use clippy_config::Conf;
use clippy_utils::diagnostics::span_lint;
use clippy_utils::is_in_test;
use clippy_utils::macros::{is_panic, root_macro_call_first_node};
use rustc_hir::def::{DefKind, Res};
use rustc_hir::{Expr, ExprKind, QPath};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::impl_lint_pass;
use rustc_span::sym;

pub struct PanicUnimplemented {
    allow_panic_in_tests: bool,
}

impl PanicUnimplemented {
    pub fn new(conf: &'static Conf) -> Self {
        Self {
            allow_panic_in_tests: conf.allow_panic_in_tests,
        }
    }
}

declare_clippy_lint! {
    /// ### What it does
    /// Checks for usage of `panic!`.
    ///
    /// ### Why restrict this?
    /// This macro, or panics in general, may be unwanted in production code.
    ///
    /// ### Example
    /// ```no_run
    /// panic!("even with a good reason");
    /// ```
    #[clippy::version = "1.40.0"]
    pub PANIC,
    restriction,
    "usage of the `panic!` macro"
}

declare_clippy_lint! {
    /// ### What it does
    /// Checks for usage of `unimplemented!`.
    ///
    /// ### Why restrict this?
    /// This macro, or panics in general, may be unwanted in production code.
    ///
    /// ### Example
    /// ```no_run
    /// unimplemented!();
    /// ```
    #[clippy::version = "pre 1.29.0"]
    pub UNIMPLEMENTED,
    restriction,
    "`unimplemented!` should not be present in production code"
}

declare_clippy_lint! {
    /// ### What it does
    /// Checks for usage of `todo!`.
    ///
    /// ### Why restrict this?
    /// The `todo!` macro indicates the presence of unfinished code,
    /// so it should not be present in production code.
    ///
    /// ### Example
    /// ```no_run
    /// todo!();
    /// ```
    /// Finish the implementation, or consider marking it as explicitly unimplemented.
    /// ```no_run
    /// unimplemented!();
    /// ```
    #[clippy::version = "1.40.0"]
    pub TODO,
    restriction,
    "`todo!` should not be present in production code"
}

declare_clippy_lint! {
    /// ### What it does
    /// Checks for usage of `unreachable!`.
    ///
    /// ### Why restrict this?
    /// This macro, or panics in general, may be unwanted in production code.
    ///
    /// ### Example
    /// ```no_run
    /// unreachable!();
    /// ```
    #[clippy::version = "1.40.0"]
    pub UNREACHABLE,
    restriction,
    "usage of the `unreachable!` macro"
}

impl_lint_pass!(PanicUnimplemented => [UNIMPLEMENTED, UNREACHABLE, TODO, PANIC]);

impl<'tcx> LateLintPass<'tcx> for PanicUnimplemented {
    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
        if let Some(macro_call) = root_macro_call_first_node(cx, expr) {
            if is_panic(cx, macro_call.def_id) {
                if cx.tcx.hir().is_inside_const_context(expr.hir_id)
                    || self.allow_panic_in_tests && is_in_test(cx.tcx, expr.hir_id)
                {
                    return;
                }

                span_lint(
                    cx,
                    PANIC,
                    macro_call.span,
                    "`panic` should not be present in production code",
                );
                return;
            }
            match cx.tcx.item_name(macro_call.def_id).as_str() {
                "todo" => {
                    span_lint(
                        cx,
                        TODO,
                        macro_call.span,
                        "`todo` should not be present in production code",
                    );
                },
                "unimplemented" => {
                    span_lint(
                        cx,
                        UNIMPLEMENTED,
                        macro_call.span,
                        "`unimplemented` should not be present in production code",
                    );
                },
                "unreachable" => {
                    span_lint(cx, UNREACHABLE, macro_call.span, "usage of the `unreachable!` macro");
                },
                _ => {},
            }
        } else if let ExprKind::Call(func, [_]) = expr.kind
            && let ExprKind::Path(QPath::Resolved(None, expr_path)) = func.kind
            && let Res::Def(DefKind::Fn, def_id) = expr_path.res
            && cx.tcx.is_diagnostic_item(sym::panic_any, def_id)
        {
            if cx.tcx.hir().is_inside_const_context(expr.hir_id)
                || self.allow_panic_in_tests && is_in_test(cx.tcx, expr.hir_id)
            {
                return;
            }

            span_lint(
                cx,
                PANIC,
                expr.span,
                "`panic_any` should not be present in production code",
            );
            return;
        }
    }
}