@top Program {
  StatementList
}

StatementList {
  Statement*
}

@skip { Whitespace }

IfStatement {
  If LParen ConditionalExpression RParen PartIfStatement Else Statement | If LParen ConditionalExpression RParen Statement
}

PartIfStatement {
  If LParen ConditionalExpression RParen PartIfStatement Else PartIfStatement | NoIfStatement
}

ConditionalExpression {
  Expression Operator Expression | Expression
}

Expression {
  Term (AddLike Term)*
}

Statement {
  IfStatement | NoIfStatement
}

NoIfStatement {
  AssignmentStatement Semicolon | VariableDefinition Semicolon | LBrace Statement* RBrace | ConstantDefinition Semicolon | Semicolon
}

AssignmentStatement {
  Identifier Equal Expression
}

Term {
  Factor (MultiplyLike Factor)*
}

ConstantDefinition {
  Const VariableDefinition
}

VariableDefinition {
  Type (Identifier | AssignmentStatement)+ (Comma Identifier | Comma AssignmentStatement)*
}

Type {
  Int | Char
}

Factor {
  Identifier | Number | Character | LParen Expression RParen
}

AddLike {
  Plus | Minus
}

MultiplyLike {
  Multiply | Divide | Modulo
}

Number {
  UnsignedNumber | Minus UnsignedNumber | Plus UnsignedNumber
}

Operator {
  EuqalTo | NotEqualTo | LessThan | GreaterThan | LessThanOrEqual | GreaterThanOrEqual
}

@tokens {
  If { "!if" }
  Else { "!else" }
  Int {"!int"}
  Char {"!char"}
  Const { "!const" }
  Plus { "+" }
  Minus { "-" }
  Multiply { "*" }
  Modulo { "%" }
  Divide { "/" }
  LParen { "(" }
  RParen { ")" }
  LBrace { "{" }
  RBrace { "}" }
  Comma { "," }
  Semicolon { ";" }
  Identifier { $[a-zA-Z_]$[a-zA-Z0-9_]* } 
  UnsignedNumber { $[0-9]+ }
  String { "\"" $[\x00-\x7F]* "\"" }
  Character { "'" $[\x00-\x7F] "'" }
  EuqalTo { "==" }
  NotEqualTo { "!=" }
  LessThan { "<" }
  GreaterThan { ">" }
  LessThanOrEqual { "<=" }
  GreaterThanOrEqual { ">=" }
  Equal { "=" }
  Whitespace { $[\t\n\r]+ }
}