from __future__ import annotations

from dataclasses import dataclass
from typing import Tuple

import numpy as np
import torch
import torch.nn.functional as F
from PIL import Image, ImageOps


@dataclass(frozen=True)
class PreparedImage:
    full_pil: Image.Image
    model_pil: Image.Image
    full_tensor: torch.Tensor
    model_tensor: torch.Tensor


def normalize_pil(image: Image.Image) -> Image.Image:
    image = ImageOps.exif_transpose(image)
    return image.convert("RGB")


def resize_max_side(image: Image.Image, max_side: int) -> Image.Image:
    max_side = int(max(256, min(max_side, 2048)))
    width, height = image.size
    longest = max(width, height)
    if longest <= max_side:
        return image.copy()
    scale = max_side / float(longest)
    new_size = (max(1, round(width * scale)), max(1, round(height * scale)))
    return image.resize(new_size, Image.Resampling.LANCZOS)


def pil_to_tensor(image: Image.Image) -> torch.Tensor:
    arr = np.asarray(image, dtype=np.float32) / 255.0
    tensor = torch.from_numpy(arr).permute(2, 0, 1).contiguous()
    return tensor.unsqueeze(0)


def tensor_to_pil(tensor: torch.Tensor) -> Image.Image:
    tensor = tensor.detach().float().cpu().clamp(0, 1)
    if tensor.ndim == 4:
        tensor = tensor[0]
    arr = (tensor.permute(1, 2, 0).numpy() * 255.0).round().astype(np.uint8)
    return Image.fromarray(arr, mode="RGB")


def prepare_image(image: Image.Image, max_side: int, model_size: int = 512) -> PreparedImage:
    full_pil = resize_max_side(normalize_pil(image), max_side)
    model_pil = full_pil.resize((model_size, model_size), Image.Resampling.BICUBIC)
    return PreparedImage(
        full_pil=full_pil,
        model_pil=model_pil,
        full_tensor=pil_to_tensor(full_pil),
        model_tensor=pil_to_tensor(model_pil),
    )


def match_tensor_size(tensor: torch.Tensor, target_hw: Tuple[int, int]) -> torch.Tensor:
    if tuple(tensor.shape[-2:]) == tuple(target_hw):
        return tensor
    return F.interpolate(tensor, size=target_hw, mode="bilinear", align_corners=False)


def blend_strength(input_tensor: torch.Tensor, output_tensor: torch.Tensor, strength: float) -> torch.Tensor:
    strength = float(max(0.0, min(2.0, strength)))
    output_tensor = match_tensor_size(output_tensor, input_tensor.shape[-2:])
    return (input_tensor + strength * (output_tensor - input_tensor)).clamp(0, 1)