"""
WavTokenizer model implementation for HuggingFace.

This implementation exactly matches the checkpoint structure for direct weight loading.
"""

import math
from typing import Optional, Tuple, Union

import torch
import torch.nn as nn
import torch.nn.functional as F
from transformers import PreTrainedModel
from transformers.modeling_outputs import BaseModelOutput

from .configuration_wavtokenizer import WavTokenizerConfig


# =============================================================================
# Audio Utilities
# =============================================================================

def convert_audio(wav, sr, target_sr, target_channels=1):
    """Convert audio to target sample rate and channels."""
    if wav.dim() == 1:
        wav = wav.unsqueeze(0).unsqueeze(0)
    elif wav.dim() == 2:
        wav = wav.unsqueeze(1)
    
    if wav.shape[1] > target_channels:
        wav = wav[:, :target_channels, :]
    elif wav.shape[1] < target_channels:
        wav = wav.repeat(1, target_channels, 1)
    
    if sr != target_sr:
        wav = F.interpolate(wav, size=int(wav.shape[-1] * target_sr / sr), mode='linear', align_corners=False)
    
    return wav


# =============================================================================
# Weight-Normalized Conv1d (matching checkpoint's weight_g/weight_v structure)
# =============================================================================

class WNConv1d(nn.Module):
    """Weight-normalized Conv1d matching checkpoint structure with weight_g/weight_v."""
    def __init__(self, in_channels, out_channels, kernel_size, stride=1, padding=0, dilation=1, groups=1, bias=True):
        super().__init__()
        self.conv = nn.utils.weight_norm(
            nn.Conv1d(in_channels, out_channels, kernel_size, stride, padding, dilation, groups, bias)
        )
    
    def forward(self, x):
        return self.conv(x)


class WNConvTranspose1d(nn.Module):
    """Weight-normalized ConvTranspose1d."""
    def __init__(self, in_channels, out_channels, kernel_size, stride=1, padding=0, output_padding=0, groups=1, bias=True):
        super().__init__()
        self.convtr = nn.utils.weight_norm(
            nn.ConvTranspose1d(in_channels, out_channels, kernel_size, stride, padding, output_padding, groups, bias)
        )
    
    def forward(self, x):
        return self.convtr(x)


# =============================================================================
# Encoder (EnCodec-style, matching feature_extractor.encodec.encoder.model.*)
# =============================================================================

class _ConvWrapper(nn.Module):
    """Wrapper to match checkpoint structure: conv.conv.weight_g, conv.conv.weight_v, conv.conv.bias"""
    def __init__(self, in_ch, out_ch, kernel_size, stride=1, padding=0):
        super().__init__()
        self.conv = WNConv1d(in_ch, out_ch, kernel_size, stride=stride, padding=padding)
    
    def forward(self, x):
        return self.conv(x)


class _ResBlockWrapper(nn.Module):
    """Wrapper to match checkpoint structure: block.1.conv.conv, block.3.conv.conv, shortcut.conv.conv"""
    def __init__(self, dim):
        super().__init__()
        self.block = nn.Sequential()
        self.block.add_module('0', nn.ELU())
        self.block.add_module('1', _ConvWrapper(dim, dim // 2, 3, padding=1))
        self.block.add_module('2', nn.ELU())
        self.block.add_module('3', _ConvWrapper(dim // 2, dim, 1))
        self.shortcut = _ConvWrapper(dim, dim, 1)
    
    def forward(self, x):
        return self.shortcut(x) + self.block(x)


class _LSTMWrapper(nn.Module):
    """LSTM wrapper matching checkpoint: lstm.weight_ih_l0, etc."""
    def __init__(self, dim, num_layers=2):
        super().__init__()
        self.lstm = nn.LSTM(dim, dim, num_layers=num_layers, batch_first=True)
    
    def forward(self, x):
        x = x.transpose(1, 2)
        y, _ = self.lstm(x)
        y = y + x
        return y.transpose(1, 2)


class EncoderModel(nn.Module):
    """
    Encoder matching checkpoint: feature_extractor.encodec.encoder.model.*
    
    Structure based on checkpoint:
    - model.0: initial conv (1 -> 32)
    - model.1: residual block (32)
    - model.2: ELU (not saved)
    - model.3: downsample conv (32->64, stride=2)
    - model.4: residual block (64)
    - model.5: ELU
    - model.6: downsample conv (64->128, stride=4)
    - model.7: residual block (128)
    - model.8: ELU
    - model.9: downsample conv (128->256, stride=5)
    - model.10: residual block (256)
    - model.11: ELU
    - model.12: downsample conv (256->512, stride=8)
    - model.13: LSTM
    - model.14: ELU
    - model.15: output conv (512->512)
    """
    def __init__(self, channels=1, n_filters=32, dimension=512, ratios=[2, 4, 5, 8]):
        super().__init__()
        
        layers = []
        
        # model.0: Initial conv
        layers.append(_ConvWrapper(channels, n_filters, 7, padding=3))
        
        # Encoder blocks with downsampling
        in_ch = n_filters
        for ratio in ratios:
            out_ch = in_ch * 2
            # Residual block
            layers.append(_ResBlockWrapper(in_ch))
            # ELU (implicit in original, but we need it)
            layers.append(nn.ELU())
            # Downsample conv
            layers.append(_ConvWrapper(in_ch, out_ch, ratio * 2, stride=ratio, padding=ratio // 2))
            in_ch = out_ch
        
        # LSTM
        layers.append(_LSTMWrapper(in_ch))
        
        # ELU
        layers.append(nn.ELU())
        
        # Output conv
        layers.append(_ConvWrapper(in_ch, dimension, 7, padding=3))
        
        self.model = nn.Sequential(*layers)
    
    def forward(self, x):
        return self.model(x)


# =============================================================================
# Quantizer (matching feature_extractor.encodec.quantizer.vq.layers.0._codebook.*)
# =============================================================================

class Codebook(nn.Module):
    """Codebook matching checkpoint: _codebook.embed, _codebook.inited, _codebook.cluster_size, _codebook.embed_avg"""
    def __init__(self, num_embeddings, embedding_dim):
        super().__init__()
        # These match checkpoint structure exactly
        self.register_buffer('inited', torch.zeros(1))
        self.register_buffer('cluster_size', torch.zeros(num_embeddings))
        self.register_buffer('embed', torch.randn(num_embeddings, embedding_dim))
        self.register_buffer('embed_avg', torch.randn(num_embeddings, embedding_dim))
    
    def forward(self, x):
        """
        Args:
            x: (B, T, D) input
        Returns:
            quantized: (B, T, D) quantized output
            indices: (B, T) codebook indices
        """
        # L2 normalize
        embed = F.normalize(self.embed, dim=-1)
        x_norm = F.normalize(x, dim=-1)
        
        # Find nearest
        dist = torch.cdist(x_norm, embed)
        indices = dist.argmin(dim=-1)
        
        # Quantize
        quantized = F.embedding(indices, embed)
        
        # Straight-through
        quantized = x_norm + (quantized - x_norm).detach()
        
        return quantized, indices
    
    def decode(self, indices):
        embed = F.normalize(self.embed, dim=-1)
        return F.embedding(indices, embed)


class VQLayer(nn.Module):
    """VQ layer matching checkpoint: vq.layers.0._codebook.*"""
    def __init__(self, dim, codebook_size):
        super().__init__()
        self._codebook = Codebook(codebook_size, dim)
    
    def forward(self, x):
        # x: (B, D, T)
        x = x.transpose(1, 2)  # (B, T, D)
        quantized, indices = self._codebook(x)
        return quantized.transpose(1, 2), indices
    
    def decode(self, indices):
        quantized = self._codebook.decode(indices)
        return quantized.transpose(1, 2)


class VQ(nn.Module):
    """VQ wrapper matching checkpoint: vq.layers"""
    def __init__(self, dim, codebook_size, num_quantizers=1):
        super().__init__()
        self.layers = nn.ModuleList([
            VQLayer(dim, codebook_size) for _ in range(num_quantizers)
        ])
    
    def forward(self, x):
        indices_list = []
        quantized = torch.zeros_like(x)
        residual = x
        
        for layer in self.layers:
            q, idx = layer(residual)
            residual = residual - q
            quantized = quantized + q
            indices_list.append(idx)
        
        indices = torch.stack(indices_list, dim=1)
        return quantized, indices
    
    def decode(self, indices):
        quantized = None
        for i, layer in enumerate(self.layers):
            q = layer.decode(indices[:, i])
            quantized = q if quantized is None else quantized + q
        return quantized


class Quantizer(nn.Module):
    """Quantizer matching checkpoint: quantizer.vq"""
    def __init__(self, dim, codebook_size, num_quantizers=1):
        super().__init__()
        self.vq = VQ(dim, codebook_size, num_quantizers)
    
    def forward(self, x):
        return self.vq(x)
    
    def decode(self, indices):
        return self.vq.decode(indices)


class EnCodecWrapper(nn.Module):
    """Wrapper matching checkpoint: encodec.encoder, encodec.quantizer"""
    def __init__(self, channels=1, n_filters=32, dimension=512, ratios=[2, 4, 5, 8], 
                 codebook_size=4096, num_quantizers=1):
        super().__init__()
        self.encoder = EncoderModel(channels, n_filters, dimension, ratios)
        self.quantizer = Quantizer(dimension, codebook_size, num_quantizers)
        # Note: decoder exists in checkpoint but we use Vocos backbone instead
    
    def encode(self, x):
        z = self.encoder(x)
        z_q, codes = self.quantizer(z)
        return z_q, codes


class FeatureExtractor(nn.Module):
    """Feature extractor matching checkpoint: feature_extractor.encodec"""
    def __init__(self, **kwargs):
        super().__init__()
        self.encodec = EnCodecWrapper(**kwargs)
    
    def encode(self, x):
        return self.encodec.encode(x)
    
    def decode_codes(self, codes):
        return self.encodec.quantizer.decode(codes)


# =============================================================================
# Backbone (Vocos-style with bandwidth-conditioned AdaLayerNorm)
# =============================================================================

class AdaLayerNorm(nn.Module):
    """
    Bandwidth-conditioned Adaptive LayerNorm.
    
    Checkpoint structure:
    - norm.scale.weight: [4, 768] (4 bandwidth conditions)
    - norm.shift.weight: [4, 768]
    """
    def __init__(self, dim, num_bandwidths=4, eps=1e-6):
        super().__init__()
        self.eps = eps
        self.dim = dim
        # Match checkpoint: scale.weight and shift.weight are [num_bandwidths, dim]
        self.scale = nn.Embedding(num_bandwidths, dim)
        self.shift = nn.Embedding(num_bandwidths, dim)
        
        # Initialize
        nn.init.ones_(self.scale.weight)
        nn.init.zeros_(self.shift.weight)
    
    def forward(self, x, bandwidth_id=None):
        """
        Args:
            x: (B, C, T) input
            bandwidth_id: (B,) bandwidth index, or None for default (0)
        """
        # Normalize
        mean = x.mean(dim=1, keepdim=True)
        var = x.var(dim=1, keepdim=True, unbiased=False)
        x = (x - mean) / torch.sqrt(var + self.eps)
        
        # Get scale/shift based on bandwidth_id
        if bandwidth_id is None:
            bandwidth_id = torch.zeros(x.shape[0], dtype=torch.long, device=x.device)
        
        scale = self.scale(bandwidth_id)  # (B, dim)
        shift = self.shift(bandwidth_id)  # (B, dim)
        
        # Apply: (B, dim, 1) for broadcasting
        x = x * scale.unsqueeze(-1) + shift.unsqueeze(-1)
        
        return x


class ConvNeXtBlock(nn.Module):
    """
    ConvNeXt block matching checkpoint structure exactly.
    
    Checkpoint keys:
    - dwconv.weight: [768, 1, 7]
    - dwconv.bias: [768]
    - norm.scale.weight: [4, 768]
    - norm.shift.weight: [4, 768]
    - pwconv1.weight: [2304, 768]
    - pwconv1.bias: [2304]
    - pwconv2.weight: [768, 2304]
    - pwconv2.bias: [768]
    - gamma: [768]
    """
    def __init__(self, dim, intermediate_dim, kernel_size=7, layer_scale_init=1e-6, num_bandwidths=4):
        super().__init__()
        padding = (kernel_size - 1) // 2
        
        self.dwconv = nn.Conv1d(dim, dim, kernel_size, padding=padding, groups=dim)
        self.norm = AdaLayerNorm(dim, num_bandwidths)
        self.pwconv1 = nn.Linear(dim, intermediate_dim)
        self.pwconv2 = nn.Linear(intermediate_dim, dim)
        self.gamma = nn.Parameter(layer_scale_init * torch.ones(dim))
    
    def forward(self, x, bandwidth_id=None):
        residual = x
        x = self.dwconv(x)
        x = self.norm(x, bandwidth_id)
        x = x.transpose(1, 2)  # (B, T, C)
        x = self.pwconv1(x)
        x = F.gelu(x)
        x = self.pwconv2(x)
        x = x.transpose(1, 2)  # (B, C, T)
        x = self.gamma.unsqueeze(0).unsqueeze(-1) * x
        return residual + x


class Backbone(nn.Module):
    """
    Vocos backbone matching checkpoint structure.
    
    Checkpoint keys:
    - embed.weight, embed.bias
    - norm.scale.weight, norm.shift.weight
    - convnext.0-11.*
    - final_layer_norm.weight, final_layer_norm.bias
    """
    def __init__(self, input_dim=512, dim=768, intermediate_dim=2304, num_blocks=12,
                 num_bandwidths=4):
        super().__init__()
        
        # Input projection: backbone.embed
        self.embed = nn.Conv1d(input_dim, dim, kernel_size=3, padding=1)
        
        # Input normalization: backbone.norm
        self.norm = AdaLayerNorm(dim, num_bandwidths)
        
        # ConvNeXt blocks: backbone.convnext.0-11
        self.convnext = nn.ModuleList([
            ConvNeXtBlock(dim, intermediate_dim, num_bandwidths=num_bandwidths)
            for _ in range(num_blocks)
        ])
        
        # Final norm: backbone.final_layer_norm
        self.final_layer_norm = nn.LayerNorm(dim)
    
    def forward(self, x, bandwidth_id=None):
        # Input projection
        x = self.embed(x)
        x = self.norm(x, bandwidth_id)
        
        # ConvNeXt blocks
        for block in self.convnext:
            x = block(x, bandwidth_id)
        
        # Final norm
        x = x.transpose(1, 2)  # (B, T, C)
        x = self.final_layer_norm(x)
        x = x.transpose(1, 2)  # (B, C, T)
        
        return x


# =============================================================================
# Head (iSTFT)
# =============================================================================

class ISTFT(nn.Module):
    """ISTFT module matching checkpoint: istft.window"""
    def __init__(self, n_fft=1280):
        super().__init__()
        self.n_fft = n_fft
        self.register_buffer('window', torch.hann_window(n_fft))


class ISTFTHead(nn.Module):
    """
    iSTFT head matching checkpoint structure.
    
    Checkpoint keys:
    - out.weight: [1282, 768]
    - out.bias: [1282]
    - istft.window: [1280]
    """
    def __init__(self, dim, n_fft=1280, hop_length=320, padding='center'):
        super().__init__()
        self.n_fft = n_fft
        self.hop_length = hop_length
        self.padding = padding
        
        # Output projection: head.out
        self.out = nn.Linear(dim, n_fft + 2)
        
        # ISTFT window: head.istft.window
        self.istft = ISTFT(n_fft)
    
    def forward(self, x):
        """
        Args:
            x: (B, C, T) backbone output
        Returns:
            audio: (B, 1, samples)
        """
        B, C, T = x.shape
        x = x.transpose(1, 2)  # (B, T, C)
        x = self.out(x)  # (B, T, n_fft + 2)
        
        # Split magnitude and phase
        n_bins = self.n_fft // 2 + 1  # 641
        mag = torch.exp(x[:, :, :n_bins])
        phase = x[:, :, n_bins:]
        
        # Construct complex STFT
        stft = torch.complex(mag * torch.cos(phase), mag * torch.sin(phase))
        stft = stft.transpose(1, 2)  # (B, n_bins, T)
        
        # Inverse STFT
        audio = torch.istft(
            stft,
            n_fft=self.n_fft,
            hop_length=self.hop_length,
            win_length=self.n_fft,
            window=self.istft.window,
            center=(self.padding == 'center'),
            return_complex=False,
        )
        
        return audio.unsqueeze(1)


# =============================================================================
# Main WavTokenizer Model
# =============================================================================

class WavTokenizer(PreTrainedModel):
    """
    WavTokenizer model for audio tokenization.
    
    This implementation exactly matches the checkpoint structure for direct weight loading.
    """
    
    config_class = WavTokenizerConfig
    base_model_prefix = "wavtokenizer"
    
    def __init__(self, config: WavTokenizerConfig):
        super().__init__(config)
        self.config = config
        
        # Feature extractor (encoder + quantizer)
        # Matches: feature_extractor.encodec.*
        self.feature_extractor = FeatureExtractor(
            channels=1,
            n_filters=config.encoder_dim,
            dimension=config.latent_dim,
            ratios=config.encoder_rates,
            codebook_size=config.codebook_size,
            num_quantizers=config.num_quantizers,
        )
        
        # Backbone (Vocos-style decoder)
        # Matches: backbone.*
        self.backbone = Backbone(
            input_dim=config.latent_dim,
            dim=config.backbone_dim,
            intermediate_dim=config.backbone_intermediate_dim,
            num_blocks=config.backbone_num_blocks,
            num_bandwidths=4,
        )
        
        # Head (iSTFT)
        # Matches: head.*
        self.head = ISTFTHead(
            dim=config.backbone_dim,
            n_fft=config.n_fft,
            hop_length=config.hop_length,
            padding=config.padding,
        )
        
        self.post_init()
    
    def encode(self, audio, bandwidth_id=None):
        """
        Encode audio to quantized features and codes.
        
        Args:
            audio: (B, 1, T) audio waveform
            bandwidth_id: Optional (B,) bandwidth index
            
        Returns:
            features: (B, D, T') quantized features
            codes: (B, num_quantizers, T') discrete codes
        """
        return self.feature_extractor.encode(audio)
    
    def encode_infer(self, audio, bandwidth_id=None):
        """
        Encode audio for inference.
        
        Args:
            audio: (B, 1, T) audio waveform
            bandwidth_id: Optional bandwidth index (scalar or tensor)
            
        Returns:
            features: (B, D, T') quantized features
            codes: (B, T') discrete codes (squeezed for single quantizer)
        """
        features, codes = self.encode(audio, bandwidth_id)
        if codes.shape[1] == 1:
            codes = codes.squeeze(1)
        return features, codes
    
    def decode(self, features, bandwidth_id=None):
        """
        Decode features to audio.
        
        Args:
            features: (B, D, T') quantized features
            bandwidth_id: Optional (B,) bandwidth index
            
        Returns:
            audio: (B, 1, T) reconstructed waveform
        """
        x = self.backbone(features, bandwidth_id)
        return self.head(x)
    
    def codes_to_features(self, codes):
        """
        Convert discrete codes back to continuous features.
        
        Args:
            codes: (B, T) or (B, num_quantizers, T) discrete codes
            
        Returns:
            features: (B, D, T) continuous features
        """
        if codes.dim() == 2:
            codes = codes.unsqueeze(1)
        return self.feature_extractor.decode_codes(codes)
    
    def forward(
        self,
        input_values: Optional[torch.Tensor] = None,
        input_ids: Optional[torch.Tensor] = None,
        bandwidth_id: Optional[torch.Tensor] = None,
        **kwargs,
    ):
        """
        HuggingFace-style forward pass.
        
        Args:
            input_values: (B, 1, T) or (B, T) audio waveform
            input_ids: (B, T) or (B, num_quantizers, T) discrete codes
            bandwidth_id: Optional (B,) bandwidth index
            
        Returns:
            BaseModelOutput with last_hidden_state (features) and hidden_states (codes, audio)
        """
        if input_values is not None:
            if input_values.dim() == 2:
                input_values = input_values.unsqueeze(1)
            
            features, codes = self.encode(input_values, bandwidth_id)
            audio = self.decode(features, bandwidth_id)
            
            return BaseModelOutput(
                last_hidden_state=features,
                hidden_states=(codes, audio),
            )
        
        elif input_ids is not None:
            features = self.codes_to_features(input_ids)
            audio = self.decode(features, bandwidth_id)
            
            return BaseModelOutput(
                last_hidden_state=features,
                hidden_states=(input_ids, audio),
            )
        
        else:
            raise ValueError("Either input_values or input_ids must be provided")