# coding=utf-8

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import unittest
from parameterized import parameterized, parameterized_class

# import math
import numpy as np
import torch
import torch.nn as nn

# from torch.autograd import gradcheck
from torch_harmonics import AttentionS2, NeighborhoodAttentionS2

from torch_harmonics._neighborhood_attention import (
    _neighborhood_attention_s2_torch,
    _neighborhood_attention_s2_fwd_torch,
    _neighborhood_attention_s2_bwd_dv_torch,
    _neighborhood_attention_s2_bwd_dk_torch,
    _neighborhood_attention_s2_bwd_dq_torch,
)

# import custom C++/CUDA extensions
try:
    import attention_cuda_extension

    _cuda_extension_available = True
except ImportError as err:
    print(f"Warning: Couldn't Import cuda attention: {err}")
    attention_cuda_extension = None
    _cuda_extension_available = False

_devices = [(torch.device("cpu"),)]
if torch.cuda.is_available():
    _devices.append((torch.device("cuda"),))

_perf_test_thresholds = {"fwd_ms": 50, "bwd_ms": 150}


@parameterized_class(("device"), _devices)
class TestNeighborhoodAttentionS2(unittest.TestCase):
    def setUp(self):
        torch.manual_seed(333)
        if self.device.type == "cuda":
            torch.cuda.manual_seed(333)

    @parameterized.expand(
        [
            # Format: [batch_size, channels, heads, in_shape, out_shape, grid_in, grid_out, atol, rtol]
            [4, 4, 1, (6, 12), (6, 12), "equiangular", "equiangular", 1e-5, 1e-3],
            [4, 4, 2, (6, 12), (6, 12), "equiangular", "equiangular", 1e-5, 1e-3],
            [4, 4, 4, (6, 12), (6, 12), "equiangular", "equiangular", 1e-5, 1e-3],
            [4, 1, 1, (2, 4), (2, 4), "equiangular", "equiangular", 1e-5, 1e-3],
            [4, 4, 4, (6, 12), (6, 12), "legendre-gauss", "legendre-gauss", 1e-5, 1e-3],
            [4, 4, 1, (6, 12), (6, 12), "lobatto", "lobatto", 1e-5, 1e-3],
        ],
        skip_on_empty=True,
    )
    def test_custom_implementation(self, batch_size, channels, heads, in_shape, out_shape, grid_in, grid_out, atol, rtol, verbose=False):
        """Tests numerical equivalence between the custom (CUDA) implementation and the reference torch implementation"""

        nlat_in, nlon_in = in_shape
        nlat_out, nlon_out = out_shape

        # Helper: create inputs
        inputs_ref = {
            "k": torch.randn(batch_size, channels, nlat_in, nlon_in, requires_grad=True, device=self.device, dtype=torch.float32),
            "v": torch.randn(batch_size, channels, nlat_in, nlon_in, requires_grad=True, device=self.device, dtype=torch.float32),
            "q": torch.randn(batch_size, channels, nlat_out, nlon_out, requires_grad=True, device=self.device, dtype=torch.float32),
        }
        inputs = {k: v.detach().clone().to(self.device).requires_grad_() for k, v in inputs_ref.items()}

        # reference input and model
        model_ref = NeighborhoodAttentionS2(in_channels=channels, num_heads=heads, in_shape=in_shape, out_shape=out_shape, grid_in=grid_in, grid_out=grid_out, bias=True).to(
            self.device
        )

        # Device model and inputs
        model = NeighborhoodAttentionS2(in_channels=channels, num_heads=heads, in_shape=in_shape, out_shape=out_shape, grid_in=grid_in, grid_out=grid_out, bias=True)

        # Synchronize parameters of model
        model.load_state_dict(model_ref.state_dict())
        model = model.to(self.device)
        for (name_ref, p_ref), (name, p) in zip(model_ref.named_parameters(), model.named_parameters()):
            self.assertTrue(torch.allclose(p_ref, p))

        # reference forward passes
        out_ref = _neighborhood_attention_s2_torch(
            inputs_ref["k"],
            inputs_ref["v"],
            inputs_ref["q"] * model_ref.scale,
            model_ref.k_weights,
            model_ref.v_weights,
            model_ref.q_weights,
            model_ref.k_bias,
            model_ref.v_bias,
            model_ref.q_bias,
            model_ref.quad_weights,
            model_ref.psi_col_idx,
            model_ref.psi_roff_idx,
            model_ref.num_heads,
            model_ref.nlon_in,
            model_ref.nlat_out,
            model_ref.nlon_out,
        )
        out_ref = nn.functional.conv2d(out_ref, model_ref.proj_weights, bias=model_ref.proj_bias)
        out = model(inputs["q"], inputs["k"], inputs["v"])

        # Check forward equivalence
        self.assertTrue(torch.allclose(out, out_ref, atol=atol, rtol=rtol), "Forward outputs differ between torch reference and custom implementation")

        # Backward passes
        grad = torch.randn_like(out_ref)
        out_ref.backward(grad)
        out.backward(grad.to(self.device))

        # Check input gradient equivalence
        for inp in ["q", "k", "v"]:
            grad_ref = inputs_ref[inp].grad.cpu()
            grad = inputs[inp].grad.cpu()
            self.assertTrue(torch.allclose(grad, grad_ref, atol=atol, rtol=rtol), f"Input gradient mismatch in {inp}")

        # Check parameter gradient equivalence
        for p_ref, p in zip(model_ref.parameters(), model.parameters()):
            self.assertTrue(torch.allclose(p.grad, p_ref.grad, atol=atol, rtol=rtol), f"Parameter gradient mismatch: {type(p_ref).__name__}")

    # caution: multihead-implementation between full and neighborhood attention still seem to differ. tests are only done for single head
    @parameterized.expand(
        [
            # Format: [batch_size, channels, heads, in_shape, out_shape, grid_in, grid_out, atol, rtol]
            [4, 4, 1, (6, 12), (6, 12), "equiangular", "equiangular", 1e-2, 0],
            [4, 4, 1, (6, 12), (6, 12), "legendre-gauss", "legendre-gauss", 1e-2, 0],
            [4, 4, 1, (6, 12), (6, 12), "lobatto", "lobatto", 1e-2, 0],
        ],
        skip_on_empty=True,
    )
    def test_neighborhood_global_equivalence(self, batch_size, channels, heads, in_shape, out_shape, grid_in, grid_out, atol, rtol, verbose=False):
        """Tests numerical equivalence between the global spherical attention module and the neighborhood spherical attention module with the neighborhood set ot the whole sphere"""

        nlat_in, nlon_in = in_shape
        nlat_out, nlon_out = out_shape

        # Helper: create inputs
        inputs_ref = {
            "k": torch.randn(batch_size, channels, nlat_in, nlon_in, requires_grad=True, device=self.device, dtype=torch.float32),
            "v": torch.randn(batch_size, channels, nlat_in, nlon_in, requires_grad=True, device=self.device, dtype=torch.float32),
            "q": torch.randn(batch_size, channels, nlat_out, nlon_out, requires_grad=True, device=self.device, dtype=torch.float32),
        }
        inputs = {k: v.detach().clone().to(self.device).requires_grad_() for k, v in inputs_ref.items()}

        # reference input and model
        model_ref = AttentionS2(in_channels=channels, num_heads=heads, in_shape=in_shape, out_shape=out_shape, grid_in=grid_in, grid_out=grid_out, bias=False).to(self.device)

        # Device model and inputs
        model = NeighborhoodAttentionS2(
            in_channels=channels, num_heads=heads, in_shape=in_shape, out_shape=out_shape, grid_in=grid_in, grid_out=grid_out, bias=False, theta_cutoff=2 * torch.pi
        )

        # Synchronize parameters of model
        model.load_state_dict(model_ref.state_dict())
        model = model.to(self.device)
        for (name_ref, p_ref), (name, p) in zip(model_ref.named_parameters(), model.named_parameters()):
            self.assertTrue(torch.allclose(p_ref, p))

        # reference forward passes
        out_ref = model_ref(inputs_ref["q"], inputs_ref["k"], inputs_ref["v"])
        out = model(inputs["q"], inputs["k"], inputs["v"])

        # Check forward equivalence
        self.assertTrue(torch.allclose(out, out_ref, atol=atol, rtol=rtol), "Forward outputs differ between torch reference and custom implementation")

        # Backward passes
        grad = torch.randn_like(out_ref)
        out_ref.backward(grad)
        out.backward(grad.to(self.device))

        # Check input gradient equivalence
        for inp in ["q", "k", "v"]:
            grad_ref = inputs_ref[inp].grad
            grad = inputs[inp].grad
            self.assertTrue(torch.allclose(grad, grad_ref, atol=atol, rtol=rtol), f"Input gradient mismatch in {inp}")

        # Check parameter gradient equivalence - check only q,k, v weights
        for key in ["q_weights", "k_weights", "v_weights"]:
            grad_ref = getattr(model_ref, key).grad
            grad = getattr(model, key).grad
            self.assertTrue(torch.allclose(grad, grad_ref, atol=atol, rtol=rtol), f"Parameter gradient mismatch")


    @parameterized.expand(
        [
            # self attention
            [1, 256, 1, (361, 720), (361, 720), "equiangular", "equiangular", 1e-5, 1e-5],
        ],
        skip_on_empty=True,
    )
    @unittest.skipUnless((torch.cuda.is_available() and _cuda_extension_available), "skipping performance test because CUDA is not available")
    def test_perf(self, batch_size, channels, heads, in_shape, out_shape, grid_in, grid_out, atol, rtol, verbose=False):

        # skip this test if we are not running on GPU, it will take very long otherwise
        if self.device.type != "cuda":
            self.assertFalse(False)
            return
        
        # extract some parameters
        nlat_in, nlon_in = in_shape
        nlat_out, nlon_out = out_shape

        # TODO: this test seems hardcoded for GPU. Is this necessary?
        k_gpu = torch.randn(batch_size, channels, nlat_in, nlon_in, dtype=torch.float32, device=self.device)
        k_gpu.requires_grad = False
        v_gpu = torch.randn(batch_size, channels, nlat_in, nlon_in, dtype=torch.float32, device=self.device)
        v_gpu.requires_grad = False
        q_gpu = torch.randn(batch_size, channels, nlat_out, nlon_out, dtype=torch.float32, device=self.device)
        q_gpu.requires_grad = False

        # set up layers
        time_layer_setup_start = torch.cuda.Event(enable_timing=True)
        time_layer_setup_end = torch.cuda.Event(enable_timing=True)
        time_layer_setup_start.record()
        att_gpu = NeighborhoodAttentionS2(in_channels=channels, num_heads=heads,
                                          in_shape=in_shape, out_shape=out_shape,
                                          grid_in=grid_in, grid_out=grid_out, bias=True).to(self.device)
        time_layer_setup_end.record()
        torch.cuda.synchronize()

        # random weights
        with torch.no_grad():
            att_gpu.q_weights.normal_()
            att_gpu.k_weights.normal_()
            att_gpu.v_weights.normal_()
            att_gpu.q_bias.normal_()
            att_gpu.k_bias.normal_()
            att_gpu.v_bias.normal_()

            # time forward pass
            for i in range(2):
                # warmup
                out_gpu = att_gpu(q_gpu, k_gpu, v_gpu)
            time_forward_start = torch.cuda.Event(enable_timing=True)
            time_forward_end = torch.cuda.Event(enable_timing=True)
            time_forward_start.record()
            out_gpu = att_gpu(q_gpu, k_gpu, v_gpu)
            time_forward_end.record()
            torch.cuda.synchronize()
            elapsed_time = time_forward_start.elapsed_time(time_forward_end)
            if verbose:
                print(f"Forward execution time: {elapsed_time} ms")
            self.assertTrue(elapsed_time < _perf_test_thresholds["fwd_ms"])

        # sync weights:
        with torch.no_grad():
            att_gpu.q_weights.copy_(att_gpu.q_weights)
            att_gpu.k_weights.copy_(att_gpu.k_weights)
            att_gpu.v_weights.copy_(att_gpu.v_weights)
            att_gpu.q_bias.copy_(att_gpu.q_bias)
            att_gpu.k_bias.copy_(att_gpu.k_bias)
            att_gpu.v_bias.copy_(att_gpu.v_bias)

        q_gpu = q_gpu.detach().clone().to(self.device)
        q_gpu.requires_grad = True
        k_gpu = k_gpu.detach().clone().to(self.device)
        k_gpu.requires_grad = True
        v_gpu = v_gpu.detach().clone().to(self.device)
        v_gpu.requires_grad = True

        out_gpu = att_gpu(q_gpu, k_gpu, v_gpu)
        out_grad = torch.randn(out_gpu.shape, dtype=torch.float32, device=self.device)
        time_backward_start = torch.cuda.Event(enable_timing=True)
        time_backward_end = torch.cuda.Event(enable_timing=True)

        for i in range(2):
            # warmup
            out_gpu.backward(out_grad, retain_graph=True)

        time_backward_start.record()
        out_gpu.backward(out_grad)
        time_backward_end.record()
        torch.cuda.synchronize()
        elapsed_time = time_backward_start.elapsed_time(time_backward_end)
        if verbose:
            print(f"Backward execution time: {elapsed_time} ms")
        self.assertTrue(elapsed_time < _perf_test_thresholds["bwd_ms"])


if __name__ == "__main__":
    unittest.main()
