use rustc_attr as attr;
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::struct_span_err;
use rustc_hir as hir;
use rustc_hir::itemlikevisit::ItemLikeVisitor;
use rustc_middle::middle::cstore::NativeLib;
use rustc_middle::ty::TyCtxt;
use rustc_session::parse::feature_err;
use rustc_session::utils::NativeLibKind;
use rustc_session::Session;
use rustc_span::source_map::Span;
use rustc_span::symbol::{kw, sym, Symbol};
use rustc_target::spec::abi::Abi;

crate fn collect(tcx: TyCtxt<'_>) -> Vec<NativeLib> {
    let mut collector = Collector { tcx, libs: Vec::new() };
    tcx.hir().krate().visit_all_item_likes(&mut collector);
    collector.process_command_line();
    collector.libs
}

crate fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
    match lib.cfg {
        Some(ref cfg) => attr::cfg_matches(cfg, &sess.parse_sess, None),
        None => true,
    }
}

struct Collector<'tcx> {
    tcx: TyCtxt<'tcx>,
    libs: Vec<NativeLib>,
}

impl ItemLikeVisitor<'tcx> for Collector<'tcx> {
    fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
        let abi = match it.kind {
            hir::ItemKind::ForeignMod { abi, .. } => abi,
            _ => return,
        };

        if abi == Abi::Rust || abi == Abi::RustIntrinsic || abi == Abi::PlatformIntrinsic {
            return;
        }

        // Process all of the #[link(..)]-style arguments
        let sess = &self.tcx.sess;
        for m in it.attrs.iter().filter(|a| sess.check_name(a, sym::link)) {
            let items = match m.meta_item_list() {
                Some(item) => item,
                None => continue,
            };
            let mut lib = NativeLib {
                name: None,
                kind: NativeLibKind::Unspecified,
                cfg: None,
                foreign_module: Some(self.tcx.hir().local_def_id(it.hir_id).to_def_id()),
                wasm_import_module: None,
            };
            let mut kind_specified = false;

            for item in items.iter() {
                if item.has_name(sym::kind) {
                    kind_specified = true;
                    let kind = match item.value_str() {
                        Some(name) => name,
                        None => continue, // skip like historical compilers
                    };
                    lib.kind = match &*kind.as_str() {
                        "static" => NativeLibKind::StaticBundle,
                        "static-nobundle" => NativeLibKind::StaticNoBundle,
                        "dylib" => NativeLibKind::Dylib,
                        "framework" => NativeLibKind::Framework,
                        "raw-dylib" => NativeLibKind::RawDylib,
                        k => {
                            struct_span_err!(sess, item.span(), E0458, "unknown kind: `{}`", k)
                                .span_label(item.span(), "unknown kind")
                                .span_label(m.span, "")
                                .emit();
                            NativeLibKind::Unspecified
                        }
                    };
                } else if item.has_name(sym::name) {
                    lib.name = item.value_str();
                } else if item.has_name(sym::cfg) {
                    let cfg = match item.meta_item_list() {
                        Some(list) => list,
                        None => continue, // skip like historical compilers
                    };
                    if cfg.is_empty() {
                        sess.span_err(item.span(), "`cfg()` must have an argument");
                    } else if let cfg @ Some(..) = cfg[0].meta_item() {
                        lib.cfg = cfg.cloned();
                    } else {
                        sess.span_err(cfg[0].span(), "invalid argument for `cfg(..)`");
                    }
                } else if item.has_name(sym::wasm_import_module) {
                    match item.value_str() {
                        Some(s) => lib.wasm_import_module = Some(s),
                        None => {
                            let msg = "must be of the form `#[link(wasm_import_module = \"...\")]`";
                            sess.span_err(item.span(), msg);
                        }
                    }
                } else {
                    // currently, like past compilers, ignore unknown
                    // directives here.
                }
            }

            // In general we require #[link(name = "...")] but we allow
            // #[link(wasm_import_module = "...")] without the `name`.
            let requires_name = kind_specified || lib.wasm_import_module.is_none();
            if lib.name.is_none() && requires_name {
                struct_span_err!(
                    sess,
                    m.span,
                    E0459,
                    "`#[link(...)]` specified without \
                                  `name = \"foo\"`"
                )
                .span_label(m.span, "missing `name` argument")
                .emit();
            }
            self.register_native_lib(Some(m.span), lib);
        }
    }

    fn visit_trait_item(&mut self, _it: &'tcx hir::TraitItem<'tcx>) {}
    fn visit_impl_item(&mut self, _it: &'tcx hir::ImplItem<'tcx>) {}
    fn visit_foreign_item(&mut self, _it: &'tcx hir::ForeignItem<'tcx>) {}
}

impl Collector<'tcx> {
    fn register_native_lib(&mut self, span: Option<Span>, lib: NativeLib) {
        if lib.name.as_ref().map(|&s| s == kw::Empty).unwrap_or(false) {
            match span {
                Some(span) => {
                    struct_span_err!(
                        self.tcx.sess,
                        span,
                        E0454,
                        "`#[link(name = \"\")]` given with empty name"
                    )
                    .span_label(span, "empty name given")
                    .emit();
                }
                None => {
                    self.tcx.sess.err("empty library name given via `-l`");
                }
            }
            return;
        }
        let is_osx = self.tcx.sess.target.is_like_osx;
        if lib.kind == NativeLibKind::Framework && !is_osx {
            let msg = "native frameworks are only available on macOS targets";
            match span {
                Some(span) => struct_span_err!(self.tcx.sess, span, E0455, "{}", msg).emit(),
                None => self.tcx.sess.err(msg),
            }
        }
        if lib.cfg.is_some() && !self.tcx.features().link_cfg {
            feature_err(
                &self.tcx.sess.parse_sess,
                sym::link_cfg,
                span.unwrap(),
                "kind=\"link_cfg\" is unstable",
            )
            .emit();
        }
        if lib.kind == NativeLibKind::StaticNoBundle && !self.tcx.features().static_nobundle {
            feature_err(
                &self.tcx.sess.parse_sess,
                sym::static_nobundle,
                span.unwrap_or(rustc_span::DUMMY_SP),
                "kind=\"static-nobundle\" is unstable",
            )
            .emit();
        }
        if lib.kind == NativeLibKind::RawDylib && !self.tcx.features().raw_dylib {
            feature_err(
                &self.tcx.sess.parse_sess,
                sym::raw_dylib,
                span.unwrap_or(rustc_span::DUMMY_SP),
                "kind=\"raw-dylib\" is unstable",
            )
            .emit();
        }
        self.libs.push(lib);
    }

    // Process libs passed on the command line
    fn process_command_line(&mut self) {
        // First, check for errors
        let mut renames = FxHashSet::default();
        for (name, new_name, _) in &self.tcx.sess.opts.libs {
            if let Some(ref new_name) = new_name {
                let any_duplicate = self
                    .libs
                    .iter()
                    .filter_map(|lib| lib.name.as_ref())
                    .any(|n| &n.as_str() == name);
                if new_name.is_empty() {
                    self.tcx.sess.err(&format!(
                        "an empty renaming target was specified for library `{}`",
                        name
                    ));
                } else if !any_duplicate {
                    self.tcx.sess.err(&format!(
                        "renaming of the library `{}` was specified, \
                                                however this crate contains no `#[link(...)]` \
                                                attributes referencing this library.",
                        name
                    ));
                } else if !renames.insert(name) {
                    self.tcx.sess.err(&format!(
                        "multiple renamings were \
                                                specified for library `{}` .",
                        name
                    ));
                }
            }
        }

        // Update kind and, optionally, the name of all native libraries
        // (there may be more than one) with the specified name.  If any
        // library is mentioned more than once, keep the latest mention
        // of it, so that any possible dependent libraries appear before
        // it.  (This ensures that the linker is able to see symbols from
        // all possible dependent libraries before linking in the library
        // in question.)
        for &(ref name, ref new_name, kind) in &self.tcx.sess.opts.libs {
            // If we've already added any native libraries with the same
            // name, they will be pulled out into `existing`, so that we
            // can move them to the end of the list below.
            let mut existing = self
                .libs
                .drain_filter(|lib| {
                    if let Some(lib_name) = lib.name {
                        if lib_name.as_str() == *name {
                            if kind != NativeLibKind::Unspecified {
                                lib.kind = kind;
                            }
                            if let Some(new_name) = new_name {
                                lib.name = Some(Symbol::intern(new_name));
                            }
                            return true;
                        }
                    }
                    false
                })
                .collect::<Vec<_>>();
            if existing.is_empty() {
                // Add if not found
                let new_name = new_name.as_ref().map(|s| &**s); // &Option<String> -> Option<&str>
                let lib = NativeLib {
                    name: Some(Symbol::intern(new_name.unwrap_or(name))),
                    kind,
                    cfg: None,
                    foreign_module: None,
                    wasm_import_module: None,
                };
                self.register_native_lib(None, lib);
            } else {
                // Move all existing libraries with the same name to the
                // end of the command line.
                self.libs.append(&mut existing);
            }
        }
    }
}