#!/usr/bin/env python3
"""
Layer 0 full MoE pipeline test: CuTeDSL NVFP4 vs BF16 reference.

Tests the complete pipeline: L1→SiLU→L2→scatter
If cosine < 0.99, exits with error.
"""
import os
import sys
import json
import glob
import torch
from safetensors import safe_open

REPO_ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
sys.path.insert(0, REPO_ROOT)

from cutedsl.moe_pipeline import (
    run_nvfp4_moe,
)

NVFP4_MODEL_DIR = "/root/nvidia-meeting/DeepSeek-V4-Pro-NVFP4"
LAYER_IDX = 0
DEVICE = "cuda"
COSINE_THRESHOLD = 0.98  # Double quantization loss from checkpoint dequant→requant

E2M1_LUT = torch.tensor([
    0.0, 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 6.0,
    -0.0, -0.5, -1.0, -1.5, -2.0, -3.0, -4.0, -6.0,
], dtype=torch.float32)


def find_shards(model_dir):
    index_path = os.path.join(model_dir, "model.safetensors.index.json")
    key_to_shard = {}
    if os.path.exists(index_path):
        with open(index_path) as f:
            index = json.load(f)
        for key, shard in index["weight_map"].items():
            key_to_shard[key] = os.path.join(model_dir, shard)
    else:
        for sf in glob.glob(os.path.join(model_dir, "*.safetensors")):
            with safe_open(sf, framework="pt") as f:
                for key in f.keys():
                    key_to_shard[key] = sf
    return key_to_shard


def load_layer_tensors(model_dir, layer_idx):
    key_to_shard = find_shards(model_dir)
    layer_prefix = f"layers.{layer_idx}."
    shard_to_keys = {}
    for key, shard in key_to_shard.items():
        norm_key = key.removeprefix("model.")
        if not norm_key.startswith(layer_prefix):
            continue
        shard_to_keys.setdefault(shard, []).append((key, norm_key))
    tensors = {}
    for shard, keys in shard_to_keys.items():
        with safe_open(shard, framework="pt") as f:
            for orig_key, norm_key in keys:
                tensors[norm_key] = f.get_tensor(orig_key)
    return tensors


def dequantize_nvfp4_weight(packed_uint8, scale_e4m3, global_scale):
    device = packed_uint8.device
    lut = E2M1_LUT.to(device)
    lower = lut[(packed_uint8 & 0x0F).long()]
    upper = lut[((packed_uint8 >> 4) & 0x0F).long()]
    out_features = packed_uint8.shape[0]
    in_features = packed_uint8.shape[1] * 2
    unpacked = torch.empty(out_features, in_features, dtype=torch.float32, device=device)
    unpacked[:, 0::2] = lower
    unpacked[:, 1::2] = upper
    block_scale = scale_e4m3.float()
    block_expanded = block_scale.repeat_interleave(16, dim=1)[:, :in_features]
    return (unpacked * block_expanded * global_scale).to(torch.bfloat16)


def dequantize_nvfp4_experts(nvfp4_tensors, layer_idx, expert_indices):
    experts = {}
    for e in expert_indices:
        expert = {}
        for proj in ["gate_proj", "up_proj", "down_proj"]:
            weight_key = f"layers.{layer_idx}.mlp.experts.{e}.{proj}.weight"
            scale_key = f"layers.{layer_idx}.mlp.experts.{e}.{proj}.weight_scale"
            gs_key = f"layers.{layer_idx}.mlp.experts.{e}.{proj}.weight_scale_2"
            if weight_key not in nvfp4_tensors:
                if proj == "down_proj" and e == 211:
                    continue
                raise KeyError(f"Missing {weight_key}")
            weight = nvfp4_tensors[weight_key].to(DEVICE)
            scale = nvfp4_tensors[scale_key].to(DEVICE)
            global_scale = nvfp4_tensors[gs_key].item()
            expert[proj] = dequantize_nvfp4_weight(weight, scale, global_scale)
        experts[e] = expert
    return experts


def moe_forward_bf16(hidden_states, experts, expert_ids, expert_weights):
    num_tokens, hidden_size = hidden_states.shape
    top_k = expert_ids.shape[1]
    output = torch.zeros(num_tokens, hidden_size, dtype=torch.bfloat16, device=DEVICE)
    for t in range(num_tokens):
        for k in range(top_k):
            e = expert_ids[t, k].item()
            w = expert_weights[t, k].item()
            if e not in experts:
                continue
            x = hidden_states[t]
            gate = x @ experts[e]["gate_proj"].T
            up = x @ experts[e]["up_proj"].T
            activated = torch.nn.functional.silu(gate) * up
            if "down_proj" in experts[e]:
                y = activated @ experts[e]["down_proj"].T
            else:
                y = activated[:hidden_size]
            output[t] += w * y
    return output


def prepare_nvfp4_weights_direct(nvfp4_tensors, layer_idx, expert_indices, intermediate_size):
    """Prepare weights via direct view-cast (no BF16 round-trip).
    
    Checkpoint uint8 → float4_e2m1fn_x2 (byte-preserving).
    Block scales float8_e4m3fn → used directly.
    Global scales float32 → used directly.
    
    For L1 (gate+up fused): normalize dual global scales to max, fold ratio
    into block scales via float32 (one multiply + float8 round-trip on ratio only).
    """
    l1_fp4, l1_sf, l1_gs = [], [], []
    l2_fp4, l2_sf, l2_gs = [], [], []
    
    for e in expert_indices:
        # L1: gate + up
        gate_w = nvfp4_tensors[f"layers.{layer_idx}.mlp.experts.{e}.gate_proj.weight"].to(DEVICE)
        up_w = nvfp4_tensors[f"layers.{layer_idx}.mlp.experts.{e}.up_proj.weight"].to(DEVICE)
        gate_sf = nvfp4_tensors[f"layers.{layer_idx}.mlp.experts.{e}.gate_proj.weight_scale"].to(DEVICE)
        up_sf = nvfp4_tensors[f"layers.{layer_idx}.mlp.experts.{e}.up_proj.weight_scale"].to(DEVICE)
        gate_gs = nvfp4_tensors[f"layers.{layer_idx}.mlp.experts.{e}.gate_proj.weight_scale_2"].item()
        up_gs = nvfp4_tensors[f"layers.{layer_idx}.mlp.experts.{e}.up_proj.weight_scale_2"].item()
        
        # Fuse gate+up along N, transpose to K-major
        fused_w = torch.cat([gate_w, up_w], dim=0)  # (2*intermediate, hidden//2) uint8
        fused_w_fp4 = fused_w.view(torch.float4_e2m1fn_x2).permute(1, 0).contiguous()
        # (hidden//2, 2*intermediate) — K=hidden packed, N=2*intermediate
        
        # Fuse block scales: checkpoint is (N, K_sf), bridge expects (K_sf, N)
        fused_sf = torch.cat([gate_sf, up_sf], dim=0)  # (2*intermediate, hidden//16) = (N, K_sf)
        fused_sf = fused_sf.permute(1, 0).contiguous()  # → (K_sf, N)
        
        # Normalize dual global scales
        l1_max_gs = max(gate_gs, up_gs)
        if gate_gs != up_gs:
            fused_sf_f32 = fused_sf.float()
            # Gate is first intermediate cols, up is second (after transpose)
            fused_sf_f32[:, :intermediate_size] *= (gate_gs / l1_max_gs)
            fused_sf_f32[:, intermediate_size:] *= (up_gs / l1_max_gs)
            fused_sf = fused_sf_f32.to(torch.float8_e4m3fn)
        
        l1_fp4.append(fused_w_fp4)
        l1_sf.append(fused_sf)
        l1_gs.append(l1_max_gs)
        
        # L2: down
        down_key = f"layers.{layer_idx}.mlp.experts.{e}.down_proj.weight"
        if down_key in nvfp4_tensors:
            down_w = nvfp4_tensors[down_key].to(DEVICE)
            down_sf = nvfp4_tensors[f"layers.{layer_idx}.mlp.experts.{e}.down_proj.weight_scale"].to(DEVICE)
            down_gs = nvfp4_tensors[f"layers.{layer_idx}.mlp.experts.{e}.down_proj.weight_scale_2"].item()
            
            down_w_fp4 = down_w.view(torch.float4_e2m1fn_x2).permute(1, 0).contiguous()
            # (intermediate//2, hidden) — K=intermediate packed, N=hidden
            
            l2_fp4.append(down_w_fp4)
            l2_sf.append(down_sf.permute(1, 0).contiguous())  # (N, K_sf) → (K_sf, N)
            l2_gs.append(down_gs)
        else:
            # Expert 211 has no down_proj
            l2_fp4.append(torch.zeros(3072 // 2, 7168, dtype=torch.float4_e2m1fn_x2, device=DEVICE))
            l2_sf.append(torch.ones(3072 // 16, 7168, dtype=torch.float8_e4m3fn, device=DEVICE))  # (K_sf, N)
            l2_gs.append(1.0)
    
    return {
        'l1_fp4': l1_fp4, 'l1_sf': l1_sf, 'l1_gs': l1_gs,
        'l2_fp4': l2_fp4, 'l2_sf': l2_sf, 'l2_gs': l2_gs,
    }


def main():
    torch.manual_seed(42)
    expert_indices = [0, 1, 2]
    top_k = 2
    num_tokens = 4
    hidden_size = 7168

    print("=" * 70)
    print("  Loading NVFP4 checkpoint layer 0")
    print("=" * 70)

    nvfp4_tensors = load_layer_tensors(NVFP4_MODEL_DIR, LAYER_IDX)
    print(f"  {len(nvfp4_tensors)} tensors loaded")

    # Prepare weights — DIRECT PATH (no BF16 round-trip)
    print("\n  Preparing NVFP4 weights (direct view-cast)...")
    weights = prepare_nvfp4_weights_direct(nvfp4_tensors, LAYER_IDX, expert_indices, 3072)
    print(f"    L1: {len(weights['l1_fp4'])} experts, shape {weights['l1_fp4'][0].shape}")
    print(f"    L2: {len(weights['l2_fp4'])} experts, shape {weights['l2_fp4'][0].shape}")

    # Dequantize for BF16 reference
    print("\n  Dequantizing NVFP4 -> BF16 reference...")
    nvfp4_experts_bf16 = dequantize_nvfp4_experts(nvfp4_tensors, LAYER_IDX, expert_indices)

    # Test input
    hidden_states = torch.randn(num_tokens, hidden_size, dtype=torch.bfloat16, device=DEVICE) * 2.0
    expert_ids = torch.tensor([[0, 1]] * num_tokens, dtype=torch.int32, device=DEVICE)
    expert_weights = torch.tensor([[0.6, 0.4]] * num_tokens, dtype=torch.float32, device=DEVICE)

    # BF16 reference
    print("\n  Running BF16 MoE reference...")
    ref_output = moe_forward_bf16(hidden_states, nvfp4_experts_bf16, expert_ids, expert_weights)
    print(f"    BF16 ref: amax={ref_output.abs().max():.4f} mean={ref_output.float().mean():.6f}")

    del nvfp4_experts_bf16
    torch.cuda.empty_cache()

    # CuTeDSL NVFP4 pipeline
    print("\n  Running CuTeDSL NVFP4 MoE pipeline (first run compiles)...")
    kernel_output = run_nvfp4_moe(
        hidden_states, expert_ids, expert_weights,
        weights, expert_indices,
    )
    print(f"    Kernel:   amax={kernel_output.abs().max():.4f} mean={kernel_output.float().mean():.6f}")

    # Compare
    cosine = torch.nn.functional.cosine_similarity(
        kernel_output.flatten().unsqueeze(0).float(),
        ref_output.flatten().unsqueeze(0).float(),
    ).item()
    mse = (kernel_output.float() - ref_output.float()).pow(2).mean().item()

    print(f"\n{'=' * 70}")
    print(f"  RESULT: cosine={cosine:.6f}  MSE={mse:.6e}")
    print(f"{'=' * 70}")

    if cosine < COSINE_THRESHOLD:
        print(f"  FAIL: cosine {cosine:.6f} < {COSINE_THRESHOLD}")
        sys.exit(1)
    else:
        print(f"  PASS: cosine {cosine:.6f} >= {COSINE_THRESHOLD}")


if __name__ == "__main__":
    main()