// 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/modifiers.h"

#include "toolchain/check/decl_state.h"

namespace Carbon::Check {

static auto ReportNotAllowed(Context& context, Parse::NodeId modifier_node,
                             Lex::TokenKind decl_kind,
                             llvm::StringRef context_string,
                             Parse::NodeId context_node) -> void {
  CARBON_DIAGNOSTIC(ModifierNotAllowedOn, Error,
                    "`{0}` not allowed on `{1}` declaration{2}.",
                    Lex::TokenKind, Lex::TokenKind, std::string);
  auto diag = context.emitter().Build(modifier_node, ModifierNotAllowedOn,
                                      context.token_kind(modifier_node),
                                      decl_kind, context_string.str());
  if (context_node.is_valid()) {
    CARBON_DIAGNOSTIC(ModifierNotInContext, Note,
                      "Containing definition here.");
    diag.Note(context_node, ModifierNotInContext);
  }
  diag.Emit();
}

// Returns the KeywordModifierSet corresponding to the ModifierOrder entry.
static auto ModifierOrderAsSet(ModifierOrder order) -> KeywordModifierSet {
  switch (order) {
    case ModifierOrder::Access:
      return KeywordModifierSet::Access;
    case ModifierOrder::Extern:
      return KeywordModifierSet::Extern;
    case ModifierOrder::Decl:
      return KeywordModifierSet::Decl;
  }
}

auto ForbidModifiersOnDecl(Context& context, KeywordModifierSet forbidden,
                           Lex::TokenKind decl_kind,
                           llvm::StringRef context_string,
                           Parse::NodeId context_node) -> void {
  auto& s = context.decl_state_stack().innermost();
  auto not_allowed = s.modifier_set & forbidden;
  if (!not_allowed) {
    return;
  }

  for (auto order_index = 0;
       order_index <= static_cast<int8_t>(ModifierOrder::Last); ++order_index) {
    auto order = static_cast<ModifierOrder>(order_index);
    if (!!(not_allowed & ModifierOrderAsSet(order))) {
      ReportNotAllowed(context, s.modifier_node_id(order), decl_kind,
                       context_string, context_node);
      s.set_modifier_node_id(order, Parse::NodeId::Invalid);
    }
  }

  s.modifier_set &= ~forbidden;
}

// Returns the instruction that owns the given scope, or Invalid if the scope is
// not associated with an instruction.
static auto GetScopeInstId(Context& context, SemIR::NameScopeId scope_id)
    -> SemIR::InstId {
  if (!scope_id.is_valid()) {
    return SemIR::InstId::Invalid;
  }
  return context.name_scopes().Get(scope_id).inst_id;
}

// Returns the instruction that owns the given scope, or Invalid if the scope is
// not associated with an instruction.
static auto GetScopeInst(Context& context, SemIR::NameScopeId scope_id)
    -> std::optional<SemIR::Inst> {
  auto inst_id = GetScopeInstId(context, scope_id);
  if (!inst_id.is_valid()) {
    return std::nullopt;
  }
  return context.insts().Get(inst_id);
}

auto CheckAccessModifiersOnDecl(Context& context, Lex::TokenKind decl_kind,
                                SemIR::NameScopeId target_scope_id) -> void {
  auto target = GetScopeInst(context, target_scope_id);
  if (target && target->Is<SemIR::Namespace>()) {
    // TODO: This assumes that namespaces can only be declared at file scope. If
    // we add support for non-file-scope namespaces, we will need to check the
    // parents of the target scope to determine whether we're at file scope.
    ForbidModifiersOnDecl(
        context, KeywordModifierSet::Protected, decl_kind,
        " at file scope, `protected` is only allowed on class members");
    return;
  }

  if (target && target->Is<SemIR::ClassDecl>()) {
    // Both `private` and `protected` allowed in a class definition.
    return;
  }

  // Otherwise neither `private` nor `protected` allowed.
  ForbidModifiersOnDecl(context, KeywordModifierSet::Protected, decl_kind,
                        ", `protected` is only allowed on class members");
  ForbidModifiersOnDecl(
      context, KeywordModifierSet::Private, decl_kind,
      ", `private` is only allowed on class members and at file scope");
}

auto CheckMethodModifiersOnFunction(Context& context,
                                    SemIR::NameScopeId target_scope_id)
    -> void {
  const Lex::TokenKind decl_kind = Lex::TokenKind::Fn;
  auto target_id = GetScopeInstId(context, target_scope_id);
  if (target_id.is_valid()) {
    if (auto class_decl =
            context.insts().TryGetAs<SemIR::ClassDecl>(target_id)) {
      auto inheritance_kind =
          context.classes().Get(class_decl->class_id).inheritance_kind;
      if (inheritance_kind == SemIR::Class::Final) {
        ForbidModifiersOnDecl(context, KeywordModifierSet::Virtual, decl_kind,
                              " in a non-abstract non-base `class` definition",
                              context.insts().GetNodeId(target_id));
      }
      if (inheritance_kind != SemIR::Class::Abstract) {
        ForbidModifiersOnDecl(context, KeywordModifierSet::Abstract, decl_kind,
                              " in a non-abstract `class` definition",
                              context.insts().GetNodeId(target_id));
      }
      return;
    }
  }

  ForbidModifiersOnDecl(context, KeywordModifierSet::Method, decl_kind,
                        " outside of a class");
}

auto ForbidExternModifierOnDefinition(Context& context,
                                      Lex::TokenKind decl_kind) -> void {
  ForbidModifiersOnDecl(context, KeywordModifierSet::Extern, decl_kind,
                        " that provides a definition");
}

auto RequireDefaultFinalOnlyInInterfaces(Context& context,
                                         Lex::TokenKind decl_kind,
                                         SemIR::NameScopeId target_scope_id)
    -> void {
  auto target = GetScopeInst(context, target_scope_id);
  if (target && target->Is<SemIR::InterfaceDecl>()) {
    // Both `default` and `final` allowed in an interface definition.
    return;
  }
  ForbidModifiersOnDecl(context, KeywordModifierSet::Interface, decl_kind,
                        " outside of an interface");
}

}  // namespace Carbon::Check