from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path
from typing import List, Optional

from PIL import Image

from .styles import Style
from .utils import timestamp

IMG_EXTS = {".png", ".jpg", ".jpeg", ".webp"}


def _list_images(folder: Path) -> List[Path]:
    if not folder.exists():
        return []
    files: List[Path] = []
    for p in folder.iterdir():
        if p.is_file() and p.suffix.lower() in IMG_EXTS:
            files.append(p)
    return sorted(files)


def _load_pil(path: Path) -> Image.Image:
    return Image.open(path).convert("RGB")


def _pick_reference_images(
    style_folder: Path,
    max_images: int,
    sample_mode: str = "random",
    seed: Optional[int] = None,
) -> List[Image.Image]:
    import torch

    paths = _list_images(style_folder)
    if not paths or max_images <= 0:
        return []

    max_images = min(max_images, len(paths))

    if sample_mode == "first":
        chosen = paths[:max_images]
    else:
        generator = torch.Generator(device="cpu")
        generator.manual_seed(0 if seed is None else int(seed))
        idx = torch.randperm(len(paths), generator=generator).tolist()
        chosen = [paths[i] for i in idx[:max_images]]

    return [_load_pil(p) for p in chosen]


@dataclass
class GenerateConfig:
    model_id: str
    steps: int = 6
    guidance: float = 1.0
    height: int = 512
    width: int = 512
    device: str = "cuda"
    torch_dtype_name: str = "bfloat16"
    cpu_offload: bool = True
    use_ref_images: bool = True
    ref_max_images: int = 4
    ref_sample_mode: str = "random"
    seed: Optional[int] = None
    num_outputs: int = 1


def _is_flux2(model_id: str) -> bool:
    mid = model_id.lower()
    return "flux.2" in mid or "flux2" in mid


def _resolve_torch_dtype(dtype_name: str):
    import torch

    if dtype_name == "float16":
        return torch.float16
    if dtype_name == "float32":
        return torch.float32
    return torch.bfloat16


def _load_flux2_pipeline(model_id: str, cfg: GenerateConfig):
    import torch
    from diffusers import Flux2KleinPipeline, Flux2Pipeline

    torch_dtype = _resolve_torch_dtype(cfg.torch_dtype_name)

    if "klein" in model_id.lower():
        pipe = Flux2KleinPipeline.from_pretrained(model_id, torch_dtype=torch_dtype)
    else:
        pipe = Flux2Pipeline.from_pretrained(model_id, torch_dtype=torch_dtype)

    if cfg.device == "cuda" and torch.cuda.is_available():
        if cfg.cpu_offload:
            pipe.enable_model_cpu_offload()
        else:
            pipe.to("cuda")
    else:
        pipe.to("cpu")

    return pipe


def generate_one(
    user_prompt: str,
    style: Style,
    out_root: Path,
    cfg: GenerateConfig,
) -> List[Path]:
    import torch

    out_root.mkdir(parents=True, exist_ok=True)

    if not _is_flux2(cfg.model_id):
        raise ValueError(
            "This generate.py expects a FLUX.2 model_id "
            f"(got: {cfg.model_id})"
        )

    pipe = _load_flux2_pipeline(cfg.model_id, cfg)

    if cfg.seed is None:
        generator = None
    else:
        gen_device = "cuda" if (cfg.device == "cuda" and torch.cuda.is_available()) else "cpu"
        generator = torch.Generator(device=gen_device).manual_seed(int(cfg.seed))

    ref_images: Optional[List[Image.Image]] = None
    if cfg.use_ref_images:
        ref_images = _pick_reference_images(
            style.folder,
            max_images=cfg.ref_max_images,
            sample_mode=cfg.ref_sample_mode,
            seed=cfg.seed,
        )
        if ref_images:
            print(
                f"FLUX.2 reference images used: {len(ref_images)} "
                f"(mode={cfg.ref_sample_mode}, max={cfg.ref_max_images})"
            )
        else:
            print("FLUX.2 reference images: none found (running txt2img).")

    call_kwargs = dict(
        prompt=user_prompt,
        height=int(cfg.height),
        width=int(cfg.width),
        num_inference_steps=max(1, int(cfg.steps)),
        guidance_scale=float(cfg.guidance),
        generator=generator,
        num_images_per_prompt=max(1, int(cfg.num_outputs)),
    )

    if ref_images:
        call_kwargs["image"] = ref_images

    result = pipe(**call_kwargs)
    out_images: List[Image.Image] = list(result.images)

    time_id = timestamp()
    out_dir = out_root / style.name
    out_dir.mkdir(parents=True, exist_ok=True)

    paths: List[Path] = []
    for i, img in enumerate(out_images, start=1):
        out_path = out_dir / f"{time_id}_{i:02d}.png"
        img.save(out_path)
        paths.append(out_path)

    return paths