import tilelang
import tilelang.language as T
from tilelang.quantize import _tir_u8_to_f4_to_bf16
from tilelang import tvm as tvm
from tvm import DataType
import torch
from dequantize_utils import torch_convert_bit_twiddling, assert_similar
from tilelang.autotuner import set_autotune_inputs


def get_configs():
    """
    Generate a list of hyperparameter configuration dictionaries for tuning.

    Each configuration is a dict with keys: 'block_M', 'block_N', 'block_K',
    'num_stages', 'threads', and 'split'. The function returns the Cartesian
    product of the parameter value lists:
    - block_M, block_N, block_K: tiling sizes
    - num_stages: pipeline stages
    - threads: thread counts
    - split: K-splitting factor

    Returns:
        List[dict]: A list of configuration dictionaries covering all combinations.
    """
    import itertools
    iter_params = dict(
        block_M=[128],
        block_N=[64, 128, 256],
        block_K=[128],
        num_stages=[0, 1, 2],
        threads=[128, 256, 512],
        split=[1],
    )
    return [{
        k: v for k, v in zip(iter_params, values)
    } for values in itertools.product(*iter_params.values())]


@tilelang.autotune(configs=get_configs())
@tilelang.jit(out_idx=[-1])
def matmul(M,
           N,
           K,
           topk,
           E,
           padding_M,
           in_dtype,
           out_dtype,
           accum_dtype,
           source_format='uint',
           num_bits=4,
           scale_size=32,
           fast_dequant=True,
           with_bias=False,
           block_M=128,
           block_N=256,
           block_K=128,
           num_stages=2,
           threads=256,
           split=1):
    """
    Construct and return a grouped (Mixture-of-Experts) matrix-multiply TIR kernel that multiplies A (shape MxK) by a quantized, expert-grouped B (shape ExNxQK) and writes an output of shape (M, topk, N) in out_dtype.

    The generated kernel accepts:
    - A: dense matrix with element type `in_dtype` and shape (M, K).
    - B: packed quantized matrix for all experts, stored as uint8 with `num_bits` bits per element, shape (E, N, QK), where QK = K / (8/num_bits).
    - Scale: per-expert, per-block scale/exponent information for dequantizing B, shape (E, N, K // scale_size).
    - Bias: per-expert, per-output bias, shape (E, N).
    - topk_weights: router weights for the top-k experts for each token, shape (M, topk).
    - sorted_token_ids: flattened and padded tensor of token indices, shape (padding_M,).
    - expert_ids: expert id for each token in the padded batch, shape (padding_M // block_M,).
    - C: output tensor, shape (M, topk, N).

    The kernel dequantizes B to a working floating format (out_dtype/accum_dtype) using one of two paths:
    - fast_dequant (True): uses an external, hardware/implementation-specific intrinsic group (twiddling) for batch dequantization.
    - fast_dequant (False): uses a simple elementwise dequantization helper.

    Parameters:
        M, N, K (int): matrix dimensions (A is MxK, result is (M, topk, N)). K must be divisible by (block_K * split).
        topk (int): number of experts selected per token.
        E (int): number of experts.
        padding_M (int): padded number of tokens after grouping and block alignment.
        in_dtype (str): element type of A (e.g., "bfloat16").
        out_dtype (str): output tensor element type (e.g., "bfloat16").
        accum_dtype (str): accumulation type used for the inner GEMM.
        source_format (str, optional): format string passed to intrinsic selector (default "uint").
        num_bits (int, optional): number of bits per quantized element in B (default 4).
        scale_size (int, optional): number of elements grouped per scale entry (default 32).
        fast_dequant (bool, optional): choose the fast intrinsic dequantization path when available (default True).
        block_M, block_N, block_K (int, optional): tile sizes for M, N, and K dimensions (defaults 256, 128, 128).
        num_stages (int, optional): pipelining stages for K loop (default 2).
        threads (int, optional): threads per block used by the kernel (default 256).
        split (int, optional): split factor along K used by the scheduler (default 1).
        with_bias (bool, optional): whether to add Bias to the output (default False).

    Returns:
        A T.prim_func implementing the grouped, pipelined GEMM that:
        - loads tiled blocks of A and packed B for each expert to shared memory,
        - dequantizes B via the chosen path into a shared dequantized tile,
        - performs a tiled GEMM accumulating into local fragments,
        - applies per-token topk weights and bias,
        - writes the final (M, topk, N) block to the global output tensor.

    Notes:
        - The function queries an intrinsic group to obtain a fast dequantization implementation when fast_dequant is enabled; that intrinsic must supply a valid C source and function name.
        - The kernel layout uses swizzled shared-memory layouts for A, B, and the shared C tile.
        - An assertion enforces that K % (block_K * split) == 0.
    """

    num_elems_per_byte = 8 // num_bits
    storage_dtype = "uint8"
    QK = K // num_elems_per_byte
    Block_QK = block_K // num_elems_per_byte
    A_shared_shape = (block_M, block_K)
    B_shared_shape = (block_N, Block_QK)
    Bias_shared_shape = (block_N)
    B_dequantize_shared_shape = (block_N, block_K)
    assert K % (block_K * split) == 0

    from tilelang.quantize import get_mxfp_intrin_group
    # fast_dequant_bf16_fp4_twiddling
    mxfp_intrin_info = get_mxfp_intrin_group(
        out_dtype=in_dtype,
        source_format=source_format,
        source_bit=num_bits,
        storage_dtype=storage_dtype,
        use_twiddling=True,
    )
    import_source = mxfp_intrin_info["c_source"]
    func_name = mxfp_intrin_info["func_name"]
    assert import_source is not None, "mxfp_intrin_info is not found"
    assert func_name is not None, "mxfp_intrin_info is not found"
    import_source = import_source

    # the dequant part is the same as in dequant_gemm
    def get_fast_dequant_twiddling_func(in_dtype="fp4", out_dtype="bfloat16"):
        """
        Return a TileLang macro that performs fast dequantization of twiddled FP4-packed data into BF16.
        The returned macro has signature (B_shared, B_dequantize_shared, Scale, k) and:
        - Loads packed FP4 elements from B_shared into per-thread local registers.
        - Calls an external fast dequantization intrinsic (provided via `import_source` / `func_name` in the outer scope) to expand packed FP4 -> BF16 values.
        - Applies a per-block scale factor derived from the Scale tensor (using exponentiation by powers of two).
        - Writes the scaled BF16 results into B_dequantize_shared.

        Notes:
        - This factory only supports in_dtype="fp4" and out_dtype="bfloat16".
        - The macro depends on several names from the enclosing scope (e.g., import_source, func_name, DataType, num_elems_per_byte, storage_dtype, block_N, block_K, threads, scale_size); those must be defined and consistent with the kernel that will use the macro.
        - The macro issues a T.import_source and T.call_extern to invoke the external intrinsic; ensure the external implementation matching `func_name` is available at compilation/runtime.
        """
        assert in_dtype in ["fp4"]
        assert out_dtype in ["bfloat16"]

        # Some variables for dequantization in each thread
        MAX_TRANSACTION_SIZE_BITS = 128
        local_size = MAX_TRANSACTION_SIZE_BITS // DataType(out_dtype).bits
        local_compress_size = local_size // num_elems_per_byte

        @T.macro
        def fast_dequant_bf16_fp4_twiddling(B_shared, B_dequantize_shared, Scale_shared, k):
            # import fast_dequantize plugin
            """
            Fast dequantization kernel: convert packed 4-bit quantized values in B_shared to bfloat16
            in B_dequantize_shared using an external intrinsic optimized for twiddled (bit-packed) FP4,
            applying per-block scale factors from Scale.

            This routine is a tiled, thread-parallel helper that:
            - Imports and calls an external dequantization function (via `import_source`/`func_name`)
              to expand compressed uint8-packed FP4 values into BF16 fragments in-thread.
            - Loads the corresponding per-block scale entry, interprets it as an exponent bias
              (applies 2^(Scale - 127)), and multiplies the dequantized BF16 fragment by that factor.
            - Writes the scaled BF16 results back into the shared B_dequantize_shared buffer in-place.

            Parameters:
            - B_shared: read-only shared buffer containing compressed FP4 data (packed uint8 layout).
            - B_dequantize_shared: shared output buffer that is overwritten with BF16 dequantized values.
            - Scale_shared: per-block scale tensor; entries are interpreted such that the multiplicative scale
              = 2^(Scale - 127).
            - k: block index along the K dimension used to select the appropriate Scale entries.

            Side effects:
            - Mutates B_dequantize_shared in shared memory.
            - Calls an external intrinsic function (must be provided by the environment via `import_source`
              and `func_name`) to perform the low-level unpacking/dequantization.
            """
            T.import_source(import_source)

            tx = T.get_thread_binding()

            B_local_thread = T.alloc_local((local_compress_size,), storage_dtype)
            B_dequantize_local_thread = T.alloc_local((local_size,), out_dtype)
            Scale_local_thread = T.alloc_local((1,), storage_dtype)
            Scale_local_thread_exponent = T.alloc_local((1,), out_dtype)

            for i in T.serial(0, block_N * block_K // threads // local_size):
                # First, load data from share memory to register.
                # Prepare for dequant.
                index_base = i * threads * local_compress_size + tx * local_compress_size
                for v in T.vectorized(0, local_compress_size):
                    index = index_base + v
                    B_local_thread[v] = B_shared[index // Block_QK, index % Block_QK]
                index_scale = index_base // (scale_size // num_elems_per_byte)
                si = index_scale // (block_K // scale_size)
                sj = index_scale % (block_K // scale_size)
                Scale_local_thread[0] = Scale_shared[si, k * block_K // scale_size + sj]
                Scale_local_thread_exponent[0] = T.shift_left(1, (Scale_local_thread[0]))

                # Then, dequant.
                T.call_extern(
                    func_name,
                    T.address_of(B_local_thread[0]),
                    T.address_of(B_dequantize_local_thread[0]),
                    1,
                    dtype=out_dtype,
                )

                # Finally, store the dequantized data to shared memory.
                for v in T.Parallel(local_size):
                    B_dequantize_local_thread[v] *= Scale_local_thread_exponent[0]

                for v in T.vectorized(0, local_size):
                    index = i * threads * local_size + tx * local_size + v
                    B_dequantize_shared[index // block_K,
                                        index % block_K] = B_dequantize_local_thread[v]

        return fast_dequant_bf16_fp4_twiddling

    def get_simple_dequant_func(in_dtype="fp4", out_dtype="bfloat16"):

        assert in_dtype in ["fp4"]
        assert out_dtype in ["bfloat16"]

        @T.macro
        def simple_dequant_bf16_fp4(B_shared, B_dequantize_shared, Scale_shared, k):

            B_local = T.alloc_fragment(B_shared_shape, storage_dtype)
            B_dequantize_local = T.alloc_fragment(B_dequantize_shared_shape, out_dtype)

            T.copy(B_shared, B_local)
            for i, j in T.Parallel(block_N, block_K):
                B_dequantize_local[i, j] = _tir_u8_to_f4_to_bf16(
                    num_bits,
                    B_local[i, j // num_elems_per_byte],
                    j % num_elems_per_byte,
                    Scale_shared[
                        i, k * block_K // scale_size + j //
                        scale_size],  # Scale is the exponential part, within the representation of uint8
                    dtype=out_dtype,
                ) * T.shift_left(1, (Scale_shared[i, k * block_K // scale_size + j // scale_size]))
            T.copy(B_dequantize_local, B_dequantize_shared)

        return simple_dequant_bf16_fp4

    @T.prim_func
    def main(
            A: T.Tensor((M, K), in_dtype),
            B: T.Tensor((E, N, QK), storage_dtype),
            Scale: T.Tensor((E, N, K // scale_size), storage_dtype),
            Bias: T.Tensor((E, N), out_dtype),
            # Add fusedmoe tensors
            topk_weights: T.Tensor((M * topk), out_dtype),
            sorted_token_ids: T.Tensor((padding_M), "int32"),
            expert_ids: T.Tensor((padding_M // block_M), "int32"),
            C: T.Tensor((M, topk, N), out_dtype),
    ):

        with T.Kernel(
                T.ceildiv(N, block_N), T.ceildiv(padding_M, block_M), threads=threads) as (bx, by):
            A_shared = T.alloc_shared(A_shared_shape, in_dtype)
            B_shared = T.alloc_shared(B_shared_shape, storage_dtype)
            B_dequantize_shared = T.alloc_shared(B_dequantize_shared_shape, in_dtype)
            Bias_shared = T.alloc_shared(Bias_shared_shape, out_dtype)
            C_local = T.alloc_fragment((block_M, block_N), accum_dtype)
            C_shared = T.alloc_shared((block_M, block_N), out_dtype)
            topk_weights_shared = T.alloc_shared((block_M), out_dtype)
            sorted_token_ids_shared = T.alloc_shared((block_M), "int32")
            expert_id = T.alloc_local((1), "int32")  # the expert id for the current block
            # To use 1D TMA, the last dim of Scale_shared must have stride=1
            # May use much more shared memory than necessary
            Scale_shared = T.alloc_shared((block_N, K // scale_size), storage_dtype)

            T.annotate_layout({
                A_shared: tilelang.layout.make_swizzled_layout(A_shared),
                B_shared: tilelang.layout.make_swizzled_layout(B_shared),
                C_shared: tilelang.layout.make_swizzled_layout(C_shared),
            })
            T.use_swizzle(10)

            if threads == 512:
                T.disable_warp_group_reg_alloc()

            T.copy(sorted_token_ids[by * block_M:(by + 1) * block_M], sorted_token_ids_shared)
            expert_id[0] = expert_ids[by]

            # Get the topk weights of each token in the current block
            for i in T.Parallel(block_M):
                if sorted_token_ids_shared[i] != -1:
                    topk_weights_shared[i] = topk_weights[sorted_token_ids_shared[i]]

            # Get bias and scale based on the expert id
            if with_bias:
                T.copy(Bias[expert_id[0], bx * block_N:(bx + 1) * block_N], Bias_shared)
            else:
                T.clear(Bias_shared)

            T.copy(Scale[expert_id[0], bx * block_N:(bx + 1) * block_N, :], Scale_shared)

            for i, j in T.Parallel(block_M, block_N):
                C_local[i, j] = Bias_shared[j]

            tx = T.get_thread_binding()

            for k in T.Pipelined(K // block_K, num_stages=num_stages):
                # Each thread copies 4 bytes, local size is 16
                for copy_i in T.serial(block_M * block_K // threads // 16):
                    base = copy_i * threads * 16 + tx * 16
                    if sorted_token_ids_shared[base // block_K] != -1:
                        for copy_j in T.vectorized(16):
                            A_shared[base // block_K, base % block_K +
                                     copy_j] = A[sorted_token_ids_shared[base // block_K] // topk,
                                                 k * block_K + base % block_K + copy_j]

                T.copy(B[expert_id[0], bx * block_N, k * block_K // num_elems_per_byte], B_shared)
                if fast_dequant:
                    get_fast_dequant_twiddling_func()(B_shared, B_dequantize_shared, Scale_shared,
                                                      k)
                else:
                    get_simple_dequant_func()(B_shared, B_dequantize_shared, Scale_shared, k)

                T.gemm(A_shared, B_dequantize_shared, C_local, transpose_B=True)

            for i, j in T.Parallel(block_M, block_N):
                C_local[i, j] = C_local[i, j] * topk_weights_shared[i]

            T.copy(C_local, C_shared)
            for copy_i in T.serial(block_M * block_N // threads // 16):
                base = copy_i * threads * 16 + tx * 16
                if sorted_token_ids_shared[base // block_N] != -1:
                    for copy_j in T.vectorized(16):
                        C[sorted_token_ids_shared[base // block_N] // topk,
                          sorted_token_ids_shared[base // block_N] % topk, bx * block_N +
                          base % block_N + copy_j] = C_shared[base // block_N,
                                                              base % block_N + copy_j]

    return main


def ref_moe(A, qB, Scale, Bias, topk_weights, sorted_token_ids, expert_ids, block_M=256):
    dtypeC = "bfloat16"
    M, K = A.shape
    E, N, QK = qB.shape
    topk = topk_weights.shape[0] // M
    scale_size = K // Scale.shape[2]
    assert scale_size == 32  # MXFP4

    # Initialize output tensor
    C = torch.ones((M, topk, N), dtype=getattr(torch, dtypeC), device='cuda')

    # Iterate over sorted_token_ids
    for idx in range(len(sorted_token_ids)):  # padding_M
        token_id = sorted_token_ids[idx]
        if token_id == -1:
            continue
        expert_id = expert_ids[idx // block_M]
        topk_idx = token_id % topk

        # Get the token embedding
        token_embedding = A[token_id // topk]

        # Dequantize the expert weights
        B = torch_convert_bit_twiddling(qB[expert_id])  # shape: (N, K)
        B *= 2**(
            Scale[expert_id][:, (torch.arange(B.shape[1], device=B.device) // scale_size)].to(
                torch.bfloat16))

        # Compute the output for this token-expert pair
        # token_embedding @ B.T + bias
        output = torch.matmul(token_embedding.to(torch.bfloat16), B.T.to(
            torch.bfloat16)) + Bias[expert_id]
        output = output.to(torch.__getattribute__(dtypeC))

        # Apply the topk weight
        weight = topk_weights[token_id]
        output = output * weight

        # Store the result
        C[token_id // topk, topk_idx] = output

    return C


def get_data(m, n, k, qk, scale_size, topk, E, block_M):
    A = torch.empty(m, k, dtype=torch.bfloat16, device='cuda').uniform_(-1, 1)
    qB = torch.randint(
        0, 256, (E, n, qk), dtype=torch.uint8,
        device='cuda')  #  Quantized weight tensor for E experts.
    Scale = torch.randint(0, 8, (E, n, k // scale_size), dtype=torch.uint8, device='cuda')
    Bias = torch.empty(E, n, dtype=torch.bfloat16, device='cuda').uniform_(-1, 1)

    weights = torch.empty(m, E, dtype=torch.bfloat16, device='cuda').uniform_(-1, 1)
    # topk_weights: Router weights for the top-k experts for each token.
    # Shape: (m, topk)
    # tokens_experts: A flattened tensor of expert assignments for each token.
    # For each of m tokens, topk unique experts are chosen. Shape: (m * topk,)
    topk_weights, tokens_experts = torch.topk(weights, topk, dim=-1)
    tokens_experts = tokens_experts.reshape(m * topk)
    topk_weights = topk_weights / topk_weights.sum(dim=-1, keepdim=True)
    topk_weights = topk_weights.reshape(m * topk)

    sorted_expert_vals, sorted_indices = torch.sort(tokens_experts, stable=True)
    sorted_token_ids = sorted_indices
    unique_expert_ids, counts = torch.unique_consecutive(sorted_expert_vals, return_counts=True)
    expert_ids = []
    padded_token_ids = []
    start = 0
    for eid, cnt in zip(unique_expert_ids.tolist(), counts.tolist()):
        end = start + cnt
        group_token_ids = sorted_token_ids[start:end]
        pad_len = ((cnt + block_M - 1) // block_M) * block_M - cnt
        if pad_len > 0:
            # -1 for padding (`M` instead in vLLM moe_align_block_size())
            group_token_ids = torch.cat([
                group_token_ids,
                torch.full((pad_len,), -1, dtype=group_token_ids.dtype, device='cuda')
            ])
        padded_token_ids.append(group_token_ids)
        expert_ids.extend([eid] * ((cnt + block_M - 1) // block_M))
        start = end

    # sorted_token_ids: The final flattened and padded tensor of token indices.
    sorted_token_ids = torch.cat(padded_token_ids, dim=0).to(torch.int32)  # (padding_M,)
    # expert_ids: The final tensor of expert IDs corresponding to `sorted_token_ids`.
    expert_ids = torch.tensor(expert_ids, dtype=torch.int32, device='cuda')  # （padding_M,）
    padding_M = sorted_token_ids.shape[0]  # padding_M: token number after padding

    print(f'{sorted_token_ids=}')
    print(f'{expert_ids=}')

    return A, qB, Scale, Bias, topk_weights, sorted_token_ids, expert_ids, padding_M


def main(m=256, n=256, k=256, scale_size=32, fast_dequant=True, with_bias=False, topk=4, E=32):
    # Tunable parameters
    block_M, block_N, block_K = 128, 256, 128  # noqa: F841
    num_stages = 1  # noqa: F841
    threads = 512  # noqa: F841
    split = 1  # noqa: F841

    total_flops = 2 * m * n * k * topk
    num_bits = 4
    num_elems_per_byte = 8 // num_bits
    qk = k // num_elems_per_byte
    A, qB, Scale, Bias, topk_weights, sorted_token_ids, expert_ids, padding_M = get_data(
        m, n, k, qk, scale_size, topk, E, block_M)

    with set_autotune_inputs([A, qB, Scale, Bias, topk_weights, sorted_token_ids, expert_ids]):
        # Autotune with inputs manually composed
        kernel = matmul(
            m,
            n,
            k,
            topk,
            E,
            padding_M,
            "bfloat16",
            "bfloat16",
            "float32",
            num_bits=num_bits,
            scale_size=scale_size,
            fast_dequant=fast_dequant,
            with_bias=with_bias,
        )
        print(f'Best config: {kernel.config}')

    output = kernel(
        A,
        qB,
        Scale,
        Bias,
        topk_weights,
        sorted_token_ids,
        expert_ids,
    )

    print('Tilelang kernel run finished.')

    ref_output = ref_moe(
        A, qB, Scale, Bias, topk_weights, sorted_token_ids, expert_ids,
        block_M=block_M)  # Maybe a little bit slow...

    latency = tilelang.profiler.do_bench(
        lambda: kernel(A, qB, Scale, Bias, topk_weights, sorted_token_ids, expert_ids), warmup=100)
    print("Tilelang: {:.2f} ms".format(latency))
    print("Tilelang: {:.2f} TFlops".format(total_flops / latency * 1e-9))

    diff = (output - ref_output).abs()
    max_val = diff.max()
    max_idx = diff.argmax()
    print(f"max abs diff: {max_val} at index: {max_idx}")
    assert_similar(
        output, ref_output, name="output",
        eps=1e-5)  # We care about the similarity rather than abs. difference
    print("All checks pass. ✅")


if __name__ == "__main__":
    M, N, K = 16384, 5760, 2944  # From gpt-oss-20b MoE's first gemm
    scale_size = 32
    topk = 4  # experts activated for each token
    E = 32  # number of experts
    main(M, N, K, scale_size, fast_dequant=True, with_bias=True, topk=topk, E=E)
