use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::is_in_test_function;
use clippy_utils::macros::root_macro_call_first_node;
use clippy_utils::source::snippet_with_applicability;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;

declare_clippy_lint! {
    /// ### What it does
    /// Checks for usage of dbg!() macro.
    ///
    /// ### Why is this bad?
    /// `dbg!` macro is intended as a debugging tool. It
    /// should not be in version control.
    ///
    /// ### Example
    /// ```rust,ignore
    /// // Bad
    /// dbg!(true)
    ///
    /// // Good
    /// true
    /// ```
    #[clippy::version = "1.34.0"]
    pub DBG_MACRO,
    restriction,
    "`dbg!` macro is intended as a debugging tool"
}

declare_lint_pass!(DbgMacro => [DBG_MACRO]);

impl LateLintPass<'_> for DbgMacro {
    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
        let Some(macro_call) = root_macro_call_first_node(cx, expr) else { return };
        if cx.tcx.is_diagnostic_item(sym::dbg_macro, macro_call.def_id) {
            // we make an exception for test code
            if is_in_test_function(cx.tcx, expr.hir_id) {
                return;
            }
            let mut applicability = Applicability::MachineApplicable;
            let suggestion = match expr.peel_drop_temps().kind {
                // dbg!()
                ExprKind::Block(_, _) => String::new(),
                // dbg!(1)
                ExprKind::Match(val, ..) => {
                    snippet_with_applicability(cx, val.span.source_callsite(), "..", &mut applicability).to_string()
                },
                // dbg!(2, 3)
                ExprKind::Tup(
                    [
                        Expr {
                            kind: ExprKind::Match(first, ..),
                            ..
                        },
                        ..,
                        Expr {
                            kind: ExprKind::Match(last, ..),
                            ..
                        },
                    ],
                ) => {
                    let snippet = snippet_with_applicability(
                        cx,
                        first.span.source_callsite().to(last.span.source_callsite()),
                        "..",
                        &mut applicability,
                    );
                    format!("({snippet})")
                },
                _ => return,
            };

            span_lint_and_sugg(
                cx,
                DBG_MACRO,
                macro_call.span,
                "`dbg!` macro is intended as a debugging tool",
                "ensure to avoid having uses of it in version control",
                suggestion,
                applicability,
            );
        }
    }
}