use crate::common::*;

/// An expression. Note that the Just language grammar has both an
/// `expression` production of additions (`a + b`) and values, and a
/// `value` production of all other value types (for example strings,
/// function calls, and parenthetical groups).
///
/// The parser parses both values and expressions into `Expression`s.
#[derive(PartialEq, Debug)]
pub(crate) enum Expression<'src> {
  /// `contents`
  Backtick {
    contents: &'src str,
    token: Token<'src>,
  },
  /// `name(arguments)`
  Call {
    function: Name<'src>,
    arguments: Vec<Expression<'src>>,
  },
  /// `lhs + rhs`
  Concatination {
    lhs: Box<Expression<'src>>,
    rhs: Box<Expression<'src>>,
  },
  /// `(contents)`
  Group { contents: Box<Expression<'src>> },
  /// `"string_literal"` or `'string_literal'`
  StringLiteral { string_literal: StringLiteral<'src> },
  /// `variable`
  Variable { name: Name<'src> },
}

impl<'src> Expression<'src> {
  pub(crate) fn variables<'expression>(&'expression self) -> Variables<'expression, 'src> {
    Variables::new(self)
  }

  pub(crate) fn functions<'expression>(&'expression self) -> Functions<'expression, 'src> {
    Functions::new(self)
  }
}

impl<'src> Display for Expression<'src> {
  fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
    match self {
      Expression::Backtick { contents, .. } => write!(f, "`{}`", contents)?,
      Expression::Concatination { lhs, rhs } => write!(f, "{} + {}", lhs, rhs)?,
      Expression::StringLiteral { string_literal } => write!(f, "{}", string_literal)?,
      Expression::Variable { name } => write!(f, "{}", name.lexeme())?,
      Expression::Call {
        function,
        arguments,
      } => {
        write!(f, "{}(", function.lexeme())?;
        for (i, argument) in arguments.iter().enumerate() {
          if i > 0 {
            write!(f, ", {}", argument)?;
          } else {
            write!(f, "{}", argument)?;
          }
        }
        write!(f, ")")?;
      }
      Expression::Group { contents } => write!(f, "({})", contents)?,
    }
    Ok(())
  }
}