# mypy: ignore-errors
import random
from typing import NamedTuple, Optional, Union

import torch


# Global configuration for tensor fuzzing
class FuzzerConfig:
    """Global configuration for tensor fuzzing behavior."""

    use_real_values: bool = True  # If False, use zeros; if True, use random values
    avoid_complex: bool = False  # If True, exclude complex dtypes from fuzzing


class TensorSpec(NamedTuple):
    """Specification for a tensor argument."""

    size: tuple[int, ...]
    stride: tuple[int, ...]
    dtype: torch.dtype


class ScalarSpec(NamedTuple):
    """Specification for a scalar argument."""

    dtype: torch.dtype
    constant: Optional[Union[int, float, bool, complex]] = (
        None  # If set, use this constant value instead of fuzzing
    )


# Union type for specs
Spec = Union[TensorSpec, ScalarSpec]


def fuzz_torch_tensor_type(template: str = "default") -> torch.dtype:
    """
    Fuzzes PyTorch tensor data types by randomly selecting and returning different dtypes.

    Args:
        template: Template name to determine supported dtypes

    Returns:
        torch.dtype: A randomly selected PyTorch tensor data type based on template constraints
    """

    # Get template-specific dtypes
    if template == "dtensor":
        # Import here to avoid circular imports
        from torchfuzz.codegen import DTensorFuzzTemplate

        fuzz_template = DTensorFuzzTemplate()
        tensor_dtypes = fuzz_template.supported_dtypes()
    elif template == "unbacked":
        # Import here to avoid circular imports
        from torchfuzz.codegen import UnbackedFuzzTemplate

        fuzz_template = UnbackedFuzzTemplate()
        tensor_dtypes = fuzz_template.supported_dtypes()
    else:
        from torchfuzz.codegen import DefaultFuzzTemplate

        fuzz_template = DefaultFuzzTemplate()
        tensor_dtypes = fuzz_template.supported_dtypes()

    # Randomly select and return a data type
    return random.choice(tensor_dtypes)


def fuzz_tensor_size(max_dims: int = 6, max_size_per_dim: int = 30) -> tuple[int, ...]:
    """
    Fuzzes PyTorch tensor sizes by generating random tensor shapes.

    Args:
        max_dims: Maximum number of dimensions (default: 6)
        max_size_per_dim: Maximum size for each dimension (default: 100)

    Returns:
        Tuple[int, ...]: A tuple representing tensor shape/size
    """

    # Randomly choose number of dimensions (0 to max_dims)
    # 0 dimensions = scalar tensor
    num_dims: int = random.randint(0, max_dims)

    if num_dims == 0:
        # Scalar tensor (0-dimensional)
        return ()

    # Generate random sizes for each dimension
    sizes: list[int] = []
    for _ in range(num_dims):
        # Include edge cases:
        # - 5% chance of size 0 (empty tensor in that dimension)
        # - 10% chance of size 1 (singleton dimension)
        # - 80% chance of normal size (2 to max_size_per_dim)

        rand_val: float = random.random()
        if rand_val < 0.05:
            # Empty dimension
            size: int = 0
        elif rand_val < 0.2:
            # Singleton dimension
            size = 1
        else:
            # Normal size
            size = random.randint(2, max_size_per_dim)

        sizes.append(size)

    return tuple(sizes)


def fuzz_valid_stride(size: tuple[int, ...]) -> tuple[int, ...]:
    """
    Fuzzes PyTorch tensor strides by generating valid stride patterns for a given size.

    Args:
        size: Tensor shape/size as a tuple of integers

    Returns:
        Tuple[int, ...]: A tuple representing valid tensor strides
    """

    if len(size) == 0:
        # Scalar tensor has no strides
        return ()

    # Choose stride pattern type
    stride_types = [
        "contiguous",  # Normal contiguous memory layout
        "transposed",  # Transposed dimensions
        "custom_gaps",  # Custom strides with gaps (non-dense)
        "minimal",  # Minimal valid strides (all ones)
        "nonoverlapping_and_dense",  # Non-overlapping and dense (contiguous)
        "nonoverlapping_and_dense_non_contig",  # Non-overlapping and dense but not contiguous
        "overlapping",  # Overlapping memory access (zero strides)
        "sparse_gaps",  # Large gaps (definitely non-dense)
    ]

    stride_type: str = random.choice(stride_types)

    if stride_type in ["contiguous", "nonoverlapping_and_dense"]:
        # Standard contiguous strides: stride[i] = product of sizes[i+1:]
        return tuple(_compute_contiguous_strides(size))

    elif stride_type == "transposed":
        # Create transposed version - swap some dimensions' strides
        base_strides = list(_compute_contiguous_strides(size))

        if len(base_strides) >= 2:
            # Randomly swap strides of two dimensions
            i, j = random.sample(range(len(base_strides)), 2)
            base_strides[i], base_strides[j] = base_strides[j], base_strides[i]

        return tuple(base_strides)

    elif stride_type == "custom_gaps":
        # Create strides with custom gaps/spacing
        base_strides = list(_compute_contiguous_strides(size))

        # Add random gaps to some strides
        for i in range(len(base_strides)):
            if size[i] != 0 and random.random() < 0.3:  # 30% chance to add gap
                gap_multiplier: int = random.randint(2, 5)
                base_strides[i] *= gap_multiplier

        return tuple(base_strides)

    elif stride_type == "minimal":
        # Minimal valid strides (all ones)
        return tuple([1] * len(size))

    elif stride_type == "nonoverlapping_and_dense_non_contig":
        # Non-overlapping and dense but not contiguous (e.g., column-major)
        return tuple(_compute_non_contiguous_dense_strides(size))

    elif stride_type == "overlapping":
        # Create overlapping strides (zero strides for some dimensions)
        base_strides = list(_compute_contiguous_strides(size))

        # Randomly set some strides to 0 to cause overlapping
        for i in range(len(base_strides)):
            if size[i] > 1 and random.random() < 0.4:  # 40% chance to make overlapping
                base_strides[i] = 0

        return tuple(base_strides)

    elif stride_type == "sparse_gaps":
        # Create strides with very large gaps (definitely non-dense)
        base_strides = list(_compute_contiguous_strides(size))

        # Add very large gaps to create sparse layout
        for i in range(len(base_strides)):
            if size[i] > 1:
                gap_multiplier: int = random.randint(10, 100)  # Much larger gaps
                base_strides[i] *= gap_multiplier

        return tuple(base_strides)

    # Fallback to contiguous
    return tuple(_compute_contiguous_strides(size))


def _compute_contiguous_strides(size: tuple[int, ...]) -> list[int]:
    """
    Helper function to compute standard contiguous strides for a given size.

    Args:
        size: Tensor shape/size as a tuple of integers

    Returns:
        list[int]: List of contiguous strides
    """
    strides: list[int] = []
    current_stride: int = 1

    # Calculate strides from right to left
    for i in range(len(size) - 1, -1, -1):
        strides.insert(0, current_stride)
        # For dimensions with size 0, keep stride as is
        if size[i] != 0:
            current_stride *= size[i]

    return strides


def _compute_non_contiguous_dense_strides(size: tuple[int, ...]) -> list[int]:
    """
    Helper function to compute non-contiguous but dense strides (e.g., column-major order).

    Args:
        size: Tensor shape/size as a tuple of integers

    Returns:
        list[int]: List of non-contiguous dense strides
    """
    if len(size) <= 1:
        # For 0D or 1D tensors, return same as contiguous
        return _compute_contiguous_strides(size)

    # Generate different dense patterns
    patterns = [
        "column_major",  # Reverse order (left to right instead of right to left)
        "random_permute",  # Random permutation of dimensions
        "middle_out",  # Start from middle dimension
    ]

    pattern: str = random.choice(patterns)

    if pattern == "column_major":
        # Column-major order: calculate strides from left to right
        strides: list[int] = [0] * len(size)
        current_stride: int = 1

        # Calculate strides from left to right (opposite of contiguous)
        for i in range(len(size)):
            strides[i] = current_stride
            # For dimensions with size 0, keep stride as is
            if size[i] != 0:
                current_stride *= size[i]

        return strides

    elif pattern == "random_permute":
        # Create a valid permutation that's still dense
        # Create dimension permutation
        indices = list(range(len(size)))
        random.shuffle(indices)

        # Apply permutation to get new dense layout
        new_strides = [0] * len(size)
        current_stride = 1

        # Sort indices by their corresponding size to maintain density
        sorted_indices = sorted(
            indices, key=lambda i: size[i] if size[i] != 0 else float("inf")
        )

        for idx in sorted_indices:
            new_strides[idx] = current_stride
            if size[idx] != 0:
                current_stride *= size[idx]

        return new_strides

    elif pattern == "middle_out":
        # Start from middle dimension and work outward
        strides = [0] * len(size)
        current_stride = 1

        # Start from middle
        middle = len(size) // 2
        processed = [False] * len(size)

        # Process middle first
        strides[middle] = current_stride
        if size[middle] != 0:
            current_stride *= size[middle]
        processed[middle] = True

        # Process alternating left and right
        for offset in range(1, len(size)):
            for direction in [-1, 1]:
                idx = middle + direction * offset
                if 0 <= idx < len(size) and not processed[idx]:
                    strides[idx] = current_stride
                    if size[idx] != 0:
                        current_stride *= size[idx]
                    processed[idx] = True
                    break

        return strides

    # Fallback to contiguous
    return _compute_contiguous_strides(size)


def _compute_storage_size_needed(
    size: tuple[int, ...], strides: tuple[int, ...]
) -> int:
    """Compute minimum storage size needed for given shape and strides."""
    if not size:
        return 1

    # Find maximum offset
    max_offset = 0
    for dim_size, stride in zip(size, strides):
        if dim_size > 1:
            max_offset += (dim_size - 1) * abs(stride)

    return max_offset + 1


def fuzz_tensor(
    size: Optional[tuple[int, ...]] = None,
    stride: Optional[tuple[int, ...]] = None,
    dtype: Optional[torch.dtype] = None,
    seed: Optional[int] = None,
) -> tuple[torch.Tensor, int]:
    """
    Create a tensor with fuzzed size, stride, and dtype.

    Args:
        size: Tensor shape. If None, will be randomly generated.
        stride: Tensor stride. If None, will be randomly generated based on size.
        dtype: Tensor data type. If None, will be randomly generated.
        seed: Random seed for reproducibility. If None, will be randomly generated.

    Returns:
        Tuple[torch.Tensor, int]: A tuple of (tensor, seed_used) where tensor has
        the specified or randomly generated properties, and seed_used is the seed
        that was used for generation (for reproducibility).
    """
    # Generate or use provided seed
    if seed is None:
        seed = random.randint(0, 2**32 - 1)

    # Set the random seed for reproducibility
    torch.manual_seed(seed)
    random.seed(seed)

    # Generate random values if not provided
    if size is None:
        size = fuzz_tensor_size()

    if dtype is None:
        dtype = fuzz_torch_tensor_type("default")

    if stride is None:
        stride = fuzz_valid_stride(size)

    # Handle empty tensor case
    if len(size) == 0:
        return torch.ones((), dtype=dtype), seed

    # Calculate required storage size for the custom stride
    required_storage = _compute_storage_size_needed(size, stride)

    # Create base tensor with sufficient storage
    if FuzzerConfig.use_real_values:
        # Use random values based on dtype
        if dtype.is_floating_point:
            base_tensor = torch.randn(required_storage, dtype=dtype)
        elif dtype in [torch.complex64, torch.complex128]:
            # Create complex tensor with random real and imaginary parts
            real_part = torch.randn(
                required_storage,
                dtype=torch.float32 if dtype == torch.complex64 else torch.float64,
            )
            imag_part = torch.randn(
                required_storage,
                dtype=torch.float32 if dtype == torch.complex64 else torch.float64,
            )
            base_tensor = torch.complex(real_part, imag_part).to(dtype)
        elif dtype == torch.bool:
            base_tensor = torch.randint(0, 2, (required_storage,), dtype=torch.bool)
        else:  # integer types
            base_tensor = torch.randint(-100, 100, (required_storage,), dtype=dtype)
    else:
        # Use zeros (default behavior)
        base_tensor = torch.ones(required_storage, dtype=dtype)

    # Create strided tensor view
    strided_tensor = torch.as_strided(base_tensor, size, stride)

    return strided_tensor, seed


def fuzz_tensor_simple(
    size: Optional[tuple[int, ...]] = None,
    stride: Optional[tuple[int, ...]] = None,
    dtype: Optional[torch.dtype] = None,
    seed: Optional[int] = None,
) -> torch.Tensor:
    """
    Convenience function that returns just the tensor without the seed.

    Args:
        size: Tensor shape. If None, will be randomly generated.
        stride: Tensor stride. If None, will be randomly generated based on size.
        dtype: Tensor data type. If None, will be randomly generated.
        seed: Random seed for reproducibility. If None, uses current random state.

    Returns:
        torch.Tensor: A tensor with the specified or randomly generated properties.
    """
    tensor, _ = fuzz_tensor(size, stride, dtype, seed)
    return tensor


def fuzz_non_contiguous_dense_tensor(
    size: Optional[tuple[int, ...]] = None, dtype: Optional[torch.dtype] = None
) -> torch.Tensor:
    """
    Specifically generates tensors that are non-contiguous but dense and non-overlapping.

    Args:
        size: Tensor shape/size. If None, auto-generated.
        dtype: PyTorch tensor data type. If None, auto-generated.

    Returns:
        torch.Tensor: A non-contiguous but dense tensor
    """
    if dtype is None:
        dtype = fuzz_torch_tensor_type("default")

    if size is None:
        size = fuzz_tensor_size()

    # Force non-contiguous but dense stride patterns
    if len(size) <= 1:
        # For 0D or 1D tensors, return contiguous (they're trivially dense)
        tensor, _ = fuzz_tensor(size, None, dtype)
        return tensor

    # Choose from patterns that guarantee non-contiguous but dense
    patterns = ["column_major", "transposed", "permuted_dense"]

    pattern = random.choice(patterns)

    if pattern == "column_major":
        # Column-major order (non-contiguous but dense)
        stride = tuple(_compute_non_contiguous_dense_strides(size))
    elif pattern == "transposed":
        # Simple transpose of last two dimensions
        base_strides = _compute_contiguous_strides(size)
        if len(base_strides) >= 2:
            # Swap last two dimensions' strides
            base_strides[-1], base_strides[-2] = base_strides[-2], base_strides[-1]
        stride = tuple(base_strides)
    else:  # permuted_dense
        # Random permutation that maintains density
        stride = tuple(_compute_non_contiguous_dense_strides(size))

    tensor, _ = fuzz_tensor(size, stride, dtype)
    return tensor


def fuzz_scalar(spec, seed: Optional[int] = None) -> Union[float, int, bool, complex]:
    """
    Create a Python scalar value from a ScalarSpec.

    Args:
        spec: ScalarSpec containing the desired dtype and optionally a constant value
        seed: Random seed for reproducibility. If None, uses current random state.

    Returns:
        Python scalar (float, int, bool, complex) matching the dtype
    """
    # If a constant value is specified, use it directly
    if spec.constant is not None:
        return spec.constant

    # Set seed for reproducibility if provided
    if seed is not None:
        random.seed(seed)

    # Create a scalar value based on dtype
    if spec.dtype.is_floating_point:
        return random.uniform(-10.0, 10.0)
    elif spec.dtype in [torch.complex64, torch.complex128]:
        # Only generate complex values if not avoiding complex dtypes
        if FuzzerConfig.avoid_complex:
            raise ValueError("Cannot generate complex values with avoid_complex=True")
        return complex(random.uniform(-10.0, 10.0), random.uniform(-10.0, 10.0))
    else:  # integer or bool
        if spec.dtype == torch.bool:
            return random.choice([True, False])
        else:
            return random.randint(-10, 10)


def specs_compatible(spec1: Spec, spec2: Spec) -> bool:
    """Check if two specifications are compatible (one can be used where the other is expected)."""
    if type(spec1) != type(spec2):
        return False

    if isinstance(spec1, ScalarSpec):
        # For scalars, require exact dtype match for simplicity
        return spec1.dtype == spec2.dtype
    elif isinstance(spec1, TensorSpec):
        assert isinstance(spec2, TensorSpec)
        # For tensors, shape and dtype should match exactly
        return spec1.size == spec2.size and spec1.dtype == spec2.dtype

    return False