import json
from pathlib import Path
from typing import List, Dict, Any


def read_file(path: str, supported_formats: str = ".json") -> dict:
    """Read a file and return its content as a string

    Args:
        path (str): the path to the file to read
        supported_formats (str, optional): the supported file formats. Defaults to ".json".

    Returns:
        dict: the json content of the file

    Raises:
        FileNotFoundError: if the file does not exist
        ValueError: if the file format is not supported
    """

    path = Path(path)

    # check if the file exists and is a file
    if not path.exists() or not path.is_file():
        raise FileNotFoundError(f"File {path} not found")

    # check if the file format is supported
    if path.suffix not in supported_formats:
        raise ValueError(f"File format {path.suffix} not supported")

    with path.open("r") as file:
        file_content = json.load(file)

    return file_content


def create_directory(path: str) -> None:
    """Create a directory if it does not exist

    Args:
        path (str): the path to the directory to create
    """

    path = Path(path)

    if not path.exists():
        path.mkdir(parents=True, exist_ok=True)


def read_file_paths(path: str, supported_formats: List[str] = [".jpg"]) -> List[str]:
    """Read files in a directory and return their content as a list of strings

    Args:
        path (str): the path to the directory containing the file paths to read
        supported_formats (List[str], optional): the supported file formats. Defaults to [".jpg"].

    Returns:
        list: list of valid file paths

    Raises:
        FileNotFoundError: if the directory does not exist
    """

    path = Path(path)

    # check if the directory exists and is a directory
    if not path.exists() or not path.is_dir():
        raise FileNotFoundError(f"Directory {path} not found")

    # get the list of files in the directory
    file_paths = [file for file in path.iterdir() if file.is_file()]

    # filter file paths based on the supported formats
    if supported_formats:
        file_paths = [file for file in file_paths if file.suffix in supported_formats]
    else:
        file_paths = []

    return file_paths


def check_dataset_format(data: dict, image_key: str, is_prediction: bool = False) -> bool:
    """Check the format of the dataset

    Args:
        data (dict): the gt/prediction dataset to check
        image_key (str): the image name acting as the key in the dataset
        is_prediction (bool): if True, skip entries with errors instead of raising

    Returns:
        bool: True if valid, False if entry has error (only when is_prediction=True)

    Raises:
        ValueError: if a key is missing in the dataset (only when is_prediction=False)
    """
    # For predictions, allow entries with "error" key - they will be skipped
    if is_prediction and "error" in data[image_key]:
        return False
    
    if data[image_key].get("elements") is None:
        if is_prediction:
            return False
        raise ValueError(
            f"{image_key} does not have 'elements' key in the json file. "
            "Check if you are passing the correct data."
        )

    elements = data[image_key]["elements"]
    for elem in elements:
        if elem.get("category") is None:
            if is_prediction:
                return False
            raise ValueError(
                f"{image_key} does not have 'category' key in the ground truth file. "
                "Check if you are passing the correct data."
            )

        if elem.get("content") is None:
            if is_prediction:
                return False
            raise ValueError(
                f"{image_key} does not have 'content' key in the ground truth file. "
                "Check if you are passing the correct data."
            )
        else:
            content = elem["content"]
            if content.get("text") is None:
                if is_prediction:
                    return False
                raise ValueError(
                    f"{image_key} does not have 'text' key in the ground truth file. "
                    "Check if you are passing the correct data."
                )
    
    return True


def check_data_validity(gt_data: dict, pred_data: dict) -> tuple:
    """Check the validity of the ground truth and prediction data

    Args:
        gt_data (dict): the ground truth data
        pred_data (dict): the prediction data

    Returns:
        tuple: (valid_keys, error_keys, missing_keys) - lists of valid, error, and missing prediction keys

    Raises:
        ValueError: if the ground truth or prediction data is invalid
    """

    if not gt_data:
        raise ValueError("Ground truth data is empty")

    if not pred_data:
        raise ValueError("Prediction data is empty")

    # Check ground truth format (must be valid)
    for image_key in gt_data.keys():
        check_dataset_format(gt_data, image_key, is_prediction=False)

    # Check prediction format (allow errors)
    valid_keys = []
    error_keys = []
    missing_keys = []
    
    for image_key in gt_data.keys():
        pred_elem = pred_data.get(image_key)
        if pred_elem is None:
            missing_keys.append(image_key)
        elif check_dataset_format(pred_data, image_key, is_prediction=True):
            valid_keys.append(image_key)
        else:
            error_keys.append(image_key)
    
    return valid_keys, error_keys, missing_keys

def _merge_bboxes(bboxes: List[List[float]]) -> List[float]:
    """
    Merge multiple bounding boxes into a single union bbox.
    
    Args:
        bboxes: List of bboxes in 4-corner format [{'x': x1, 'y': y1}, {'x': x2, 'y': y1}, {'x': x2, 'y': y2}, {'x': x1, 'y': y2}]
    
    Returns:
        Union bbox covering all input boxes: [x1_min, y1_min, x2_max, y2_max]
    """
    if not bboxes:
        return [0.0, 0.0, 0.0, 0.0]
    x1_min = min(bbox[0]['x'] for bbox in bboxes)
    y1_min = min(bbox[1]['y'] for bbox in bboxes)
    x2_max = max(bbox[2]['x'] for bbox in bboxes)
    y2_max = max(bbox[3]['y'] for bbox in bboxes)
    
    return [x1_min, y1_min, x2_max, y2_max]

def preprocess_merged_tables(data: Dict[str, Any]) -> Dict[str, Any]:
    """
    Preprocess data to merge tables according to merged_tables information.
    
    For each document with merged_tables:
    1. Remove child tables from elements list
    2. Keep the representative (first) table
    3. Replace representative table's HTML with merged_html
    4. Update representative table's BBox to union of all child bboxes
    
    Args:
        data: Dictionary of document data in OAC format
    
    Returns:
        Preprocessed data with merged tables
    """
    processed_data = {}
    
    for doc_key, doc in data.items():
        if not isinstance(doc, dict):
            processed_data[doc_key] = doc
            continue
        
        # Deep copy to avoid modifying original
        doc_copy = json.loads(json.dumps(doc))
        
        merged_tables = doc_copy.get("merged_tables", [])
        if not merged_tables:
            # No merging needed
            processed_data[doc_key] = doc_copy
            continue
        
        elements = doc_copy.get("elements", [])
        if not elements:
            processed_data[doc_key] = doc_copy
            continue
        
        # Build element "page-id" to index mapping for quick lookup
        # Format: "page-id" (e.g., "1-7") -> element index
        key_to_idx = {}
        for idx, elem in enumerate(elements):
            page = elem.get("page")
            elem_id = elem.get("id")
            if page is not None and elem_id is not None:
                key = f"{int(page)}-{int(elem_id)}"
                key_to_idx[key] = idx
    
        # Track indices to remove (child tables that are merged)
        indices_to_remove = set()
        
        # Process each merge group
        for merge_group in merged_tables:
            table_ids = merge_group.get("table_ids", [])
            if len(table_ids) < 2:
                continue
            
            # table_ids are strings in format "page-id" (e.g., "1-7", "2-11")
            # No conversion needed, use as-is
            table_ids = sorted([str(tid) for tid in table_ids])
            
            # Get merged HTML - check both 'html' and 'table_html' keys
            merged_html = merge_group.get("table_html") or merge_group.get("html")
            
            # Find representative table (first one in the list)
            representative_id = table_ids[0]
            representative_idx = key_to_idx.get(representative_id)
            
            # Collect bboxes from all tables in the merge group
            bboxes_to_merge = []
            for tid in table_ids:
                idx = key_to_idx.get(tid)
                elem = elements[idx]
                bboxes_to_merge.append(elem.get("coordinates"))
                if tid != representative_id:
                    indices_to_remove.add(idx)
            
            # Update representative table
            elements[representative_idx]["content"]["html"] = merged_html
            elements[representative_idx]["coordinates"] = _merge_bboxes(bboxes_to_merge)
        
        # Remove child tables (in reverse order to maintain indices)
        new_elements = [
            elem for idx, elem in enumerate(elements)
            if idx not in indices_to_remove
        ]
        doc_copy["elements"] = new_elements
        
        # Remove merged_tables key as it's been applied
        doc_copy.pop("merged_tables", None)
        
        processed_data[doc_key] = doc_copy
    
    return processed_data