Pattern Compilation and Utilities

def compile(pattern, flags=0, ignore_unused=False, cache_pattern=None, **kwargs):
    """
    Compile a regular expression pattern, returning a Pattern object.
    
    Args:
        pattern (str): Regular expression pattern to compile
        flags (int, optional): Regex flags to modify pattern behavior
        ignore_unused (bool, optional): Ignore unused keyword arguments
        cache_pattern (bool, optional): Override default caching behavior
        **kwargs: Additional compilation arguments (version, etc.)
    
    Returns:
        Pattern: Compiled pattern object with matching methods
    """

import regex

# Basic pattern compilation
pattern = regex.compile(r'\b\w+@\w+\.\w+\b')
emails = pattern.findall('Contact: user@example.com or admin@site.org')
print(emails)  # ['user@example.com', 'admin@site.org']

# Compile with flags
pattern = regex.compile(r'hello\s+world', regex.IGNORECASE | regex.VERBOSE)
result = pattern.search('HELLO   WORLD')
print(result.group())  # 'HELLO   WORLD'

# Reuse compiled pattern for efficiency
email_pattern = regex.compile(r'\b[\w.-]+@[\w.-]+\.\w+\b')
for line in file_lines:
    if email_pattern.search(line):
        process_line_with_email(line)

# Compile with version specification
v1_pattern = regex.compile(r'(?V1)pattern', regex.IGNORECASE)  # Enhanced mode
v0_pattern = regex.compile(r'(?V0)pattern', regex.IGNORECASE)  # Legacy mode

# Fuzzy pattern compilation
fuzzy_pattern = regex.compile(r'(?e)(search){e<=2}', regex.BESTMATCH)
result = fuzzy_pattern.search('serch text searching')
print(result.group())  # Best fuzzy match

# Control pattern caching
pattern = regex.compile(r'\d+', cache_pattern=False)  # Don't cache this pattern

def template(pattern, flags=0):
    """
    Compile a template pattern, returning a Pattern object.
    
    Args:
        pattern (str): Template pattern to compile
        flags (int, optional): Regex flags to modify template behavior
    
    Returns:
        Pattern: Compiled template pattern object
    """

import regex

# Basic template compilation
template_pattern = regex.template(r'\1-\2-\3')
result = regex.sub(r'(\d{4})(\d{2})(\d{2})', template_pattern, '20231225')
print(result)  # '2023-12-25'

# Named group template
template_pattern = regex.template(r'\g<last>, \g<first>')
pattern = r'(?P<first>\w+) (?P<last>\w+)'
result = regex.sub(pattern, template_pattern, 'John Doe')
print(result)  # 'Doe, John'

# Template with flags
template_pattern = regex.template(r'\1:\2', regex.IGNORECASE)

def escape(pattern, special_only=True, literal_spaces=False):
    """
    Escape a string for use as a literal in a pattern.
    
    Args:
        pattern (str): String to escape for literal use
        special_only (bool, optional): Escape only special regex characters
        literal_spaces (bool, optional): Treat spaces as literal (don't escape)
    
    Returns:
        str: Escaped string safe for use in regex patterns
    """

import regex

# Basic string escaping
literal_text = "Price: $19.99 (special!)"
escaped = regex.escape(literal_text)
print(escaped)  # 'Price:\\ \\$19\\.99\\ \\(special!\\)'

# Use escaped string in pattern
pattern = r'Item: ' + regex.escape("$19.99 (sale)")
result = regex.search(pattern, 'Item: $19.99 (sale) - Buy now!')
print(result.group())  # 'Item: $19.99 (sale)'

# Escape only special characters
text = "hello.world*test"
escaped = regex.escape(text, special_only=True)
print(escaped)  # 'hello\\.world\\*test'

# Control space escaping
text = "hello world test"
escaped_with_spaces = regex.escape(text, literal_spaces=False)
escaped_literal_spaces = regex.escape(text, literal_spaces=True)
print(escaped_with_spaces)    # 'hello\\ world\\ test'
print(escaped_literal_spaces) # 'hello world test'

# Build patterns with literals and regex parts
user_input = "user@domain.com"
pattern = r'\b' + regex.escape(user_input) + r'\b'
result = regex.search(pattern, 'Email: user@domain.com is valid')
print(result.group())  # 'user@domain.com'

def purge():
    """Clear the regular expression cache."""

def cache_all(value=True):
    """
    Set/get whether to cache all patterns, even those compiled explicitly.
    
    Args:
        value (bool or None): True to enable caching all, False to disable,
                             None to return current setting
    
    Returns:
        bool or None: Current caching setting when value is None
    """

import regex

# Clear the pattern cache
regex.purge()

# Check current cache setting
current_setting = regex.cache_all(None)
print(f"Current cache setting: {current_setting}")

# Enable caching of all patterns
regex.cache_all(True)

# Disable caching of explicitly compiled patterns
regex.cache_all(False)

# Typical cache management workflow
def process_many_patterns(patterns, text):
    # Clear cache before processing many patterns
    regex.purge()
    
    # Disable caching to prevent memory buildup
    old_setting = regex.cache_all(None)
    regex.cache_all(False)
    
    try:
        results = []
        for pattern in patterns:
            compiled = regex.compile(pattern)
            results.append(compiled.findall(text))
        return results
    finally:
        # Restore original cache setting
        regex.cache_all(old_setting)

# Monitor cache usage in long-running applications
def periodic_cache_cleanup():
    import gc
    regex.purge()  # Clear regex cache
    gc.collect()   # Run garbage collection

# Version 0 (legacy re-compatible)
v0_pattern = regex.compile(r'(?V0)\w+', regex.IGNORECASE)

# Version 1 (enhanced behavior with full case-folding)  
v1_pattern = regex.compile(r'(?V1)\w+', regex.IGNORECASE)

# Default version control
regex.DEFAULT_VERSION = regex.VERSION1  # Set global default

# Basic fuzzy compilation
fuzzy = regex.compile(r'(?e)(hello){e<=2}')  # Allow up to 2 errors

# Best match fuzzy compilation
best_fuzzy = regex.compile(r'(?be)(search){i<=1,d<=1,s<=2}', regex.BESTMATCH)

# Enhanced fuzzy matching
enhanced = regex.compile(r'(?ee)(pattern){e<=1}', regex.ENHANCEMATCH)

# Pre-compile frequently used patterns
EMAIL_PATTERN = regex.compile(r'\b[\w.-]+@[\w.-]+\.\w+\b')
PHONE_PATTERN = regex.compile(r'\b\d{3}-\d{3}-\d{4}\b')
DATE_PATTERN = regex.compile(r'\b\d{4}-\d{2}-\d{2}\b')

def extract_info(text):
    emails = EMAIL_PATTERN.findall(text)
    phones = PHONE_PATTERN.findall(text)
    dates = DATE_PATTERN.findall(text)
    return {'emails': emails, 'phones': phones, 'dates': dates}

# Cache control for dynamic patterns
def process_user_patterns(user_patterns, text):
    # Disable caching for one-time patterns
    regex.cache_all(False)
    
    results = {}
    for name, pattern in user_patterns.items():
        try:
            compiled = regex.compile(pattern)
            results[name] = compiled.findall(text)
        except regex.error as e:
            results[name] = f"Error: {e}"
    
    # Re-enable caching
    regex.cache_all(True)
    return results

def safe_compile(pattern_str, flags=0):
    """Safely compile a pattern with error handling."""
    try:
        return regex.compile(pattern_str, flags)
    except regex.error as e:
        print(f"Pattern compilation failed: {e}")
        print(f"Pattern: {pattern_str}")
        if hasattr(e, 'pos') and e.pos is not None:
            print(f"Error at position {e.pos}")
        return None

# Validate user input patterns
def validate_pattern(user_pattern):
    escaped_input = regex.escape(user_pattern)
    try:
        test_pattern = regex.compile(escaped_input)
        return True, f"Valid literal pattern: {escaped_input}"
    except regex.error as e:
        return False, f"Cannot create valid pattern: {e}"

# Test pattern against sample text
def test_pattern(pattern_str, test_text="test sample text 123"):
    try:
        pattern = regex.compile(pattern_str)
        matches = pattern.findall(test_text)
        return True, f"Pattern works. Found {len(matches)} matches: {matches}"
    except regex.error as e:
        return False, f"Pattern error: {e}"