import functools
from collections import OrderedDict

import torch
import torch.nn as nn
import torch.nn.functional as F
from torch import autocast
from x_transformers.x_transformers import AbsolutePositionalEmbedding, AttentionLayers

from models.diffusion.nn import timestep_embedding, normalization, zero_module, conv_nd, linear
from models.diffusion.unet_diffusion import AttentionBlock, TimestepEmbedSequential, \
    Downsample, Upsample, TimestepBlock
from models.gpt_voice.mini_encoder import AudioMiniEncoder
from scripts.audio.gen.use_diffuse_tts import ceil_multiple
from trainer.networks import register_model
from utils.util import checkpoint
from x_transformers import Encoder, ContinuousTransformerWrapper


class CheckpointedLayer(nn.Module):
    """
    Wraps a module. When forward() is called, passes kwargs that require_grad through torch.checkpoint() and bypasses
    checkpoint for all other args.
    """
    def __init__(self, wrap):
        super().__init__()
        self.wrap = wrap

    def forward(self, x, **kwargs):
        kw_requires_grad = {}
        kw_no_grad = {}
        for k, v in kwargs.items():
            if v is not None and isinstance(v, torch.Tensor) and v.requires_grad:
                kw_requires_grad[k] = v
            else:
                kw_no_grad[k] = v
        partial = functools.partial(self.wrap, **kw_no_grad)
        return torch.utils.checkpoint.checkpoint(partial, x, **kw_requires_grad)


class CheckpointedXTransformerEncoder(nn.Module):
    """
    Wraps a ContinuousTransformerWrapper and applies CheckpointedLayer to each layer and permutes from channels-mid
    to channels-last that XTransformer expects.
    """
    def __init__(self, **xtransformer_kwargs):
        super().__init__()
        self.transformer = ContinuousTransformerWrapper(**xtransformer_kwargs)

        for i in range(len(self.transformer.attn_layers.layers)):
            n, b, r = self.transformer.attn_layers.layers[i]
            self.transformer.attn_layers.layers[i] = nn.ModuleList([n, CheckpointedLayer(b), r])

    def forward(self, x):
        x = x.permute(0,2,1)
        h = self.transformer(x)
        return h.permute(0,2,1)


class ResBlock(TimestepBlock):
    def __init__(
        self,
        channels,
        emb_channels,
        dropout,
        out_channels=None,
        dims=2,
        kernel_size=3,
    ):
        super().__init__()
        self.channels = channels
        self.emb_channels = emb_channels
        self.dropout = dropout
        self.out_channels = out_channels or channels
        padding = 1 if kernel_size == 3 else 2

        self.in_layers = nn.Sequential(
            normalization(channels),
            nn.SiLU(),
            conv_nd(dims, channels, self.out_channels, 1, padding=0),
        )

        self.emb_layers = nn.Sequential(
            nn.SiLU(),
            linear(
                emb_channels,
                self.out_channels,
            ),
        )
        self.out_layers = nn.Sequential(
            normalization(self.out_channels),
            nn.SiLU(),
            nn.Dropout(p=dropout),
            zero_module(
                conv_nd(dims, self.out_channels, self.out_channels, kernel_size, padding=padding)
            ),
        )

        if self.out_channels == channels:
            self.skip_connection = nn.Identity()
        else:
            self.skip_connection = conv_nd(dims, channels, self.out_channels, 1)

    def forward(self, x, emb):
        """
        Apply the block to a Tensor, conditioned on a timestep embedding.

        :param x: an [N x C x ...] Tensor of features.
        :param emb: an [N x emb_channels] Tensor of timestep embeddings.
        :return: an [N x C x ...] Tensor of outputs.
        """
        return checkpoint(
            self._forward, x, emb
        )

    def _forward(self, x, emb):
        h = self.in_layers(x)
        emb_out = self.emb_layers(emb).type(h.dtype)
        while len(emb_out.shape) < len(h.shape):
            emb_out = emb_out[..., None]
        h = h + emb_out
        h = self.out_layers(h)
        return self.skip_connection(x) + h


class DiffusionTts(nn.Module):
    """
    The full UNet model with attention and timestep embedding.

    Customized to be conditioned on an aligned token prior.

    :param in_channels: channels in the input Tensor.
    :param num_tokens: number of tokens (e.g. characters) which can be provided.
    :param model_channels: base channel count for the model.
    :param out_channels: channels in the output Tensor.
    :param num_res_blocks: number of residual blocks per downsample.
    :param attention_resolutions: a collection of downsample rates at which
        attention will take place. May be a set, list, or tuple.
        For example, if this contains 4, then at 4x downsampling, attention
        will be used.
    :param dropout: the dropout probability.
    :param channel_mult: channel multiplier for each level of the UNet.
    :param conv_resample: if True, use learned convolutions for upsampling and
        downsampling.
    :param dims: determines if the signal is 1D, 2D, or 3D.
    :param num_heads: the number of attention heads in each attention layer.
    :param num_heads_channels: if specified, ignore num_heads and instead use
                               a fixed channel width per attention head.
    :param num_heads_upsample: works with num_heads to set a different number
                               of heads for upsampling. Deprecated.
    :param use_scale_shift_norm: use a FiLM-like conditioning mechanism.
    :param resblock_updown: use residual blocks for up/downsampling.
    :param use_new_attention_order: use a different attention pattern for potentially
                                    increased efficiency.
    """

    def __init__(
            self,
            model_channels,
            in_channels=1,
            num_tokens=32,
            out_channels=2,  # mean and variance
            dropout=0,
            # res           1, 2, 4, 8,16,32,64,128,256,512, 1K, 2K
            channel_mult=  (1,1.5,2, 3, 4, 6, 8, 12, 16, 24, 32, 48),
            num_res_blocks=(1, 1, 1, 1, 1, 2, 2, 2,   2,  2,  2,  2),
            # spec_cond:    1, 0, 0, 1, 0, 0, 1, 0,   0,  1,  0,  0)
            # attn:         0, 0, 0, 0, 0, 0, 0, 0,   0,  1,  1,  1
            token_conditioning_resolutions=(1,16,),
            attention_resolutions=(512,1024,2048),
            conv_resample=True,
            dims=1,
            use_fp16=False,
            num_heads=1,
            num_head_channels=-1,
            num_heads_upsample=-1,
            kernel_size=3,
            scale_factor=2,
            conditioning_inputs_provided=True,
            time_embed_dim_multiplier=4,
            transformer_depths=8,
            nil_guidance_fwd_proportion=.3,
    ):
        super().__init__()

        if num_heads_upsample == -1:
            num_heads_upsample = num_heads

        self.in_channels = in_channels
        self.model_channels = model_channels
        self.out_channels = out_channels
        self.attention_resolutions = attention_resolutions
        self.dropout = dropout
        self.channel_mult = channel_mult
        self.conv_resample = conv_resample
        self.dtype = torch.float16 if use_fp16 else torch.float32
        self.num_heads = num_heads
        self.num_head_channels = num_head_channels
        self.num_heads_upsample = num_heads_upsample
        self.dims = dims
        self.nil_guidance_fwd_proportion = nil_guidance_fwd_proportion
        self.mask_token_id = num_tokens

        padding = 1 if kernel_size == 3 else 2

        time_embed_dim = model_channels * time_embed_dim_multiplier
        self.time_embed = nn.Sequential(
            linear(model_channels, time_embed_dim),
            nn.SiLU(),
            linear(time_embed_dim, time_embed_dim),
        )

        embedding_dim = model_channels * 8
        self.code_embedding = nn.Embedding(num_tokens+1, embedding_dim)
        self.conditioning_enabled = conditioning_inputs_provided
        if conditioning_inputs_provided:
            self.contextual_embedder = AudioMiniEncoder(in_channels, embedding_dim, base_channels=32, depth=6, resnet_blocks=1,
                             attn_blocks=2, num_attn_heads=2, dropout=dropout, downsample_factor=4, kernel_size=5)
        self.conditioning_encoder = CheckpointedXTransformerEncoder(
                max_seq_len=-1,  # Should be unused
                use_pos_emb=False,
                attn_layers=Encoder(
                    dim=embedding_dim,
                    depth=transformer_depths,
                    heads=num_heads,
                    ff_dropout=dropout,
                    attn_dropout=dropout,
                    use_rmsnorm=True,
                    ff_glu=True,
                    rotary_pos_emb=True,
                )
        )

        self.input_blocks = nn.ModuleList(
            [
                TimestepEmbedSequential(
                    conv_nd(dims, in_channels, model_channels, kernel_size, padding=padding)
                )
            ]
        )
        token_conditioning_blocks = []
        self._feature_size = model_channels
        input_block_chans = [model_channels]
        ch = model_channels
        ds = 1

        for level, (mult, num_blocks) in enumerate(zip(channel_mult, num_res_blocks)):
            if ds in token_conditioning_resolutions:
                token_conditioning_block = nn.Conv1d(embedding_dim, ch, 1)
                token_conditioning_block.weight.data *= .02
                self.input_blocks.append(token_conditioning_block)
                token_conditioning_blocks.append(token_conditioning_block)

            for _ in range(num_blocks):
                layers = [
                    ResBlock(
                        ch,
                        time_embed_dim,
                        dropout,
                        out_channels=int(mult * model_channels),
                        dims=dims,
                        kernel_size=kernel_size,
                    )
                ]
                ch = int(mult * model_channels)
                if ds in attention_resolutions:
                    layers.append(
                        AttentionBlock(
                            ch,
                            num_heads=num_heads,
                            num_head_channels=num_head_channels,
                        )
                    )
                self.input_blocks.append(TimestepEmbedSequential(*layers))
                self._feature_size += ch
                input_block_chans.append(ch)
            if level != len(channel_mult) - 1:
                out_ch = ch
                self.input_blocks.append(
                    TimestepEmbedSequential(
                        Downsample(
                            ch, conv_resample, dims=dims, out_channels=out_ch, factor=scale_factor, ksize=1, pad=0
                        )
                    )
                )
                ch = out_ch
                input_block_chans.append(ch)
                ds *= 2
                self._feature_size += ch

        mid_transformer = CheckpointedXTransformerEncoder(
                max_seq_len=-1,  # Should be unused
                use_pos_emb=False,
                attn_layers=Encoder(
                    dim=ch,
                    depth=transformer_depths,
                    heads=num_heads,
                    ff_dropout=dropout,
                    attn_dropout=dropout,
                    use_rmsnorm=True,
                    ff_glu=True,
                    rotary_pos_emb=True,
                )
            )
        self.middle_block = TimestepEmbedSequential(
            ResBlock(
                ch,
                time_embed_dim,
                dropout,
                dims=dims,
                kernel_size=kernel_size,
            ),
            mid_transformer,
            ResBlock(
                ch,
                time_embed_dim,
                dropout,
                dims=dims,
                kernel_size=kernel_size,
            ),
        )
        self._feature_size += ch

        self.output_blocks = nn.ModuleList([])
        for level, (mult, num_blocks) in list(enumerate(zip(channel_mult, num_res_blocks)))[::-1]:
            for i in range(num_blocks + 1):
                ich = input_block_chans.pop()
                layers = [
                    ResBlock(
                        ch + ich,
                        time_embed_dim,
                        dropout,
                        out_channels=int(model_channels * mult),
                        dims=dims,
                        kernel_size=kernel_size,
                    )
                ]
                ch = int(model_channels * mult)
                if ds in attention_resolutions:
                    layers.append(
                        AttentionBlock(
                            ch,
                            num_heads=num_heads_upsample,
                            num_head_channels=num_head_channels,
                        )
                    )
                if level and i == num_blocks:
                    out_ch = ch
                    layers.append(
                        Upsample(ch, conv_resample, dims=dims, out_channels=out_ch, factor=scale_factor)
                    )
                    ds //= 2
                self.output_blocks.append(TimestepEmbedSequential(*layers))
                self._feature_size += ch

        self.out = nn.Sequential(
            normalization(ch),
            nn.SiLU(),
            zero_module(conv_nd(dims, model_channels, out_channels, kernel_size, padding=padding)),
        )

    def load_state_dict(self, state_dict: 'OrderedDict[str, Tensor]',
                        strict: bool = True):
        # Temporary hack to allow the addition of nil-guidance token embeddings to the existing guidance embeddings.
        lsd = self.state_dict()
        revised = 0
        for i, blk in enumerate(self.input_blocks):
            if isinstance(blk, nn.Embedding):
                key = f'input_blocks.{i}.weight'
                if state_dict[key].shape[0] != lsd[key].shape[0]:
                    t = torch.randn_like(lsd[key]) * .02
                    t[:state_dict[key].shape[0]] = state_dict[key]
                    state_dict[key] = t
                    revised += 1
        print(f"Loaded experimental unet_diffusion_net with {revised} modifications.")
        return super().load_state_dict(state_dict, strict)



    def forward(self, x, timesteps, tokens, conditioning_input=None):
        """
        Apply the model to an input batch.

        :param x: an [N x C x ...] Tensor of inputs.
        :param timesteps: a 1-D batch of timesteps.
        :param tokens: an aligned text input.
        :return: an [N x C x ...] Tensor of outputs.
        """
        with autocast(x.device.type):
            orig_x_shape = x.shape[-1]
            cm = ceil_multiple(x.shape[-1], 2048)
            if cm != 0:
                pc = (cm-x.shape[-1])/x.shape[-1]
                x = F.pad(x, (0,cm-x.shape[-1]))
                tokens = F.pad(tokens, (0,int(pc*tokens.shape[-1])))
            if self.conditioning_enabled:
                assert conditioning_input is not None

            hs = []
            time_emb = self.time_embed(timestep_embedding(timesteps, self.model_channels))

            # Mask out guidance tokens for un-guided diffusion.
            if self.training and self.nil_guidance_fwd_proportion > 0:
                token_mask = torch.rand(tokens.shape, device=tokens.device) < self.nil_guidance_fwd_proportion
                tokens = torch.where(token_mask, self.mask_token_id, tokens)
            code_emb = self.code_embedding(tokens).permute(0,2,1)
            if self.conditioning_enabled:
                cond_emb = self.contextual_embedder(conditioning_input)
                code_emb = cond_emb.unsqueeze(-1) * code_emb
            code_emb = self.conditioning_encoder(code_emb)

            first = True
            time_emb = time_emb.float()
            h = x
            for k, module in enumerate(self.input_blocks):
                if isinstance(module, nn.Conv1d):
                    h_tok = F.interpolate(module(code_emb), size=(h.shape[-1]), mode='nearest')
                    h = h + h_tok
                else:
                    with autocast(x.device.type, enabled=not first):
                        # First block has autocast disabled to allow a high precision signal to be properly vectorized.
                        h = module(h, time_emb)
                    hs.append(h)
                first = False
            h = self.middle_block(h, time_emb)
            for module in self.output_blocks:
                h = torch.cat([h, hs.pop()], dim=1)
                h = module(h, time_emb)

        # Last block also has autocast disabled for high-precision outputs.
        h = h.float()
        out = self.out(h)
        return out[:, :, :orig_x_shape]


@register_model
def register_diffusion_tts5(opt_net, opt):
    return DiffusionTts(**opt_net['kwargs'])


# Test for ~4 second audio clip at 22050Hz
if __name__ == '__main__':
    clip = torch.randn(2, 1, 32768)
    tok = torch.randint(0,30, (2,388))
    cond = torch.randn(2, 1, 44000)
    ts = torch.LongTensor([600, 600])
    model = DiffusionTts(128,
                         channel_mult=[1,1.5,2, 3, 4, 6, 8],
                         num_res_blocks=[2, 2, 2, 2, 2, 2, 1],
                         token_conditioning_resolutions=[1,4,16,64],
                         attention_resolutions=[],
                         num_heads=8,
                         kernel_size=3,
                         scale_factor=2,
                         conditioning_inputs_provided=True,
                         time_embed_dim_multiplier=4)
    model(clip, ts, tok, cond)
    torch.save(model.state_dict(), 'test_out.pth')