C++ port: port FSTFieldPath and FSTResourcePath to C++ (#749)

Similar to Objective-C, FieldPath and ResourcePath share most of their interface (and implementation) by deriving from BasePath (using CRTP, so that factory methods in BasePath can return an instance of the derived class).

1 files changed, 176 insertions, 0 deletions

diff --git a/Firestore/core/src/firebase/firestore/model/field_path.cc b/Firestore/core/src/firebase/firestore/model/field_path.cc
new file mode 100644
index 0000000..6c40600
--- /dev/null
+++ b/Firestore/core/src/firebase/firestore/model/field_path.cc
@@ -0,0 +1,176 @@
+/*
+ * 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/model/field_path.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "Firestore/core/src/firebase/firestore/util/firebase_assert.h"
+#include "absl/strings/str_join.h"
+#include "absl/strings/str_replace.h"
+#include "absl/strings/str_split.h"
+
+namespace firebase {
+namespace firestore {
+namespace model {
+
+namespace {
+
+// TODO(varconst): move to C++ equivalent of FSTDocumentKey.{h,cc}
+const char* const kDocumentKeyPath = "__name__";
+
+/**
+ * True if the string could be used as a segment in a field path without
+ * escaping. Valid identifies follow the regex [a-zA-Z_][a-zA-Z0-9_]*
+ */
+bool IsValidIdentifier(const std::string& segment) {
+  if (segment.empty()) {
+    return false;
+  }
+
+  // Note: strictly speaking, only digits are guaranteed by the Standard to
+  // be a contiguous range, while alphabetic characters may have gaps. Ignoring
+  // this peculiarity, because it doesn't affect the platforms that Firestore
+  // supports.
+  const unsigned char first = segment.front();
+  if (first != '_' && (first < 'a' || first > 'z') &&
+      (first < 'A' || first > 'Z')) {
+    return false;
+  }
+  for (int i = 1; i != segment.size(); ++i) {
+    const unsigned char c = segment[i];
+    if (c != '_' && (c < 'a' || c > 'z') && (c < 'A' || c > 'Z') &&
+        (c < '0' || c > '9')) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+}  // namespace
+
+FieldPath FieldPath::FromServerFormat(const absl::string_view path) {
+  // TODO(b/37244157): Once we move to v1beta1, we should make this more
+  // strict. Right now, it allows non-identifier path components, even if they
+  // aren't escaped. Technically, this will mangle paths with backticks in
+  // them used in v1alpha1, but that's fine.
+
+  SegmentsT segments;
+  std::string segment;
+  segment.reserve(path.size());
+
+  // string_view doesn't have a c_str() method, because it might not be
+  // null-terminated. Assertions expect C strings, so construct std::string on
+  // the fly, so that c_str() might be called on it.
+  const auto to_string = [](const absl::string_view view) {
+    return std::string{view.data(), view.data() + view.size()};
+  };
+  const auto finish_segment = [&segments, &segment, &path, &to_string] {
+    FIREBASE_ASSERT_MESSAGE(
+        !segment.empty(),
+        "Invalid field path (%s). Paths must not be empty, begin with "
+        "'.', end with '.', or contain '..'",
+        to_string(path).c_str());
+    // Move operation will clear segment, but capacity will remain the same
+    // (not, strictly speaking, required by the standard, but true in practice).
+    segments.push_back(std::move(segment));
+  };
+
+  // Inside backticks, dots are treated literally.
+  bool inside_backticks = false;
+  int i = 0;
+  while (i < path.size()) {
+    const char c = path[i];
+    // std::string (and string_view) may contain embedded nulls. For full
+    // compatibility with Objective C behavior, finish upon encountering the
+    // first terminating null.
+    if (c == '\0') {
+      break;
+    }
+
+    switch (c) {
+      case '.':
+        if (!inside_backticks) {
+          finish_segment();
+        } else {
+          segment += c;
+        }
+        break;
+
+      case '`':
+        inside_backticks = !inside_backticks;
+        break;
+
+      case '\\':
+        // TODO(b/37244157): Make this a user-facing exception once we
+        // finalize field escaping.
+        FIREBASE_ASSERT_MESSAGE(i + 1 != path.size(),
+                                "Trailing escape characters not allowed in %s",
+                                to_string(path).c_str());
+        ++i;
+        segment += path[i];
+        break;
+
+      default:
+        segment += c;
+        break;
+    }
+    ++i;
+  }
+  finish_segment();
+
+  FIREBASE_ASSERT_MESSAGE(!inside_backticks, "Unterminated ` in path %s",
+                          to_string(path).c_str());
+
+  return FieldPath{std::move(segments)};
+}
+
+const FieldPath& FieldPath::EmptyPath() {
+  static const FieldPath empty_path;
+  return empty_path;
+}
+
+const FieldPath& FieldPath::KeyFieldPath() {
+  static const FieldPath key_field_path{kDocumentKeyPath};
+  return key_field_path;
+}
+
+bool FieldPath::IsKeyFieldPath() const {
+  return size() == 1 && first_segment() == kDocumentKeyPath;
+}
+
+std::string FieldPath::CanonicalString() const {
+  const auto escaped_segment = [](const std::string& segment) {
+    auto escaped = absl::StrReplaceAll(segment, {{"\\", "\\\\"}, {"`", "\\`"}});
+    const bool needs_escaping = !IsValidIdentifier(escaped);
+    if (needs_escaping) {
+      escaped.insert(escaped.begin(), '`');
+      escaped.push_back('`');
+    }
+    return escaped;
+  };
+  return absl::StrJoin(
+      begin(), end(), ".",
+      [escaped_segment](std::string* out, const std::string& segment) {
+        out->append(escaped_segment(segment));
+      });
+}
+
+}  // namespace model
+}  // namespace firestore
+}  // namespace firebase