use crate::{pat::WitnessPat, usefulness::MatchCheckCtxt};

use rustc_errors::{AddToDiagnostic, Diagnostic, SubdiagnosticMessage};
use rustc_macros::{LintDiagnostic, Subdiagnostic};
use rustc_middle::thir::Pat;
use rustc_middle::ty::Ty;
use rustc_span::Span;

#[derive(Subdiagnostic)]
#[label(pattern_analysis_uncovered)]
pub struct Uncovered<'tcx> {
    #[primary_span]
    span: Span,
    count: usize,
    witness_1: Pat<'tcx>,
    witness_2: Pat<'tcx>,
    witness_3: Pat<'tcx>,
    remainder: usize,
}

impl<'tcx> Uncovered<'tcx> {
    pub fn new<'p>(
        span: Span,
        cx: &MatchCheckCtxt<'p, 'tcx>,
        witnesses: Vec<WitnessPat<'tcx>>,
    ) -> Self {
        let witness_1 = witnesses.get(0).unwrap().to_diagnostic_pat(cx);
        Self {
            span,
            count: witnesses.len(),
            // Substitute dummy values if witnesses is smaller than 3. These will never be read.
            witness_2: witnesses
                .get(1)
                .map(|w| w.to_diagnostic_pat(cx))
                .unwrap_or_else(|| witness_1.clone()),
            witness_3: witnesses
                .get(2)
                .map(|w| w.to_diagnostic_pat(cx))
                .unwrap_or_else(|| witness_1.clone()),
            witness_1,
            remainder: witnesses.len().saturating_sub(3),
        }
    }
}

#[derive(LintDiagnostic)]
#[diag(pattern_analysis_overlapping_range_endpoints)]
#[note]
pub struct OverlappingRangeEndpoints<'tcx> {
    #[label]
    pub range: Span,
    #[subdiagnostic]
    pub overlap: Vec<Overlap<'tcx>>,
}

pub struct Overlap<'tcx> {
    pub span: Span,
    pub range: Pat<'tcx>,
}

impl<'tcx> AddToDiagnostic for Overlap<'tcx> {
    fn add_to_diagnostic_with<F>(self, diag: &mut Diagnostic, _: F)
    where
        F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
    {
        let Overlap { span, range } = self;

        // FIXME(mejrs) unfortunately `#[derive(LintDiagnostic)]`
        // does not support `#[subdiagnostic(eager)]`...
        let message = format!("this range overlaps on `{range}`...");
        diag.span_label(span, message);
    }
}

#[derive(LintDiagnostic)]
#[diag(pattern_analysis_non_exhaustive_omitted_pattern)]
#[help]
#[note]
pub(crate) struct NonExhaustiveOmittedPattern<'tcx> {
    pub scrut_ty: Ty<'tcx>,
    #[subdiagnostic]
    pub uncovered: Uncovered<'tcx>,
}

#[derive(LintDiagnostic)]
#[diag(pattern_analysis_non_exhaustive_omitted_pattern_lint_on_arm)]
#[help]
pub(crate) struct NonExhaustiveOmittedPatternLintOnArm {
    #[label]
    pub lint_span: Span,
    #[suggestion(code = "#[{lint_level}({lint_name})]\n", applicability = "maybe-incorrect")]
    pub suggest_lint_on_match: Option<Span>,
    pub lint_level: &'static str,
    pub lint_name: &'static str,
}