import torch
import open_clip
import json
import numpy as np
from PIL import Image
from pathlib import Path
from huggingface_hub import hf_hub_download
from typing import List, Dict, Tuple, Optional

from .preprocessing import preprocess_file, preprocess_image

# Constants
MODEL_NAME = "numansaeed/fetalclip-model"
INPUT_SIZE = 224
TOP_N_PROBS = 15

# GA Text prompts - view-specific prompts for brain, abdomen, and femur
GA_TEXT_PROMPTS = {
    "brain": [
        "Ultrasound image at {weeks} weeks and {day} days gestation focusing on the fetal brain, highlighting anatomical structures with a pixel spacing of {pixel_spacing} mm/pixel.",
        "Fetal ultrasound image at {weeks} weeks, {day} days of gestation, focusing on the developing brain, with a pixel spacing of {pixel_spacing} mm/pixel, highlighting the structures of the fetal brain.",
        "Fetal ultrasound image at {weeks} weeks and {day} days gestational age, highlighting the developing brain structures with a pixel spacing of {pixel_spacing} mm/pixel, providing important visual insights for ongoing prenatal assessments.",
        "Ultrasound image at {weeks} weeks and {day} days gestation, highlighting the fetal brain structures with a pixel spacing of {pixel_spacing} mm/pixel.",
        "Fetal ultrasound at {weeks} weeks and {day} days, showing a clear view of the developing brain, with an image pixel spacing of {pixel_spacing} mm/pixel."
    ],
    "abdomen": [
        "Fetal ultrasound at {weeks} weeks and {day} days gestation, focusing on the abdominal area, highlighting structural development with a pixel spacing of {pixel_spacing} mm/pixel.",
        "Ultrasound image at {weeks} weeks and {day} days gestation, focusing on the fetal abdomen, with pixel spacing of {pixel_spacing} mm/pixel, highlighting the structural development in this stage of gestation.",
        "Ultrasound image of the fetal abdomen at {weeks} weeks and {day} days gestational age, highlighting anatomical structures with a pixel spacing of {pixel_spacing} mm/pixel.",
        "Ultrasound image of the fetal abdomen at {weeks} weeks and {day} days gestational age, highlighting the development of abdominal structures, with a pixel spacing of {pixel_spacing} mm/pixel.",
        "Fetal ultrasound image at {weeks} weeks and {day} days gestational age, focusing on the abdomen with a pixel spacing of {pixel_spacing} mm/pixel."
    ],
    "femur": [
        "Ultrasound image at {weeks} weeks and {day} days gestation, focusing on the developing fetal femur, with a pixel spacing of {pixel_spacing} mm/pixel, highlighting bone length and structure.",
        "The ultrasound image highlights the fetal femur at {weeks} weeks and {day} days of gestation, with a pixel spacing of {pixel_spacing} mm/pixel, providing a detailed view of the developing bone.",
        "Ultrasound image at {weeks} weeks and {day} days gestation, focusing on the fetal femur, highlighting skeletal development at a pixel spacing of {pixel_spacing} mm/pixel.",
        "Fetal ultrasound image at {weeks} weeks and {day} days gestation, highlighting the femur with a pixel spacing of {pixel_spacing} mm/pixel, providing a detailed view of bone development.",
        "Ultrasound image at {weeks} weeks and {day} days gestation, highlighting the fetal femur with a pixel spacing of {pixel_spacing} mm/pixel."
    ]
}

LIST_GA_IN_DAYS = [weeks * 7 + days for weeks in range(14, 39) for days in range(0, 7)]


class FetalCLIPService:
    _instance = None
    _initialized = False

    def __new__(cls):
        if cls._instance is None:
            cls._instance = super().__new__(cls)
        return cls._instance

    def __init__(self):
        if FetalCLIPService._initialized:
            return
        
        self.device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
        self.model = None
        self.preprocess = None
        self.tokenizer = None
        self.text_features = None
        self.list_plane = []
        
        FetalCLIPService._initialized = True

    def load_model(self, assets_dir: Path):
        """Load the FetalCLIP model and precompute text features."""
        config_path = assets_dir / "FetalCLIP_config.json"
        prompts_path = assets_dir / "prompt_fetal_view.json"
        
        # Load config
        with open(config_path, "r") as f:
            config = json.load(f)
        open_clip.factory._MODEL_CONFIGS["FetalCLIP"] = config
        
        # Download weights
        weights_path = hf_hub_download(
            repo_id=MODEL_NAME,
            filename="FetalCLIP_weights.pt"
        )
        
        # Create model
        self.model, _, self.preprocess = open_clip.create_model_and_transforms(
            "FetalCLIP",
            pretrained=weights_path
        )
        self.tokenizer = open_clip.get_tokenizer("FetalCLIP")
        
        self.model = self.model.float()
        self.model.eval()
        self.model.to(self.device)
        
        # Load text prompts and compute features
        with open(prompts_path, 'r') as f:
            text_prompts = json.load(f)
        
        list_text_features = []
        self.list_plane = []
        
        with torch.no_grad():
            for plane, prompts in text_prompts.items():
                self.list_plane.append(plane)
                
                tokens = self.tokenizer(prompts).to(self.device)
                features = self.model.encode_text(tokens)
                features /= features.norm(dim=-1, keepdim=True)
                
                features = features.mean(dim=0).unsqueeze(0)
                features /= features.norm(dim=-1, keepdim=True)
                
                list_text_features.append(features)
        
        self.text_features = torch.stack(list_text_features)[:, 0]
        
        print(f"✓ FetalCLIP model loaded on {self.device}")
        return True

    def classify_view(self, image: Image.Image, top_k: int = 5) -> List[Dict]:
        """Classify fetal ultrasound view from preprocessed image."""
        if self.model is None:
            raise RuntimeError("Model not loaded. Call load_model() first.")
        
        top_k = min(top_k, len(self.list_plane))
        
        # Apply model preprocessing (resize to 224, normalize)
        img_tensor = self.preprocess(image).unsqueeze(0).to(self.device)
        
        # Inference
        with torch.no_grad():
            image_features = self.model.encode_image(img_tensor)
            image_features /= image_features.norm(dim=-1, keepdim=True)
        
        # Compute similarity
        similarity = (99.2198 * image_features @ self.text_features.T).softmax(dim=-1)
        values, indices = similarity[0].topk(top_k)
        
        results = []
        for idx, val in zip(indices, values):
            results.append({
                "label": self.list_plane[idx],
                "confidence": round(val.item() * 100, 2)
            })
        
        return results

    def classify_from_file(self, file_bytes: bytes, filename: str, top_k: int = 5) -> Tuple[List[Dict], Dict]:
        """
        Classify from raw file bytes with automatic preprocessing.
        
        Returns:
            Tuple of (predictions, preprocessing_info)
        """
        # Preprocess based on file type
        processed_image, preprocessing_info = preprocess_file(file_bytes, filename)
        
        # Classify
        predictions = self.classify_view(processed_image, top_k)
        
        return predictions, preprocessing_info

    def _get_ga_text_features(self, template: str, pixel_spacing: float) -> torch.Tensor:
        """Generate text features for GA estimation."""
        prompts = []
        for weeks in range(14, 39):
            for days in range(0, 7):
                prompt = template.format(
                    weeks=weeks,
                    day=days,
                    pixel_spacing=f"{pixel_spacing:.2f}"
                )
                prompts.append(prompt)
        
        with torch.no_grad():
            tokens = self.tokenizer(prompts).to(self.device)
            features = self.model.encode_text(tokens)
            features /= features.norm(dim=-1, keepdim=True)
        
        return features

    def _get_unnormalized_dot_products(self, image_features: torch.Tensor, list_text_features: List[torch.Tensor]) -> torch.Tensor:
        """Compute dot products between image and text features."""
        text_features = torch.cat(list_text_features, dim=0)
        text_dot_prods = (100.0 * image_features @ text_features.T)
        
        n_prompts = len(list_text_features)
        n_days = len(list_text_features[0])
        
        text_dot_prods = text_dot_prods.view(image_features.shape[0], n_prompts, n_days)
        text_dot_prods = text_dot_prods.mean(dim=1)
        
        return text_dot_prods

    def _find_median_from_top_n(self, text_dot_prods: np.ndarray, n: int) -> int:
        """Find median index from top N predictions."""
        tmp = [[i, t] for i, t in enumerate(text_dot_prods)]
        tmp = sorted(tmp, key=lambda x: x[1], reverse=True)[:n]
        tmp = sorted(tmp, key=lambda x: x[0])
        return tmp[n // 2][0]

    def _get_biometry_from_ga(self, ga_days: int, biometry_type: str, percentile: str = '0.5') -> float:
        """
        Calculate expected fetal biometry from gestational age using WHO coefficients.
        
        Formula: measurement = exp(b0 + b1*GA + b2*GA² + b3*GA³ + b4*GA⁴)
        where GA is in weeks.
        
        Args:
            ga_days: Gestational age in days
            biometry_type: 'HC', 'AC', or 'FL'
            percentile: '0.025', '0.5', or '0.975'
        
        Returns:
            Expected measurement in mm
        """
        ga_weeks = ga_days / 7
        
        # WHO Fetal Growth Coefficients (from coefficientsGlobalV3.csv)
        WHO_COEFFICIENTS = {
            # Head Circumference (mm)
            'HC': {
                '0.025': [1.59317517131532e+0, 2.9459800552433e-1, -7.3860372566707e-3, 6.56951770216148e-5, 0e+0],
                '0.5':   [2.09924879247164e+0, 2.53373656106037e-1, -6.05647816678282e-3, 5.14256072059917e-5, 0e+0],
                '0.975': [2.50074069629423e+0, 2.20067854715719e-1, -4.93623111462443e-3, 3.89066000946519e-5, 0e+0],
            },
            # Abdominal Circumference (mm)
            'AC': {
                '0.025': [1.19202778944614e+0, 3.14756681991964e-1, -8.01581308902169e-3, 7.51395976546808e-5, 0e+0],
                '0.5':   [1.58552931028045e+0, 2.89936781915424e-1, -7.32651929135797e-3, 6.9261631643994e-5, 0e+0],
                '0.975': [2.03674472691951e+0, 2.57138461817474e-1, -6.34918788914223e-3, 6.0053745113196e-5, 0e+0],
            },
            # Femur Length (mm) - uses all 5 coefficients
            'FL': {
                '0.025': [-7.27187176976836e+0, 1.28298928826162e+0, -5.80601892487905e-2, 1.21314319801879e-3, -9.60171505470123e-6],
                '0.5':   [-5.54922620776446e+0, 1.09559990166124e+0, -5.01310925949098e-2, 1.0678072569586e-3, -8.63970606288493e-6],
                '0.975': [-3.64483930811801e+0, 8.57028131514986e-1, -3.84005685481303e-2, 8.12062784461527e-4, -6.55932416998498e-6],
            },
        }
        
        if biometry_type not in WHO_COEFFICIENTS:
            raise ValueError(f"Unknown biometry type: {biometry_type}")
        if percentile not in WHO_COEFFICIENTS[biometry_type]:
            raise ValueError(f"Unknown percentile: {percentile}")
        
        b0, b1, b2, b3, b4 = WHO_COEFFICIENTS[biometry_type][percentile]
        return np.exp(b0 + b1*ga_weeks + b2*ga_weeks**2 + b3*ga_weeks**3 + b4*ga_weeks**4)

    def estimate_gestational_age(self, image: Image.Image, pixel_size: float, view: str = "brain") -> Dict:
        """Estimate gestational age from preprocessed fetal ultrasound."""
        if self.model is None:
            raise RuntimeError("Model not loaded. Call load_model() first.")
        
        # Calculate effective pixel spacing
        pixel_spacing = max(image.size) / INPUT_SIZE * pixel_size
        
        # Apply model preprocessing
        img_tensor = self.preprocess(image).unsqueeze(0).to(self.device)
        
        # Inference
        with torch.no_grad():
            image_features = self.model.encode_image(img_tensor)
            image_features /= image_features.norm(dim=-1, keepdim=True)
            
            # Get text features for all prompts for the specified view
            view_prompts = GA_TEXT_PROMPTS.get(view, GA_TEXT_PROMPTS["brain"])
            text_features_list = [
                self._get_ga_text_features(template, pixel_spacing)
                for template in view_prompts
            ]
            
            text_dot_prods = self._get_unnormalized_dot_products(image_features, text_features_list)
        
        # Compute prediction
        text_dot_prod = text_dot_prods.detach().cpu().numpy()[0]
        med_idx = self._find_median_from_top_n(text_dot_prod, TOP_N_PROBS)
        pred_day = LIST_GA_IN_DAYS[med_idx]
        
        pred_weeks = pred_day // 7
        pred_days = pred_day % 7
        
        # Map view to biometry type
        VIEW_TO_BIOMETRY = {
            "brain": "HC",
            "abdomen": "AC",
            "femur": "FL"
        }
        biometry_type = VIEW_TO_BIOMETRY.get(view, "HC")
        
        # Compute view-specific biometry percentiles using WHO formulas
        q025 = self._get_biometry_from_ga(pred_day, biometry_type, '0.025')
        q500 = self._get_biometry_from_ga(pred_day, biometry_type, '0.5')
        q975 = self._get_biometry_from_ga(pred_day, biometry_type, '0.975')
        
        # Biometry labels for response
        BIOMETRY_LABELS = {
            "HC": "head_circumference",
            "AC": "abdominal_circumference", 
            "FL": "femur_length"
        }
        biometry_key = BIOMETRY_LABELS.get(biometry_type, "head_circumference")
        
        # Biometry units
        BIOMETRY_UNITS = {
            "HC": "mm",
            "AC": "mm",
            "FL": "mm"
        }
        
        return {
            "gestational_age": {
                "weeks": pred_weeks,
                "days": pred_days,
                "total_days": pred_day
            },
            "view": view,
            biometry_key: {
                "p2_5": round(q025, 2),
                "p50": round(q500, 2),
                "p97_5": round(q975, 2)
            }
        }

    def estimate_ga_from_file(self, file_bytes: bytes, filename: str, pixel_size: float, view: str = "brain") -> Tuple[Dict, Dict]:
        """
        Estimate GA from raw file bytes with automatic preprocessing.
        
        Returns:
            Tuple of (ga_results, preprocessing_info)
        """
        # Preprocess based on file type
        processed_image, preprocessing_info = preprocess_file(file_bytes, filename)
        
        # Use pixel spacing from DICOM if available
        if preprocessing_info["type"] == "dicom":
            pixel_size = preprocessing_info["metadata"].get("pixel_spacing", pixel_size)
        
        # Estimate GA with the specified view
        ga_results = self.estimate_gestational_age(processed_image, pixel_size, view)
        
        return ga_results, preprocessing_info


# Singleton instance
model_service = FetalCLIPService()