Filter System

class Filter:
    name = None  # Filter name for registration
    options = {}  # Supported configuration options
    max_debug_level = None  # Maximum debug level where filter runs
    
    def setup(self):
        """Initialize filter (called before use)."""
    
    def set_context(self, ctx):
        """Set processing context."""
    
    def get_config(self, setting, env=None, require=True, what='dependency', type=None):
        """
        Get configuration values.
        
        Parameters:
        - setting: Configuration key
        - env: Environment instance
        - require: Whether setting is required
        - what: Description for error messages
        - type: Expected value type
        
        Returns:
        Configuration value
        """
    
    def input(self, _in, out, **kw):
        """
        Process input files.
        
        Parameters:
        - _in: Input stream/file
        - out: Output stream/file
        - **kw: Additional context
        """
    
    def output(self, _in, out, **kw):
        """
        Process output files.
        
        Parameters:
        - _in: Input stream/file  
        - out: Output stream/file
        - **kw: Additional context
        """
    
    def open(self, out, source_path, **kw):
        """
        Direct file processing.
        
        Parameters:
        - out: Output stream
        - source_path: Source file path
        - **kw: Additional context
        """
    
    def concat(self, out, hunks, **kw):
        """
        Concatenate multiple sources.
        
        Parameters:
        - out: Output stream
        - hunks: List of input hunks
        - **kw: Additional context
        """
    
    def unique(self):
        """Return unique identifier for filter instance."""
    
    def id(self):
        """Get filter cache key."""
    
    def get_additional_cache_keys(self, **kw):
        """Additional cache dependencies."""

class CallableFilter:
    def __init__(self, callable):
        """
        Wrapper to create filters from callable functions.
        
        Parameters:
        - callable: Function to wrap as filter
        """

class ExternalTool(Filter):
    argv = []  # Command line arguments template  
    method = None  # Filter method to implement ('input', 'output', 'open')
    
    def subprocess(self, argv, out, data=None, cwd=None):
        """
        Execute external command.
        
        Parameters:
        - argv: Command arguments
        - out: Output stream
        - data: Input data
        - cwd: Working directory
        """
    
    def parse_binary(self, string):
        """Parse binary path string."""

class JavaTool(Filter):
    """Base for Java-based filters (JAR files)."""

def get_filter(f, *args, **kwargs):
    """
    Resolve filter specification to filter instance.
    
    Parameters:
    - f: Filter name, class, or instance
    - *args: Filter arguments
    - **kwargs: Filter options
    
    Returns:
    Filter instance
    """

def register_filter(f):
    """
    Register filter class with system.
    
    Parameters:
    - f: Filter class to register
    """

from webassets.filter import get_filter, register_filter

# Get filter by name
jsmin_filter = get_filter('jsmin')
uglify_filter = get_filter('uglifyjs', compress=False)

# Register custom filter
class MyCustomFilter(Filter):
    name = 'mycustom'
    def input(self, _in, out, **kw):
        # Custom processing
        pass

register_filter(MyCustomFilter)

# Built-in JavaScript filters (import from webassets.filter.*)
class JSMin:
    """JavaScript minification using jsmin library."""

class RJSMin:
    """rJSMin JavaScript minifier with better performance."""
    
class UglifyJS:
    """UglifyJS minifier with advanced optimization."""
    options = {
        'binary': 'uglifyjs',
        'compress': True,
        'mangle': True
    }

class ClosureJS:
    """Google Closure Compiler for JavaScript optimization."""
    options = {
        'binary': 'closure-compiler',
        'compilation_level': 'SIMPLE_OPTIMIZATIONS'
    }

class YUIJS:
    """YUI JavaScript compressor."""
    options = {
        'binary': 'yuicompressor',
        'jar': None
    }

class Slimit:
    """Slimit JavaScript minifier."""

class JSPacker:
    """JavaScript packer for extreme compression."""

# Built-in CSS filters
class CSSMin:
    """CSS minification using cssmin library."""

class RCSSMin:
    """rCSSMin CSS minifier with better performance."""

class CleanCSS:
    """CleanCSS minifier with advanced optimization."""
    options = {
        'binary': 'cleancss',
        'level': 1
    }

class YUICSS:
    """YUI CSS compressor."""
    options = {
        'binary': 'yuicompressor',
        'jar': None
    }

class CSSSlimmer:
    """CSS Slimmer for CSS optimization."""

class CSSUtils:
    """CSS utilities for parsing and processing."""

class CSSRewrite:
    """CSS URL rewriting for asset path correction."""
    options = {
        'replace': None,
        'base': None
    }

class CSSDataUri:
    """Convert CSS references to data URIs."""
    options = {
        'max_size': 8192,
        'include_pattern': None
    }

class CSSPrefixer:
    """CSS prefixer for vendor prefixes."""

class AutoPrefixer:
    """Autoprefixer for automatic vendor prefix addition."""
    options = {
        'binary': 'autoprefixer',
        'browsers': None
    }

# CSS preprocessor filters
class Sass:
    """Sass/SCSS compilation using Ruby Sass."""
    options = {
        'binary': 'sass',
        'style': 'compressed',
        'includes': []
    }

class SCSS:
    """SCSS compilation (alias for Sass)."""

class LibSass:
    """LibSass compilation using libsass library."""
    options = {
        'style': 'compressed',
        'include_paths': []
    }

class NodeSass:
    """Node-sass compilation."""
    options = {
        'binary': 'node-sass',
        'output_style': 'compressed'
    }

class RubySass:  
    """Ruby Sass compilation."""

class RubySCSS:
    """Ruby SCSS compilation."""

class Less:
    """Less compilation."""
    options = {
        'binary': 'lessc',
        'compress': True
    }

class Stylus:
    """Stylus compilation."""
    options = {
        'binary': 'stylus',
        'compress': True
    }

class CleverCSS:
    """CleverCSS compilation."""

class PyScss:
    """pyScss compilation using Python library."""
    options = {
        'style': 'compressed',
        'imports': []
    }

class Compass:
    """Compass compilation framework."""
    options = {
        'binary': 'compass',
        'style': 'compressed',
        'images_dir': 'images'
    }

class PostCSS:
    """PostCSS processing with plugins."""
    options = {
        'binary': 'postcss',
        'plugins': []
    }

# JavaScript preprocessors
class CoffeeScript:
    """CoffeeScript compilation."""
    options = {
        'binary': 'coffee',
        'bare': False
    }

class TypeScript:
    """TypeScript compilation."""
    options = {
        'binary': 'tsc',
        'target': 'es5',
        'module': 'commonjs'
    }

class Babel:
    """Babel transpilation for modern JavaScript."""
    options = {
        'binary': 'babel',
        'presets': ['env']
    }

# Template engines
class Handlebars:
    """Handlebars template compilation."""
    options = {
        'binary': 'handlebars',
        'namespace': 'templates'
    }

class Jinja2:
    """Jinja2 template processing."""

class JST:
    """JavaScript templates (Underscore.js style)."""
    options = {
        'namespace': 'JST',
        'bare': False
    }

class DustJS:
    """Dust.js template compilation."""
    options = {
        'binary': 'dustc',
        'name': None
    }

class Jade:
    """Jade template compilation."""
    options = {
        'binary': 'jade',
        'pretty': False
    }

# Specialized filters
class RequireJS:
    """RequireJS optimizer (r.js)."""
    options = {
        'binary': 'r.js',
        'baseUrl': None,
        'optimize': 'uglify2'
    }

class Spritemapper:
    """CSS sprite generation."""
    options = {
        'binary': 'spritemapper',
        'output_css': None,
        'output_image': None
    }

class ClosureTemplateFilter:
    """Closure Templates compilation."""
    options = {
        'binary': 'SoyToJsSrcCompiler.jar',
        'jar': None
    }

class ClosureStylesheetsCompiler:
    """Closure Stylesheets compiler."""
    options = {
        'binary': 'closure-stylesheets.jar',
        'jar': None
    }

class ClosureStylesheetsMinifier:
    """Closure Stylesheets minifier."""
    options = {
        'binary': 'closure-stylesheets.jar',
        'jar': None
    }

from webassets.filter import Filter

class CustomSassFilter(Filter):
    name = 'custom_sass'
    options = {
        'style': 'compressed',
        'include_paths': []
    }
    
    def input(self, _in, out, **kw):
        import sass
        
        # Get configuration  
        style = self.get_config('style', require=False) or 'compressed'
        include_paths = self.get_config('include_paths', require=False) or []
        
        # Process input
        source = _in.read()
        result = sass.compile(
            string=source,
            output_style=style,
            include_paths=include_paths
        )
        
        out.write(result)

# Register and use
from webassets.filter import register_filter
register_filter(CustomSassFilter)

# Use in bundle
Bundle('style.scss', filters='custom_sass', output='style.css')

# Chain multiple filters
Bundle(
    'app.js',
    'utils.js',
    filters=['babel', 'uglifyjs'],  # Babel first, then UglifyJS
    output='gen/app.js'
)

# CSS preprocessing and optimization
Bundle(
    'style.scss',
    filters=['sass', 'autoprefixer', 'cssmin'],
    output='gen/style.css'
)

# Complex filter chain
Bundle(
    'template.handlebars',
    'app.coffee',
    filters=['handlebars', 'coffeescript', 'uglifyjs'],
    output='gen/compiled.js'
)

from webassets import Environment, Bundle

env = Environment('./static', '/static')

# Global filter configuration
env.config['uglifyjs_binary'] = '/usr/local/bin/uglifyjs'
env.config['sass_style'] = 'compressed'
env.config['autoprefixer_browsers'] = ['last 2 versions', 'ie >= 9']

# Bundle-specific filter options
Bundle(
    'app.js',
    filters={'uglifyjs': {'compress': False, 'mangle': True}},
    output='gen/app.js'
)

# Environment-specific settings
if env.debug:
    js_filters = None  # No minification in debug
else:
    js_filters = ['babel', 'uglifyjs']

Bundle('app.js', filters=js_filters, output='gen/app.js')

def get_js_filters(debug=False):
    if debug:
        return ['babel']  # Only transpile, don't minify
    else:
        return ['babel', 'uglifyjs']  # Transpile and minify

def get_css_filters(debug=False):
    base_filters = ['sass', 'autoprefixer']
    if not debug:
        base_filters.append('cssmin')
    return base_filters

# Create bundles with conditional filters
js_bundle = Bundle(
    'app.js',
    filters=get_js_filters(env.debug),
    output='gen/app.js'
)

css_bundle = Bundle(
    'style.scss', 
    filters=get_css_filters(env.debug),
    output='gen/style.css'
)