import json
import math
import os
import sys
from contextlib import contextmanager
from dataclasses import dataclass
from pathlib import Path

import torch
from safetensors.torch import load_file
from torch import nn
from torchdyn.core import NeuralODE

from .modules import AdaLNFlowPredictor, AutoEncoder


@contextmanager
def suppress_stdout():
    original_stdout = sys.stdout
    try:
        sys.stdout = open(os.devnull, "w")
        yield
    finally:
        sys.stdout.close()
        sys.stdout = original_stdout


def cosine_schedule_with_warmup(warmup_steps, total_steps, start_lr, end_lr):
    def lr_lambda(step):
        if step < warmup_steps:
            return step / max(1, warmup_steps)
        progress = (step - warmup_steps) / max(1, total_steps - warmup_steps)
        cosine_decay = 0.5 * (1 + math.cos(math.pi * progress))
        return (start_lr - end_lr) * cosine_decay / start_lr + end_lr / start_lr

    return lr_lambda


@dataclass
class PatchVAEConfig:
    latent_dim: int
    hidden_dim: int
    latent_scaling: tuple[list[float], list[float]] | None
    flow_factory: str
    num_flow_layers: int
    autoencoder_factory: str
    num_autoencoder_layers: int
    convnextformer_num_conv_per_transformer: int = 3
    wavvae_path: str | None = None
    fsq_levels: list[int] | None = None
    bottleneck_size: int | None = None
    latent_stride: int = 2
    vae: bool = False
    causal_transformer: bool = False
    cond_dim: int | None = None
    is_causal: bool = False


class PatchVAE(nn.Module):
    def __init__(self, cfg: PatchVAEConfig):
        super().__init__()
        self.flow_net = AdaLNFlowPredictor(
            feat_dim=cfg.latent_dim * cfg.latent_stride,
            dim=cfg.hidden_dim,
            n_layer=cfg.num_flow_layers,
            layer_factory=cfg.flow_factory,
            cond_dim=cfg.cond_dim,
            is_causal=cfg.is_causal,
        )
        self.autoencoder = AutoEncoder(
            cfg.latent_dim * cfg.latent_stride,
            cfg.hidden_dim,
            cfg.num_autoencoder_layers,
            cfg.autoencoder_factory,
            out_dim=cfg.cond_dim,
            vae=cfg.vae,
            bottleneck_size=cfg.bottleneck_size,
            convnextformer_num_conv_per_transformer=cfg.convnextformer_num_conv_per_transformer,
            is_causal=cfg.is_causal,
        )
        if cfg.latent_scaling is not None:
            mean, std = cfg.latent_scaling
            self.register_buffer("mean_latent_scaling", torch.tensor(mean))
            self.register_buffer("std_latent_scaling", torch.tensor(std))
        else:
            self.mean_latent_scaling = None
            self.std_latent_scaling = None

        self.latent_stride = cfg.latent_stride
        self.latent_dim = cfg.latent_dim
        self.wavvae = None

    @classmethod
    def from_pretrained(
        cls,
        pretrained_model_name_or_path: str,
        map_location: str = "cpu",
    ):
        if Path(pretrained_model_name_or_path).exists():
            path = pretrained_model_name_or_path
        else:
            from huggingface_hub import snapshot_download

            path = snapshot_download(pretrained_model_name_or_path)

        with open(Path(path) / "config.json", "r") as f:
            config = json.load(f)
        config = PatchVAEConfig(**config)
        model = cls(config).to(map_location)
        state_dict = load_file(
            Path(path) / "model.st",
            device=map_location,
        )
        model.load_state_dict(state_dict, assign=True)
        if config.wavvae_path is not None:
            from .. import WavVAE

            model.wavvae = WavVAE.from_pretrained(config.wavvae_path).to(map_location)
        else:
            model.wavvae = None

        return model

    def wavvae_from_pretrained(
        self,
        pretrained_model_name_or_path: str,
        *args,
        **kwargs,
    ):
        from .. import WavVAE

        self.wavvae = WavVAE.from_pretrained(
            pretrained_model_name_or_path,
            *args,
            **kwargs,
        )

    def encode(self, wav: torch.Tensor):
        assert self.wavvae is not None, (
            "please provide WavVAE model to encode from waveform"
        )
        z = self.wavvae.encode(wav)
        zz = self.encode_patch(z)
        return zz

    def decode(self, patchvae_latent: torch.Tensor, **kwargs):
        assert self.wavvae is not None, (
            "please provide WavVAE model to decode to waveform"
        )
        z = self.decode_patch(patchvae_latent, **kwargs)
        wav = self.wavvae.decode(z)
        return wav

    def normalize_z(self, z: torch.Tensor):
        if self.mean_latent_scaling is not None:
            z = (z - self.mean_latent_scaling) / self.std_latent_scaling
        return z

    def denormalize_z(self, z: torch.Tensor):
        if self.std_latent_scaling is not None:
            z = z * self.std_latent_scaling + self.mean_latent_scaling
        return z

    def encode_patch(self, z: torch.Tensor, deterministic: bool = False):
        B, T, D = z.shape
        z = self.normalize_z(z)
        if self.latent_stride > 1:
            z = z[:, : T - T % self.latent_stride]
            z = z.reshape(B, T // self.latent_stride, D * self.latent_stride)
        return self.autoencoder.encode(z, deterministic=deterministic)

    def decode_patch(
        self,
        latent: torch.Tensor,
        cfg: float = 2.0,
        num_steps: int = 15,
        solver: str = "euler",
        sensitivity: str = "adjoint",
        temperature: float = 1.0,
        **kwargs,
    ):
        with torch.no_grad():
            z_cond = self.autoencoder.decode(latent).transpose(1, 2)
            if cfg == 1.0:

                def solver_fn(t, Xt, *args, **kwargs):
                    flow = self.flow_net(Xt, z_cond, t.unsqueeze(0))
                    return flow
            else:
                z_cond_uncond = torch.cat((z_cond, torch.zeros_like(z_cond)), dim=0)

                def solver_fn(t, Xt, *args, **kwargs):
                    flow = self.flow_net(
                        Xt.repeat(2, 1, 1), z_cond_uncond, t.unsqueeze(0)
                    )
                    cond, uncond = flow.chunk(2, dim=0)

                    return uncond + cfg * (cond - uncond)

            with suppress_stdout():
                node_ = NeuralODE(
                    solver_fn,
                    solver=solver,
                    sensitivity=sensitivity,
                    **kwargs,
                )
            t_span = torch.linspace(0, 1, num_steps + 1, device=z_cond.device)
            patch_dim = self.latent_dim * self.latent_stride
            x0 = torch.randn(
                z_cond.shape[0],
                patch_dim,
                z_cond.shape[2],
                device=z_cond.device,
            )
            traj = node_.trajectory(
                x0 * temperature,
                t_span=t_span,
            )

            y_hat = traj[-1]
            y_hat = y_hat.transpose(1, 2)
            B, T, D = y_hat.shape
            y_hat = y_hat.reshape(B, T * self.latent_stride, D // self.latent_stride)
            y_hat = self.denormalize_z(y_hat)
        return y_hat

    def forward(
        self,
        z: torch.Tensor,
        t: torch.Tensor,
        drop_cond_rate: float = 0.0,
        drop_vae_rate: float = 0.0,
        sigma: float = 1e-4,
    ):
        z = self.normalize_z(z)
        B, T, D = z.shape
        if self.latent_stride > 1:
            z = z.reshape(B, T // self.latent_stride, D * self.latent_stride)

        prior, ae_loss = self.autoencoder(z, drop_vae_rate=drop_vae_rate)

        if drop_cond_rate > 0.0:
            to_drop = torch.rand(prior.shape[0], device=prior.device) < drop_cond_rate
            prior[to_drop] = 0.0

        x0 = torch.randn_like(z)
        x1 = z

        flow_target = x1 - (1 - sigma) * x0

        alpha = (1 - (1 - sigma) * t).view(-1, 1, 1)
        xt = alpha * x0 + t.view(-1, 1, 1) * x1

        pred = self.flow_net(
            xt.transpose(1, 2),
            prior.transpose(1, 2),
            t,
        )

        flow_loss = nn.functional.mse_loss(flow_target.transpose(1, 2), pred)

        return flow_loss, ae_loss, prior