// 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_state.h"
#include "toolchain/lex/token_kind.h"

namespace Carbon::Check {

CARBON_DIAGNOSTIC(ModifierPrevious, Note, "`{0}` previously appeared here.",
                  Lex::TokenKind);

static auto EmitRepeatedDiagnostic(Context& context, Parse::NodeId first_node,
                                   Parse::NodeId second_node) -> void {
  CARBON_DIAGNOSTIC(ModifierRepeated, Error, "`{0}` repeated on declaration.",
                    Lex::TokenKind);
  context.emitter()
      .Build(second_node, ModifierRepeated, context.token_kind(second_node))
      .Note(first_node, ModifierPrevious, context.token_kind(first_node))
      .Emit();
}

static auto EmitNotAllowedWithDiagnostic(Context& context,
                                         Parse::NodeId first_node,
                                         Parse::NodeId second_node) -> void {
  CARBON_DIAGNOSTIC(ModifierNotAllowedWith, Error,
                    "`{0}` not allowed on declaration with `{1}`.",
                    Lex::TokenKind, Lex::TokenKind);
  context.emitter()
      .Build(second_node, ModifierNotAllowedWith,
             context.token_kind(second_node), context.token_kind(first_node))
      .Note(first_node, ModifierPrevious, context.token_kind(first_node))
      .Emit();
}

static auto HandleModifier(Context& context, Parse::NodeId node_id,
                           KeywordModifierSet keyword) -> bool {
  auto& s = context.decl_state_stack().innermost();

  ModifierOrder order;
  KeywordModifierSet later_modifiers;
  if (!!(keyword & KeywordModifierSet::Access)) {
    order = ModifierOrder::Access;
    later_modifiers = KeywordModifierSet::Extern | KeywordModifierSet::Decl;
  } else if (keyword == KeywordModifierSet::Extern) {
    order = ModifierOrder::Extern;
    later_modifiers = KeywordModifierSet::Decl;
  } else {
    order = ModifierOrder::Decl;
    later_modifiers = KeywordModifierSet::None;
  }

  auto current_modifier_node_id = s.modifier_node_id(order);
  if (!!(s.modifier_set & keyword)) {
    EmitRepeatedDiagnostic(context, current_modifier_node_id, node_id);
  } else if (current_modifier_node_id.is_valid()) {
    EmitNotAllowedWithDiagnostic(context, current_modifier_node_id, node_id);
  } else if (auto later_modifier_set = s.modifier_set & later_modifiers;
             !!later_modifier_set) {
    // At least one later modifier is present. Diagnose using the closest.
    Parse::NodeId closest_later_modifier = Parse::NodeId::Invalid;
    for (auto later_order = static_cast<int8_t>(order) + 1;
         later_order <= static_cast<int8_t>(ModifierOrder::Last);
         ++later_order) {
      if (s.ordered_modifier_node_ids[later_order] != Parse::NodeId::Invalid) {
        closest_later_modifier = s.ordered_modifier_node_ids[later_order];
        break;
      }
    }
    CARBON_CHECK(closest_later_modifier.is_valid());

    CARBON_DIAGNOSTIC(ModifierMustAppearBefore, Error,
                      "`{0}` must appear before `{1}`.", Lex::TokenKind,
                      Lex::TokenKind);
    context.emitter()
        .Build(node_id, ModifierMustAppearBefore, context.token_kind(node_id),
               context.token_kind(closest_later_modifier))
        .Note(closest_later_modifier, ModifierPrevious,
              context.token_kind(closest_later_modifier))
        .Emit();
  } else {
    s.modifier_set |= keyword;
    s.set_modifier_node_id(order, node_id);
  }
  return true;
}

#define CARBON_PARSE_NODE_KIND(...)
#define CARBON_PARSE_NODE_KIND_TOKEN_MODIFIER(Name, ...)                 \
  auto Handle##Name##Modifier(Context& context,                          \
                              Parse::Name##ModifierId node_id) -> bool { \
    return HandleModifier(context, node_id, KeywordModifierSet::Name);   \
  }
#include "toolchain/parse/node_kind.def"

}  // namespace Carbon::Check