use clippy_config::msrvs::{self, Msrv};
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_context;
use rustc_errors::Applicability;
use rustc_hir::def_id::DefId;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, Ty};
use rustc_span::sym;

use super::CAST_SLICE_FROM_RAW_PARTS;

enum RawPartsKind {
    Immutable,
    Mutable,
}

fn raw_parts_kind(cx: &LateContext<'_>, did: DefId) -> Option<RawPartsKind> {
    match cx.tcx.get_diagnostic_name(did)? {
        sym::slice_from_raw_parts => Some(RawPartsKind::Immutable),
        sym::slice_from_raw_parts_mut => Some(RawPartsKind::Mutable),
        _ => None,
    }
}

pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>, cast_to: Ty<'_>, msrv: &Msrv) {
    if msrv.meets(msrvs::PTR_SLICE_RAW_PARTS)
        && let ty::RawPtr(ptrty, _) = cast_to.kind()
        && let ty::Slice(_) = ptrty.kind()
        && let ExprKind::Call(fun, [ptr_arg, len_arg]) = cast_expr.peel_blocks().kind
        && let ExprKind::Path(ref qpath) = fun.kind
        && let Some(fun_def_id) = cx.qpath_res(qpath, fun.hir_id).opt_def_id()
        && let Some(rpk) = raw_parts_kind(cx, fun_def_id)
        && let ctxt = expr.span.ctxt()
        && cast_expr.span.ctxt() == ctxt
    {
        let func = match rpk {
            RawPartsKind::Immutable => "from_raw_parts",
            RawPartsKind::Mutable => "from_raw_parts_mut",
        };
        let span = expr.span;
        let mut applicability = Applicability::MachineApplicable;
        let ptr = snippet_with_context(cx, ptr_arg.span, ctxt, "ptr", &mut applicability).0;
        let len = snippet_with_context(cx, len_arg.span, ctxt, "len", &mut applicability).0;
        span_lint_and_sugg(
            cx,
            CAST_SLICE_FROM_RAW_PARTS,
            span,
            format!("casting the result of `{func}` to {cast_to}"),
            "replace with",
            format!("core::ptr::slice_{func}({ptr}, {len})"),
            applicability,
        );
    }
}