"""CRS-Diff modular loading utilities for custom diffusers pipeline."""

import importlib
import json
import sys
from pathlib import Path
from typing import Dict, Optional, Union

import torch
from diffusers import DDIMScheduler

_PIPELINE_DIR = Path(__file__).resolve().parent
if str(_PIPELINE_DIR) not in sys.path:
    sys.path.insert(0, str(_PIPELINE_DIR))

_COMPONENT_NAMES = (
    "unet",
    "vae",
    "text_encoder",
    "local_adapter",
    "global_content_adapter",
    "global_text_adapter",
    "metadata_encoder",
)

_TARGET_MAP = {
    "crs_core.local_adapter.LocalControlUNetModel": "crs_core.local_adapter.LocalControlUNetModel",
    "crs_core.autoencoder.AutoencoderKL": "crs_core.autoencoder.AutoencoderKL",
    "crs_core.text_encoder.FrozenCLIPEmbedder": "crs_core.text_encoder.FrozenCLIPEmbedder",
    "crs_core.local_adapter.LocalAdapter": "crs_core.local_adapter.LocalAdapter",
    "crs_core.global_adapter.GlobalContentAdapter": "crs_core.global_adapter.GlobalContentAdapter",
    "crs_core.global_adapter.GlobalTextAdapter": "crs_core.global_adapter.GlobalTextAdapter",
    "crs_core.metadata_embedding.metadata_embeddings": "crs_core.metadata_embedding.metadata_embeddings",
}


def ensure_model_path(pretrained_model_name_or_path: Union[str, Path]) -> Path:
    """Resolve local path or download HF repo snapshot."""
    path = Path(pretrained_model_name_or_path)
    if not path.exists():
        from huggingface_hub import snapshot_download

        path = Path(snapshot_download(str(pretrained_model_name_or_path)))
    path = path.resolve()
    if str(path) not in sys.path:
        sys.path.insert(0, str(path))
    return path


def resolve_model_root(candidate: Optional[Union[str, Path]]) -> Optional[Path]:
    """Resolve to folder containing model_index.json."""
    if not candidate:
        return None
    path = ensure_model_path(candidate)
    if (path / "model_index.json").exists():
        return path
    cur = path
    for _ in range(5):
        parent = cur.parent
        if parent == cur:
            break
        if (parent / "model_index.json").exists():
            return parent
        cur = parent
    return None


def _get_class(target: str):
    module_path, cls_name = target.rsplit(".", 1)
    mod = importlib.import_module(module_path)
    return getattr(mod, cls_name)


def load_component(model_root: Path, name: str):
    """Load single split component from <repo>/<name>/."""
    root = Path(model_root)
    comp_path = root / name
    with (comp_path / "config.json").open("r", encoding="utf-8") as f:
        cfg = json.load(f)
    target = cfg.pop("_target", None)
    if not target:
        raise ValueError(f"No _target in {comp_path / 'config.json'}")
    target = _TARGET_MAP.get(target, target)
    cls_ref = _get_class(target)
    params = {k: v for k, v in cfg.items() if not k.startswith("_")}
    module = cls_ref(**params)

    weight_file = comp_path / "diffusion_pytorch_model.safetensors"
    if weight_file.exists():
        from safetensors.torch import load_file

        state = load_file(str(weight_file))
        module.load_state_dict(state, strict=True)
    module.eval()
    return module


class CRSModelWrapper(torch.nn.Module):
    """Wrap split components to mimic CRSControlNet APIs used by pipeline."""

    def __init__(
        self,
        unet,
        vae,
        text_encoder,
        local_adapter,
        global_content_adapter,
        global_text_adapter,
        metadata_encoder,
        channels: int = 4,
    ):
        super().__init__()
        self.model = torch.nn.Module()
        self.model.add_module("diffusion_model", unet)
        self.first_stage_model = vae
        self.cond_stage_model = text_encoder
        self.local_adapter = local_adapter
        self.global_content_adapter = global_content_adapter
        self.global_text_adapter = global_text_adapter
        self.metadata_emb = metadata_encoder
        self.local_control_scales = [1.0] * 13
        self.channels = channels

    @torch.no_grad()
    def get_learned_conditioning(self, prompts):
        if hasattr(self.cond_stage_model, "device"):
            self.cond_stage_model.device = str(next(self.parameters()).device)
        return self.cond_stage_model.encode(prompts)

    def apply_model(self, x_noisy, t, cond, metadata=None, global_strength=1.0, **kwargs):
        del kwargs
        if metadata is None:
            metadata = cond["metadata"]
        cond_txt = torch.cat(cond["c_crossattn"], 1)

        if cond.get("global_control") is not None and cond["global_control"][0] is not None:
            metadata = self.metadata_emb(metadata)
            content_t, _ = cond["global_control"][0].chunk(2, dim=1)
            global_control = self.global_content_adapter(content_t)
            cond_txt = self.global_text_adapter(cond_txt)
            cond_txt = torch.cat([cond_txt, global_strength * global_control], dim=1)

        local_control = None
        if cond.get("local_control") is not None and cond["local_control"][0] is not None:
            local_control = torch.cat(cond["local_control"], 1)
            local_control = self.local_adapter(
                x=x_noisy, timesteps=t, context=cond_txt, local_conditions=local_control
            )
            local_control = [c * s for c, s in zip(local_control, self.local_control_scales)]

        return self.model.diffusion_model(
            x=x_noisy,
            timesteps=t,
            metadata=metadata,
            context=cond_txt,
            local_control=local_control,
            meta=True,
        )

    def decode_first_stage(self, z):
        return self.first_stage_model.decode(z)


def load_components(model_root: Union[str, Path]) -> Dict[str, object]:
    """Load pipeline components from split directories."""
    root = ensure_model_path(model_root)
    scheduler = DDIMScheduler.from_pretrained(root, subfolder="scheduler")

    scale_factor = 0.18215
    channels = 4
    if (root / "model_index.json").exists():
        with (root / "model_index.json").open("r", encoding="utf-8") as f:
            idx = json.load(f)
        scale_factor = float(idx.get("scale_factor", scale_factor))
        channels = int(idx.get("channels", channels))

    has_split_components = all((root / name / "config.json").exists() for name in _COMPONENT_NAMES)
    if not has_split_components:
        missing = [name for name in _COMPONENT_NAMES if not (root / name / "config.json").exists()]
        raise FileNotFoundError(
            f"CRS-Diff split component export incomplete. Missing: {missing}. "
            "Expected split folders with config.json and weights."
        )

    loaded = {name: load_component(root, name) for name in _COMPONENT_NAMES}
    crs_model = CRSModelWrapper(
        unet=loaded["unet"],
        vae=loaded["vae"],
        text_encoder=loaded["text_encoder"],
        local_adapter=loaded["local_adapter"],
        global_content_adapter=loaded["global_content_adapter"],
        global_text_adapter=loaded["global_text_adapter"],
        metadata_encoder=loaded["metadata_encoder"],
        channels=channels,
    )

    return {"crs_model": crs_model, "scheduler": scheduler, "scale_factor": scale_factor}