Implement Firestore DatabaseInfo and port both Database{Id,Info} C++ to the iOS code (#738)

* implement Firestore DatabaseInfo in C++

* temporary stash changes; blocking on the massive renaming of .m to .mm

* add database_info_test to project

* finish port DatabaseId and fix style, modular fixing DatabaseInfo

* port DatabaseInfo

* remove FSTDatabase{ID,Info} and their tests from project

* fix unit test

* use namespace alias

* use namespace alias, leftover

* address more changes

* refactoring to use raw pointer instead of value for property

* address changes

* remove self->

* fix style

* remove the name suffix Alloc

* fix a bug

6 files changed, 147 insertions, 7 deletions

diff --git a/Firestore/core/src/firebase/firestore/core/CMakeLists.txt b/Firestore/core/src/firebase/firestore/core/CMakeLists.txt
index a62985c..cf3cafe 100644
--- a/Firestore/core/src/firebase/firestore/core/CMakeLists.txt
+++ b/Firestore/core/src/firebase/firestore/core/CMakeLists.txt
@@ -15,6 +15,11 @@
 cc_library(
   firebase_firestore_core
   SOURCES
+    database_info.cc
+    database_info.h
     target_id_generator.cc
     target_id_generator.h
+  DEPENDS
+    absl_strings
+    firebase_firestore_model
 )
diff --git a/Firestore/core/src/firebase/firestore/core/database_info.cc b/Firestore/core/src/firebase/firestore/core/database_info.cc
new file mode 100644
index 0000000..b83da37
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/core/database_info.cc
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2018 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "Firestore/core/src/firebase/firestore/core/database_info.h"
+
+namespace firebase {
+namespace firestore {
+namespace core {
+
+DatabaseInfo::DatabaseInfo(
+    const firebase::firestore::model::DatabaseId& database_id,
+    const absl::string_view persistence_key,
+    const absl::string_view host,
+    bool ssl_enabled)
+    : database_id_(database_id),
+      persistence_key_(persistence_key),
+      host_(host),
+      ssl_enabled_(ssl_enabled) {
+}
+
+}  // namespace core
+}  // namespace firestore
+}  // namespace firebase
diff --git a/Firestore/core/src/firebase/firestore/core/database_info.h b/Firestore/core/src/firebase/firestore/core/database_info.h
new file mode 100644
index 0000000..2e1303e
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/core/database_info.h
@@ -0,0 +1,79 @@
+/*
+ * Copyright 2018 Google
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_CORE_DATABASE_INFO_H_
+#define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_CORE_DATABASE_INFO_H_
+
+#include <string>
+
+#include "Firestore/core/src/firebase/firestore/model/database_id.h"
+#include "absl/strings/string_view.h"
+
+namespace firebase {
+namespace firestore {
+namespace core {
+
+/** DatabaseInfo contains data about the database. */
+class DatabaseInfo {
+ public:
+#if defined(__OBJC__)
+  // For objective-c++ initialization; to be removed after migration.
+  // Do NOT use in C++ code.
+  DatabaseInfo() = default;
+#endif  // defined(__OBJC__)
+
+  /**
+   * Creates a new DatabaseInfo.
+   *
+   * @param database_id The project/database to use.
+   * @param persistence_key A unique identifier for this Firestore's local
+   *        storage. Usually derived from -[FIRApp appName].
+   * @param host The hostname of the datastore backend.
+   * @param ssl_enabled Whether to use SSL when connecting.
+   */
+  DatabaseInfo(const firebase::firestore::model::DatabaseId& database_id,
+               const absl::string_view persistence_key,
+               const absl::string_view host,
+               bool ssl_enabled);
+
+  const firebase::firestore::model::DatabaseId& database_id() const {
+    return database_id_;
+  }
+
+  const std::string& persistence_key() const {
+    return persistence_key_;
+  }
+
+  const std::string& host() const {
+    return host_;
+  }
+
+  bool ssl_enabled() const {
+    return ssl_enabled_;
+  }
+
+ private:
+  firebase::firestore::model::DatabaseId database_id_;
+  std::string persistence_key_;
+  std::string host_;
+  bool ssl_enabled_;
+};
+
+}  // namespace core
+}  // namespace firestore
+}  // namespace firebase
+
+#endif  // FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_CORE_DATABASE_INFO_H_
diff --git a/Firestore/core/src/firebase/firestore/model/database_id.cc b/Firestore/core/src/firebase/firestore/model/database_id.cc
index af12d30..d7e8a85 100644
--- a/Firestore/core/src/firebase/firestore/model/database_id.cc
+++ b/Firestore/core/src/firebase/firestore/model/database_id.cc
@@ -31,10 +31,6 @@ DatabaseId::DatabaseId(const absl::string_view project_id,
   FIREBASE_ASSERT(!database_id.empty());
 }
 
-bool DatabaseId::IsDefaultDatabase() {
-  return database_id_ == kDefaultDatabaseId;
-}
-
 }  // namespace model
 }  // namespace firestore
 }  // namespace firebase
diff --git a/Firestore/core/src/firebase/firestore/model/database_id.h b/Firestore/core/src/firebase/firestore/model/database_id.h
index 48c547c..648f982 100644
--- a/Firestore/core/src/firebase/firestore/model/database_id.h
+++ b/Firestore/core/src/firebase/firestore/model/database_id.h
@@ -17,6 +17,8 @@
 #ifndef FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_MODEL_DATABASE_ID_H_
 #define FIRESTORE_CORE_SRC_FIREBASE_FIRESTORE_MODEL_DATABASE_ID_H_
 
+#include <stdint.h>
+
 #include <string>
 
 #include "absl/strings/string_view.h"
@@ -31,6 +33,12 @@ class DatabaseId {
   /** The default name for "unset" database ID in resource names. */
   static constexpr const char* kDefaultDatabaseId = "(default)";
 
+#if defined(__OBJC__)
+  // For objective-c++ initialization; to be removed after migration.
+  // Do NOT use in C++ code.
+  DatabaseId() = default;
+#endif  // defined(__OBJC__)
+
   /**
    * Creates and returns a new DatabaseId.
    *
@@ -49,13 +57,24 @@ class DatabaseId {
   }
 
   /** Whether this is the default database of the project. */
-  bool IsDefaultDatabase();
+  bool IsDefaultDatabase() const {
+    return database_id_ == kDefaultDatabaseId;
+  }
+
+#if defined(__OBJC__)
+  // For objective-c++ hash; to be removed after migration.
+  // Do NOT use in C++ code.
+  uint64_t Hash() const {
+    std::hash<std::string> hash_fn;
+    return hash_fn(project_id_) * 31u + hash_fn(database_id_);
+  }
+#endif  // defined(__OBJC__)
 
   friend bool operator<(const DatabaseId& lhs, const DatabaseId& rhs);
 
  private:
-  const std::string project_id_;
-  const std::string database_id_;
+  std::string project_id_;
+  std::string database_id_;
 };
 
 /** Compares against another DatabaseId. */
diff --git a/Firestore/core/src/firebase/firestore/util/string_apple.h b/Firestore/core/src/firebase/firestore/util/string_apple.h
index 108ade7..fe2a487 100644
--- a/Firestore/core/src/firebase/firestore/util/string_apple.h
+++ b/Firestore/core/src/firebase/firestore/util/string_apple.h
@@ -37,6 +37,11 @@ inline NSString* WrapNSStringNoCopy(const char* c_str) {
              freeWhenDone:NO];
 }
 
+// Translates a string_view to the equivalent NSString without making a copy.
+inline NSString* WrapNSStringNoCopy(const absl::string_view str) {
+  return WrapNSStringNoCopy(str.data());
+}
+
 // Creates an absl::string_view wrapper for the contents of the given NSString.
 inline absl::string_view MakeStringView(NSString* str) {
   return absl::string_view(