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use crate::ast;
use crate::ast::{Kind, Token};
use crate::error::ParseError;
use crate::parser::Parser;
use crate::traits::{Parse, Peek};
use runestick::Span;

/// Things that we can break on.
#[derive(Debug, Clone)]
pub enum ExprBreakValue {
    /// Breaking a value out of a loop.
    Expr(Box<ast::Expr>),
    /// Break and jump to the given label.
    Label(ast::Label),
}

impl ExprBreakValue {
    /// Access the span of the expression.
    pub fn span(&self) -> Span {
        match self {
            Self::Expr(expr) => expr.span(),
            Self::Label(label) => label.span(),
        }
    }
}

impl Parse for ExprBreakValue {
    fn parse(parser: &mut Parser<'_>) -> Result<Self, ParseError> {
        let token = parser.token_peek_eof()?;

        Ok(match token.kind {
            ast::Kind::Label => Self::Label(parser.parse()?),
            _ => Self::Expr(Box::new(parser.parse()?)),
        })
    }
}

impl Peek for ExprBreakValue {
    fn peek(t1: Option<Token>, t2: Option<Token>) -> bool {
        match t1.map(|t| t.kind) {
            Some(Kind::Label) => true,
            _ => ast::Expr::peek(t1, t2),
        }
    }
}

/// A return statement `break [expr]`.
#[derive(Debug, Clone)]
pub struct ExprBreak {
    /// The return token.
    pub break_: ast::Break,
    /// An optional expression to break with.
    pub expr: Option<ExprBreakValue>,
}

impl ExprBreak {
    /// Access the span of the expression.
    pub fn span(&self) -> Span {
        if let Some(expr) = &self.expr {
            self.break_.span().join(expr.span())
        } else {
            self.break_.span()
        }
    }
}

impl Parse for ExprBreak {
    fn parse(parser: &mut Parser<'_>) -> Result<Self, ParseError> {
        Ok(Self {
            break_: parser.parse()?,
            expr: parser.parse()?,
        })
    }
}