use rustc::lint::*;
use syntax::ast::*;
use syntax::codemap::Span;
use syntax::symbol::InternedString;
use utils::span_lint;

/// **What it does:** Checks for imports that remove "unsafe" from an item's
/// name.
///
/// **Why is this bad?** Renaming makes it less clear which traits and
/// structures are unsafe.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust,ignore
/// use std::cell::{UnsafeCell as TotallySafeCell};
///
/// extern crate crossbeam;
/// use crossbeam::{spawn_unsafe as spawn};
/// ```
declare_lint! {
    pub UNSAFE_REMOVED_FROM_NAME,
    Warn,
    "`unsafe` removed from API names on import"
}

pub struct UnsafeNameRemoval;

impl LintPass for UnsafeNameRemoval {
    fn get_lints(&self) -> LintArray {
        lint_array!(UNSAFE_REMOVED_FROM_NAME)
    }
}

impl EarlyLintPass for UnsafeNameRemoval {
    fn check_item(&mut self, cx: &EarlyContext, item: &Item) {
        if let ItemKind::Use(ref item_use) = item.node {
            match item_use.node {
                ViewPath_::ViewPathSimple(ref name, ref path) => {
                    unsafe_to_safe_check(path.segments
                                             .last()
                                             .expect("use paths cannot be empty")
                                             .identifier,
                                         *name,
                                         cx,
                                         &item.span);
                },
                ViewPath_::ViewPathList(_, ref path_list_items) => {
                    for path_list_item in path_list_items.iter() {
                        let plid = path_list_item.node;
                        if let Some(rename) = plid.rename {
                            unsafe_to_safe_check(plid.name, rename, cx, &item.span);
                        };
                    }
                },
                ViewPath_::ViewPathGlob(_) => {},
            }
        }
    }
}

fn unsafe_to_safe_check(old_name: Ident, new_name: Ident, cx: &EarlyContext, span: &Span) {
    let old_str = old_name.name.as_str();
    let new_str = new_name.name.as_str();
    if contains_unsafe(&old_str) && !contains_unsafe(&new_str) {
        span_lint(cx,
                  UNSAFE_REMOVED_FROM_NAME,
                  *span,
                  &format!("removed \"unsafe\" from the name of `{}` in use as `{}`", old_str, new_str));
    }
}

fn contains_unsafe(name: &InternedString) -> bool {
    name.contains("Unsafe") || name.contains("unsafe")
}