src/table_evaluation.py

"""
Most of the code in this file is derived from the paper "Image-based table recognition: data, model, and evaluation".
The original paper can be accessed at: https://arxiv.org/pdf/1911.10683.
The code is available at: https://github.com/ibm-aur-nlp/PubTabNet.
A slight modification has been added to the code to improve the evaluation process.
"""

import re
import distance
import numpy as np
from concurrent.futures import ThreadPoolExecutor
try:
    from scipy.optimize import linear_sum_assignment
except Exception as _e:
    linear_sum_assignment = None

from lxml import etree, html
from collections import deque
from apted.helpers import Tree
from apted import APTED, Config


class TableTree(Tree):
    """Table Tree class for APTED"""
    def __init__(self, tag, colspan=None, rowspan=None, content=None, *children):
        self.tag = tag
        self.colspan = colspan
        self.rowspan = rowspan
        self.content = content
        self.children = list(children)

    def bracket(self):
        """Show tree using brackets notation"""
        if self.tag == 'td':
            result = '"tag": %s, "colspan": %d, "rowspan": %d, "text": %s' % \
                     (self.tag, self.colspan, self.rowspan, self.content)
        else:
            result = '"tag": %s' % self.tag
        for child in self.children:
            result += child.bracket()
        return "{{{}}}".format(result)

    def visualize(self, indent=0, prefix="", is_last=True):
        """Visualize tree structure in ASCII art format
        
        Args:
            indent (int): Current indentation level
            prefix (str): Prefix for tree branches
            is_last (bool): Whether this is the last child of its parent
            
        Returns:
            str: ASCII tree visualization
        """
        # Prepare node information
        if self.tag == 'td':
            content_preview = ''
            if self.content:
                content_str = ''.join(self.content) if isinstance(self.content, list) else str(self.content)
                content_preview = content_str[:30] + '...' if len(content_str) > 30 else content_str
                content_preview = f' "{content_preview}"' if content_preview else ''
            
            node_info = f"{self.tag}"
            attrs = []
            if self.colspan and self.colspan > 1:
                attrs.append(f"colspan={self.colspan}")
            if self.rowspan and self.rowspan > 1:
                attrs.append(f"rowspan={self.rowspan}")
            if attrs:
                node_info += f" [{', '.join(attrs)}]"
            if content_preview:
                node_info += content_preview
        else:
            node_info = self.tag
        
        # Build the tree line
        if indent == 0:
            result = f"{node_info}\n"
        else:
            connector = "└── " if is_last else "├── "
            result = f"{prefix}{connector}{node_info}\n"
        
        # Process children
        for i, child in enumerate(self.children):
            is_last_child = (i == len(self.children) - 1)
            if indent == 0:
                child_prefix = ""
            else:
                child_prefix = prefix + ("    " if is_last else "│   ")
            result += child.visualize(indent + 1, child_prefix, is_last_child)
        
        return result

class CustomConfig(Config):
    """Custom Configuration for APTED"""
    @staticmethod
    def maximum(*sequences):
        """Get maximum possible value"""
        return max(map(len, sequences))

    def normalized_distance(self, *sequences):
        """Get distance from 0 to 1"""
        return float(distance.levenshtein(*sequences)) / self.maximum(*sequences)

    def rename(self, node1, node2):
        """Compares attributes of trees"""
        if (node1.tag != node2.tag) or \
                (node1.colspan != node2.colspan) or \
                (node1.rowspan != node2.rowspan):
            return 1.
        if node1.tag == 'td':
            if node1.content or node2.content:
                return self.normalized_distance(
                    node1.content, node2.content
                )
        return 0.


class TEDSEvaluator(object):
    """Tree Edit Distance basead Similarity"""
    def __init__(
        self,
        structure_only=False,
        n_jobs=1,
        ignore_nodes=None,
    ):
        assert isinstance(n_jobs, int) and (n_jobs >= 1), (
            'n_jobs must be an integer greather than 1'
        )
        self.structure_only = structure_only
        self.n_jobs = n_jobs
        self.ignore_nodes = ignore_nodes
        self.__tokens__ = []

    def tokenize(self, node):
        """Tokenizes table cells"""
        self.__tokens__.append('<%s>' % node.tag)
        if node.text is not None:
            self.__tokens__ += list(node.text)
        for n in node.getchildren():
            self.tokenize(n)
        if node.tag != 'unk':
            self.__tokens__.append('</%s>' % node.tag)
        if node.tag != 'td' and node.tail is not None:
            self.__tokens__ += list(node.tail)

    def load_html_tree(self, node, parent=None):
        """Converts HTML tree to the format required by apted
        This version treats nested tables as separate tree nodes rather than content.
        """
        global __tokens__
        if node.tag == 'td':
            # Check if td contains nested table(s)
            nested_tables = [n for n in node.getchildren() if n.tag == 'table']
            
            if nested_tables:
                # td has nested table(s) - create td node and add tables as children
                if self.structure_only:
                    cell = []
                else:
                    self.__tokens__ = []
                    if node.text is not None:
                        self.__tokens__ += list(node.text)
                    for n in node.getchildren():
                        if n.tag != 'table':
                            self.tokenize(n)
                        if n.tail is not None:
                            self.__tokens__ += list(n.tail)
                    cell = self.__tokens__.copy() if self.__tokens__ else []
                
                new_node = TableTree(
                    node.tag,
                    int(node.attrib.get('colspan', '1')),
                    int(node.attrib.get('rowspan', '1')),
                    cell, *deque()
                )
                # Add nested tables as children
                if parent is not None:
                    parent.children.append(new_node)
                for table in nested_tables:
                    self.load_html_tree(table, new_node)
            else:
                if self.structure_only:
                    cell = []
                else:
                    self.__tokens__ = []
                    self.tokenize(node)
                    cell = self.__tokens__[1:-1].copy()
                new_node = TableTree(
                    node.tag,
                    int(node.attrib.get('colspan', '1')),
                    int(node.attrib.get('rowspan', '1')),
                    cell, *deque()
                )
                if parent is not None:
                    parent.children.append(new_node)
        else:
            new_node = TableTree(node.tag, None, None, None, *deque())
            if parent is not None:
                parent.children.append(new_node)
            for n in node.getchildren():
                self.load_html_tree(n, new_node)
        if parent is None:
            return new_node

    def evaluate(self, pred, true):
        """Computes TEDS score between the prediction and the ground truth of a given sample"""
        if (not pred) or (not true):
            return 0.0

        parser = html.HTMLParser(remove_comments=True, encoding='utf-8')
        pred = html.fromstring(pred, parser=parser)
        true = html.fromstring(true, parser=parser)
        if pred.xpath('body/table') and true.xpath('body/table'):
            pred_tables = pred.xpath('body/table')
            true_tables = true.xpath('body/table')
            # Default behavior: if multiple tables present, compare concatenated wrappers by matching counts
            # Here keep legacy single-table by choosing the first only when both are singletons
            if len(pred_tables) == 1 and len(true_tables) == 1:
                pred = pred_tables[0]
                true = true_tables[0]
            else:
                # Fallback: wrap the entire body as a single root for structural comparison
                pred = pred.xpath('body')[0]
                true = true.xpath('body')[0]
            if self.ignore_nodes:
                etree.strip_tags(pred, *self.ignore_nodes)
                etree.strip_tags(true, *self.ignore_nodes)
            n_nodes_pred = len(pred.xpath('.//*'))
            n_nodes_true = len(true.xpath('.//*'))
            n_nodes = max(n_nodes_pred, n_nodes_true)
            tree_pred = self.load_html_tree(pred)
            tree_true = self.load_html_tree(true)
            distance = APTED(tree_pred, tree_true, CustomConfig()).compute_edit_distance()
            return 1.0 - (float(distance) / n_nodes)
        else:
            return 0.0


def get_table_contents(text):
    # Regular expression to capture content within <table ...> and </table> tags
    table_contents = re.findall(r'<table[^>]*?>(.*?)</table>', text, flags=re.DOTALL)

    if len(table_contents) == 0:
        table_contents = [text]

    return table_contents


def extract_tables(data : dict) -> str:
    """Extract tables from the dictionary data.

    Args:
        data (dict): The data to extract tables from.

    Returns:
        str: The extracted tables from the data and a boolean indicating if the data has a table.
    """

    # return as is if data is a string
    html = '<html><body>'
    for elem in data['elements']:
        if elem['category'].lower() == 'table':
            table_html_elements = get_table_contents(elem['content']['html'])

            for table_html in table_html_elements:
                html += f'<table>{table_html}</table>'

    html += '</body></html>'

    return html


def extract_table_list(data: dict):
    """Return a list of individual <table>...</table> HTML snippets from a doc dict.

    Each returned entry is a complete single-table HTML fragment (wrapped with <table> tags).
    """
    tables: list = []
    elements = (data or {}).get('elements', []) or []
    for elem in elements:
        try:
            category = (elem or {}).get('category', '')
            if isinstance(category, str) and category.lower() == 'table':
                html_contents = ((elem or {}).get('content', {}) or {}).get('html') or ''
                if isinstance(html_contents, str):
                    tables.append(html_contents)
                elif isinstance(html_contents, list):
                    for html_content in html_contents:
                        if isinstance(html_content, str):
                            tables.append(html_content)
        except Exception:
            continue
    return tables

def _simplify_single_table(table_elem):
    """
    Simplify a single table element. (Recursive handling of nested tables)
    
    Args:
        table_elem: lxml element - MUST be a <table> element
    
    Returns:
        lxml element: The simplified table element
    """

    # 1. Remove all attributes of the table element
    table_elem.attrib.clear()
    
    # 2. Remove thead, tbody, tfoot wrappers (keep their children)
    #    Only process wrappers that belong to this table, not nested tables
    for wrapper_tag in ('thead', 'tbody', 'tfoot'):
        # Find all wrappers but only process those directly under this table
        for wrapper in list(table_elem.xpath(f'./{wrapper_tag}')):
            parent = wrapper.getparent()
            index = list(parent).index(wrapper)
            for child in list(wrapper):
                parent.insert(index, child)
                index += 1
            parent.remove(wrapper)

    # 3. Get direct tr children, excluding those in nested tables
    direct_rows = []
    for tr in table_elem.xpath('.//tr'):
        # Find the closest table ancestor
        parent = tr.getparent()
        while parent is not None and parent.tag != 'table':
            parent = parent.getparent()
        # Only include if the closest table ancestor is our table_elem
        if parent is table_elem:
            direct_rows.append(tr)
    
    # 4. Remove attributes of the tr and cell except for colspan and rowspan
    for tr in direct_rows:
        tr.attrib.clear()    
        for cell in tr:
            if cell.tag in ('th', 'td'): # Replace th with td
                if cell.tag == 'th':
                    cell.tag = 'td'
                
                # Keep only colspan and rowspan attributes
                new_attrib = {}
                if 'colspan' in cell.attrib:
                    new_attrib['colspan'] = cell.attrib['colspan']
                if 'rowspan' in cell.attrib:
                    new_attrib['rowspan'] = cell.attrib['rowspan']
                cell.attrib.clear()
                cell.attrib.update(new_attrib)
                
                # Check if there is a nested table
                nested_tables = cell.xpath('.//table')
                
                # Recursively handle nested tables
                for nested in nested_tables:
                    _simplify_single_table(nested)
                
                # Remove unnecessary tags (keep content, remove tag wrapper)
                # These tags are stripped but their text content is preserved
                unnecessary_tags = [
                    'div', 'span', 'p', 'br', 'b', 'i', 'strong', 'em', 'u', 
                    'font', 'a', 'sup', 'sub', 'small', 'big', 'center',
                    'label', 'section', 'article', 'header', 'footer', 'nav'
                ]
                etree.strip_tags(cell, *unnecessary_tags)

                # Get text content (include text of all sub-tags)
                text_content = cell.text_content()
                if text_content:
                    text_content = text_content.strip().replace('\xa0', '').replace('&nbsp;', '').strip()
                
                # If completely empty, set it as an empty cell (no text and no nested table)
                if (not text_content or text_content == '') and not nested_tables:
                    for child in list(cell):
                        cell.remove(child)
                    cell.text = ''
                    cell.tail = None
    
    return table_elem

def preprocess_table(table_html_list):
    """
    Preprocess the HTML table list to the basic structure.
    Recursively handle nested tables (TINT).

    Args:
        table_html_list (list): List of HTML table strings

    Returns:
        list: Simplified list of HTML table strings
    """
    preprocessed_tables = []
    
    for html_string in table_html_list:
        try:
            parser = html.HTMLParser(remove_comments=True, encoding='utf-8')
            
            # Extract outermost <table>...</table> if exists, otherwise wrap with <table>
            table_start = html_string.find('<table')
            table_end = html_string.rfind('</table>')
            if table_start != -1 and table_end != -1:
                # Extract the outermost table
                html_string = html_string[table_start:table_end + len('</table>')]
            else:
                # No table tag found, wrap content with <table>
                html_string = f'<table>{html_string}</table>'
            
            root = html.fromstring(html_string, parser=parser)
            
            # root itself might be the table element
            if root.tag == 'table':
                table = root
            else:
                table = root.xpath('.//table')[0]
    
            # Simplify the table
            table = _simplify_single_table(table)

            table_string = etree.tostring(table, encoding='unicode', method='html')
            table_string = '<html><body>' + re.sub(r'>\s+<', '><', table_string).strip() + '</body></html>'
            preprocessed_tables.append(table_string)
            
        except Exception as e:
            print(f"[WARNING] Failed to simplify table: {e}, {html_string}")
            preprocessed_tables.append(html_string)
    
    return preprocessed_tables

def _compute_single_pair_score(args):
    """Helper function to compute score for a single (i, j) pair."""
    i, j, gt_table, pred_table, evaluator = args
    try:
        s = float(evaluator.evaluate(pred_table, gt_table))
    except Exception:
        s = 0.0
    return i, j, s

def _compute_teds_s_score(args):
    """Helper function to compute TEDS-S score for a matched pair."""
    gt_table, pred_table, evaluator = args
    try:
        return float(evaluator.evaluate(pred_table, gt_table))
    except Exception:
        return 0.0

def _hungarian_match_tables_by_score(
    gt_tables: list,
    pred_tables: list,
    evaluator: TEDSEvaluator,
    min_match_score: float = 0.1,
    max_workers: int = 1,
):
    """Hungarian one-to-one matching of GT and Pred tables using the provided evaluator.

    Returns list of tuples: (gt_idx, pred_idx, score)
    """
    matches: list = []
    if not gt_tables or not pred_tables:
        return matches
    if linear_sum_assignment is None:
        # Fallback: no scipy available, return empty
        return matches

    n = max(len(gt_tables), len(pred_tables))
    cost = np.zeros((n, n), dtype=float)
    score_mat = np.zeros((n, n), dtype=float)

    # Initialize all costs to 1.0 (dummy pairs)
    cost.fill(1.0)

    # Build list of valid (i, j) pairs to compute
    tasks = [
        (i, j, gt_tables[i], pred_tables[j], evaluator)
        for i in range(len(gt_tables))
        for j in range(len(pred_tables))
    ]

    # Use ThreadPoolExecutor for parallel score computation within this process
    if tasks:
        with ThreadPoolExecutor(max_workers=max_workers) as executor:
            results = list(executor.map(_compute_single_pair_score, tasks))
        
        for i, j, s in results:
            score_mat[i, j] = s
            cost[i, j] = 1.0 - s

    row_ind, col_ind = linear_sum_assignment(cost)

    for i, j in zip(row_ind, col_ind):
        if i < len(gt_tables) and j < len(pred_tables):
            s = float(score_mat[i, j])
            if s >= min_match_score:
                matches.append((i, j, s))
    return matches


def has_table_content(html_data : str) -> bool:
    """Check if the table has content between <html><body> and </body></html>.

    Args:
        html_data (str): The html data to check.
    Returns:
        bool: True if the table has content, False otherwise
    """
    has_content = True
    if html_data.replace('<html><body>', '').replace('</body></html>', '') == '':
        has_content = False

    return has_content


def prepare_table_dataset(gt_data, pred_data):
    """Prepare the tables for evaluation.
    Args:
        gt_data (dict): The ground truth dataset to evaluate.
        pred_data (dict): The predicted dataset to evaluate.

    Returns:
        tuple (list, list): The list of ground truth and predicted tables.
    """

    gt_table_list = []
    pred_table_list = []
    for image_key in gt_data.keys():

        gt_elem = gt_data.get(image_key)
        pred_elem = pred_data.get(image_key)

        gt_tables = extract_tables(gt_elem)
        pred_tables = extract_tables(pred_elem)

        if not has_table_content(gt_tables):
            continue

        gt_table_list.append(gt_tables)
        pred_table_list.append(pred_tables)

    return gt_table_list, pred_table_list


def evaluate_table(
    gt : dict,
    pred : dict,
    min_match_score: float = 0.0,
    max_workers: int = 1,
) -> tuple:
    """Evaluate the table of the gt against the pred.

    Args:
        gt (dict): The gt layout to evaluate.
        pred (dict): The pred layout to evaluate against.

    Returns:
        tuple(float, float, float, dict): The Table F1, TEDS, TEDS-S scores and per-image results.
    """
    avg_teds_score = 0.0
    avg_teds_s_score = 0.0

    eval_s = TEDSEvaluator(structure_only=True)
    eval_full = TEDSEvaluator(structure_only=False)

    n_gt_tables = 0
    n_pred_tables = 0
    n_matched_tables = 0
    teds_scores = []
    teds_s_scores = []
    per_image_scores = {}

    for image_key in gt.keys():
        gt_elem = gt.get(image_key)
        pred_elem = pred.get(image_key)
        gt_tables = extract_table_list(gt_elem)
        pred_tables = extract_table_list(pred_elem)

        n_gt_tables += len(gt_tables)
        n_pred_tables += len(pred_tables)
        
        # Initialize per-image result
        per_image_scores[image_key] = {
            "n_gt_tables": int(len(gt_tables)),
            "n_pred_tables": int(len(pred_tables)),
            "n_matched_tables": 0,
            "matched_tables": []
        }
        
        if not gt_tables and not pred_tables:
            continue

        # Simplify tables before comparison
        gt_tables = preprocess_table(gt_tables)
        pred_tables = preprocess_table(pred_tables)
        # TEDS (structure+content) for matching via Hungarian
        matches = _hungarian_match_tables_by_score(
            gt_tables, pred_tables, eval_full, 
            min_match_score=min_match_score,
            max_workers=max_workers,
            )

        if matches:
            n_matched_tables += len(matches)
            per_image_scores[image_key]["n_matched_tables"] = int(len(matches))
            
            # Extract TEDS scores from matches
            teds_scores.extend([s for _, _, s in matches])
            
            # Parallel computation of TEDS-S scores for matched pairs
            teds_s_tasks = [(gt_tables[i], pred_tables[j], eval_s) for i, j, _ in matches]
            with ThreadPoolExecutor(max_workers=max_workers) as executor:
                teds_s_results = list(executor.map(_compute_teds_s_score, teds_s_tasks))
            
            # Store results and per-image details
            for (i, j, teds_score), teds_s_score in zip(matches, teds_s_results):
                teds_s_scores.append(teds_s_score)
                
                per_image_scores[image_key]["matched_tables"].append({
                    "gt_table_idx": int(i),
                    "pred_table_idx": int(j),
                    "teds_score": float(teds_score),
                    "teds_s_score": float(teds_s_score)
                })

    if len(teds_scores) > 0:
        table_f1_score = 2 * n_matched_tables / (n_gt_tables + n_pred_tables)
        avg_teds_score = sum(teds_scores) / len(teds_scores)
        avg_teds_s_score = sum(teds_s_scores) / len(teds_s_scores)
    else: 
        print('[Warning] No matched tables found in the ground truth and prediction datasets.')
        table_f1_score = 0.0
        avg_teds_score = 0.0
        avg_teds_s_score = 0.0
        

    return table_f1_score, avg_teds_score, avg_teds_s_score, per_image_scores