/*
 * 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.
 */

// independent from idl_parser, since this code is not needed for most clients

#include <sstream>
#include <string>

#include "flatbuffers/code_generators.h"
#include "flatbuffers/flatbuffers.h"
#include "flatbuffers/idl.h"
#include "flatbuffers/util.h"

#ifdef _WIN32
#  include <direct.h>
#  define PATH_SEPARATOR "\\"
#  define mkdir(n, m) _mkdir(n)
#else
#  include <sys/stat.h>
#  define PATH_SEPARATOR "/"
#endif

namespace flatbuffers {

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

namespace go {

// see https://golang.org/ref/spec#Keywords
static const char * const g_golang_keywords[] = {
  "break",  "default", "func",        "interface", "select", "case", "defer",
  "go",     "map",     "struct",      "chan",      "else",   "goto", "package",
  "switch", "const",   "fallthrough", "if",        "range",  "type", "continue",
  "for",    "import",  "return",      "var",
};

static std::string GenGetter(const Type &type);
static std::string GenMethod(const FieldDef &field);
static void GenStructBuilder(const StructDef &struct_def,
                             std::string *code_ptr);
static void GenReceiver(const StructDef &struct_def, std::string *code_ptr);
static std::string GenTypeBasic(const Type &type);
static std::string GenTypeGet(const Type &type);
static std::string TypeName(const FieldDef &field);
static std::string GoIdentity(const std::string &name) {
  for (size_t i = 0;
       i < sizeof(g_golang_keywords) / sizeof(g_golang_keywords[0]); i++) {
    if (name == g_golang_keywords[i]) { return MakeCamel(name + "_", false); }
  }

  return MakeCamel(name, false);
}

// Most field accessors need to retrieve and test the field offset first,
// this is the prefix code for that.
std::string OffsetPrefix(const FieldDef &field) {
  return "{\n\to := flatbuffers.UOffsetT(rcv._tab.Offset(" +
         NumToString(field.value.offset) + "))\n\tif o != 0 {\n";
}

// Begin a class declaration.
static void BeginClass(const StructDef &struct_def, std::string *code_ptr) {
  std::string &code = *code_ptr;

  code += "type " + struct_def.name + " struct {\n\t";

  // _ is reserved in flatbuffers field names, so no chance of name conflict:
  code += "_tab ";
  code += struct_def.fixed ? "flatbuffers.Struct" : "flatbuffers.Table";
  code += "\n}\n\n";
}

// Begin enum code with a class declaration.
static void BeginEnum(std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "const (\n";
}

// A single enum member.
static void EnumMember(const EnumDef &enum_def, const EnumVal ev,
                       std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "\t";
  code += enum_def.name;
  code += ev.name;
  code += " = ";
  code += NumToString(ev.value) + "\n";
}

// End enum code.
static void EndEnum(std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += ")\n\n";
}

// Begin enum name code.
static void BeginEnumNames(const EnumDef &enum_def, std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "var EnumNames";
  code += enum_def.name;
  code += " = map[int]string{\n";
}

// A single enum name member.
static void EnumNameMember(const EnumDef &enum_def, const EnumVal ev,
                           std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "\t";
  code += enum_def.name;
  code += ev.name;
  code += ":\"";
  code += ev.name;
  code += "\",\n";
}

// End enum name code.
static void EndEnumNames(std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "}\n\n";
}

// Initialize a new struct or table from existing data.
static void NewRootTypeFromBuffer(const StructDef &struct_def,
                                  std::string *code_ptr) {
  std::string &code = *code_ptr;

  code += "func GetRootAs";
  code += struct_def.name;
  code += "(buf []byte, offset flatbuffers.UOffsetT) ";
  code += "*" + struct_def.name + "";
  code += " {\n";
  code += "\tn := flatbuffers.GetUOffsetT(buf[offset:])\n";
  code += "\tx := &" + struct_def.name + "{}\n";
  code += "\tx.Init(buf, n+offset)\n";
  code += "\treturn x\n";
  code += "}\n\n";
}

// Initialize an existing object with other data, to avoid an allocation.
static void InitializeExisting(const StructDef &struct_def,
                               std::string *code_ptr) {
  std::string &code = *code_ptr;

  GenReceiver(struct_def, code_ptr);
  code += " Init(buf []byte, i flatbuffers.UOffsetT) ";
  code += "{\n";
  code += "\trcv._tab.Bytes = buf\n";
  code += "\trcv._tab.Pos = i\n";
  code += "}\n\n";
}

// Implement the table accessor
static void GenTableAccessor(const StructDef &struct_def,
                             std::string *code_ptr) {
  std::string &code = *code_ptr;

  GenReceiver(struct_def, code_ptr);
  code += " Table() flatbuffers.Table ";
  code += "{\n";

  if (struct_def.fixed) {
    code += "\treturn rcv._tab.Table\n";
  } else {
    code += "\treturn rcv._tab\n";
  }
  code += "}\n\n";
}

// Get the length of a vector.
static void GetVectorLen(const StructDef &struct_def, const FieldDef &field,
                         std::string *code_ptr) {
  std::string &code = *code_ptr;

  GenReceiver(struct_def, code_ptr);
  code += " " + MakeCamel(field.name) + "Length(";
  code += ") int " + OffsetPrefix(field);
  code += "\t\treturn rcv._tab.VectorLen(o)\n\t}\n";
  code += "\treturn 0\n}\n\n";
}

// Get a [ubyte] vector as a byte slice.
static void GetUByteSlice(const StructDef &struct_def, const FieldDef &field,
                          std::string *code_ptr) {
  std::string &code = *code_ptr;

  GenReceiver(struct_def, code_ptr);
  code += " " + MakeCamel(field.name) + "Bytes(";
  code += ") []byte " + OffsetPrefix(field);
  code += "\t\treturn rcv._tab.ByteVector(o + rcv._tab.Pos)\n\t}\n";
  code += "\treturn nil\n}\n\n";
}

// Get the value of a struct's scalar.
static void GetScalarFieldOfStruct(const StructDef &struct_def,
                                   const FieldDef &field,
                                   std::string *code_ptr) {
  std::string &code = *code_ptr;
  std::string getter = GenGetter(field.value.type);
  GenReceiver(struct_def, code_ptr);
  code += " " + MakeCamel(field.name);
  code += "() " + TypeName(field) + " {\n";
  code += "\treturn " + getter;
  code += "(rcv._tab.Pos + flatbuffers.UOffsetT(";
  code += NumToString(field.value.offset) + "))\n}\n";
}

// Get the value of a table's scalar.
static void GetScalarFieldOfTable(const StructDef &struct_def,
                                  const FieldDef &field,
                                  std::string *code_ptr) {
  std::string &code = *code_ptr;
  std::string getter = GenGetter(field.value.type);
  GenReceiver(struct_def, code_ptr);
  code += " " + MakeCamel(field.name);
  code += "() " + TypeName(field) + " ";
  code += OffsetPrefix(field) + "\t\treturn " + getter;
  code += "(o + rcv._tab.Pos)\n\t}\n";
  code += "\treturn " + field.value.constant + "\n";
  code += "}\n\n";
}

// Get a struct by initializing an existing struct.
// Specific to Struct.
static void GetStructFieldOfStruct(const StructDef &struct_def,
                                   const FieldDef &field,
                                   std::string *code_ptr) {
  std::string &code = *code_ptr;
  GenReceiver(struct_def, code_ptr);
  code += " " + MakeCamel(field.name);
  code += "(obj *" + TypeName(field);
  code += ") *" + TypeName(field);
  code += " {\n";
  code += "\tif obj == nil {\n";
  code += "\t\tobj = new(" + TypeName(field) + ")\n";
  code += "\t}\n";
  code += "\tobj.Init(rcv._tab.Bytes, rcv._tab.Pos+";
  code += NumToString(field.value.offset) + ")";
  code += "\n\treturn obj\n";
  code += "}\n";
}

// Get a struct by initializing an existing struct.
// Specific to Table.
static void GetStructFieldOfTable(const StructDef &struct_def,
                                  const FieldDef &field,
                                  std::string *code_ptr) {
  std::string &code = *code_ptr;
  GenReceiver(struct_def, code_ptr);
  code += " " + MakeCamel(field.name);
  code += "(obj *";
  code += TypeName(field);
  code += ") *" + TypeName(field) + " " + OffsetPrefix(field);
  if (field.value.type.struct_def->fixed) {
    code += "\t\tx := o + rcv._tab.Pos\n";
  } else {
    code += "\t\tx := rcv._tab.Indirect(o + rcv._tab.Pos)\n";
  }
  code += "\t\tif obj == nil {\n";
  code += "\t\t\tobj = new(" + TypeName(field) + ")\n";
  code += "\t\t}\n";
  code += "\t\tobj.Init(rcv._tab.Bytes, x)\n";
  code += "\t\treturn obj\n\t}\n\treturn nil\n";
  code += "}\n\n";
}

// Get the value of a string.
static void GetStringField(const StructDef &struct_def, const FieldDef &field,
                           std::string *code_ptr) {
  std::string &code = *code_ptr;
  GenReceiver(struct_def, code_ptr);
  code += " " + MakeCamel(field.name);
  code += "() " + TypeName(field) + " ";
  code += OffsetPrefix(field) + "\t\treturn " + GenGetter(field.value.type);
  code += "(o + rcv._tab.Pos)\n\t}\n\treturn nil\n";
  code += "}\n\n";
}

// Get the value of a union from an object.
static void GetUnionField(const StructDef &struct_def, const FieldDef &field,
                          std::string *code_ptr) {
  std::string &code = *code_ptr;
  GenReceiver(struct_def, code_ptr);
  code += " " + MakeCamel(field.name) + "(";
  code += "obj " + TypeName(field) + ") bool ";
  code += OffsetPrefix(field);
  code += "\t\t" + GenGetter(field.value.type);
  code += "(obj, o)\n\t\treturn true\n\t}\n";
  code += "\treturn false\n";
  code += "}\n\n";
}

// Get the value of a vector's struct member.
static void GetMemberOfVectorOfStruct(const StructDef &struct_def,
                                      const FieldDef &field,
                                      std::string *code_ptr) {
  std::string &code = *code_ptr;
  auto vectortype = field.value.type.VectorType();

  GenReceiver(struct_def, code_ptr);
  code += " " + MakeCamel(field.name);
  code += "(obj *" + TypeName(field);
  code += ", j int) bool " + OffsetPrefix(field);
  code += "\t\tx := rcv._tab.Vector(o)\n";
  code += "\t\tx += flatbuffers.UOffsetT(j) * ";
  code += NumToString(InlineSize(vectortype)) + "\n";
  if (!(vectortype.struct_def->fixed)) {
    code += "\t\tx = rcv._tab.Indirect(x)\n";
  }
  code += "\t\tobj.Init(rcv._tab.Bytes, x)\n";
  code += "\t\treturn true\n\t}\n";
  code += "\treturn false\n";
  code += "}\n\n";
}

// Get the value of a vector's non-struct member. Uses a named return
// argument to conveniently set the zero value for the result.
static void GetMemberOfVectorOfNonStruct(const StructDef &struct_def,
                                         const FieldDef &field,
                                         std::string *code_ptr) {
  std::string &code = *code_ptr;
  auto vectortype = field.value.type.VectorType();

  GenReceiver(struct_def, code_ptr);
  code += " " + MakeCamel(field.name);
  code += "(j int) " + TypeName(field) + " ";
  code += OffsetPrefix(field);
  code += "\t\ta := rcv._tab.Vector(o)\n";
  code += "\t\treturn " + GenGetter(field.value.type) + "(";
  code += "a + flatbuffers.UOffsetT(j*";
  code += NumToString(InlineSize(vectortype)) + "))\n";
  code += "\t}\n";
  if (vectortype.base_type == BASE_TYPE_STRING) {
    code += "\treturn nil\n";
  } else {
    code += "\treturn 0\n";
  }
  code += "}\n\n";
}

// Begin the creator function signature.
static void BeginBuilderArgs(const StructDef &struct_def,
                             std::string *code_ptr) {
  std::string &code = *code_ptr;

  if (code.substr(code.length() - 2) != "\n\n") {
    // a previous mutate has not put an extra new line
    code += "\n";
  }
  code += "func Create" + struct_def.name;
  code += "(builder *flatbuffers.Builder";
}

// Recursively generate arguments for a constructor, to deal with nested
// structs.
static void StructBuilderArgs(const StructDef &struct_def,
                              const char *nameprefix, std::string *code_ptr) {
  for (auto it = struct_def.fields.vec.begin();
       it != struct_def.fields.vec.end(); ++it) {
    auto &field = **it;
    if (IsStruct(field.value.type)) {
      // Generate arguments for a struct inside a struct. To ensure names
      // don't clash, and to make it obvious these arguments are constructing
      // a nested struct, prefix the name with the field name.
      StructBuilderArgs(*field.value.type.struct_def,
                        (nameprefix + (field.name + "_")).c_str(), code_ptr);
    } else {
      std::string &code = *code_ptr;
      code += (std::string) ", " + nameprefix;
      code += GoIdentity(field.name);
      code += " " + GenTypeBasic(field.value.type);
    }
  }
}

// End the creator function signature.
static void EndBuilderArgs(std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += ") flatbuffers.UOffsetT {\n";
}

// Recursively generate struct construction statements and instert manual
// padding.
static void StructBuilderBody(const StructDef &struct_def,
                              const char *nameprefix, std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "\tbuilder.Prep(" + NumToString(struct_def.minalign) + ", ";
  code += NumToString(struct_def.bytesize) + ")\n";
  for (auto it = struct_def.fields.vec.rbegin();
       it != struct_def.fields.vec.rend(); ++it) {
    auto &field = **it;
    if (field.padding)
      code += "\tbuilder.Pad(" + NumToString(field.padding) + ")\n";
    if (IsStruct(field.value.type)) {
      StructBuilderBody(*field.value.type.struct_def,
                        (nameprefix + (field.name + "_")).c_str(), code_ptr);
    } else {
      code += "\tbuilder.Prepend" + GenMethod(field) + "(";
      code += nameprefix + GoIdentity(field.name) + ")\n";
    }
  }
}

static void EndBuilderBody(std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "\treturn builder.Offset()\n";
  code += "}\n";
}

// Get the value of a table's starting offset.
static void GetStartOfTable(const StructDef &struct_def,
                            std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "func " + struct_def.name + "Start";
  code += "(builder *flatbuffers.Builder) {\n";
  code += "\tbuilder.StartObject(";
  code += NumToString(struct_def.fields.vec.size());
  code += ")\n}\n";
}

// Set the value of a table's field.
static void BuildFieldOfTable(const StructDef &struct_def,
                              const FieldDef &field, const size_t offset,
                              std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "func " + struct_def.name + "Add" + MakeCamel(field.name);
  code += "(builder *flatbuffers.Builder, ";
  code += GoIdentity(field.name) + " ";
  if (!IsScalar(field.value.type.base_type) && (!struct_def.fixed)) {
    code += "flatbuffers.UOffsetT";
  } else {
    code += GenTypeBasic(field.value.type);
  }
  code += ") {\n";
  code += "\tbuilder.Prepend";
  code += GenMethod(field) + "Slot(";
  code += NumToString(offset) + ", ";
  if (!IsScalar(field.value.type.base_type) && (!struct_def.fixed)) {
    code += "flatbuffers.UOffsetT";
    code += "(";
    code += GoIdentity(field.name) + ")";
  } else {
    code += GoIdentity(field.name);
  }
  code += ", " + field.value.constant;
  code += ")\n}\n";
}

// Set the value of one of the members of a table's vector.
static void BuildVectorOfTable(const StructDef &struct_def,
                               const FieldDef &field, std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "func " + struct_def.name + "Start";
  code += MakeCamel(field.name);
  code += "Vector(builder *flatbuffers.Builder, numElems int) ";
  code += "flatbuffers.UOffsetT {\n\treturn builder.StartVector(";
  auto vector_type = field.value.type.VectorType();
  auto alignment = InlineAlignment(vector_type);
  auto elem_size = InlineSize(vector_type);
  code += NumToString(elem_size);
  code += ", numElems, " + NumToString(alignment);
  code += ")\n}\n";
}

// Get the offset of the end of a table.
static void GetEndOffsetOnTable(const StructDef &struct_def,
                                std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "func " + struct_def.name + "End";
  code += "(builder *flatbuffers.Builder) flatbuffers.UOffsetT ";
  code += "{\n\treturn builder.EndObject()\n}\n";
}

// Generate the receiver for function signatures.
static void GenReceiver(const StructDef &struct_def, std::string *code_ptr) {
  std::string &code = *code_ptr;
  code += "func (rcv *" + struct_def.name + ")";
}

// Generate a struct field getter, conditioned on its child type(s).
static void GenStructAccessor(const StructDef &struct_def,
                              const FieldDef &field, std::string *code_ptr) {
  GenComment(field.doc_comment, code_ptr, nullptr, "");
  if (IsScalar(field.value.type.base_type)) {
    if (struct_def.fixed) {
      GetScalarFieldOfStruct(struct_def, field, code_ptr);
    } else {
      GetScalarFieldOfTable(struct_def, field, code_ptr);
    }
  } else {
    switch (field.value.type.base_type) {
      case BASE_TYPE_STRUCT:
        if (struct_def.fixed) {
          GetStructFieldOfStruct(struct_def, field, code_ptr);
        } else {
          GetStructFieldOfTable(struct_def, field, code_ptr);
        }
        break;
      case BASE_TYPE_STRING: GetStringField(struct_def, field, code_ptr); break;
      case BASE_TYPE_VECTOR: {
        auto vectortype = field.value.type.VectorType();
        if (vectortype.base_type == BASE_TYPE_STRUCT) {
          GetMemberOfVectorOfStruct(struct_def, field, code_ptr);
        } else {
          GetMemberOfVectorOfNonStruct(struct_def, field, code_ptr);
        }
        break;
      }
      case BASE_TYPE_UNION: GetUnionField(struct_def, field, code_ptr); break;
      default: FLATBUFFERS_ASSERT(0);
    }
  }
  if (field.value.type.base_type == BASE_TYPE_VECTOR) {
    GetVectorLen(struct_def, field, code_ptr);
    if (field.value.type.element == BASE_TYPE_UCHAR) {
      GetUByteSlice(struct_def, field, code_ptr);
    }
  }
}

// Mutate the value of a struct's scalar.
static void MutateScalarFieldOfStruct(const StructDef &struct_def,
                                      const FieldDef &field,
                                      std::string *code_ptr) {
  std::string &code = *code_ptr;
  std::string type = MakeCamel(GenTypeBasic(field.value.type));
  std::string setter = "rcv._tab.Mutate" + type;
  GenReceiver(struct_def, code_ptr);
  code += " Mutate" + MakeCamel(field.name);
  code += "(n " + TypeName(field) + ") bool {\n\treturn " + setter;
  code += "(rcv._tab.Pos+flatbuffers.UOffsetT(";
  code += NumToString(field.value.offset) + "), n)\n}\n\n";
}

// Mutate the value of a table's scalar.
static void MutateScalarFieldOfTable(const StructDef &struct_def,
                                     const FieldDef &field,
                                     std::string *code_ptr) {
  std::string &code = *code_ptr;
  std::string type = MakeCamel(GenTypeBasic(field.value.type));
  std::string setter = "rcv._tab.Mutate" + type + "Slot";
  GenReceiver(struct_def, code_ptr);
  code += " Mutate" + MakeCamel(field.name);
  code += "(n " + TypeName(field) + ") bool {\n\treturn ";
  code += setter + "(" + NumToString(field.value.offset) + ", n)\n";
  code += "}\n\n";
}

// Generate a struct field setter, conditioned on its child type(s).
static void GenStructMutator(const StructDef &struct_def, const FieldDef &field,
                             std::string *code_ptr) {
  GenComment(field.doc_comment, code_ptr, nullptr, "");
  if (IsScalar(field.value.type.base_type)) {
    if (struct_def.fixed) {
      MutateScalarFieldOfStruct(struct_def, field, code_ptr);
    } else {
      MutateScalarFieldOfTable(struct_def, field, code_ptr);
    }
  }
}

// Generate table constructors, conditioned on its members' types.
static void GenTableBuilders(const StructDef &struct_def,
                             std::string *code_ptr) {
  GetStartOfTable(struct_def, code_ptr);

  for (auto it = struct_def.fields.vec.begin();
       it != struct_def.fields.vec.end(); ++it) {
    auto &field = **it;
    if (field.deprecated) continue;

    auto offset = it - struct_def.fields.vec.begin();
    BuildFieldOfTable(struct_def, field, offset, code_ptr);
    if (field.value.type.base_type == BASE_TYPE_VECTOR) {
      BuildVectorOfTable(struct_def, field, code_ptr);
    }
  }

  GetEndOffsetOnTable(struct_def, code_ptr);
}

// Generate struct or table methods.
static void GenStruct(const StructDef &struct_def, std::string *code_ptr) {
  if (struct_def.generated) return;

  GenComment(struct_def.doc_comment, code_ptr, nullptr);
  BeginClass(struct_def, code_ptr);
  if (!struct_def.fixed) {
    // Generate a special accessor for the table that has been declared as
    // the root type.
    NewRootTypeFromBuffer(struct_def, code_ptr);
  }
  // Generate the Init method that sets the field in a pre-existing
  // accessor object. This is to allow object reuse.
  InitializeExisting(struct_def, code_ptr);
  // Generate _tab accessor
  GenTableAccessor(struct_def, code_ptr);

  // Generate struct fields accessors
  for (auto it = struct_def.fields.vec.begin();
       it != struct_def.fields.vec.end(); ++it) {
    auto &field = **it;
    if (field.deprecated) continue;

    GenStructAccessor(struct_def, field, code_ptr);
    GenStructMutator(struct_def, field, code_ptr);
  }

  // Generate builders
  if (struct_def.fixed) {
    // create a struct constructor function
    GenStructBuilder(struct_def, code_ptr);
  } else {
    // Create a set of functions that allow table construction.
    GenTableBuilders(struct_def, code_ptr);
  }
}

// Generate enum declarations.
static void GenEnum(const EnumDef &enum_def, std::string *code_ptr) {
  if (enum_def.generated) return;

  GenComment(enum_def.doc_comment, code_ptr, nullptr);
  BeginEnum(code_ptr);
  for (auto it = enum_def.vals.vec.begin(); it != enum_def.vals.vec.end();
       ++it) {
    auto &ev = **it;
    GenComment(ev.doc_comment, code_ptr, nullptr, "\t");
    EnumMember(enum_def, ev, code_ptr);
  }
  EndEnum(code_ptr);

  BeginEnumNames(enum_def, code_ptr);
  for (auto it = enum_def.vals.vec.begin(); it != enum_def.vals.vec.end();
       ++it) {
    auto &ev = **it;
    EnumNameMember(enum_def, ev, code_ptr);
  }
  EndEnumNames(code_ptr);
}

// Returns the function name that is able to read a value of the given type.
static std::string GenGetter(const Type &type) {
  switch (type.base_type) {
    case BASE_TYPE_STRING: return "rcv._tab.ByteVector";
    case BASE_TYPE_UNION: return "rcv._tab.Union";
    case BASE_TYPE_VECTOR: return GenGetter(type.VectorType());
    default: return "rcv._tab.Get" + MakeCamel(GenTypeGet(type));
  }
}

// Returns the method name for use with add/put calls.
static std::string GenMethod(const FieldDef &field) {
  return IsScalar(field.value.type.base_type)
             ? MakeCamel(GenTypeBasic(field.value.type))
             : (IsStruct(field.value.type) ? "Struct" : "UOffsetT");
}

static std::string GenTypeBasic(const Type &type) {
  static const char *ctypename[] = {
  // clang-format off
    #define FLATBUFFERS_TD(ENUM, IDLTYPE, \
      CTYPE, JTYPE, GTYPE, NTYPE, PTYPE) \
      #GTYPE,
      FLATBUFFERS_GEN_TYPES(FLATBUFFERS_TD)
    #undef FLATBUFFERS_TD
    // clang-format on
  };
  return ctypename[type.base_type];
}

static std::string GenTypePointer(const Type &type) {
  switch (type.base_type) {
    case BASE_TYPE_STRING: return "[]byte";
    case BASE_TYPE_VECTOR: return GenTypeGet(type.VectorType());
    case BASE_TYPE_STRUCT: return type.struct_def->name;
    case BASE_TYPE_UNION:
      // fall through
    default: return "*flatbuffers.Table";
  }
}

static std::string GenTypeGet(const Type &type) {
  return IsScalar(type.base_type) ? GenTypeBasic(type) : GenTypePointer(type);
}

static std::string TypeName(const FieldDef &field) {
  return GenTypeGet(field.value.type);
}

// Create a struct with a builder and the struct's arguments.
static void GenStructBuilder(const StructDef &struct_def,
                             std::string *code_ptr) {
  BeginBuilderArgs(struct_def, code_ptr);
  StructBuilderArgs(struct_def, "", code_ptr);
  EndBuilderArgs(code_ptr);

  StructBuilderBody(struct_def, "", code_ptr);
  EndBuilderBody(code_ptr);
}

class GoGenerator : public BaseGenerator {
 public:
  GoGenerator(const Parser &parser, const std::string &path,
              const std::string &file_name, const std::string &go_namespace)
      : BaseGenerator(parser, path, file_name, "" /* not used*/,
                      "" /* not used */) {
    std::istringstream iss(go_namespace);
    std::string component;
    while (std::getline(iss, component, '.')) {
      go_namespace_.components.push_back(component);
    }
  }

  bool generate() {
    std::string one_file_code;
    for (auto it = parser_.enums_.vec.begin(); it != parser_.enums_.vec.end();
         ++it) {
      std::string enumcode;
      go::GenEnum(**it, &enumcode);
      if (parser_.opts.one_file) {
        one_file_code += enumcode;
      } else {
        if (!SaveType(**it, enumcode, false)) return false;
      }
    }

    for (auto it = parser_.structs_.vec.begin();
         it != parser_.structs_.vec.end(); ++it) {
      std::string declcode;
      go::GenStruct(**it, &declcode);
      if (parser_.opts.one_file) {
        one_file_code += declcode;
      } else {
        if (!SaveType(**it, declcode, true)) return false;
      }
    }

    if (parser_.opts.one_file) {
      std::string code = "";
      BeginFile(LastNamespacePart(go_namespace_), true, &code);
      code += one_file_code;
      const std::string filename = GeneratedFileName(path_, file_name_);
      return SaveFile(filename.c_str(), code, false);
    }

    return true;
  }

 private:
  // Begin by declaring namespace and imports.
  void BeginFile(const std::string name_space_name, const bool needs_imports,
                 std::string *code_ptr) {
    std::string &code = *code_ptr;
    code = code + "// " + FlatBuffersGeneratedWarning() + "\n\n";
    code += "package " + name_space_name + "\n\n";
    if (needs_imports) {
      code += "import (\n";
      if (!parser_.opts.go_import.empty()) {
        code += "\tflatbuffers \"" + parser_.opts.go_import + "\"\n";
      } else {
        code += "\tflatbuffers \"github.com/google/flatbuffers/go\"\n";
      }
      code += ")\n\n";
    }
  }

  // Save out the generated code for a Go Table type.
  bool SaveType(const Definition &def, const std::string &classcode,
                bool needs_imports) {
    if (!classcode.length()) return true;

    Namespace &ns = go_namespace_.components.empty() ? *def.defined_namespace
                                                     : go_namespace_;
    std::string code = "";
    BeginFile(LastNamespacePart(ns), needs_imports, &code);
    code += classcode;
    std::string filename = NamespaceDir(ns) + def.name + ".go";
    return SaveFile(filename.c_str(), code, false);
  }

  Namespace go_namespace_;
};
}  // namespace go

bool GenerateGo(const Parser &parser, const std::string &path,
                const std::string &file_name) {
  go::GoGenerator generator(parser, path, file_name, parser.opts.go_namespace);
  return generator.generate();
}

}  // namespace flatbuffers