#!/usr/bin/env python3
"""
Code Duplication Detector — Issue #162

Finds duplicate functions and code blocks across Python source files.
Reports duplication percentage and outputs a duplication report.

Usage:
    python3 scripts/code_duplication_detector.py --output reports/code_duplication.json
    python3 scripts/code_duplication_detector.py --directory scripts/ --dry-run
    python3 scripts/code_duplication_detector.py --test  # Run built-in test
"""

import argparse
import hashlib
import json
import os
import re
import sys
from collections import defaultdict
from datetime import datetime, timezone
from pathlib import Path
from typing import List, Dict, Tuple, Optional


# ── AST helpers ────────────────────────────────────────────────────────────

def normalize_code(text: str) -> str:
    """Normalize code for comparison: strip comments, normalize whitespace."""
    # Remove comments (both # and docstring triple-quote strings)
    text = re.sub(r'#.*$', '', text, flags=re.MULTILINE)
    text = re.sub(r'""".*?"""', '', text, flags=re.DOTALL)
    text = re.sub(r"'''.*?'''", '', text, flags=re.DOTALL)
    # Normalize whitespace
    text = re.sub(r'\s+', ' ', text).strip()
    return text.lower()


def code_hash(text: str) -> str:
    """SHA256 hash of normalized code for exact duplicate detection."""
    normalized = normalize_code(text)
    return hashlib.sha256(normalized.encode('utf-8')).hexdigest()


# ── Function extraction via AST ────────────────────────────────────────────

class FunctionExtractor:
    """Extract function and method definitions with their full source bodies."""

    def __init__(self, source: str, filepath: str):
        self.source = source
        self.filepath = filepath
        self.lines = source.splitlines()
        self.functions: List[Dict] = []

    def _get_source_segment(self, start_lineno: int, end_lineno: int) -> str:
        """Get source code from start to end line (1-indexed, inclusive)."""
        # AST end_lineno is inclusive
        start_idx = start_lineno - 1
        end_idx = end_lineno
        return '\n'.join(self.lines[start_idx:end_idx])

    def visit(self, tree):
        """Collect all function and async function definitions."""
        for node in ast.walk(tree):
            if isinstance(node, ast.FunctionDef) or isinstance(node, ast.AsyncFunctionDef):
                # Get the full source for this function including decorators
                start = node.lineno
                end = node.end_lineno
                body_source = self._get_source_segment(start, end)

                # Also collect parent class name if this is a method
                class_name = None
                parent = node.parent if hasattr(node, 'parent') else None
                if parent and isinstance(parent, ast.ClassDef):
                    class_name = parent.name

                self.functions.append({
                    'name': node.name,
                    'file': self.filepath,
                    'start_line': start,
                    'end_line': end,
                    'body': body_source,
                    'class_name': class_name,
                    'is_method': class_name is not None,
                })


import ast

class ParentNodeVisitor(ast.NodeVisitor):
    """Annotate nodes with parent references."""
    def __init__(self, parent=None):
        self.parent = parent

    def generic_visit(self, node):
        node.parent = self.parent
        for child in ast.iter_child_nodes(node):
            self.__class__(child).parent = node
        super().generic_visit(node)


def extract_functions_from_file(filepath: str) -> List[Dict]:
    """Extract all function definitions from a Python file."""
    try:
        with open(filepath, 'r', encoding='utf-8', errors='replace') as f:
            source = f.read()
        tree = ast.parse(source, filename=str(filepath))

        # Annotate with parent references
        for node in ast.walk(tree):
            for child in ast.iter_child_nodes(node):
                child.parent = node

        extractor = FunctionExtractor(source, str(filepath))
        extractor.visit(tree)
        return extractor.functions
    except (SyntaxError, UnicodeDecodeError, OSError) as e:
        return []


def scan_directory(directory: str, extensions: Tuple[str, ...] = ('.py',)) -> List[Dict]:
    """Scan directory for Python files and extract all functions."""
    all_functions = []
    path = Path(directory)

    for filepath in path.rglob('*'):
        if filepath.is_file() and filepath.suffix in extensions:
            # Skip common non-source dirs
            parts = filepath.parts
            if any(ex in parts for ex in ('__pycache__', 'node_modules', '.git', 'venv', '.venv', 'dist', 'build')):
                continue
            if filepath.name.startswith('.'):
                continue

            functions = extract_functions_from_file(str(filepath))
            all_functions.extend(functions)

    return all_functions


# ── Duplicate detection ─────────────────────────────────────────────────────

def find_duplicates(functions: List[Dict], similarity_threshold: float = 0.95) -> Dict:
    """
    Find duplicate and near-duplicate functions.

    Returns dict with:
      - exact_duplicates: {hash: [function_info, ...]}
      - near_duplicates: [[function_info, ...], ...]
      - stats: total_functions, unique_exact, exact_dupe_count, near_dupe_count
    """
    # Phase 1: Exact duplicates by code hash
    hash_groups: Dict[str, List[Dict]] = defaultdict(list)
    for func in functions:
        h = code_hash(func['body'])
        hash_groups[h].append(func)

    exact_duplicates = {h: group for h, group in hash_groups.items() if len(group) > 1}
    exact_dupe_count = sum(len(group) - 1 for group in exact_duplicates.values())

    # Phase 2: Near-duplicates (among the unique-by-hash set)
    # We compare token overlap for functions that have different hashes
    unique_by_hash = [funcs[0] for funcs in hash_groups.values()]
    near_duplicate_groups = []

    # Simple token-based similarity
    def tokenize(code: str) -> set:
        return set(re.findall(r'[a-zA-Z_][a-zA-Z0-9_]*', code.lower()))

    i = 0
    while i < len(unique_by_hash):
        group = [unique_by_hash[i]]
        j = i + 1
        while j < len(unique_by_hash):
            tokens_i = tokenize(unique_by_hash[i]['body'])
            tokens_j = tokenize(unique_by_hash[j]['body'])
            if not tokens_i or not tokens_j:
                j += 1
                continue
            intersection = tokens_i & tokens_j
            union = tokens_i | tokens_j
            similarity = len(intersection) / len(union) if union else 0.0

            if similarity >= similarity_threshold:
                group.append(unique_by_hash[j])
                unique_by_hash.pop(j)
            else:
                j += 1

        if len(group) > 1:
            near_duplicate_groups.append(group)
        i += 1

    near_dupe_count = sum(len(g) - 1 for g in near_duplicate_groups)

    stats = {
        'total_functions': len(functions),
        'unique_exact': len(hash_groups),
        'exact_dupe_count': exact_dupe_count,
        'near_dupe_count': near_dupe_count,
        'total_duplicates': exact_dupe_count + near_dupe_count,
    }

    # Calculate duplication percentage based on lines
    total_lines = sum(f['end_line'] - f['start_line'] + 1 for f in functions)
    dupe_lines = 0
    for group in exact_duplicates.values():
        # Count all but one as duplicates
        for f in group[1:]:
            dupe_lines += f['end_line'] - f['start_line'] + 1
    for group in near_duplicate_groups:
        for f in group[1:]:
            dupe_lines += f['end_line'] - f['start_line'] + 1

    stats['total_lines'] = total_lines
    stats['duplicate_lines'] = dupe_lines
    stats['duplication_percentage'] = round((dupe_lines / total_lines * 100) if total_lines else 0, 2)

    return {
        'exact_duplicates': exact_duplicates,
        'near_duplicates': near_duplicate_groups,
        'stats': stats,
    }


# ── Report generation ────────────────────────────────────────────────────────

def generate_report(results: Dict, output_format: str = 'json') -> str:
    """Generate human-readable report from detection results."""
    stats = results['stats']

    if output_format == 'json':
        return json.dumps(results, indent=2, default=str)

    # Text report
    lines = [
        "=" * 60,
        "  CODE DUPLICATION REPORT",
        "=" * 60,
        f"  Total functions scanned:  {stats['total_functions']}",
        f"  Unique functions:         {stats['unique_exact']}",
        f"  Exact duplicates:         {stats['exact_dupe_count']}",
        f"  Near-duplicates:          {stats['near_dupe_count']}",
        f"  Total lines:              {stats['total_lines']}",
        f"  Duplicate lines:          {stats['duplicate_lines']}",
        f"  Duplication %:            {stats['duplication_percentage']}%",
        "",
    ]

    if results['exact_duplicates']:
        lines.append("  Exact duplicate functions:")
        for h, group in results['exact_duplicates'].items():
            first = group[0]
            lines.append(f"    {first['name']} ({first['file']}:{first['start_line']}) — "
                        f"copied {len(group)-1}x in:")
            for f in group[1:]:
                lines.append(f"      → {f['file']}:{f['start_line']}")
        lines.append("")

    if results['near_duplicates']:
        lines.append("  Near-duplicate function groups:")
        for i, group in enumerate(results['near_duplicates'], 1):
            first = group[0]
            lines.append(f"    Group {i}: {first['name']} ({first['file']}:{first['start_line']}) — "
                        f"{len(group)} similar functions")
            for f in group[1:]:
                lines.append(f"      → {f['file']}:{f['start_line']}")
        lines.append("")

    lines.append("=" * 60)
    return '\n'.join(lines)


# ── CLI ─────────────────────────────────────────────────────────────────────

def main():
    parser = argparse.ArgumentParser(description="Code Duplication Detector")
    parser.add_argument('--directory', default='.',
                        help='Directory to scan (default: current directory)')
    parser.add_argument('--output', help='Output file for JSON report')
    parser.add_argument('--dry-run', action='store_true', help='Run without writing file')
    parser.add_argument('--threshold', type=float, default=0.95,
                        help='Similarity threshold for near-dupes (default: 0.95)')
    parser.add_argument('--json', action='store_true', help='JSON output to stdout')
    parser.add_argument('--test', action='store_true', help='Run built-in test')
    args = parser.parse_args()

    if args.test:
        _run_test()
        return

    # Scan
    functions = scan_directory(args.directory)

    # Detect duplicates
    results = find_duplicates(functions, similarity_threshold=args.threshold)
    stats = results['stats']

    # Output
    if args.json:
        print(json.dumps(results, indent=2, default=str))
    else:
        print(generate_report(results, output_format='text'))

    # Write file if requested
    if args.output and not args.dry_run:
        os.makedirs(os.path.dirname(args.output) or '.', exist_ok=True)
        with open(args.output, 'w') as f:
            json.dump(results, f, indent=2, default=str)
        print(f"\nReport written to: {args.output}")

    # Summary for burn protocol
    print(f"\n✓ Detection complete: {stats['exact_dupe_count']} exact + "
          f"{stats['near_dupe_count']} near duplicates found "
          f"({stats['duplication_percentage']}% duplication)")


def _run_test():
    """Built-in smoke test."""
    import tempfile
    import os

    with tempfile.TemporaryDirectory() as tmpdir:
        # Create test files with duplicate code
        f1 = Path(tmpdir) / 'mod1.py'
        f1.write_text('''
def hello():
    print("hello world")

def duplicated_function():
    x = 1
    y = 2
    return x + y

def unique_func():
    return 42
''')

        f2 = Path(tmpdir) / 'mod2.py'
        f2.write_text('''
def duplicated_function():
    x = 1
    y = 2
    return x + y

def another_unique():
    return "different"
''')

        functions = scan_directory(tmpdir)
        results = find_duplicates(functions)

        stats = results['stats']
        assert stats['exact_dupe_count'] >= 1, "Should find at least 1 exact duplicate"
        assert stats['total_functions'] >= 4, "Should find at least 4 functions"

        # Check duplication percentage is calculated
        assert 'duplication_percentage' in stats
        print(f"\n✓ Test passed: {stats['total_functions']} functions, "
              f"{stats['exact_dupe_count']} exact duplicates, "
              f"{stats['duplication_percentage']}% duplication")


if __name__ == '__main__':
    main()