src/idl_gen_json_schema.cpp

/*
 * Copyright 2014 Google Inc. All rights reserved.
 *
 * 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 <iostream>
#include "flatbuffers/code_generators.h"
#include "flatbuffers/idl.h"
#include "flatbuffers/util.h"

namespace flatbuffers {

static std::string GeneratedFileName(const std::string &path,
                                     const std::string &file_name) {
  return path + file_name + ".schema.json";
}

namespace jsons {

std::string GenNativeType(BaseType type) {
  switch (type) {
    case BASE_TYPE_BOOL: return "boolean";
    case BASE_TYPE_CHAR:
    case BASE_TYPE_UCHAR:
    case BASE_TYPE_SHORT:
    case BASE_TYPE_USHORT:
    case BASE_TYPE_INT:
    case BASE_TYPE_UINT:
    case BASE_TYPE_LONG:
    case BASE_TYPE_ULONG:
    case BASE_TYPE_FLOAT:
    case BASE_TYPE_DOUBLE: return "number";
    case BASE_TYPE_STRING: return "string";
    case BASE_TYPE_ARRAY: return "array";
    default: return "";
  }
}

template<class T> std::string GenFullName(const T *enum_def) {
  std::string full_name;
  const auto &name_spaces = enum_def->defined_namespace->components;
  for (auto ns = name_spaces.cbegin(); ns != name_spaces.cend(); ++ns) {
    full_name.append(*ns + "_");
  }
  full_name.append(enum_def->name);
  return full_name;
}

template<class T> std::string GenTypeRef(const T *enum_def) {
  return "\"$ref\" : \"#/definitions/" + GenFullName(enum_def) + "\"";
}

std::string GenType(const std::string &name) {
  return "\"type\" : \"" + name + "\"";
}

std::string GenType(const Type &type) {
  if (type.enum_def != nullptr && !type.enum_def->is_union) {
    // it is a reference to an enum type
    return GenTypeRef(type.enum_def);
  }
  switch (type.base_type) {
    case BASE_TYPE_ARRAY: FLATBUFFERS_FALLTHROUGH();  // fall thru
    case BASE_TYPE_VECTOR: {
      std::string typeline;
      typeline.append("\"type\" : \"array\", \"items\" : { ");
      if (type.element == BASE_TYPE_STRUCT) {
        typeline.append(GenTypeRef(type.struct_def));
      } else {
        typeline.append(GenType(GenNativeType(type.element)));
      }
      typeline.append(" }");
      return typeline;
    }
    case BASE_TYPE_STRUCT: {
      return GenTypeRef(type.struct_def);
    }
    case BASE_TYPE_UNION: {
      std::string union_type_string("\"anyOf\": [");
      const auto &union_types = type.enum_def->Vals();
      for (auto ut = union_types.cbegin(); ut < union_types.cend(); ++ut) {
        auto &union_type = *ut;
        if (union_type->union_type.base_type == BASE_TYPE_NONE) { continue; }
        if (union_type->union_type.base_type == BASE_TYPE_STRUCT) {
          union_type_string.append(
              "{ " + GenTypeRef(union_type->union_type.struct_def) + " }");
        }
        if (union_type != *type.enum_def->Vals().rbegin()) {
          union_type_string.append(",");
        }
      }
      union_type_string.append("]");
      return union_type_string;
    }
    case BASE_TYPE_UTYPE: return GenTypeRef(type.enum_def);
    default: return GenType(GenNativeType(type.base_type));
  }
}

class JsonSchemaGenerator : public BaseGenerator {
 private:
  CodeWriter code_;

 public:
  JsonSchemaGenerator(const Parser &parser, const std::string &path,
                      const std::string &file_name)
      : BaseGenerator(parser, path, file_name, "", "") {}

  explicit JsonSchemaGenerator(const BaseGenerator &base_generator)
      : BaseGenerator(base_generator) {}

  bool generate() {
    code_.Clear();
    code_ += "{";
    code_ += "  \"$schema\": \"http://json-schema.org/draft-04/schema#\",";
    code_ += "  \"definitions\": {";
    for (auto e = parser_.enums_.vec.cbegin(); e != parser_.enums_.vec.cend();
         ++e) {
      code_ += "    \"" + GenFullName(*e) + "\" : {";
      code_ += "      " + GenType("string") + ",";
      std::string enumdef("      \"enum\": [");
      for (auto enum_value = (*e)->Vals().begin();
           enum_value != (*e)->Vals().end(); ++enum_value) {
        enumdef.append("\"" + (*enum_value)->name + "\"");
        if (*enum_value != (*e)->Vals().back()) { enumdef.append(", "); }
      }
      enumdef.append("]");
      code_ += enumdef;
      code_ += "    },";  // close type
    }
    for (auto s = parser_.structs_.vec.cbegin();
         s != parser_.structs_.vec.cend(); ++s) {
      const auto &structure = *s;
      code_ += "    \"" + GenFullName(structure) + "\" : {";
      code_ += "      " + GenType("object") + ",";
      std::string comment;
      const auto &comment_lines = structure->doc_comment;
      for (auto comment_line = comment_lines.cbegin();
           comment_line != comment_lines.cend(); ++comment_line) {
        comment.append(*comment_line);
      }
      if (comment.size() > 0) {
        code_ += "      \"description\" : \"" + comment + "\",";
      }
      code_ += "      \"properties\" : {";

      const auto &properties = structure->fields.vec;
      for (auto prop = properties.cbegin(); prop != properties.cend(); ++prop) {
        const auto &property = *prop;
        std::string arrayInfo = "";
        if (IsArray(property->value.type)) {
          arrayInfo = ",\n                \"minItems\": " +
                      NumToString(property->value.type.fixed_length) +
                      ",\n                \"maxItems\": " +
                      NumToString(property->value.type.fixed_length);
        }
        std::string typeLine =
            "        \"" + property->name + "\" : {\n" + "                " +
            GenType(property->value.type) + arrayInfo + "\n              }";
        if (property != properties.back()) { typeLine.append(","); }
        code_ += typeLine;
      }
      code_ += "      },";  // close properties

      std::vector<FieldDef *> requiredProperties;
      std::copy_if(properties.begin(), properties.end(),
                   back_inserter(requiredProperties),
                   [](FieldDef const *prop) { return prop->required; });
      if (requiredProperties.size() > 0) {
        std::string required_string("      \"required\" : [");
        for (auto req_prop = requiredProperties.cbegin();
             req_prop != requiredProperties.cend(); ++req_prop) {
          required_string.append("\"" + (*req_prop)->name + "\"");
          if (*req_prop != requiredProperties.back()) {
            required_string.append(", ");
          }
        }
        required_string.append("],");
        code_ += required_string;
      }
      code_ += "      \"additionalProperties\" : false";
      std::string closeType("    }");
      if (*s != parser_.structs_.vec.back()) { closeType.append(","); }
      code_ += closeType;  // close type
    }
    code_ += "  },";  // close definitions

    // mark root type
    code_ += "  \"$ref\" : \"#/definitions/" +
             GenFullName(parser_.root_struct_def_) + "\"";

    code_ += "}";  // close schema root
    const std::string file_path = GeneratedFileName(path_, file_name_);
    const std::string final_code = code_.ToString();
    return SaveFile(file_path.c_str(), final_code, false);
  }
};
}  // namespace jsons

bool GenerateJsonSchema(const Parser &parser, const std::string &path,
                        const std::string &file_name) {
  jsons::JsonSchemaGenerator generator(parser, path, file_name);
  return generator.generate();
}
}  // namespace flatbuffers