#include "lex_utils.h"
#include "message_handler.h"
#include "query_utils.h"
#include "queue_manager.h"

#include <ctype.h>
#include <limits.h>
#include <cstdlib>

namespace {

struct Ipc_TextDocumentDefinition
    : public RequestMessage<Ipc_TextDocumentDefinition> {
  const static IpcId kIpcId = IpcId::TextDocumentDefinition;
  lsTextDocumentPositionParams params;
};
MAKE_REFLECT_STRUCT(Ipc_TextDocumentDefinition, id, params);
REGISTER_IPC_MESSAGE(Ipc_TextDocumentDefinition);

struct Out_TextDocumentDefinition
    : public lsOutMessage<Out_TextDocumentDefinition> {
  lsRequestId id;
  std::vector<lsLocationEx> result;
};
MAKE_REFLECT_STRUCT(Out_TextDocumentDefinition, jsonrpc, id, result);

std::vector<Use> GetGotoDefinitionTargets(QueryDatabase* db, SymbolRef sym) {
  switch (sym.kind) {
    case SymbolKind::Var: {
      std::vector<Use> ret = GetNonDefDeclarations(db, sym);
      // If there is no declaration, jump the its type.
      if (ret.empty()) {
        for (auto& def : db->GetVar(sym).def)
          if (def.type) {
            if (Maybe<Use> use = GetDefinitionSpellingOfSymbol(
                    db, SymbolIdx{*def.type, SymbolKind::Type})) {
              ret.push_back(*use);
              break;
            }
          }
      }
      return ret;
    }
    default:
      return GetNonDefDeclarations(db, sym);
  }
}

struct TextDocumentDefinitionHandler
    : BaseMessageHandler<Ipc_TextDocumentDefinition> {
  void Run(Ipc_TextDocumentDefinition* request) override {
    QueryFileId file_id;
    QueryFile* file;
    if (!FindFileOrFail(db, project, request->id,
                        request->params.textDocument.uri.GetPath(), &file,
                        &file_id)) {
      return;
    }

    WorkingFile* working_file =
        working_files->GetFileByFilename(file->def->path);

    Out_TextDocumentDefinition out;
    out.id = request->id;

    Maybe<Use> on_def;
    bool has_symbol = false;
    int target_line = request->params.position.line;
    int target_column = request->params.position.character;

    for (SymbolRef sym :
         FindSymbolsAtLocation(working_file, file, request->params.position)) {
      // Found symbol. Return definition.
      has_symbol = true;

      // Special cases which are handled:
      //  - symbol has declaration but no definition (ie, pure virtual)
      //  - start at spelling but end at extent for better mouse tooltip
      //  - goto declaration while in definition of recursive type
      std::vector<Use> uses;
      EachEntityDef(db, sym, [&](const auto& def) {
        if (def.spell && def.extent) {
          Use spell = *def.spell;
          // If on a definition, clear |uses| to find declarations below.
          if (spell.file == file_id &&
              spell.range.Contains(target_line, target_column)) {
            on_def = spell;
            uses.clear();
            return false;
          }
          // We use spelling start and extent end because this causes vscode
          // to highlight the entire definition when previewing / hoving with
          // the mouse.
          spell.range.end = def.extent->range.end;
          uses.push_back(spell);
        }
        return true;
      });

      if (uses.empty()) {
        // The symbol has no definition or the cursor is on a definition.
        uses = GetGotoDefinitionTargets(db, sym);
        // There is no declaration but the cursor is on a definition.
        if (uses.empty() && on_def)
          uses.push_back(*on_def);
      }
      AddRange(&out.result,
               GetLsLocationExs(db, working_files, uses, config->xref.container,
                                config->xref.maxNum));
      if (!out.result.empty())
        break;
    }

    // No symbols - check for includes.
    if (out.result.empty()) {
      for (const IndexInclude& include : file->def->includes) {
        if (include.line == target_line) {
          lsLocationEx result;
          result.uri = lsDocumentUri::FromPath(include.resolved_path);
          out.result.push_back(result);
          has_symbol = true;
          break;
        }
      }
      // Find the best match of the identifier at point.
      if (!has_symbol) {
        lsPosition position = request->params.position;
        const std::string& buffer = working_file->buffer_content;
        std::string_view query = LexIdentifierAroundPos(position, buffer);
        bool has_scope = query.find(':') != std::string::npos;

        // For symbols whose short/detailed names contain |query| as a
        // substring, we use the tuple <length difference, matching position,
        // not in the same file, line distance> to find the best match.
        std::tuple<int, int, bool, int> best_score{INT_MAX, 0, true, 0};
        int best_i = -1;
        for (int i = 0; i < (int)db->symbols.size(); ++i) {
          if (db->symbols[i].kind == SymbolKind::Invalid)
            continue;

          std::string_view name = has_scope ? db->GetSymbolDetailedName(i)
                                            : db->GetSymbolShortName(i);
          auto pos = name.find(query);
          if (pos == std::string::npos)
            continue;
          Maybe<Use> use = GetDefinitionSpellingOfSymbol(db, db->symbols[i]);
          if (!use)
            continue;

          std::tuple<int, int, bool, int> score{
              int(name.size() - query.size()), int(pos), use->file != file_id,
              std::abs(use->range.start.line - position.line)};
          if (score < best_score) {
            best_score = score;
            best_i = i;
          }
        }
        if (best_i != -1) {
          Maybe<Use> use =
              GetDefinitionSpellingOfSymbol(db, db->symbols[best_i]);
          assert(use);
          if (auto ls_loc = GetLsLocationEx(db, working_files, *use,
                                            config->xref.container))
            out.result.push_back(*ls_loc);
        }
      }
    }

    QueueManager::WriteStdout(IpcId::TextDocumentDefinition, out);
  }
};
REGISTER_MESSAGE_HANDLER(TextDocumentDefinitionHandler);
}  // namespace