mynt 0.1.1

//! Fallback implementation of the diagnostic interface for the stable channel.

use std::cell::{Cell, RefCell};

use proc_macro::{Group, Ident, Literal, Punct, Spacing, Span, TokenStream, TokenTree};

/// An enum representing a diagnostic level.
#[derive(Clone, Copy, Debug)]
#[non_exhaustive]
pub enum Level {
    /// An error.
    Error,
    /// A warning.
    Warning,
    /// A note.
    Note,
    /// A help message.
    Help,
}

/// Trait implemented by types that can be converted into a set of `Span`s.
pub trait MultiSpan {
    /// Converts `self` into a `Vec<Span>`.
    fn into_spans(self) -> Vec<Span>;
}

impl MultiSpan for Span {
    fn into_spans(self) -> Vec<Span> {
        vec![self]
    }
}

impl MultiSpan for Vec<Span> {
    fn into_spans(self) -> Vec<Span> {
        self
    }
}

impl<'a> MultiSpan for &'a [Span] {
    fn into_spans(self) -> Vec<Span> {
        self.to_vec()
    }
}

/// A structure representing a diagnostic message and associated children
/// messages.
#[derive(Clone, Debug)]
pub struct Diagnostic {
    level: Level,
    message: String,
    spans: Vec<Span>,
    children: Vec<Diagnostic>,
}

macro_rules! diagnostic_child_methods {
    ($spanned:ident, $regular:ident, $level:expr) => {
        #[doc = concat!("Adds a new child diagnostics message to `self` with the [`",
                        stringify!($level), "`] level, and the given `spans` and `message`.")]
        pub fn $spanned<S, T>(mut self, spans: S, message: T) -> Diagnostic
        where
            S: MultiSpan,
            T: Into<String>,
        {
            self.children.push(Diagnostic::spanned(spans, $level, message));
            self
        }

        #[doc = concat!("Adds a new child diagnostic message to `self` with the [`",
                        stringify!($level), "`] level, and the given `message`.")]
        pub fn $regular<T: Into<String>>(mut self, message: T) -> Diagnostic {
            self.children.push(Diagnostic::new($level, message));
            self
        }
    };
}

/// Iterator over the children diagnostics of a `Diagnostic`.
#[derive(Debug, Clone)]
pub struct Children<'a>(std::slice::Iter<'a, Diagnostic>);

impl<'a> Iterator for Children<'a> {
    type Item = &'a Diagnostic;

    fn next(&mut self) -> Option<Self::Item> {
        self.0.next()
    }
}

impl Diagnostic {
    /// Creates a new diagnostic with the given `level` and `message`.
    pub fn new<T: Into<String>>(level: Level, message: T) -> Diagnostic {
        Diagnostic {
            level,
            message: message.into(),
            spans: vec![],
            children: vec![],
        }
    }

    /// Creates a new diagnostic with the given `level` and `message` pointing to
    /// the given set of `spans`.
    pub fn spanned<S, T>(spans: S, level: Level, message: T) -> Diagnostic
    where
        S: MultiSpan,
        T: Into<String>,
    {
        Diagnostic {
            level,
            message: message.into(),
            spans: spans.into_spans(),
            children: vec![],
        }
    }

    diagnostic_child_methods!(span_error, error, Level::Error);
    diagnostic_child_methods!(span_warning, warning, Level::Warning);
    diagnostic_child_methods!(span_note, note, Level::Note);
    diagnostic_child_methods!(span_help, help, Level::Help);

    /// Returns the diagnostic `level` for `self`.
    pub fn level(&self) -> Level {
        self.level
    }

    /// Sets the level in `self` to `level`.
    pub fn set_level(&mut self, level: Level) {
        self.level = level;
    }

    /// Returns the message in `self`.
    pub fn message(&self) -> &str {
        &self.message
    }

    /// Sets the message in `self` to `message`.
    pub fn set_message<T: Into<String>>(&mut self, message: T) {
        self.message = message.into();
    }

    /// Returns the `Span`s in `self`.
    pub fn spans(&self) -> &[Span] {
        &self.spans
    }

    /// Sets the `Span`s in `self` to `spans`.
    pub fn set_spans<S: MultiSpan>(&mut self, spans: S) {
        self.spans = spans.into_spans();
    }

    /// Returns an iterator over the children diagnostics of `self`.
    pub fn children(&self) -> Children<'_> {
        Children(self.children.iter())
    }

    /// Emit the diagnostic.
    pub fn emit(self) {
        assert!(
            MYNT_ACTIVE.get(),
            "mynt diagnostic emitted outside of mynt scope"
        );
        DIAGNOSTICS.with(|store| store.borrow_mut().push(self));
    }
}

thread_local! {
    static MYNT_ACTIVE: Cell<bool> = const { Cell::new(false) };
    static DIAGNOSTICS: RefCell<Vec<Diagnostic>> = const { RefCell::new(Vec::new()) };
}

#[doc(hidden)]
// enter the diagnostics scope
pub fn enter_diagnostics() {
    DIAGNOSTICS.with(|store| store.replace(Vec::new()));
    MYNT_ACTIVE.replace(true);
}

fn write_diagnostic(tokens: &mut TokenStream, diagnostic: &Diagnostic) {
    let (start, end, file) = match diagnostic.spans.first() {
        Some(span) => (span.start(), span.end(), Some(span.file())),
        None => (Span::call_site(), Span::call_site(), None),
    };

    match diagnostic.level {
        Level::Error => {
            tokens.push_tt(Ident::new("compile_error", start));
            tokens.push_tt(Punct::new('!', Spacing::Alone).with_span(start));

            let mut message_tokens = TokenStream::new();
            message_tokens.push_tt(Literal::string(&diagnostic.message).with_span(start));

            tokens.push_tt(Group::new(proc_macro::Delimiter::Brace, message_tokens).with_span(end));
        }
        Level::Warning => {
            #[cfg(feature = "yansi")]
            {
                use yansi::Paint;
                eprintln!(
                    "{}{}{}",
                    "warning".bright_yellow().bold(),
                    ": ".bold(),
                    diagnostic.message.bold()
                );

                if let Some(file) = file {
                    eprintln!(
                        " {} {}:{}:{}",
                        "-->".blue().bold(),
                        file,
                        start.line(),
                        start.column()
                    );
                }
            }

            #[cfg(not(feature = "yansi"))]
            {
                eprintln!("warning: {}", diagnostic.message);

                if let Some(file) = file {
                    eprintln!("  --> {}:{}:{}", file, start.line(), start.column());
                }
            }
        }
        Level::Note => {
            #[cfg(feature = "yansi")]
            {
                use yansi::Paint;
                eprintln!(
                    "{}{}{}",
                    "note".bright_cyan().bold(),
                    ": ".bold(),
                    diagnostic.message.bold()
                );

                if let Some(file) = file {
                    eprintln!(
                        " {} {}:{}:{}",
                        "-->".blue(),
                        file,
                        start.line(),
                        start.column()
                    );
                }
            }

            #[cfg(not(feature = "yansi"))]
            {
                eprintln!("note: {}", diagnostic.message);

                if let Some(file) = file {
                    eprintln!("  --> {}:{}:{}", file, start.line(), start.column());
                }
            }
        }
        Level::Help => {
            #[cfg(feature = "yansi")]
            {
                use yansi::Paint;

                eprintln!(
                    "{}{}{}",
                    "help".bright_white().bold(),
                    ": ".bold(),
                    diagnostic.message.bold()
                );

                if let Some(file) = file {
                    eprintln!(
                        " {} {}:{}:{}",
                        "-->".blue(),
                        file,
                        start.line(),
                        start.column()
                    );
                }
            }

            #[cfg(not(feature = "yansi"))]
            {
                eprintln!("help: {}", diagnostic.message);

                if let Some(file) = file {
                    eprintln!("  --> {}:{}:{}", file, start.line(), start.column());
                }
            }
        }
    }

    for child_diagnostic in &diagnostic.children {
        write_diagnostic(tokens, child_diagnostic);
    }
}

#[doc(hidden)]
// writes diagnostics using available means:
// - errors are emitted as `compile_error!`s
// - other diagnostics are printed to stderr
pub fn exit_diagnostics(tokens: &mut TokenStream) {
    MYNT_ACTIVE.replace(false);
    DIAGNOSTICS.with(|store| {
        for diagnostic in store.borrow().iter() {
            write_diagnostic(tokens, diagnostic);
        }
    });
}

trait TokenTreeExt {
    fn to_tt(self) -> TokenTree;

    fn with_span(self, span: Span) -> Self;
}

impl TokenTreeExt for TokenTree {
    fn to_tt(self) -> TokenTree {
        self
    }

    fn with_span(mut self, span: Span) -> Self {
        self.set_span(span);
        self
    }
}

impl TokenTreeExt for Group {
    fn to_tt(self) -> TokenTree {
        TokenTree::Group(self)
    }

    fn with_span(mut self, span: Span) -> Self {
        self.set_span(span);
        self
    }
}

impl TokenTreeExt for Ident {
    fn to_tt(self) -> TokenTree {
        TokenTree::Ident(self)
    }

    fn with_span(mut self, span: Span) -> Self {
        self.set_span(span);
        self
    }
}

impl TokenTreeExt for Punct {
    fn to_tt(self) -> TokenTree {
        TokenTree::Punct(self)
    }

    fn with_span(mut self, span: Span) -> Self {
        self.set_span(span);
        self
    }
}

impl TokenTreeExt for Literal {
    fn to_tt(self) -> TokenTree {
        TokenTree::Literal(self)
    }

    fn with_span(mut self, span: Span) -> Self {
        self.set_span(span);
        self
    }
}

trait PushTokenTreeExt {
    fn push_tt(&mut self, tt: impl TokenTreeExt);
}

impl PushTokenTreeExt for TokenStream {
    fn push_tt(&mut self, tt: impl TokenTreeExt) {
        self.extend(Some(tt.to_tt()));
    }
}