import math

import torch
import torch.nn.functional as F
import pytest

from einops import rearrange

from flash_attn.ops.fused_dense import FusedDense, FusedDenseGeluDense


@pytest.mark.parametrize('dtype', [torch.float16, torch.bfloat16])
@pytest.mark.parametrize('return_residual', [False, True])
@pytest.mark.parametrize('has_bias', [True, False])
@pytest.mark.parametrize('out_features', [1024, 4096])
@pytest.mark.parametrize('in_features', [1024, 4096])
def test_fused_linear_bias(in_features, out_features, has_bias, return_residual, dtype):
    device = 'cuda'
    rtol, atol = (3e-3, 1e-2) if dtype == torch.bfloat16 else (3e-3, 1e-3)
    # set seed
    torch.random.manual_seed(0)
    batch_size = 8
    seqlen = 512
    x_pt = torch.randn(batch_size, seqlen, in_features, device=device, dtype=dtype,
                       requires_grad=True)
    x = x_pt.detach().clone().requires_grad_()
    model_pt = torch.nn.Linear(in_features, out_features, bias=has_bias, device=device, dtype=dtype)
    model = FusedDense(in_features, out_features, bias=has_bias, return_residual=return_residual,
                       device=device, dtype=dtype)
    with torch.no_grad():
        model.weight.copy_(model_pt.weight)
        if has_bias:
            model.bias.copy_(model_pt.bias)
    out_pt = model_pt(x_pt)
    if not return_residual:
        out = model(x)
    else:
        out, x_copy = model(x)
        x_copy = (x_copy[..., :out_features] if out_features < in_features
                  else F.pad(x_copy, (0, out_features - in_features)))
        x_pt_copy = (x_pt[..., :out_features] if out_features < in_features
                     else F.pad(x_pt, (0, out_features - in_features)))
        # Just add some random function of the residual
        out_pt = out_pt + F.gelu(x_pt_copy)
        out = out + F.gelu(x_copy)

    # with torch.no_grad():
    #     out_fl = F.linear(x_pt.float(), model.weight.float(), model.bias.float()).half()
    assert torch.allclose(out, out_pt, rtol=rtol, atol=atol)

    # If we don't divide by batch_size, the gradient gets a bit too large.
    g = torch.randn_like(out) / 32
    out_pt.backward(g)
    out.backward(g)
    assert torch.allclose(x.grad, x_pt.grad, rtol=rtol, atol=atol)
    # The error for d_weight and d_bias is quite a bit higher
    assert torch.allclose(model.weight.grad, model_pt.weight.grad, rtol=rtol, atol=atol * 10)
    if has_bias:
        assert torch.allclose(model.bias.grad, model_pt.bias.grad, rtol=rtol, atol=atol * 5)


@pytest.mark.parametrize('dtype', [torch.float16, torch.bfloat16])
@pytest.mark.parametrize('heuristic', [0, -1])
@pytest.mark.parametrize('checkpoint_lvl', [0, 1, 2])
@pytest.mark.parametrize('return_residual', [False, True])
@pytest.mark.parametrize('has_bias2', [True, False])
@pytest.mark.parametrize('has_bias1', [True, False])
@pytest.mark.parametrize('out_features', [1024, 4096])
@pytest.mark.parametrize('in_features', [1024, 4096])
def test_fused_dense_gelu_dense(in_features, out_features, has_bias1, has_bias2, return_residual,
                                checkpoint_lvl, heuristic, dtype):
    device = 'cuda'
    rtol, atol = (3e-3, 3e-2) if dtype == torch.bfloat16 else (3e-3, 1e-3)
    # set seed
    torch.random.manual_seed(0)
    batch_size = 8
    seqlen = 512
    x_pt = torch.randn(batch_size, seqlen, in_features, device=device, dtype=dtype,
                       requires_grad=True)
    x = x_pt.detach().clone().requires_grad_()
    model_pt_fc1 = torch.nn.Linear(in_features, out_features, bias=has_bias1, device=device,
                                   dtype=dtype)
    model_pt_fc2 = torch.nn.Linear(out_features, in_features, bias=has_bias2, device=device,
                                   dtype=dtype)
    model = FusedDenseGeluDense(in_features, out_features, in_features, bias1=has_bias1,
                                bias2=has_bias2, return_residual=return_residual,
                                checkpoint_lvl=checkpoint_lvl, heuristic=heuristic,
                                device=device, dtype=dtype)
    with torch.no_grad():
        model.fc1.weight.copy_(model_pt_fc1.weight)
        if has_bias1:
            model.fc1.bias.copy_(model_pt_fc1.bias)
        model.fc2.weight.copy_(model_pt_fc2.weight)
        if has_bias2:
            model.fc2.bias.copy_(model_pt_fc2.bias)
    out_pt = model_pt_fc2(F.gelu(model_pt_fc1(x_pt), approximate='tanh'))
    if not return_residual:
        out = model(x)
    else:
        out, x_copy = model(x)
        # Just add some random function of the residual
        out_pt = out_pt + F.gelu(x_pt)
        out = out + F.gelu(x_copy)
    assert torch.allclose(out, out_pt, rtol=rtol, atol=atol)

    # If we don't divide by batch_size, the gradient gets a bit too large.
    g = torch.randn_like(out) / 32
    out_pt.backward(g)
    out.backward(g)
    assert torch.allclose(x.grad, x_pt.grad, rtol=rtol, atol=atol)
    # The error for d_weight and d_bias is quite a bit higher
    assert torch.allclose(model.fc1.weight.grad, model_pt_fc1.weight.grad, rtol=rtol, atol=atol * 10)
    if has_bias1:
        assert torch.allclose(model.fc1.bias.grad, model_pt_fc1.bias.grad, rtol=rtol, atol=atol * 5)
    assert torch.allclose(model.fc2.weight.grad, model_pt_fc2.weight.grad, rtol=rtol, atol=atol * 10)
    if has_bias2:
        assert torch.allclose(model.fc2.bias.grad, model_pt_fc2.bias.grad, rtol=rtol, atol=atol * 5)
