use proc_macro2_diagnostics::Diagnostic;
use quote::ToTokens;

/// A collection of diagnostics
///
/// This is a wrapper type since we want it to be transparent in terms of PartialEq and Eq.
/// This also lets us choose the expansion strategy for the diagnostics.
#[derive(Debug, Clone, Default)]
pub struct Diagnostics {
    pub diagnostics: Vec<Diagnostic>,
}

impl Diagnostics {
    pub fn new() -> Self {
        Self {
            diagnostics: vec![],
        }
    }

    pub fn push(&mut self, diagnostic: Diagnostic) {
        self.diagnostics.push(diagnostic);
    }

    pub fn extend(&mut self, diagnostics: Vec<Diagnostic>) {
        self.diagnostics.extend(diagnostics);
    }

    pub fn is_empty(&self) -> bool {
        self.diagnostics.is_empty()
    }

    pub fn into_diagnostics(self) -> Vec<Diagnostic> {
        self.diagnostics
    }

    pub fn len(&self) -> usize {
        self.diagnostics.len()
    }
}

impl PartialEq for Diagnostics {
    fn eq(&self, _other: &Self) -> bool {
        true
    }
}

impl Eq for Diagnostics {}

impl ToTokens for Diagnostics {
    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
        for diagnostic in &self.diagnostics {
            tokens.extend(diagnostic.clone().emit_as_expr_tokens());
        }
    }
}

// TODO: Ideally this would be integrated into the existing diagnostics struct, but currently all fields are public so adding
// new fields would be a breaking change. Diagnostics also doesn't expose the message directly so we can't just modify
// the expansion
pub(crate) mod new_diagnostics {
    use proc_macro2_diagnostics::SpanDiagnosticExt;
    use std::fmt::Display;

    use proc_macro2::{Span, TokenStream as TokenStream2};
    use quote::quote_spanned;

    pub(crate) fn warning_diagnostic(span: Span, message: impl Display) -> TokenStream2 {
        let note = message.to_string();
        // If we are compiling on nightly, use diagnostics directly which supports proper warnings through new span apis
        if rustversion::cfg!(nightly) {
            return span.warning(note).emit_as_item_tokens();
        }
        quote_spanned! { span =>
            const _: () = {
                #[deprecated(note = #note)]
                struct Warning;
                _ = Warning;
            };
        }
    }
}