"""
Condition Encoder — reads config to select the right VAE, encodes all
conditions, and produces concat-ready latents.

Usage:
    config = ActionConditioningConfig(backbone="wan", vae_path="path/to/vae.pt")
    cond_enc = ConditionEncoder(config, device="cuda")

    encoded = cond_enc.encode(
        obs_image=obs,            # (B, 3, H, W)
        actions=delta_actions,    # (B, T, action_dim)
        masked_traj=traj_imgs,    # (B, 3, T, H, W)
    )
    # encoded.concat_latent: (B, C_concat, T', H', W') — ready for input_concat
    # encoded.action_tokens: (B, T, embed_dim) — for adaln or cross_attn
"""

from dataclasses import dataclass
from typing import Optional

import torch
import torch.nn as nn

from .config import ActionConditioningConfig
from .model_paths import resolve_vae_ckpt_path
# from .encoders.action_encoder import ActionFFNEncoder

# Prepended to visual_latent on channel dim when `noisy_latent` is passed (must match pipeline expectations).
VISUAL_CONDITION_MASK_CHANNELS = 4


class ActionFFNEncoder(nn.Module):
    def __init__(self, action_dim: int, embed_dim: int, num_layers: int = 2):
        super().__init__()
        layers = [nn.Linear(action_dim, embed_dim), nn.GELU()]
        for _ in range(max(0, num_layers - 2)):
            layers += [nn.Linear(embed_dim, embed_dim), nn.GELU()]
        self.mlp = nn.Sequential(*layers)
        self.norm = nn.LayerNorm(embed_dim)
    def forward(self, actions: torch.Tensor) -> torch.Tensor:
        return self.norm(self.mlp(actions))


@dataclass
class EncodedConditions:
    """All encoded conditions, ready for the DiT wrapper."""

    action_tokens: Optional[torch.Tensor] = None   # (B, T, embed_dim)
    obs_latent: Optional[torch.Tensor] = None       # (B, C, 1, H', W')
    traj_latent: Optional[torch.Tensor] = None      # (B, C, T', H', W')
    history_latent: Optional[torch.Tensor] = None    # (B, C, K', H', W')
    visual_latent: Optional[torch.Tensor] = None     # (B, C, T_vis, H', W') — unified visual condition
    concat_latent: Optional[torch.Tensor] = None     # (B, C_total, T', H', W') — all input_concat streams merged


def _build_vae(config: ActionConditioningConfig):
    # model-name driven
    if config.vae_model_name == "wan_video_vae":
        from diffsynth.models.wan_video_vae import WanVideoVAE
        vae = WanVideoVAE(z_dim=config.vae_z_dim)
    elif config.vae_model_name == "wan_video_vae38":
        from diffsynth.models.wan_video_vae import WanVideoVAE38
        vae = WanVideoVAE38(z_dim=config.vae_z_dim)
    else:
        raise ValueError(f"Unknown vae_model_name: {config.vae_model_name!r}")

    # optional load from explicit path or model_root-derived path
    vae_ckpt_path = resolve_vae_ckpt_path(config)
    missing_keys = []
    unexpected_keys = []
    if vae_ckpt_path is not None:
        from diffsynth.core.loader.file import load_state_dict
        state_dict = load_state_dict(vae_ckpt_path, device="cpu")
        if hasattr(vae, "state_dict_converter"):
            converter = vae.state_dict_converter()
            state_dict = converter.from_civitai(state_dict)
        incompatible = vae.load_state_dict(state_dict, strict=False)
        if incompatible is not None:
            missing_keys = list(getattr(incompatible, "missing_keys", []))
            unexpected_keys = list(getattr(incompatible, "unexpected_keys", []))
    else:
        raise ValueError(
            "VAE checkpoint path is not resolved. Please set config.vae_path "
            "or config.model_root with a valid Wan VAE file."
        )

    vae.eval()
    for p in vae.parameters():
        p.requires_grad = False
    # Attach debug metadata for verification in tests/scripts.
    vae._loaded_ckpt_path = vae_ckpt_path
    vae._missing_keys = missing_keys
    vae._unexpected_keys = unexpected_keys
    return vae


class ConditionEncoder(nn.Module):
    """
    Reads config.backbone to select the right VAE, encodes all visual
    conditions through it, and produces concat-ready latents.

    The VAE is frozen. Only the action_encoder is trainable.
    """

    def __init__(self, config: ActionConditioningConfig, device: torch.device = torch.device("cuda")):
        super().__init__()
        self.config = config
        self.device = device

        # Build frozen VAE (not registered as submodule to avoid saving its weights)
        self._vae = _build_vae(config)

        # Trainable action encoder
        self.action_encoder = ActionFFNEncoder(
            action_dim=config.action_dim,
            embed_dim=config.action_embed_dim,
            num_layers=config.action_num_layers,
        )

    @property
    def vae(self):
        return self._vae

    def to(self, *args, **kwargs):
        """Override to also move the frozen VAE."""
        super().to(*args, **kwargs)
        self._vae = self._vae.to(*args, **kwargs)
        return self

    # ------------------------------------------------------------------
    # VAE encoding helpers
    # ------------------------------------------------------------------

    @torch.no_grad()
    def _vae_encode_image(self, image: torch.Tensor) -> torch.Tensor:
        """(B, 3, H, W) → (B, C, 1, H', W')"""
        videos = [img.unsqueeze(1) for img in image]
        return self._vae.encode(videos, self.device)

    @torch.no_grad()
    def _vae_encode_video(self, video: torch.Tensor) -> torch.Tensor:
        """(B, 3, T, H, W) → (B, C, T', H', W')"""
        videos = [v for v in video]
        return self._vae.encode(videos, self.device)

    # ------------------------------------------------------------------
    # Main encode method
    # ------------------------------------------------------------------

    def encode(
        self,
        obs_image: Optional[torch.Tensor] = None,
        actions: Optional[torch.Tensor] = None,
        masked_traj: Optional[torch.Tensor] = None,
        history: Optional[torch.Tensor] = None,
        noisy_latent: Optional[torch.Tensor] = None,
    ) -> EncodedConditions:
        """
        Encode all conditions and assemble concat_latent.

        Parameters
        ----------
        obs_image : (B, 3, H, W) — observation frame
        actions : (B, T, action_dim) — delta action vectors
        masked_traj : (B, 3, T, H, W) — rendered trajectory images
        history : (B, 3, K, H, W) — past frames
        noisy_latent : (B, C, T', H', W') — the noisy latent (needed for
            shape reference when broadcasting obs to T' frames)

        Returns
        -------
        EncodedConditions
        """
        result = EncodedConditions()
        cfg = self.config

        # --- Action tokens (trainable) ---
        if actions is not None:
            result.action_tokens = self.action_encoder(actions)

        # --- VAE encode visual conditions (frozen) ---
        # Past context rule:
        # 1) force history length to cfg.history_frames
        # 2) past stream is [observation + history] (total cfg.history_frames + 1 frames)
        # 3) if history is missing, repeat observation to fill all past frames
        if obs_image is not None and (cfg.obs_injection is not None or cfg.history_injection is not None):
            target_past_len = cfg.history_frames + 1
            obs_seq = obs_image.unsqueeze(2)  # (B, 3, 1, H, W)
            if history is None:
                past_video = obs_seq.repeat(1, 1, target_past_len, 1, 1)
            else:
                # history: (B, 3, K, H, W) -> normalize to exactly cfg.history_frames
                if history.shape[2] >= cfg.history_frames:
                    history_norm = history[:, :, :cfg.history_frames]
                else:
                    pad_len = cfg.history_frames - history.shape[2]
                    pad_hist = obs_seq.repeat(1, 1, pad_len, 1, 1)
                    history_norm = torch.cat([history, pad_hist], dim=2)
                past_video = torch.cat([obs_seq, history_norm], dim=2)
            result.history_latent = self._vae_encode_video(past_video)
            result.obs_latent = None
        elif obs_image is not None and cfg.obs_injection is not None:
            result.obs_latent = self._vae_encode_image(obs_image)

        if cfg.traj_injection is not None:
            if masked_traj is not None:
                result.traj_latent = self._vae_encode_video(masked_traj)
            elif noisy_latent is not None:
                # Placeholder trajectory latent for true no-traj ablation.
                # Keeps visual_latent temporal length aligned with noisy_latent.
                B, C, T_lat, H_lat, W_lat = noisy_latent.shape

                # history_latent is usually obs + history compressed to T=1
                T_hist = result.history_latent.shape[2] if result.history_latent is not None else 0
                T_traj = T_lat - T_hist

                if T_traj < 0:
                    raise ValueError(
                        f"history latent is longer than noisy latent: "
                        f"T_hist={T_hist}, T_lat={T_lat}"
                    )

                result.traj_latent = torch.zeros(
                    B, C, T_traj, H_lat, W_lat,
                    device=noisy_latent.device,
                    dtype=noisy_latent.dtype,
                )

        if history is not None and cfg.history_injection is not None and result.history_latent is None:
            result.history_latent = self._vae_encode_video(history)

        # --- Assemble unified visual condition ---
        # Merge observation into history first, then concat with trajectory.
        # This keeps one "past context" stream + one "future trajectory" stream.
        visual_parts = []

        history_merged = result.history_latent
        if result.obs_latent is not None:
            if history_merged is None:
                history_merged = result.obs_latent
            else:
                history_merged = torch.cat([result.obs_latent, history_merged], dim=2)

        if result.traj_latent is not None:
            visual_parts.append(result.traj_latent)
        if history_merged is not None:
            visual_parts.append(history_merged)

        if visual_parts:
            result.visual_latent = torch.cat(visual_parts, dim=2)

        # Wan DiT does `torch.cat([latents, y], dim=1)` — T and spatial sizes must match latents.
        # Past-only history often yields T_vis=1 while generation uses T_lat=(num_frames-1)//4+1.
        if result.visual_latent is not None and noisy_latent is not None:
            T_lat = noisy_latent.shape[2]
            Bv, Cv, Tv, Hv, Wv = result.visual_latent.shape
            if Tv != T_lat:
                if Tv < T_lat:
                    pad_t = T_lat - Tv
                    tail = torch.zeros(
                        Bv, Cv, pad_t, Hv, Wv,
                        device=result.visual_latent.device,
                        dtype=result.visual_latent.dtype,
                    )
                    result.visual_latent = torch.cat([result.visual_latent, tail], dim=2)
                else:
                    result.visual_latent = result.visual_latent[:, :, :T_lat, :, :]

        # --- Build condition mask (4-channel, per sub-frame) ---
        if result.visual_latent is not None and noisy_latent is not None:
            B = noisy_latent.shape[0]
            _, C_vis, T_vis, H_lat, W_lat = result.visual_latent.shape  # ← 用 visual_latent 的维度

            mask = torch.zeros(B, VISUAL_CONDITION_MASK_CHANNELS, T_vis, H_lat, W_lat,  # ← T_vis 而不是 T_lat
                               device=result.visual_latent.device,
                               dtype=result.visual_latent.dtype)

            n_traj_pixels = masked_traj.shape[2] if masked_traj is not None else 0
            real_start_lat = (n_traj_pixels + 3) // 4
            mask[:, :, real_start_lat:] = 1.0

            result.visual_latent = torch.cat([mask, result.visual_latent], dim=1)
            result.concat_latent = result.visual_latent

        return result