= 0

    # Token payload = rank id (cast to bf16) so we can check correctness
    x = torch.ones((num_tokens, hidden), dtype=torch.bfloat16, device="cuda") * float(rank)

    # Allocate Buffer (intranode only: num_rdma_bytes=0). Size the NVL buffer
    # using max(hidden, bench_hidden) so the optional bench phase fits.
    cfg = ep.Config(20, 8, 256)
    _bench_on = os.environ.get("MSCCLPP_EP_BENCH", "0") == "1"
    _buf_hidden = max(hidden, int(os.environ.get("MSCCLPP_EP_BENCH_HIDDEN", "0"))) if _bench_on else hidden
    num_nvl_bytes = cfg.get_nvl_buffer_size_hint(_buf_hidden * x.element_size(), num_ranks)
    if rank == 0:
        print(f"[cfg] num_ranks={num_ranks} num_tokens={num_tokens} hidden={hidden} "
              f"num_experts={num_experts} num_topk={num_topk} num_nvl_bytes={num_nvl_bytes}",
              flush=True)

    print(f"[rank {rank}] creating Buffer", flush=True)
    buf = ep.Buffer(group, num_nvl_bytes=num_nvl_bytes, num_rdma_bytes=0, low_latency_mode=False)
    print(f"[rank {rank}] Buffer created is_available={buf.is_available()}", flush=True)
    assert buf.is_available()

    # get_dispatch_layout sanity
    ref_rank, _, ref_exp, ref_in_rank, _ = buf.runtime.get_dispatch_layout(topk_idx, num_experts, None, False, False)
    assert torch.allclose(ref_rank, num_tokens_per_rank)
    assert torch.allclose(ref_exp, num_tokens_per_expert)
    assert torch.allclose(ref_in_rank, is_token_in_rank)
    if rank == 0:
        print("[layout] OK", flush=True)

    # Dispatch
    (recv_x, recv_x_scales, recv_topk_idx, recv_topk_weights,
     num_recv_tokens_per_expert_list,
     rank_prefix_matrix, channel_prefix_matrix, recv_channel_prefix_matrix, recv_src_idx,
     send_head, _event) = buf.runtime.intranode_dispatch(
        x, None, topk_idx, topk_weights,
        num_tokens_per_rank, is_token_in_rank, num_tokens_per_expert,
        0, None, None,
        1, cfg, None, False, False,
    )
    dist.barrier(group=group)

    # Validate received payloads: for each source rank i, the block of tokens
    # we received from it should be filled with `i`.
    assert recv_x.dim() == 2 and recv_x.size(1) == hidden
    start = 0
    for src in range(num_ranks):
        end = rank_prefix_matrix[src][rank].item()
        block = recv_x[start:end]
        if block.numel():
            actual = block.float().amin().item()
            assert abs(actual - src) < 1e-3, (
                f"rank{rank}: block from src={src} has min={actual}, expected {src}"
            )
            assert abs(block.float().amax().item() - src) < 1e-3
        start = end
    if rank == 0:
        print(f"[dispatch] OK (recv {recv_x.size(0)} tokens)", flush=True)

    # Combine (scatter-reduce back). Using recv_topk_weights=None path with
    # dispatched tokens unchanged => every source rank should receive its
    # contribution back, unweighted sum across topk copies.
    handle_recv_src_idx = recv_src_idx
    handle_rank_prefix_matrix = rank_prefix_matrix
    handle_channel_prefix_matrix = recv_channel_prefix_matrix

    combined_x, combined_topk_weights, _ = buf.runtime.intranode_combine(
        recv_x, recv_topk_weights,
        handle_recv_src_idx, handle_rank_prefix_matrix, handle_channel_prefix_matrix,
        send_head, cfg, None, False, False,
    )

    # Expected: we dispatched with x = rank * ones, so every destination r
    # received the value `rank` for our token. On combine the destinations
    # send that value back and we sum: combined[t] = rank * (#destinations).
    num_dst = is_token_in_rank.sum(dim=1).to(torch.float32)
    expected = num_dst * float(rank)

    got = combined_x.float().mean(dim=1)
    diff = (got - expected).abs().max().item()
    max_exp = expected.abs().max().item()
    if rank == 0:
        print(f"[combine] max|got-expected|={diff:.4e} max|expected|={max_exp:.4e}", flush=True)
    assert diff < 1e-2, f"rank{rank}: combine mismatch max diff {diff}"

    dist.barrier(group=group)
    if rank == 0:
        print("PASS", flush=True)

    # ------------------------------------------------------------------
    # Optional benchmark (enable with MSCCLPP_EP_BENCH=1).
    # ------------------------------------------------------------------
    if os.environ.get("MSCCLPP_EP_BENCH", "0") != "1":
        return

    warmup = int(os.environ.get("MSCCLPP_EP_BENCH_WARMUP", "5"))
    iters = int(os.environ.get("MSCCLPP_EP_BENCH_ITERS", "20"))
    bench_tokens = int(os.environ.get("MSCCLPP_EP_BENCH_TOKENS", "4096"))
    bench_hidden = int(os.environ.get("MSCCLPP_EP_BENCH_HIDDEN", "7168"))
    # Allow overriding num_experts / num_topk for the bench phase to match
    # NCCL-EP's `ep_bench -a ht` defaults (256 experts, top-8). The functional
    # check above still uses the smaller (num_experts=num_ranks*4, topk=4)
    # configuration.
    bench_num_experts = int(os.environ.get(
        "MSCCLPP_EP_BENCH_EXPERTS", str(num_experts)))
    bench_num_topk = int(os.environ.get(
        "MSCCLPP_EP_BENCH_TOPK", str(num_topk)))
    if bench_num_experts % num_ranks != 0:
        if rank == 0:
            print(f"[bench] skip: num_experts={bench_num_experts} not divisible "
                  f"by num_ranks={num_ranks}", flush=True)
        return
    if bench_num_topk > bench_num_experts:
        if rank == 0:
            print(f"[bench] skip: topk={bench_num_topk} > experts={bench_num_experts}",
                  flush=True)
        return

    # Rebuild inputs at bench size. Keep same layout recipe as above but at
    # larger (num_tokens, hidden); Buffer is sized off the original cfg+hidden,
    # so bench must fit within num_nvl_bytes. If it doesn't, we skip.
    if bench_hidden * x.element_size() > (num_nvl_bytes // max(1, num_ranks)):
        if rank == 0:
            print(
                f"[bench] skip: hidden={bench_hidden} bytes/row={bench_hidden * x.element_size()} "
                f"> per-peer budget {num_nvl_bytes // num_ranks}. "
                f"Rerun with a larger Buffer or smaller hidden.",
                flush=True,
            )
        return

    scores_b = torch.randn((bench_tokens, bench_num_experts), device="cuda", dtype=torch.float32).abs() + 1
    topk_idx_b = torch.topk(scores_b, bench_num_topk, dim=-1, sorted=False).indices
    topk_weights_b = torch.ones((bench_tokens, bench_num_topk), dtype=torch.float32, device="cuda")
    rank_idx_b = topk_idx_b // (bench_num_experts // num_ranks)
    rank_idx_b.masked_fill_(topk_idx_b == -1, -1)
    inplace_unique(rank_idx_b, num_ranks)
    num_tokens_per_expert_b = torch.zeros((bench_num_experts,), dtype=torch.int, device="cuda")
    for i in range(bench_num_experts):
        num_tokens_per_expert_b[i] = (topk_idx_b == i).sum()
    num_tokens_per_rank_b = torch.empty((num_ranks,), dtype=torch.int, device="cuda")
    token_idx_in_rank_b = torch.full((num_ranks, bench_tokens), -1, dtype=torch.long, device="cuda")
    for i in range(num_ranks):
        num_tokens_per_rank_b[i] = (rank_idx_b == i).sum()
        token_sel = (rank_idx_b == i).max(dim=-1).values
        cnt = token_sel.sum().item()
        tokens = torch.sort(token_sel.to(torch.int), descending=True).indices
        tokens[:cnt] = torch.sort(tokens[:cnt]).values
        token_idx_in_rank_b[i][tokens[:cnt]] = torch.arange(cnt, dtype=torch.long, device="cuda")
    token_idx_in_rank_b = token_idx_in_rank_b.T.contiguous().to(torch.int)
    is_token_in_rank_b = token_idx_in_rank_b >= 0
    x_b = torch.ones((bench_tokens, bench_hidden), dtype=torch.bfloat16, device="cuda") * float(rank)

    def _dispatch():
        return buf.runtime.intranode_dispatch(
            x_b, None, topk_idx_b, topk_weights_b,
            num_tokens_per_rank_b, is_token_in_rank_b, num_tokens_per_expert_b,
            0, None, None, 1, cfg, None, False, False,
        )

    def _combine(dout):
        (rx, _rxs, _rti, rtw, _lst, rpm, _cpm, rcpm, rsi, sh, _ev) = dout
        buf.runtime.intranode_combine(
            rx, rtw, rsi, rpm, rcpm, sh, cfg, None, False, False,
        )

    # Warmup (full round-trip).
    for _ in range(warmup):
        _combine(_dispatch())
    torch.cuda.synchronize()
    dist.barrier(group=group)

    # Time dispatch alone.
    start_ev = torch.cuda.Event(enable_timing=True)
    end_ev = torch.cuda.Event(enable_timing=True)
    start_ev.record()
    dout = None
    for _ in range(iters):
        dout = _dispatch()
    end_ev.record()
    torch.cuda.synchronize()
    disp_us = start_ev.elapsed_time(end_ev) * 1e3 / iters

    # Time combine alone (reusing the same dispatch output each iter).
    dist.barrier(group=group)
    start_ev.record()
    for _ in range(iters):
        _combine(dout)
    end_ev.record()
    torch.cuda.synchronize()
    comb_us = start_ev.elapsed_time(end_ev) * 1e3 / iters

    # Per-rank "send bytes" matches NCCL-EP's `ep_bench` accounting (`RDMA_send`):
    # bench_tokens * hidden * sizeof(bf16). Each rank ships its `bench_tokens`
    # input rows out (some replicated to multiple peers); NCCL-EP normalizes by
    # the input footprint, not by the recv-side fan-out. We use the same
    # convention here so `per_rank_bw` is directly comparable across stacks.
    bytes_one_way = bench_tokens * bench_hidden * x_b.element_size()

    # NCCL-EP `ep_bench` six-metric breakdown
    # (intranode -> single node, so rdma_*=0; nvl_*=total_*).
    #
    # Send side follows NCCL-EP: count unique (token, dst_node) pairs. With a
    # single node every selected destination collapses to that node, so a
    # token with at least one valid expert contributes exactly one to
    # `total_send_tokens`. Recv side counts unique (src_rank, token) pairs
    # landing on this rank.
    bytes_per_token = bench_hidden * x_b.element_size()
    total_send_tokens_local = int(is_token_in_rank_b.any(dim=1).sum().item())
    rdma_send_tokens_local = 0  # intranode: no remote nodes
    recv_from_src = torch.empty(num_ranks, dtype=torch.int64, device="cuda")
    dist.all_to_all_single(
        recv_from_src,
        num_tokens_per_rank_b.to(torch.int64),
        group=group,
    )
    total_recv_tokens_local = int(recv_from_src.sum().item())
    rdma_recv_tokens_local = 0  # intranode

    # Average per-rank token counts across ranks (matches NCCL-EP `Byte counts (per rank avg)`).
    counts_t = torch.tensor(
        [total_send_tokens_local, rdma_send_tokens_local,
         total_recv_tokens_local, rdma_recv_tokens_local],
        dtype=torch.float64, device="cuda",
    )
    dist.all_reduce(counts_t, op=dist.ReduceOp.SUM, group=group)
    counts_avg = (counts_t / num_ranks).tolist()
    total_send_avg, rdma_send_avg, total_recv_avg, rdma_recv_avg = counts_avg
    total_send_bytes = total_send_avg * bytes_per_token
    rdma_send_bytes = rdma_send_avg * bytes_per_token
    total_recv_bytes = total_recv_avg * bytes_per_token
    rdma_recv_bytes = rdma_recv_avg * bytes_per_token
    nvl_send_bytes = total_send_bytes - rdma_send_bytes
    nvl_recv_bytes = total_recv_bytes - rdma_recv_bytes

    # Reduce timings: report min/avg/max and base BW on AVG to match NCCL-EP's
    # `ep_bench.cu` convention.
    disp_min_t = torch.tensor([disp_us], dtype=torch.float64, device="cuda")
    disp_avg_t = torch.tensor([disp_us], dtype=torch.float64, device="cuda")
    disp_max_t = torch.tensor([disp_us], dtype=torch.float64, device="cuda")
    comb_min_t = torch.tensor([comb_us], dtype=torch.float64, device="cuda")
    comb_avg_t = torch.tensor([comb_us], dtype=torch.float64, device="cuda")
    comb_max_t = torch.tensor([comb_us], dtype=torch.float64, device="cuda")
    dist.all_reduce(disp_min_t, op=dist.ReduceOp.MIN, group=group)
    dist.all_reduce(disp_avg_t, op=dist.ReduceOp.SUM, group=group)
    dist.all_reduce(disp_max_t, op=dist.ReduceOp.MAX, group=group)
    dist.all_reduce(comb_min_t, op=dist.ReduceOp.MIN, group=group)
    dist.all_reduce(comb_avg_t, op=dist.ReduceOp.SUM, group=group)
    dist.all_reduce(comb_max_t, op=dist.ReduceOp.MAX, group=group)
    disp_avg_us = disp_avg_t.item() / num_ranks
    comb_avg_us = comb_avg_t.item() / num_ranks
    disp_bw_per_rank = bytes_one_way / (disp_avg_us * 1e-6) / 1e9
    comb_bw_per_rank = bytes_one_way / (comb_avg_us * 1e-6) / 1e9
    # Six-metric BW (NCCL-EP convention). Combine reverses send<->recv.
    disp_t_s = disp_avg_us * 1e-6
    comb_t_s = comb_avg_us * 1e-6
    d_send_total_bw = total_send_bytes / disp_t_s / 1e9
    d_send_nvl_bw = nvl_send_bytes / disp_t_s / 1e9
    d_send_rdma_bw = rdma_send_bytes / disp_t_s / 1e9
    d_recv_total_bw = total_recv_bytes / disp_t_s / 1e9
    d_recv_nvl_bw = nvl_recv_bytes / disp_t_s / 1e9
    d_recv_rdma_bw = rdma_recv_bytes / disp_t_s / 1e9
    c_send_total_bw = total_recv_bytes / comb_t_s / 1e9  # combine sends back what dispatch received
    c_send_nvl_bw = nvl_recv_bytes / comb_t_s / 1e9
    c_send_rdma_bw = rdma_recv_bytes / comb_t_s / 1e9
    c_recv_total_bw = total_send_bytes / comb_t_s / 1e9  # combine receives back what dispatch sent
    c_recv_nvl_bw = nvl_send_bytes / comb_t_s / 1e9
    c_recv_rdma_bw = rdma_send_bytes / comb_t_s / 1e9
    if rank == 0:
        print(
            f"[bench intranode HT] tokens={bench_tokens} hidden={bench_hidden} "
            f"experts={bench_num_experts} topk={bench_num_topk} "
            f"warmup={warmup} iters={iters}",
            flush=True,
        )
        print(
            f"  dispatch: avg={disp_avg_us:.1f}us min={disp_min_t.item():.1f}us max={disp_max_t.item():.1f}us  "
            f"per_rank_bw={disp_bw_per_rank:.2f} GB/s  "
            f"agg_bw={disp_bw_per_rank * num_ranks:.2f} GB/s  (BW @ avg time)",
            flush=True,
        )
        print(
            f"            send: total={d_send_total_bw:.2f}  nvl={d_send_nvl_bw:.2f}  rdma={d_send_rdma_bw:.2f} GB/s  "
            f"recv: total={d_recv_total_bw:.2f}  nvl={d_recv_nvl_bw:.2f}  rdma={d_recv_rdma_bw:.2f} GB/s",
            flush=True,
        )
        print(
            f"  combine : avg={comb_avg_us:.1f}us min={comb_min_t.item():.1f}us max={comb_max_t.item():.1f}us  "
            f"per_rank_bw={comb_bw_per_rank:.2f} GB/s  "
            f"agg_bw={comb_bw_per_rank * num_ranks:.2f} GB/s  (BW @ avg time)",
            flush=True,
        )
        print(
            f"            send: total={c_send_total_bw:.2f}  nvl={c_send_nvl_bw:.2f}  rdma={c_send_rdma_bw:.2f} GB/s  "
            f"recv: total={c_recv_total_bw:.2f}  nvl={c_recv_nvl_bw:.2f}  rdma={c_recv_rdma_bw:.2f} GB/s",
            flush=True,
        )
        print(
            f"  byte counts (per rank avg): "
            f"total_send={total_send_bytes/1e6:.2f} MB ({total_send_avg:.0f} tok)  "
            f"rdma_send={rdma_send_bytes/1e6:.2f} MB ({rdma_send_avg:.0f} tok)  "
            f"total_recv={total_recv_bytes/1e6:.2f} MB ({total_recv_avg:.0f} tok)  "
            f"rdma_recv={rdma_recv_bytes/1e6:.2f} MB ({rdma_recv_avg:.0f} tok)",
            flush=True,
        )


if __name__ == "__main__":
    try:
        main()
    except Exception:
        import traceback
        traceback.print_exc()
        sys.exit(1)
    finally:
        # Ordered shutdown: barrier so every rank reaches teardown before the
        # TCPStore server (rank 0) exits, then destroy the PG. Avoids noisy
        # "recvValue failed / Connection was likely closed" stack traces from
        # ProcessGroupNCCL's HeartbeatMonitor.
        if dist.is_initialized():
            try:
                dist.barrier()
            except Exception:
                pass
            dist.destroy_process_group()