// 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 "toolchain/check/context.h"
#include "toolchain/check/decl_name_stack.h"
#include "toolchain/check/generic.h"
#include "toolchain/check/handle.h"
#include "toolchain/check/inst.h"
#include "toolchain/check/modifiers.h"
#include "toolchain/check/name_component.h"
#include "toolchain/check/name_lookup.h"
#include "toolchain/parse/typed_nodes.h"
#include "toolchain/sem_ir/ids.h"
#include "toolchain/sem_ir/typed_insts.h"

namespace Carbon::Check {

auto HandleParseNode(Context& context, Parse::ExportIntroducerId /*node_id*/)
    -> bool {
  // Export declarations can't be generic, but we might have parsed a generic
  // parameter in their name, so enter a generic scope just in case.
  StartGenericDecl(context);
  context.decl_introducer_state_stack().Push<Lex::TokenKind::Export>();
  // TODO: Probably need to update DeclNameStack to restrict to only namespaces.
  context.decl_name_stack().PushScopeAndStartName();
  return true;
}

auto HandleParseNode(Context& context, Parse::ExportDeclId node_id) -> bool {
  auto name_context = context.decl_name_stack().FinishName(
      PopNameComponentWithoutParams(context, Lex::TokenKind::Export));
  DiscardGenericDecl(context);
  context.decl_name_stack().PopScope();

  auto introducer =
      context.decl_introducer_state_stack().Pop<Lex::TokenKind::Export>();
  LimitModifiersOnDecl(context, introducer, KeywordModifierSet::None);

  if (name_context.state == DeclNameStack::NameContext::State::Error) {
    // Should already be diagnosed.
    return true;
  }

  // Exporting uses the decl name primarily for lookup, so treat poisoning the
  // same as "not found".
  auto inst_id =
      name_context.state == DeclNameStack::NameContext::State::Poisoned
          ? SemIR::InstId::None
          : name_context.prev_inst_id();
  if (!inst_id.has_value()) {
    DiagnoseNameNotFound(context, node_id, name_context.name_id_for_new_inst());
    return true;
  }

  auto inst = context.insts().Get(inst_id);

  if (inst.Is<SemIR::ExportDecl>()) {
    CARBON_DIAGNOSTIC(ExportRedundant, Warning,
                      "`export` matches previous `export`");
    CARBON_DIAGNOSTIC(ExportPrevious, Note, "previous `export` here");
    context.emitter()
        .Build(node_id, ExportRedundant)
        // Use the location of the export itself, not the exported instruction.
        //
        // TODO: This construction of a LocId that does not just contain the
        // InstId prevents GetAbsoluteNodeIdImpl() from seeing the `ExportDecl`
        // instruction, which prevents it from chasing through it to the entity
        // being exported. It might be nice to make this more explicit.
        .Note(context.insts().GetCanonicalLocId(inst_id), ExportPrevious)
        .Emit();
    return true;
  }

  auto import_ref = context.insts().TryGetAs<SemIR::ImportRefLoaded>(inst_id);
  if (!import_ref) {
    CARBON_DIAGNOSTIC(ExportNotImportedEntity, Error,
                      "only imported entities are valid for `export`");
    CARBON_DIAGNOSTIC(ExportNotImportedEntitySource, Note,
                      "name is declared here");
    context.emitter()
        .Build(node_id, ExportNotImportedEntity)
        .Note(inst_id, ExportNotImportedEntitySource)
        .Emit();
    return true;
  }

  auto export_id =
      AddInst<SemIR::ExportDecl>(context, node_id,
                                 {.type_id = import_ref->type_id,
                                  .entity_name_id = import_ref->entity_name_id,
                                  .value_id = inst_id});
  context.exports().push_back(export_id);

  // Replace the ImportRef in name lookup, both for the above duplicate
  // diagnostic and so that cross-package imports can find it easily.
  auto entity_name = context.entity_names().Get(import_ref->entity_name_id);
  auto& parent_scope = context.name_scopes().Get(entity_name.parent_scope_id);
  auto& scope_result =
      parent_scope.GetEntry(*parent_scope.Lookup(entity_name.name_id)).result;
  CARBON_CHECK(scope_result.target_inst_id() == inst_id);
  scope_result = SemIR::ScopeLookupResult::MakeFound(
      export_id, scope_result.access_kind());

  return true;
}

}  // namespace Carbon::Check
