diff --git a/compilation_database_loader.cc b/compilation_database_loader.cc
index b21134f4..09b8d84c 100644
--- a/compilation_database_loader.cc
+++ b/compilation_database_loader.cc
@@ -13,7 +13,6 @@ std::vector<CompilationEntry> LoadCompilationEntriesFromDirectory(const std::str
     exit(1);
   }
 
-
   CXCompileCommands cx_commands = clang_CompilationDatabase_getAllCompileCommands(cx_db);
 
   unsigned int num_commands = clang_CompileCommands_getSize(cx_commands);
diff --git a/indexer.cpp b/indexer.cpp
index a30bd3ed..1f9ad536 100644
--- a/indexer.cpp
+++ b/indexer.cpp
@@ -1,59 +1,59 @@
 #include "indexer.h"
 
-ParsingDatabase::ParsingDatabase() {}
+IndexedFile::IndexedFile() {}
 
 // TODO: Optimize for const char*?
-TypeId ParsingDatabase::ToTypeId(const std::string& usr) {
+TypeId IndexedFile::ToTypeId(const std::string& usr) {
   auto it = usr_to_type_id.find(usr);
   if (it != usr_to_type_id.end())
     return it->second;
 
   TypeId id(types.size());
-  types.push_back(TypeDef(id, usr));
+  types.push_back(IndexedTypeDef(id, usr));
   usr_to_type_id[usr] = id;
   return id;
 }
-FuncId ParsingDatabase::ToFuncId(const std::string& usr) {
+FuncId IndexedFile::ToFuncId(const std::string& usr) {
   auto it = usr_to_func_id.find(usr);
   if (it != usr_to_func_id.end())
     return it->second;
 
   FuncId id(funcs.size());
-  funcs.push_back(FuncDef(id, usr));
+  funcs.push_back(IndexedFuncDef(id, usr));
   usr_to_func_id[usr] = id;
   return id;
 }
-VarId ParsingDatabase::ToVarId(const std::string& usr) {
+VarId IndexedFile::ToVarId(const std::string& usr) {
   auto it = usr_to_var_id.find(usr);
   if (it != usr_to_var_id.end())
     return it->second;
 
   VarId id(vars.size());
-  vars.push_back(VarDef(id, usr));
+  vars.push_back(IndexedVarDef(id, usr));
   usr_to_var_id[usr] = id;
   return id;
 }
 
-TypeId ParsingDatabase::ToTypeId(const CXCursor& cursor) {
+TypeId IndexedFile::ToTypeId(const CXCursor& cursor) {
   return ToTypeId(clang::Cursor(cursor).get_usr());
 }
 
-FuncId ParsingDatabase::ToFuncId(const CXCursor& cursor) {
+FuncId IndexedFile::ToFuncId(const CXCursor& cursor) {
   return ToFuncId(clang::Cursor(cursor).get_usr());
 }
 
-VarId ParsingDatabase::ToVarId(const CXCursor& cursor) {
+VarId IndexedFile::ToVarId(const CXCursor& cursor) {
   return ToVarId(clang::Cursor(cursor).get_usr());
 }
 
 
-TypeDef* ParsingDatabase::Resolve(TypeId id) {
+IndexedTypeDef* IndexedFile::Resolve(TypeId id) {
   return &types[id.local_id];
 }
-FuncDef* ParsingDatabase::Resolve(FuncId id) {
+IndexedFuncDef* IndexedFile::Resolve(FuncId id) {
   return &funcs[id.local_id];
 }
-VarDef* ParsingDatabase::Resolve(VarId id) {
+IndexedVarDef* IndexedFile::Resolve(VarId id) {
   return &vars[id.local_id];
 }
 
@@ -148,7 +148,7 @@ void Write(Writer& writer, const char* key, uint64_t value) {
   writer.Uint64(value);
 }
 
-std::string ParsingDatabase::ToString() {
+std::string IndexedFile::ToString() {
   auto it = usr_to_type_id.find("");
   if (it != usr_to_type_id.end()) {
     Resolve(it->second)->short_name = "<fundamental>";
@@ -168,7 +168,7 @@ std::string ParsingDatabase::ToString() {
   // Types
   writer.Key("types");
   writer.StartArray();
-  for (TypeDef& def : types) {
+  for (IndexedTypeDef& def : types) {
     if (def.is_system_def) continue;
 
     writer.StartObject();
@@ -191,7 +191,7 @@ std::string ParsingDatabase::ToString() {
   // Functions
   writer.Key("functions");
   writer.StartArray();
-  for (FuncDef& def : funcs) {
+  for (IndexedFuncDef& def : funcs) {
     if (def.is_system_def) continue;
 
     writer.StartObject();
@@ -215,7 +215,7 @@ std::string ParsingDatabase::ToString() {
   // Variables
   writer.Key("variables");
   writer.StartArray();
-  for (VarDef& def : vars) {
+  for (IndexedVarDef& def : vars) {
     if (def.is_system_def) continue;
 
     writer.StartObject();
@@ -404,7 +404,7 @@ struct NamespaceHelper {
 };
 
 struct IndexParam {
-  ParsingDatabase* db;
+  IndexedFile* db;
   NamespaceHelper* ns;
 
   // Record the last type usage location we recorded. Clang will sometimes
@@ -413,7 +413,7 @@ struct IndexParam {
   Location last_type_usage_location;
   Location last_func_usage_location;
 
-  IndexParam(ParsingDatabase* db, NamespaceHelper* ns) : db(db), ns(ns) {}
+  IndexParam(IndexedFile* db, NamespaceHelper* ns) : db(db), ns(ns) {}
 };
 
 /*
@@ -443,19 +443,19 @@ bool IsTypeDefinition(const CXIdxContainerInfo* container) {
 
 
 struct VisitDeclForTypeUsageParam {
-  ParsingDatabase* db;
+  IndexedFile* db;
   bool is_interesting;
   int has_processed_any = false;
   optional<clang::Cursor> previous_cursor;
   optional<TypeId> initial_type;
 
-  VisitDeclForTypeUsageParam(ParsingDatabase* db, bool is_interesting)
+  VisitDeclForTypeUsageParam(IndexedFile* db, bool is_interesting)
     : db(db), is_interesting(is_interesting) {}
 };
 
 void VisitDeclForTypeUsageVisitorHandler(clang::Cursor cursor, VisitDeclForTypeUsageParam* param) {
   param->has_processed_any = true;
-  ParsingDatabase* db = param->db;
+  IndexedFile* db = param->db;
 
   // TODO: Something in STL (type_traits)? reports an empty USR.
   std::string referenced_usr = cursor.get_referenced().get_usr();
@@ -467,7 +467,7 @@ void VisitDeclForTypeUsageVisitorHandler(clang::Cursor cursor, VisitDeclForTypeU
     param->initial_type = ref_type_id;
 
   if (param->is_interesting) {
-    TypeDef* ref_type_def = db->Resolve(ref_type_id);
+    IndexedTypeDef* ref_type_def = db->Resolve(ref_type_id);
     Location loc = db->file_db.Resolve(cursor, true /*interesting*/);
     ref_type_def->AddUsage(loc);
   }
@@ -496,7 +496,7 @@ clang::VisiterResult VisitDeclForTypeUsageVisitor(clang::Cursor cursor, clang::C
   return clang::VisiterResult::Continue;
 }
 
-optional<TypeId> ResolveDeclToType(ParsingDatabase* db, clang::Cursor decl_cursor,
+optional<TypeId> ResolveDeclToType(IndexedFile* db, clang::Cursor decl_cursor,
   bool is_interesting, const CXIdxContainerInfo* semantic_container,
   const CXIdxContainerInfo* lexical_container) {
   //
@@ -563,7 +563,7 @@ void indexDeclaration(CXClientData client_data, const CXIdxDeclInfo* decl) {
   bool is_system_def = clang_Location_isInSystemHeader(clang_getCursorLocation(decl->cursor));
 
   IndexParam* param = static_cast<IndexParam*>(client_data);
-  ParsingDatabase* db = param->db;
+  IndexedFile* db = param->db;
   NamespaceHelper* ns = param->ns;
 
   switch (decl->entityInfo->kind) {
@@ -580,7 +580,7 @@ void indexDeclaration(CXClientData client_data, const CXIdxDeclInfo* decl) {
   {
     clang::Cursor decl_cursor = decl->cursor;
     VarId var_id = db->ToVarId(decl->entityInfo->USR);
-    VarDef* var_def = db->Resolve(var_id);
+    IndexedVarDef* var_def = db->Resolve(var_id);
 
     var_def->is_system_def = is_system_def;
 
@@ -610,7 +610,7 @@ void indexDeclaration(CXClientData client_data, const CXIdxDeclInfo* decl) {
 
     if (decl->isDefinition && IsTypeDefinition(decl->semanticContainer)) {
       TypeId declaring_type_id = db->ToTypeId(decl->semanticContainer->cursor);
-      TypeDef* declaring_type_def = db->Resolve(declaring_type_id);
+      IndexedTypeDef* declaring_type_def = db->Resolve(declaring_type_id);
       var_def->declaring_type = declaring_type_id;
       declaring_type_def->vars.push_back(var_id);
     }
@@ -627,7 +627,7 @@ void indexDeclaration(CXClientData client_data, const CXIdxDeclInfo* decl) {
   {
     clang::Cursor decl_cursor = decl->cursor;
     FuncId func_id = db->ToFuncId(decl->entityInfo->USR);
-    FuncDef* func_def = db->Resolve(func_id);
+    IndexedFuncDef* func_def = db->Resolve(func_id);
 
     func_def->is_system_def = is_system_def;
 
@@ -653,7 +653,7 @@ void indexDeclaration(CXClientData client_data, const CXIdxDeclInfo* decl) {
     // be one of those in the entire program.
     if (IsTypeDefinition(decl->semanticContainer)) {
       TypeId declaring_type_id = db->ToTypeId(decl->semanticContainer->cursor);
-      TypeDef* declaring_type_def = db->Resolve(declaring_type_id);
+      IndexedTypeDef* declaring_type_def = db->Resolve(declaring_type_id);
       func_def->declaring_type = declaring_type_id;
 
       // Mark a type reference at the ctor/dtor location.
@@ -716,7 +716,7 @@ void indexDeclaration(CXClientData client_data, const CXIdxDeclInfo* decl) {
         for (unsigned int i = 0; i < num_overridden; ++i) {
           clang::Cursor parent = overridden[i];
           FuncId parent_id = db->ToFuncId(parent.get_usr());
-          FuncDef* parent_def = db->Resolve(parent_id);
+          IndexedFuncDef* parent_def = db->Resolve(parent_id);
           func_def = db->Resolve(func_id); // ToFuncId invalidated func_def
 
           func_def->base = parent_id;
@@ -744,7 +744,7 @@ void indexDeclaration(CXClientData client_data, const CXIdxDeclInfo* decl) {
     optional<TypeId> alias_of = ResolveDeclToType(db, decl->cursor, true /*is_interesting*/, decl->semanticContainer, decl->lexicalContainer);
 
     TypeId type_id = db->ToTypeId(decl->entityInfo->USR);
-    TypeDef* type_def = db->Resolve(type_id);
+    IndexedTypeDef* type_def = db->Resolve(type_id);
 
     type_def->is_system_def = is_system_def;
 
@@ -766,7 +766,7 @@ void indexDeclaration(CXClientData client_data, const CXIdxDeclInfo* decl) {
   case CXIdxEntity_CXXClass:
   {
     TypeId type_id = db->ToTypeId(decl->entityInfo->USR);
-    TypeDef* type_def = db->Resolve(type_id);
+    IndexedTypeDef* type_def = db->Resolve(type_id);
 
     type_def->is_system_def = is_system_def;
 
@@ -805,9 +805,9 @@ void indexDeclaration(CXClientData client_data, const CXIdxDeclInfo* decl) {
         const CXIdxBaseClassInfo* base_class = class_info->bases[i];
 
         optional<TypeId> parent_type_id = ResolveDeclToType(db, base_class->cursor, true /*is_interesting*/, decl->semanticContainer, decl->lexicalContainer);
-        TypeDef* type_def = db->Resolve(type_id); // type_def ptr could be invalidated by ResolveDeclToType.
+        IndexedTypeDef* type_def = db->Resolve(type_id); // type_def ptr could be invalidated by ResolveDeclToType.
         if (parent_type_id) {
-          TypeDef* parent_type_def = db->Resolve(parent_type_id.value());
+          IndexedTypeDef* parent_type_def = db->Resolve(parent_type_id.value());
           parent_type_def->derived.push_back(type_id);
           type_def->parents.push_back(parent_type_id.value());
         }
@@ -842,7 +842,7 @@ bool IsFunction(CXCursorKind kind) {
 
 void indexEntityReference(CXClientData client_data, const CXIdxEntityRefInfo* ref) {
   IndexParam* param = static_cast<IndexParam*>(client_data);
-  ParsingDatabase* db = param->db;
+  IndexedFile* db = param->db;
   clang::Cursor cursor(ref->cursor);
 
   switch (ref->referencedEntity->kind) {
@@ -852,7 +852,7 @@ void indexEntityReference(CXClientData client_data, const CXIdxEntityRefInfo* re
   case CXIdxEntity_Field:
   {
     VarId var_id = db->ToVarId(ref->referencedEntity->cursor);
-    VarDef* var_def = db->Resolve(var_id);
+    IndexedVarDef* var_def = db->Resolve(var_id);
     var_def->uses.push_back(db->file_db.Resolve(ref->loc, false /*interesting*/));
     break;
   }
@@ -883,15 +883,15 @@ void indexEntityReference(CXClientData client_data, const CXIdxEntityRefInfo* re
     FuncId called_id = db->ToFuncId(ref->referencedEntity->USR);
     if (IsFunction(ref->container->cursor.kind)) {
       FuncId caller_id = db->ToFuncId(ref->container->cursor);
-      FuncDef* caller_def = db->Resolve(caller_id);
-      FuncDef* called_def = db->Resolve(called_id);
+      IndexedFuncDef* caller_def = db->Resolve(caller_id);
+      IndexedFuncDef* called_def = db->Resolve(called_id);
 
       caller_def->callees.push_back(FuncRef(called_id, loc));
       called_def->callers.push_back(FuncRef(caller_id, loc));
       called_def->uses.push_back(loc);
     }
     else {
-      FuncDef* called_def = db->Resolve(called_id);
+      IndexedFuncDef* called_def = db->Resolve(called_id);
       called_def->uses.push_back(loc);
     }
 
@@ -906,9 +906,9 @@ void indexEntityReference(CXClientData client_data, const CXIdxEntityRefInfo* re
       Location parent_loc = db->file_db.Resolve(ref->parentEntity->cursor, true /*interesting*/);
       Location our_loc = db->file_db.Resolve(ref->loc, true /*is_interesting*/);
       if (!parent_loc.IsEqualTo(our_loc)) {
-        FuncDef* called_def = db->Resolve(called_id);
+        IndexedFuncDef* called_def = db->Resolve(called_id);
         assert(called_def->declaring_type.has_value());
-        TypeDef* type_def = db->Resolve(called_def->declaring_type.value());
+        IndexedTypeDef* type_def = db->Resolve(called_def->declaring_type.value());
         type_def->AddUsage(our_loc);
       }
     }
@@ -923,7 +923,7 @@ void indexEntityReference(CXClientData client_data, const CXIdxEntityRefInfo* re
   case CXIdxEntity_CXXClass:
   {
     TypeId referenced_id = db->ToTypeId(ref->referencedEntity->USR);
-    TypeDef* referenced_def = db->Resolve(referenced_id);
+    IndexedTypeDef* referenced_def = db->Resolve(referenced_id);
 
     //
     // The following will generate two TypeRefs to Foo, both located at the
@@ -964,7 +964,7 @@ void indexEntityReference(CXClientData client_data, const CXIdxEntityRefInfo* re
 static bool DUMP_AST = true;
 
 
-ParsingDatabase Parse(std::string filename, std::vector<std::string> args) {
+IndexedFile Parse(std::string filename, std::vector<std::string> args) {
   clang::Index index(0 /*excludeDeclarationsFromPCH*/, 0 /*displayDiagnostics*/);
   clang::TranslationUnit tu(index, filename, args);
 
@@ -987,7 +987,7 @@ ParsingDatabase Parse(std::string filename, std::vector<std::string> args) {
     */
   };
 
-  ParsingDatabase db;
+  IndexedFile db;
   NamespaceHelper ns;
   IndexParam param(&db, &ns);
   clang_indexTranslationUnit(index_action, &param, callbacks, sizeof(callbacks),
@@ -1089,7 +1089,7 @@ void WriteToFile(const std::string& filename, const std::string& content) {
   file << content;
 }
 
-int mai2n(int argc, char** argv) {
+int main(int argc, char** argv) {
   // TODO: Assert that we need to be on clang >= 3.9.1
 
   /*
@@ -1128,7 +1128,7 @@ int mai2n(int argc, char** argv) {
 
     // Run test.
     std::cout << "[START] " << path << std::endl;
-    ParsingDatabase db = Parse(path, {});
+    IndexedFile db = Parse(path, {});
     std::string actual_output = db.ToString();
 
     //WriteToFile("output.json", actual_output);
diff --git a/indexer.h b/indexer.h
index 1dc7a775..9d8e03cf 100644
--- a/indexer.h
+++ b/indexer.h
@@ -80,11 +80,11 @@ Location WithInteresting(bool interesting) {
 
 END_BITFIELD_TYPE()
 
-struct FileDb {
+struct IndexedFileDb {
   std::unordered_map<std::string, FileId> file_path_to_file_id;
   std::unordered_map<FileId, std::string> file_id_to_file_path;
 
-  FileDb() {
+  IndexedFileDb() {
     // Reserve id 0 for unfound.
     file_path_to_file_id[""] = 0;
     file_id_to_file_path[0] = "";
@@ -167,7 +167,7 @@ using VarRef = Ref<VarDef>;
 // TODO: Either eliminate the defs created as a by-product of cross-referencing,
 //       or do not emit things we don't have definitions for.
 
-struct TypeDef {
+struct IndexedTypeDef {
   bool is_system_def = false;
 
   // General metadata.
@@ -204,7 +204,7 @@ struct TypeDef {
   // NOTE: Do not insert directly! Use AddUsage instead.
   std::vector<Location> uses;
 
-  TypeDef(TypeId id, const std::string& usr) : id(id), usr(usr) {
+  IndexedTypeDef(TypeId id, const std::string& usr) : id(id), usr(usr) {
     assert(usr.size() > 0);
     //std::cout << "Creating type with usr " << usr << std::endl;
   }
@@ -226,7 +226,7 @@ struct TypeDef {
   }
 };
 
-struct FuncDef {
+struct IndexedFuncDef {
   bool is_system_def = false;
 
   // General metadata.
@@ -260,12 +260,12 @@ struct FuncDef {
   // All usages. For interesting usages, see callees.
   std::vector<Location> uses;
 
-  FuncDef(FuncId id, const std::string& usr) : id(id), usr(usr) {
+  IndexedFuncDef(FuncId id, const std::string& usr) : id(id), usr(usr) {
     assert(usr.size() > 0);
   }
 };
 
-struct VarDef {
+struct IndexedVarDef {
   bool is_system_def = false;
 
   // General metadata.
@@ -287,26 +287,26 @@ struct VarDef {
   // Usages.
   std::vector<Location> uses;
 
-  VarDef(VarId id, const std::string& usr) : id(id), usr(usr) {
+  IndexedVarDef(VarId id, const std::string& usr) : id(id), usr(usr) {
     assert(usr.size() > 0);
   }
 };
 
 
-struct ParsingDatabase {
+struct IndexedFile {
   // NOTE: Every Id is resolved to a file_id of 0. The correct file_id needs
   //       to get fixed up when inserting into the real db.
   std::unordered_map<std::string, TypeId> usr_to_type_id;
   std::unordered_map<std::string, FuncId> usr_to_func_id;
   std::unordered_map<std::string, VarId> usr_to_var_id;
 
-  std::vector<TypeDef> types;
-  std::vector<FuncDef> funcs;
-  std::vector<VarDef> vars;
+  std::vector<IndexedTypeDef> types;
+  std::vector<IndexedFuncDef> funcs;
+  std::vector<IndexedVarDef> vars;
 
-  FileDb file_db;
+  IndexedFileDb file_db;
 
-  ParsingDatabase();
+  IndexedFile();
 
   TypeId ToTypeId(const std::string& usr);
   FuncId ToFuncId(const std::string& usr);
@@ -315,11 +315,11 @@ struct ParsingDatabase {
   FuncId ToFuncId(const CXCursor& usr);
   VarId ToVarId(const CXCursor& usr);
 
-  TypeDef* Resolve(TypeId id);
-  FuncDef* Resolve(FuncId id);
-  VarDef* Resolve(VarId id);
+  IndexedTypeDef* Resolve(TypeId id);
+  IndexedFuncDef* Resolve(FuncId id);
+  IndexedVarDef* Resolve(VarId id);
 
   std::string ToString();
 };
 
-ParsingDatabase Parse(std::string filename, std::vector<std::string> args);
\ No newline at end of file
+IndexedFile Parse(std::string filename, std::vector<std::string> args);
\ No newline at end of file
diff --git a/query_db.cc b/query_db.cc
index d7b9018c..28cdec4f 100644
--- a/query_db.cc
+++ b/query_db.cc
@@ -24,7 +24,7 @@ struct SymbolIdx {
   };
 };
 
-struct File {
+struct QueryableFile {
   // Symbols declared in the file.
   std::vector<SymbolIdx> declared_symbols;
   // Symbols which have definitions in the file.
@@ -37,7 +37,7 @@ struct QueryableEntry {
 
 // The query database is heavily optimized for fast queries. It is stored
 // in-memory.
-struct QueryDatabase {
+struct QueryableDatabase {
   // Indicies between lookup vectors are related to symbols, ie, index 5 in
   // |qualified_names| matches index 5 in |symbols|.
   std::vector<QueryableEntry> qualified_names;
@@ -51,7 +51,7 @@ struct QueryDatabase {
   // |files| is indexed by FileId. Retrieve a FileId from a path using
   // |file_locator|.
   FileDatabase file_locator;
-  std::vector<File> files;
+  std::vector<QueryableFile> files;
 };
 
 
@@ -91,27 +91,45 @@ struct Query {
 
 };
 
-void fail(const std::string& message) {
-  std::cerr << "Fatal error: " << message << std::endl;
-  std::exit(1);
-}
 
+struct CachedIndexedFile {
+  // Path to the file indexed.
+  std::string path;
+  
+  // Full in-memory storage for the index. Empty if not loaded into memory.
+  // |path| can be used to fetch the index from disk.
+  optional<rapidjson::Document> index;
+};
+
+struct DocumentDiff {
+
+};
+// Compute a diff between |original| and |updated|.
+//rapidjson::Document DiffIndex(rapidjson::Document original, rapidjson::Document updated) {
+
+//}
+
+
+
+// NOTE: If updating this enum, make sure to also update the parser and the
+//       help text.
 enum class PreferredSymbolLocation {
   Declaration,
   Definition
 };
-std::istream& operator >> (std::istream& is, PreferredSymbolLocation& obj) {
-  std::string content;
-  is >> content;
 
-  if (content == "declaration")
-    obj = PreferredSymbolLocation::Declaration;
-  else if (content == "definition")
-    obj = PreferredSymbolLocation::Definition;
-  else
-    is.setstate(std::ios::failbit);
+bool ParsePreferredSymbolLocation(const std::string& content, PreferredSymbolLocation* obj) {
+#define PARSE_AS(name, string)      \
+  if (content == #string) {         \
+    *obj = name;                    \
+    return true;                    \
+  }
 
-  return is;
+  PARSE_AS(PreferredSymbolLocation::Declaration, "declaration");
+  PARSE_AS(PreferredSymbolLocation::Definition, "definition");
+
+  return false;
+#undef PARSE_AS
 }
 
 // NOTE: If updating this enum, make sure to also update the parser and the
@@ -127,34 +145,24 @@ enum class Command {
   Search
 };
 
-//std::ostream& operator<<(std::ostream& os, const Command& obj) {
-  // write obj to stream
-//  return os;
-//}
-std::istream& operator >> (std::istream& is, Command& obj) {
-  std::string content;
-  is >> content;
+bool ParseCommand(const std::string& content, Command* obj) {
+#define PARSE_AS(name, string)      \
+  if (content == #string) {         \
+    *obj = name;                    \
+    return true;                    \
+  }
 
-  if (content == "callees")
-    obj = Command::Callees;
-  else if (content == "callers")
-    obj = Command::Callers;
-  else if (content == "find-all-usages")
-    obj = Command::FindAllUsages;
-  else if (content == "find-interesting-usages")
-    obj = Command::FindInterestingUsages;
-  else if (content == "goto-referenced")
-    obj = Command::GotoReferenced;
-  else if (content == "hierarchy")
-    obj = Command::Hierarchy;
-  else if (content == "outline")
-    obj = Command::Outline;
-  else if (content == "search")
-    obj = Command::Search;
-  else
-    is.setstate(std::ios::failbit);
+  PARSE_AS(Command::Callees, "callees");
+  PARSE_AS(Command::Callers, "callers");
+  PARSE_AS(Command::FindAllUsages, "find-all-usages");
+  PARSE_AS(Command::FindInterestingUsages, "find-interesting-usages");
+  PARSE_AS(Command::GotoReferenced, "goto-referenced");
+  PARSE_AS(Command::Hierarchy, "hierarchy");
+  PARSE_AS(Command::Outline, "outline");
+  PARSE_AS(Command::Search, "search");
 
-  return is;
+  return false;
+#undef PARSE_AS
 }
 
 // TODO: I think we can run libclang multiple times in one process. So we might
@@ -196,7 +204,7 @@ bool HasOption(const std::unordered_map<std::string, std::string>& options, cons
   return options.find(option) != options.end();
 }
 
-int main(int argc, char** argv) {
+int main2(int argc, char** argv) {
   std::unordered_map<std::string, std::string> options = ParseOptions(argc, argv);
 
   if (argc == 1 || options.find("--help") != options.end()) {
@@ -283,10 +291,10 @@ int main(int argc, char** argv) {
     std::vector<CompilationEntry> entries = LoadCompilationEntriesFromDirectory(options["--project"]);
 
 
-    std::vector<ParsingDatabase> dbs;
+    std::vector<IndexedFile> dbs;
     for (const CompilationEntry& entry : entries) {
       std::cout << "Parsing " << entry.filename << std::endl;
-      ParsingDatabase db = Parse(entry.filename, entry.args);
+      IndexedFile db = Parse(entry.filename, entry.args);
 
       dbs.emplace_back(db);
       std::cout << db.ToString() << std::endl << std::endl;
@@ -296,6 +304,13 @@ int main(int argc, char** argv) {
     exit(0);
   }
 
+  if (HasOption(options, "--command")) {
+    Command command;
+    if (!ParseCommand(options["--command"], &command))
+      Fail("Unknown command \"" + options["--command"] + "\"; see --help-commands");
+
+
+  }
 
   std::cout << "Invalid arguments. Try --help.";
   exit(1);
diff --git a/utils.cc b/utils.cc
index fd5ccab3..a73325d7 100644
--- a/utils.cc
+++ b/utils.cc
@@ -1,5 +1,6 @@
 #include "utils.h"
 
+#include <iostream>
 #include <fstream>
 
 #include "tinydir.h"
@@ -66,3 +67,9 @@ void ParseTestExpectation(std::string filename, std::string* expected_output) {
       in_output = true;
   }
 }
+
+
+void Fail(const std::string& message) {
+  std::cerr << "Fatal error: " << message << std::endl;
+  std::exit(1);
+}
\ No newline at end of file
diff --git a/utils.h b/utils.h
index 3fe81ad9..79bff3de 100644
--- a/utils.h
+++ b/utils.h
@@ -5,4 +5,6 @@
 
 std::vector<std::string> GetFilesInFolder(std::string folder);
 std::vector<std::string> ReadLines(std::string filename);
-void ParseTestExpectation(std::string filename, std::string* expected_output);
\ No newline at end of file
+void ParseTestExpectation(std::string filename, std::string* expected_output);
+
+void Fail(const std::string& message);
\ No newline at end of file