# This file is a Parsing Expression Grammar (PEG) for the Koi
# programming language. It is interpreted by the PEG engine Treetop.

# More info on PEGs: http://en.wikipedia.org/wiki/Parsing_expression_grammar
# More info on Treetop: http://treetop.rubyforge.org/

grammar KoiReferenceParser

  ##################
  # Program structure

  rule block
    statement+ <Block>
  end

  rule statement
    space? ( hash_assignment / assignment / if / unless / function_call ) ';'? space? <Statement>
  end
  
  ##################
  # Literals
  
  rule nil
    "nil" <NilLiteral>
  end
  
  rule true
    "true" <TrueLiteral>
  end
  
  rule false
    "false" <FalseLiteral>
  end

  rule integer
    ('+' / '-')? [0-9]+ <IntegerLiteral>
  end
  
  rule float
    ('+' / '-')? [0-9]+ '.' [0-9]+ <FloatLiteral>
  end
  
  rule string
    '"' ([^"\\] / "\\" . )* '"' <StringLiteral>
  end
  
  rule identifier
    '$'? [a-zA-Z] [a-zA-Z0-9_]* <Identifier>
  end
  
  ##################
  # Hash literals
  
  rule hash
    '{' key_value_list? '}' <HashLiteral>
  end
  
  rule key_value_list
    key_value+ <KeyValueList>
  end
  
  rule key_value
    space? expression space? '=>' space? expression space? ','? <KeyValue>
  end
  
  ##################
  # Assignment
  
  rule hash_assignment
    identifier hash_accessor_list space? assignment_operator space? ( hash / function_definition / expression ) <HashAssignment>
  end
  
  rule assignment
    identifier space? assignment_operator space? ( hash / function_definition / expression ) <Assignment>
  end
  
  ##################
  # Flow control
  
  rule if
    'if(' space? expression space? ')' space
      block
    space? 'end' space? <If>
  end
  
  rule unless
    'unless(' space? expression space? ')' space
      block
    space? 'end' space? <Unless>
  end
  
  ##################
  # Functions
  
  rule function_call
    identifier space? '(' space? expression? space? ','? expression? space? ')' <FunctionCall>
  end
  
  rule function_definition
    'function(' space? identifier space? ')' 
      block
    space? 'end' <FunctionDefinition>
  end  

  ##################
  # Hash component access
  
  rule hash_access
    identifier hash_accessor_list <HashAccess>
  end
  
  rule hash_accessor_list
    hash_accessor+ <HashAccessorList>
  end
  
  rule hash_accessor
    '[' expression ']' <HashAccessor>
  end

  ##################
  # Expressions
  
  rule expression
    space? (hash_access / comparative / additive) <Expression>
  end
  
  rule comparative
    additive space? comparative_operator space? additive <ComparativeExpression>
  end
  
  rule additive
    multitive space? additive_operator space? additive <AdditiveExpression>
    /
    multitive 
  end

  rule multitive
    primary space? multitive_operator space? multitive <MultitiveExpression>
    /
    primary 
  end
  
  rule primary
    function_call / nil / false / true / identifier / float / integer / string 
    /
    '(' space? expression space? ')' <Expression>
  end
  
  ##################
  # Operator sets
  
  rule comparative_operator
    equality_operator / inequality_operator / greater_than_operator / less_than_operator
  end
  
  rule additive_operator
    addition_operator / subtraction_operator 
  end
  
  rule multitive_operator
    multiplication_operator / division_operator  
  end

  ##################
  # Operators

  rule assignment_operator
    '=' <AssignmentOperator>
  end
  
  rule addition_operator
    '+' <AdditionOperator>
  end
  
  rule subtraction_operator
    '-' <SubtractionOperator>
  end
  
  rule multiplication_operator
    '*' <MultiplicationOperator>
  end
  
  rule division_operator
    '/' <DivisionOperator>
  end
  
  rule equality_operator
    '==' <EqualityOperator>
  end
  
  rule inequality_operator
    '!=' <InequalityOperator>
  end
  
  rule greater_than_operator
    '>' <GreaterThanOperator>
  end
  
  rule less_than_operator
    '<' <LessThanOperator>
  end
  
  ##################
  # Whitespace
  
  rule space
    [\s]+
  end

end