// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#include "llvm/ADT/STLExtras.h"
#include "toolchain/check/context.h"
#include "toolchain/check/convert.h"
#include "toolchain/sem_ir/node.h"

namespace Carbon::Check {

// Returns the name scope corresponding to base_id, or nullopt if not a scope.
// On invalid scopes, prints a diagnostic and still returns the scope.
static auto GetAsNameScope(Context& context, SemIR::NodeId base_id)
    -> std::optional<SemIR::NameScopeId> {
  auto base =
      context.semantics_ir().GetNode(context.FollowNameReferences(base_id));
  if (auto base_as_namespace = base.TryAs<SemIR::Namespace>()) {
    return base_as_namespace->name_scope_id;
  }
  if (auto base_as_class = base.TryAs<SemIR::ClassDeclaration>()) {
    auto& class_info = context.semantics_ir().GetClass(base_as_class->class_id);
    if (!class_info.scope_id.is_valid()) {
      CARBON_DIAGNOSTIC(QualifiedExpressionInIncompleteClassScope, Error,
                        "Member access into incomplete class `{0}`.",
                        std::string);
      auto builder = context.emitter().Build(
          context.semantics_ir().GetNode(base_id).parse_node(),
          QualifiedExpressionInIncompleteClassScope,
          context.semantics_ir().StringifyTypeExpression(base_id, true));
      context.NoteIncompleteClass(*base_as_class, builder);
      builder.Emit();
    }
    return class_info.scope_id;
  }
  return std::nullopt;
}

auto HandleMemberAccessExpression(Context& context, Parse::Node parse_node)
    -> bool {
  StringId name_id = context.node_stack().Pop<Parse::NodeKind::Name>();
  auto base_id = context.node_stack().PopExpression();

  // If the base is a name scope, such as a class or namespace, perform lookup
  // into that scope.
  if (auto name_scope_id = GetAsNameScope(context, base_id)) {
    auto node_id = name_scope_id->is_valid()
                       ? context.LookupName(parse_node, name_id, *name_scope_id,
                                            /*print_diagnostics=*/true)
                       : SemIR::NodeId::BuiltinError;
    auto node = context.semantics_ir().GetNode(node_id);
    // TODO: Track that this node was named within `base_id`.
    context.AddNodeAndPush(
        parse_node,
        SemIR::NameReference{parse_node, node.type_id(), name_id, node_id});
    return true;
  }

  // Materialize a temporary for the base expression if necessary.
  base_id = ConvertToValueOrReferenceExpression(context, base_id);
  auto base_type_id = context.semantics_ir().GetNode(base_id).type_id();

  auto base_type = context.semantics_ir().GetNode(
      context.semantics_ir().GetTypeAllowBuiltinTypes(base_type_id));

  switch (base_type.kind()) {
    case SemIR::StructType::Kind: {
      auto refs = context.semantics_ir().GetNodeBlock(
          base_type.As<SemIR::StructType>().fields_id);
      // TODO: Do we need to optimize this with a lookup table for O(1)?
      for (auto [i, ref_id] : llvm::enumerate(refs)) {
        auto field =
            context.semantics_ir().GetNodeAs<SemIR::StructTypeField>(ref_id);
        if (name_id == field.name_id) {
          context.AddNodeAndPush(
              parse_node, SemIR::StructAccess{parse_node, field.field_type_id,
                                              base_id, SemIR::MemberIndex(i)});
          return true;
        }
      }
      CARBON_DIAGNOSTIC(QualifiedExpressionNameNotFound, Error,
                        "Type `{0}` does not have a member `{1}`.", std::string,
                        llvm::StringRef);
      context.emitter().Emit(parse_node, QualifiedExpressionNameNotFound,
                             context.semantics_ir().StringifyType(base_type_id),
                             context.semantics_ir().strings().Get(name_id));
      break;
    }
    default: {
      if (base_type_id != SemIR::TypeId::Error) {
        CARBON_DIAGNOSTIC(QualifiedExpressionUnsupported, Error,
                          "Type `{0}` does not support qualified expressions.",
                          std::string);
        context.emitter().Emit(
            parse_node, QualifiedExpressionUnsupported,
            context.semantics_ir().StringifyType(base_type_id));
      }
      break;
    }
  }

  // Should only be reached on error.
  context.node_stack().Push(parse_node, SemIR::NodeId::BuiltinError);
  return true;
}

auto HandlePointerMemberAccessExpression(Context& context,
                                         Parse::Node parse_node) -> bool {
  return context.TODO(parse_node, "HandlePointerMemberAccessExpression");
}

auto HandleName(Context& context, Parse::Node parse_node) -> bool {
  auto name_id = context.tokens().GetIdentifier(
      context.parse_tree().node_token(parse_node));
  // The parent is responsible for binding the name.
  context.node_stack().Push(parse_node, name_id);
  return true;
}

auto HandleNameExpression(Context& context, Parse::Node parse_node) -> bool {
  auto name_id = context.tokens().GetIdentifier(
      context.parse_tree().node_token(parse_node));
  auto value_id =
      context.LookupName(parse_node, name_id, SemIR::NameScopeId::Invalid,
                         /*print_diagnostics=*/true);
  auto value = context.semantics_ir().GetNode(value_id);
  // This is a reference to a name binding that has a value and a type.
  CARBON_CHECK(value.kind().value_kind() == SemIR::NodeValueKind::Typed);
  context.AddNodeAndPush(
      parse_node,
      SemIR::NameReference{parse_node, value.type_id(), name_id, value_id});
  return true;
}

auto HandleQualifiedDeclaration(Context& context, Parse::Node parse_node)
    -> bool {
  auto pop_and_apply_first_child = [&]() {
    if (context.parse_tree().node_kind(context.node_stack().PeekParseNode()) !=
        Parse::NodeKind::QualifiedDeclaration) {
      // First QualifiedDeclaration in a chain.
      auto [parse_node1, node_id1] =
          context.node_stack().PopExpressionWithParseNode();
      context.declaration_name_stack().ApplyExpressionQualifier(
          parse_node1, context.FollowNameReferences(node_id1));
      // Add the QualifiedDeclaration so that it can be used for bracketing.
      context.node_stack().Push(parse_node);
    } else {
      // Nothing to do: the QualifiedDeclaration remains as a bracketing node
      // for later QualifiedDeclarations.
    }
  };

  Parse::Node parse_node2 = context.node_stack().PeekParseNode();
  if (context.parse_tree().node_kind(parse_node2) == Parse::NodeKind::Name) {
    StringId name_id2 = context.node_stack().Pop<Parse::NodeKind::Name>();
    pop_and_apply_first_child();
    context.declaration_name_stack().ApplyNameQualifier(parse_node2, name_id2);
  } else {
    SemIR::NodeId node_id2 = context.node_stack().PopExpression();
    pop_and_apply_first_child();
    context.declaration_name_stack().ApplyExpressionQualifier(parse_node2,
                                                              node_id2);
  }

  return true;
}

auto HandleSelfTypeNameExpression(Context& context, Parse::Node parse_node)
    -> bool {
  return context.TODO(parse_node, "HandleSelfTypeNameExpression");
}

auto HandleSelfValueName(Context& context, Parse::Node parse_node) -> bool {
  return context.TODO(parse_node, "HandleSelfValueName");
}

}  // namespace Carbon::Check