// Copyright (C) 2020 Free Software Foundation, Inc.

// This file is part of GCC.

// GCC is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 3, or (at your option) any later
// version.

// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.

// You should have received a copy of the GNU General Public License
// along with GCC; see the file COPYING3.  If not see
// <http://www.gnu.org/licenses/>.

#include "rust-linemap.h"
#include "rust-backend.h"
#include "rust-compile-resolve-path.h"
#include "rust-compile-item.h"
#include "rust-hir-trait-resolve.h"
#include "rust-hir-path-probe.h"

namespace Rust {
namespace Compile {

void
ResolvePathRef::visit (HIR::PathInExpression &expr)
{
  // need to look up the reference for this identifier
  NodeId ref_node_id = UNKNOWN_NODEID;
  if (ctx->get_resolver ()->lookup_resolved_name (
	expr.get_mappings ().get_nodeid (), &ref_node_id))
    {
      Resolver::Definition def;
      if (!ctx->get_resolver ()->lookup_definition (ref_node_id, &def))
	{
	  rust_error_at (expr.get_locus (),
			 "unknown reference for resolved name");
	  return;
	}
      ref_node_id = def.parent;
    }

  // this can fail because it might be a Constructor for something
  // in that case the caller should attempt ResolvePathType::Compile
  if (ref_node_id == UNKNOWN_NODEID)
    return;

  HirId ref;
  if (!ctx->get_mappings ()->lookup_node_to_hir (
	expr.get_mappings ().get_crate_num (), ref_node_id, &ref))
    {
      rust_error_at (expr.get_locus (), "reverse call path lookup failure");
      return;
    }

  // might be a constant
  if (ctx->lookup_const_decl (ref, &resolved))
    return;

  // this might be a variable reference or a function reference
  Bvariable *var = nullptr;
  if (ctx->lookup_var_decl (ref, &var))
    {
      resolved = ctx->get_backend ()->var_expression (var, expr.get_locus ());
      return;
    }

  // must be a function call but it might be a generic function which needs to
  // be compiled first
  TyTy::BaseType *lookup = nullptr;
  bool ok = ctx->get_tyctx ()->lookup_type (expr.get_mappings ().get_hirid (),
					    &lookup);
  rust_assert (ok);
  rust_assert (lookup->get_kind () == TyTy::TypeKind::FNDEF);

  Bfunction *fn = nullptr;
  if (!ctx->lookup_function_decl (lookup->get_ty_ref (), &fn))
    {
      // it must resolve to some kind of HIR::Item or HIR::InheritImplItem
      HIR::Item *resolved_item = ctx->get_mappings ()->lookup_hir_item (
	expr.get_mappings ().get_crate_num (), ref);
      if (resolved_item != nullptr)
	{
	  if (!lookup->has_subsititions_defined ())
	    CompileItem::compile (resolved_item, ctx);
	  else
	    CompileItem::compile (resolved_item, ctx, true, lookup);
	}
      else
	{
	  HirId parent_impl_id = UNKNOWN_HIRID;
	  HIR::ImplItem *resolved_item
	    = ctx->get_mappings ()->lookup_hir_implitem (
	      expr.get_mappings ().get_crate_num (), ref, &parent_impl_id);

	  if (resolved_item == nullptr)
	    {
	      // it might be resolved to a trait item
	      HIR::TraitItem *trait_item
		= ctx->get_mappings ()->lookup_hir_trait_item (
		  expr.get_mappings ().get_crate_num (), ref);
	      HIR::Trait *trait
		= ctx->get_mappings ()->lookup_trait_item_mapping (
		  trait_item->get_mappings ().get_hirid ());

	      Resolver::TraitReference *trait_ref
		= &Resolver::TraitReference::error_node ();
	      bool ok = ctx->get_tyctx ()->lookup_trait_reference (
		trait->get_mappings ().get_defid (), &trait_ref);
	      rust_assert (ok);

	      TyTy::BaseType *receiver = nullptr;
	      ok = ctx->get_tyctx ()->lookup_receiver (
		expr.get_mappings ().get_hirid (), &receiver);
	      rust_assert (ok);

	      if (receiver->get_kind () == TyTy::TypeKind::PARAM)
		{
		  TyTy::ParamType *p
		    = static_cast<TyTy::ParamType *> (receiver);
		  receiver = p->resolve ();
		}

	      // the type resolver can only resolve type bounds to their trait
	      // item so its up to us to figure out if this path should resolve
	      // to an trait-impl-block-item or if it can be defaulted to the
	      // trait-impl-item's definition
	      std::vector<Resolver::PathProbeCandidate> candidates
		= Resolver::PathProbeType::Probe (
		  receiver, expr.get_final_segment ().get_segment (), true,
		  false, true);

	      if (candidates.size () == 0)
		{
		  // this means we are defaulting back to the trait_item if
		  // possible
		  // TODO
		  gcc_unreachable ();
		}
	      else
		{
		  Resolver::PathProbeCandidate &candidate = candidates.at (0);
		  rust_assert (candidate.is_impl_candidate ());

		  HIR::ImplBlock *impl = candidate.item.impl.parent;
		  HIR::ImplItem *impl_item = candidate.item.impl.impl_item;

		  TyTy::BaseType *self = nullptr;
		  bool ok = ctx->get_tyctx ()->lookup_type (
		    impl->get_type ()->get_mappings ().get_hirid (), &self);
		  rust_assert (ok);

		  if (!lookup->has_subsititions_defined ())
		    CompileInherentImplItem::Compile (self, impl_item, ctx,
						      true);
		  else
		    CompileInherentImplItem::Compile (self, impl_item, ctx,
						      true, lookup);

		  lookup->set_ty_ref (
		    impl_item->get_impl_mappings ().get_hirid ());
		}
	    }
	  else
	    {
	      rust_assert (parent_impl_id != UNKNOWN_HIRID);
	      HIR::Item *impl_ref = ctx->get_mappings ()->lookup_hir_item (
		expr.get_mappings ().get_crate_num (), parent_impl_id);
	      rust_assert (impl_ref != nullptr);
	      HIR::ImplBlock *impl = static_cast<HIR::ImplBlock *> (impl_ref);

	      TyTy::BaseType *self = nullptr;
	      bool ok = ctx->get_tyctx ()->lookup_type (
		impl->get_type ()->get_mappings ().get_hirid (), &self);
	      rust_assert (ok);

	      if (!lookup->has_subsititions_defined ())
		CompileInherentImplItem::Compile (self, resolved_item, ctx,
						  true);
	      else
		CompileInherentImplItem::Compile (self, resolved_item, ctx,
						  true, lookup);
	    }
	}

      if (!ctx->lookup_function_decl (lookup->get_ty_ref (), &fn))
	{
	  resolved = ctx->get_backend ()->error_expression ();
	  rust_error_at (expr.get_locus (),
			 "forward declaration was not compiled");
	  return;
	}
    }

  resolved
    = ctx->get_backend ()->function_code_expression (fn, expr.get_locus ());
}

} // namespace Compile
} // namespace Rust