public/lib/fxl/strings/substitute.cc

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "lib/fxl/strings/substitute.h"

#include <array>
#include <tuple>
#include <utility>

#include "lib/fxl/logging.h"
#include "lib/fxl/macros.h"

namespace fxl {

static std::string SubstituteWithArray(StringView format, StringView* args,
                                       size_t nargs);

std::string Substitute(StringView format, StringView arg0) {
  std::array<StringView, 1> arr = {arg0};
  return SubstituteWithArray(format, arr.data(), arr.size());
}

std::string Substitute(StringView format, StringView arg0, StringView arg1) {
  std::array<StringView, 2> arr = {arg0, arg1};
  return SubstituteWithArray(format, arr.data(), arr.size());
}

std::string Substitute(StringView format, StringView arg0, StringView arg1,
                       StringView arg2) {
  std::array<StringView, 3> arr = {arg0, arg1, arg2};
  return SubstituteWithArray(format, arr.data(), arr.size());
}

std::string Substitute(StringView format, StringView arg0, StringView arg1,
                       StringView arg2, StringView arg3) {
  std::array<StringView, 4> arr = {arg0, arg1, arg2, arg3};
  return SubstituteWithArray(format, arr.data(), arr.size());
}

std::string Substitute(StringView format, StringView arg0, StringView arg1,
                       StringView arg2, StringView arg3, StringView arg4) {
  std::array<StringView, 5> arr = {arg0, arg1, arg2, arg3, arg4};
  return SubstituteWithArray(format, arr.data(), arr.size());
}

std::string Substitute(StringView format, StringView arg0, StringView arg1,
                       StringView arg2, StringView arg3, StringView arg4,
                       StringView arg5) {
  std::array<StringView, 6> arr = {arg0, arg1, arg2, arg3, arg4, arg5};
  return SubstituteWithArray(format, arr.data(), arr.size());
}

std::string Substitute(StringView format, StringView arg0, StringView arg1,
                       StringView arg2, StringView arg3, StringView arg4,
                       StringView arg5, StringView arg6) {
  std::array<StringView, 7> arr = {arg0, arg1, arg2, arg3, arg4, arg5, arg6};
  return SubstituteWithArray(format, arr.data(), arr.size());
}

std::string Substitute(StringView format, StringView arg0, StringView arg1,
                       StringView arg2, StringView arg3, StringView arg4,
                       StringView arg5, StringView arg6, StringView arg7) {
  std::array<StringView, 8> arr = {arg0, arg1, arg2, arg3,
                                   arg4, arg5, arg6, arg7};
  return SubstituteWithArray(format, arr.data(), arr.size());
}

std::string Substitute(StringView format, StringView arg0, StringView arg1,
                       StringView arg2, StringView arg3, StringView arg4,
                       StringView arg5, StringView arg6, StringView arg7,
                       StringView arg8) {
  std::array<StringView, 9> arr = {arg0, arg1, arg2, arg3, arg4,
                                   arg5, arg6, arg7, arg8};
  return SubstituteWithArray(format, arr.data(), arr.size());
}

std::string Substitute(StringView format, StringView arg0, StringView arg1,
                       StringView arg2, StringView arg3, StringView arg4,
                       StringView arg5, StringView arg6, StringView arg7,
                       StringView arg8, StringView arg9) {
  std::array<StringView, 10> arr = {arg0, arg1, arg2, arg3, arg4,
                                    arg5, arg6, arg7, arg8, arg9};
  return SubstituteWithArray(format, arr.data(), arr.size());
}

enum class CharType { kPositionalId, kMissingId, kRegularChar, kDollar };

// Returns the type of character, and positional id if type is kPositionalId.
inline static std::pair<CharType, size_t> GetCharInfo(StringView str,
                                                      size_t pos) {
  if (str[pos] == '$' && pos < str.size() - 1 && str[pos + 1] >= '0' &&
      str[pos + 1] <= '9') {
    return {CharType::kPositionalId, str[pos + 1] - '0'};
  }
  if (pos == str.size() - 1 && str[pos] == '$') {
    return {CharType::kMissingId, -1};
  }
  if (pos < str.size() - 1 && str[pos] == '$' && str[pos + 1] == '$') {
    return {CharType::kDollar, -1};
  }
  return {CharType::kRegularChar, -1};
}

std::string SubstituteWithArray(StringView format, StringView* args,
                                size_t nargs) {
  static constexpr size_t kMaxArgs = 10;
  FXL_CHECK(nargs <= kMaxArgs) << "More than " << kMaxArgs << "args: " << nargs;

  int out_size = 0;
  size_t pos = 0;
  while (pos < format.size()) {
    CharType char_type;
    size_t positional_id;
    std::tie(char_type, positional_id) = GetCharInfo(format, pos);
    switch (char_type) {
      case CharType::kPositionalId:
        if (positional_id >= nargs) {
          // Error: missing argument.
          FXL_LOG(DFATAL) << "fxl::Substitute missing argument for $"
                          << positional_id << ": \"" << format << "\"";
          return "";
        }
        out_size += args[positional_id].size();
        pos += 2;
        break;
      case CharType::kMissingId:
        FXL_LOG(DFATAL) << "fxl::Substitute encountered trailing '$': \""
                        << format << "\"";
        return "";
      case CharType::kRegularChar:
        ++out_size;
        ++pos;
        break;
      case CharType::kDollar:
        ++out_size;
        pos += 2;
        break;
    }
  }

  std::string output;
  output.resize(out_size);
  size_t format_pos = 0, out_pos = 0;
  while (format_pos < format.size()) {
    CharType char_type;
    size_t positional_id;
    std::tie(char_type, positional_id) = GetCharInfo(format, format_pos);
    switch (char_type) {
      case CharType::kPositionalId: {
        const auto& arg = args[positional_id];
        output.replace(out_pos, arg.size(), arg.data(), arg.size());
        format_pos += 2;
        out_pos += arg.size();
        break;
      }
      case CharType::kMissingId:
        assert(false);
      case CharType::kRegularChar:
        output[out_pos++] = format[format_pos++];
        break;
      case CharType::kDollar:
        output[out_pos++] = '$';
        format_pos += 2;
        break;
    }
  }
  return output;
}

}  // namespace fxl