"""
MDL Grammar using Parsley (PEG parser)

This shows how we could define a proper grammar for MDL parsing.
You would need to install parsley: pip install parsley
"""

# Example grammar definition (not executable without parsley)
GRAMMAR = """
# MDL Grammar using Parsley PEG syntax

# Top level
mdl = pack_declaration namespace_declaration* function_declaration* hook_declaration* tag_declaration*

# Pack declaration
pack_declaration = 'pack' ws string ws 'description' ws string ws 'pack_format' ws number ws
                  ('min_format' ws format_spec)? ws
                  ('max_format' ws format_spec)? ws
                  ('min_engine_version' ws string)? ws

format_spec = '[' number (',' number)* ']'

# Namespace declaration
namespace_declaration = 'namespace' ws string ws

# Function declaration
function_declaration = 'function' ws string ws ':' ws function_body

function_body = (indented_command | control_structure)*

indented_command = ws command ws

# Control structures
control_structure = if_statement | while_loop | for_loop

if_statement = 'if' ws string ws ':' ws indented_command* (else_if_statement | else_statement)?

else_if_statement = 'else' ws 'if' ws string ws ':' ws indented_command*

else_statement = 'else' ws ':' ws indented_command*

while_loop = 'while' ws string ws ':' ws indented_command*

for_loop = 'for' ws identifier ws 'in' ws selector ws ':' ws indented_command*

# Hooks
hook_declaration = on_tick_declaration | on_load_declaration

on_tick_declaration = 'on_tick' ws namespaced_id ws

on_load_declaration = 'on_load' ws namespaced_id ws

# Tags
tag_declaration = 'tag' ws tag_type ws namespaced_id ws ':' ws tag_value*

tag_type = 'function' | 'item' | 'block' | 'entity_type' | 'fluid' | 'game_event'

tag_value = 'add' ws namespaced_id ws

# Basic elements
string = '"' (~'"' anything)* '"'

number = digit+

identifier = letter (letter | digit | '_')*

namespaced_id = identifier ':' identifier

selector = '@' letter+ ('[' selector_args ']')?

selector_args = selector_arg (',' selector_arg)*

selector_arg = identifier '=' value

value = string | number | identifier

command = anything* ~newline

# Whitespace and formatting
ws = (' ' | tab | newline)*

indent = '    '

newline = '\n' | '\r\n'

tab = '\t'

letter = 'a'..'z' | 'A'..'Z'

digit = '0'..'9'

anything = letter | digit | ' ' | tab | newline | ':' | '"' | '[' | ']' | '(' | ')' | ',' | '.' | '_' | '-'
"""

# Example implementation using a simpler approach
class SimpleMDLParser:
    """A simplified MDL parser that demonstrates proper parsing concepts."""
    
    def __init__(self, source: str):
        self.source = source
        self.lines = source.splitlines()
        self.current_line = 0
        self.current_pos = 0
        
    def parse(self):
        """Parse the MDL source into a structured representation."""
        ast = {
            'pack': None,
            'namespaces': [],
            'functions': [],
            'hooks': [],
            'tags': []
        }
        
        while self.current_line < len(self.lines):
            line = self.lines[self.current_line].strip()
            
            if not line or line.startswith('#'):
                self.current_line += 1
                continue
                
            if line.startswith('pack '):
                ast['pack'] = self._parse_pack_declaration(line)
            elif line.startswith('namespace '):
                ast['namespaces'].append(self._parse_namespace_declaration(line))
            elif line.startswith('function '):
                ast['functions'].append(self._parse_function_declaration())
            elif line.startswith('on_tick ') or line.startswith('on_load '):
                ast['hooks'].append(self._parse_hook_declaration(line))
            elif line.startswith('tag '):
                ast['tags'].append(self._parse_tag_declaration())
            else:
                self.current_line += 1
                
        return ast
    
    def _parse_pack_declaration(self, line: str):
        """Parse pack declaration line."""
        import re
        pattern = r'pack\s+"([^"]+)"\s+description\s+"([^"]*)"\s+pack_format\s+(\d+)(?:\s+min_format\s+\[([^\]]+)\])?(?:\s+max_format\s+\[([^\]]+)\])?(?:\s+min_engine_version\s+"([^"]*)")?'
        match = re.match(pattern, line)
        if match:
            return {
                'name': match.group(1),
                'description': match.group(2),
                'pack_format': int(match.group(3)),
                'min_format': match.group(4),
                'max_format': match.group(5),
                'min_engine_version': match.group(6)
            }
        raise ValueError(f"Invalid pack declaration: {line}")
    
    def _parse_namespace_declaration(self, line: str):
        """Parse namespace declaration line."""
        import re
        match = re.match(r'namespace\s+"([^"]+)"', line)
        if match:
            return {'name': match.group(1)}
        raise ValueError(f"Invalid namespace declaration: {line}")
    
    def _parse_function_declaration(self):
        """Parse function declaration and its body."""
        import re
        
        # Parse function header
        line = self.lines[self.current_line]
        match = re.match(r'function\s+"([^"]+)"\s*:\s*$', line)
        if not match:
            raise ValueError(f"Invalid function declaration: {line}")
            
        func_name = match.group(1)
        self.current_line += 1
        
        # Parse function body
        body = []
        expected_indent = 4
        
        while self.current_line < len(self.lines):
            line = self.lines[self.current_line]
            
            if not line.strip():
                self.current_line += 1
                continue
                
            indent = len(line) - len(line.lstrip())
            
            if indent < expected_indent:
                break
                
            if line.strip():
                body.append(line.strip())
                
            self.current_line += 1
            
        return {
            'name': func_name,
            'body': body
        }
    
    def _parse_hook_declaration(self, line: str):
        """Parse hook declaration line."""
        import re
        match = re.match(r'(on_tick|on_load)\s+"([^"]+)"', line)
        if match:
            return {
                'type': match.group(1),
                'function': match.group(2)
            }
        raise ValueError(f"Invalid hook declaration: {line}")
    
    def _parse_tag_declaration(self):
        """Parse tag declaration and its values."""
        import re
        
        # Parse tag header
        line = self.lines[self.current_line]
        match = re.match(r'tag\s+(function|item|block|entity_type|fluid|game_event)\s+"([^"]+)"\s*:\s*$', line)
        if not match:
            raise ValueError(f"Invalid tag declaration: {line}")
            
        tag_type = match.group(1)
        tag_name = match.group(2)
        self.current_line += 1
        
        # Parse tag values
        values = []
        expected_indent = 4
        
        while self.current_line < len(self.lines):
            line = self.lines[self.current_line]
            
            if not line.strip():
                self.current_line += 1
                continue
                
            indent = len(line) - len(line.lstrip())
            
            if indent < expected_indent:
                break
                
            if line.strip().startswith('add '):
                match = re.match(r'add\s+"([^"]+)"', line.strip())
                if match:
                    values.append(match.group(1))
                    
            self.current_line += 1
            
        return {
            'type': tag_type,
            'name': tag_name,
            'values': values
        }

def parse_mdl_properly(source: str):
    """Parse MDL using proper parsing techniques."""
    parser = SimpleMDLParser(source)
    return parser.parse()
