// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! Code for translating references to other items (DefIds).

use syntax::codemap::DUMMY_SP;
use rustc::front::map;
use rustc::middle::ty::{self, Ty, TypeFoldable};
use rustc::middle::subst::Substs;
use rustc::middle::const_eval;
use rustc::middle::def_id::DefId;
use rustc::middle::traits;
use rustc::mir::repr::ItemKind;
use trans::common::{Block, fulfill_obligation};
use trans::base;
use trans::closure;
use trans::expr;
use trans::monomorphize;
use trans::meth;
use trans::inline;

use super::MirContext;
use super::operand::{OperandRef, OperandValue};

impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
    /// Translate reference to item.
    pub fn trans_item_ref(&mut self,
                          bcx: Block<'bcx, 'tcx>,
                          ty: Ty<'tcx>,
                          kind: ItemKind,
                          substs: &'tcx Substs<'tcx>,
                          did: DefId)
                          -> OperandRef<'tcx> {
        debug!("trans_item_ref(ty={:?}, kind={:?}, substs={:?}, did={})",
            ty, kind, substs, bcx.tcx().item_path_str(did));

        match kind {
            ItemKind::Function => self.trans_fn_ref(bcx, ty, substs, did),
            ItemKind::Method => match bcx.tcx().impl_or_trait_item(did).container() {
                ty::ImplContainer(_) => self.trans_fn_ref(bcx, ty, substs, did),
                ty::TraitContainer(tdid) => self.trans_trait_method(bcx, ty, did, tdid, substs)
            },
            ItemKind::Constant => {
                let did = inline::maybe_instantiate_inline(bcx.ccx(), did);
                let expr = const_eval::lookup_const_by_id(bcx.tcx(), did, None, Some(substs))
                            .expect("def was const, but lookup_const_by_id failed");
                // FIXME: this is falling back to translating from HIR. This is not easy to fix,
                // because we would have somehow adapt const_eval to work on MIR rather than HIR.
                let d = expr::trans(bcx, expr);
                OperandRef::from_rvalue_datum(d.datum.to_rvalue_datum(d.bcx, "").datum)
            }
        }
    }

    /// Translates references to a function-like items.
    ///
    /// That includes regular functions, non-static methods, struct and enum variant constructors,
    /// closures and possibly more.
    ///
    /// This is an adaptation of callee::trans_fn_ref_with_substs.
    pub fn trans_fn_ref(&mut self,
                        bcx: Block<'bcx, 'tcx>,
                        ty: Ty<'tcx>,
                        substs: &'tcx Substs<'tcx>,
                        did: DefId)
                        -> OperandRef<'tcx> {
        debug!("trans_fn_ref(ty={:?}, substs={:?}, did={})",
            ty, substs, bcx.tcx().item_path_str(did));

        let did = inline::maybe_instantiate_inline(bcx.ccx(), did);

        if !substs.types.is_empty() || is_named_tuple_constructor(bcx.tcx(), did) {
            let (val, fn_ty, _) = monomorphize::monomorphic_fn(bcx.ccx(), did, substs, None);
            // FIXME: cast fnptr to proper type if necessary
            OperandRef {
                ty: fn_ty,
                val: OperandValue::Immediate(val)
            }
        } else {
            let val = if let Some(node_id) = bcx.tcx().map.as_local_node_id(did) {
                base::get_item_val(bcx.ccx(), node_id)
            } else {
                base::trans_external_path(bcx.ccx(), did, ty)
            };
            // FIXME: cast fnptr to proper type if necessary
            OperandRef {
                ty: ty,
                val: OperandValue::Immediate(val)
            }
        }
    }

    /// Translates references to trait methods.
    ///
    /// This is an adaptation of meth::trans_static_method_callee
    pub fn trans_trait_method(&mut self,
                              bcx: Block<'bcx, 'tcx>,
                              ty: Ty<'tcx>,
                              method_id: DefId,
                              trait_id: DefId,
                              substs: &'tcx Substs<'tcx>)
                              -> OperandRef<'tcx> {
        debug!("trans_static_method(ty={:?}, method={}, trait={}, substs={:?})",
                ty,
                bcx.tcx().item_path_str(method_id),
                bcx.tcx().item_path_str(trait_id),
                substs);

        let ccx = bcx.ccx();
        let tcx = bcx.tcx();
        let trait_ref = ty::Binder(substs.to_trait_ref(tcx, trait_id));
        let vtbl = fulfill_obligation(ccx, DUMMY_SP, trait_ref);
        match vtbl {
            traits::VtableImpl(traits::VtableImplData {
                impl_def_id, substs: impl_substs, ..
            }) => {
                assert!(!impl_substs.types.needs_infer());

                let mname = tcx.item_name(method_id);

                let callee_substs = impl_substs.with_method_from(substs);
                let mth = tcx.get_impl_method(impl_def_id, callee_substs, mname);
                let mth_substs = tcx.mk_substs(mth.substs);
                self.trans_fn_ref(bcx, ty, mth_substs, mth.method.def_id)
            },
            traits::VtableClosure(data) => {
                let trait_closure_kind = bcx.tcx().lang_items.fn_trait_kind(trait_id).unwrap();
                let llfn = closure::trans_closure_method(bcx.ccx(),
                                                         data.closure_def_id,
                                                         data.substs,
                                                         trait_closure_kind);
                OperandRef {
                    ty: ty,
                    val: OperandValue::Immediate(llfn)
                }
            },
            traits::VtableObject(ref data) => {
                let idx = traits::get_vtable_index_of_object_method(tcx, data, method_id);
                OperandRef::from_rvalue_datum(
                    meth::trans_object_shim(ccx, data.upcast_trait_ref.clone(), method_id, idx)
                )
            }
            _ => {
                tcx.sess.bug(&format!("static call to invalid vtable: {:?}", vtbl));
            }
        }
   }
}

fn is_named_tuple_constructor(tcx: &ty::ctxt, def_id: DefId) -> bool {
    let node_id = match tcx.map.as_local_node_id(def_id) {
        Some(n) => n,
        None => { return false; }
    };
    match tcx.map.find(node_id).expect("local item should be in ast map") {
        map::NodeVariant(v) => {
            v.node.data.is_tuple()
        }
        map::NodeStructCtor(_) => true,
        _ => false
    }
}