// Copyright 2020 The Pigweed Authors

//

// 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

//

//     https://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 "pw_tokenizer/internal/decode.h"

#include <algorithm>

#include <array>

#include <cctype>

#include <cstring>

#include "pw_varint/varint.h"

namespace pw::tokenizer {

namespace {

// Functions for parsing a printf format specifier.

size_t SkipFlags(const char* str) {

  size_t i = 0;

  while (str[i] == '-' || str[i] == '+' || str[i] == '#' || str[i] == ' ' ||

         str[i] == '0') {

    i += 1;

  }

  return i;

}

size_t SkipAsteriskOrInteger(const char* str) {

  if (str[0] == '*') {

    return 1;

  }

  size_t i = (str[0] == '-' || str[0] == '+') ? 1 : 0;

  while (std::isdigit(str[i])) {

    i += 1;

  }

  return i;

}

std::array<char, 2> ReadLengthModifier(const char* str) {

  // Check for ll or hh.

  if (str[0] == str[1] && (str[0] == 'l' || str[0] == 'h')) {

    return {str[0], str[1]};

  }

  if (std::strchr("hljztL", str[0]) != nullptr) {

    return {str[0]};

  }

  return {};

}

// Returns the error message that is used in place of a decoded arg when an

// error occurs.

std::string ErrorMessage(ArgStatus status,

                         std::string_view spec,

                         std::string_view value) {

  const char* message;

  if (status.HasError(ArgStatus::kSkipped)) {

    message = "SKIPPED";

  } else if (status.HasError(ArgStatus::kMissing)) {

    message = "MISSING";

  } else if (status.HasError(ArgStatus::kDecodeError)) {

    message = "ERROR";

  } else {

    message = "INTERNAL ERROR";

  }

  std::string result(PW_TOKENIZER_ARG_DECODING_ERROR_PREFIX);

  result.append(spec);

  result.push_back(' ');

  result.append(message);

  if (!value.empty()) {

    result.push_back(' ');

    result.push_back('(');

    result.append(value);

    result.push_back(')');

  }

  result.append(PW_TOKENIZER_ARG_DECODING_ERROR_SUFFIX);

  return result;

}

}  // namespace

DecodedArg::DecodedArg(ArgStatus error,

                       std::string_view spec,

                       size_t raw_size_bytes,

                       std::string_view value)

    : value_(ErrorMessage(error, spec, value)),

      spec_(spec),

      raw_data_size_bytes_(raw_size_bytes),

      status_(error) {}

StringSegment StringSegment::ParseFormatSpec(const char* format) {

  if (format[0] != '%' || format[1] == '\0') {

    return StringSegment();

  }

  // Parse the format specifier.

  size_t i = 1;

  // Skip the flags.

  i += SkipFlags(&format[i]);

  // Skip the field width.

  i += SkipAsteriskOrInteger(&format[i]);

  // Skip the precision.

  if (format[i] == '.') {

    i += 1;

    i += SkipAsteriskOrInteger(&format[i]);

  }

  // Read the length modifier.

  const std::array<char, 2> length = ReadLengthModifier(&format[i]);

  i += (length[0] == '\0' ? 0 : 1) + (length[1] == '\0' ? 0 : 1);

  // Read the conversion specifier.

  const char spec = format[i];

  Type type;

  if (spec == 's') {

    type = kString;

  } else if (spec == 'c' || spec == 'd' || spec == 'i') {

    type = kSignedInt;

  } else if (std::strchr("oxXup", spec) != nullptr) {

    // The source size matters for unsigned integers because they need to be

    // masked off to their correct length, since zig-zag decode sign extends.

    // TODO(hepler): 64-bit targets likely have 64-bit l, j, z, and t. Also, p

    // needs to be 64-bit on these targets.

    type = length[0] == 'j' || length[1] == 'l' ? kUnsigned64 : kUnsigned32;

  } else if (std::strchr("fFeEaAgG", spec) != nullptr) {

    type = kFloatingPoint;

  } else if (spec == '%' && i == 1) {

    type = kPercent;

  } else {

    return StringSegment();

  }

  return {std::string_view(format, i + 1), type, VarargSize(length, spec)};

}

StringSegment::ArgSize StringSegment::VarargSize(std::array<char, 2> length,

                                                 char spec) {

  // Use pointer size for %p or any other type (for which this doesn't matter).

  if (std::strchr("cdioxXu", spec) == nullptr) {

    return VarargSize<void*>();

  }

  if (length[0] == 'l') {

    return length[1] == 'l' ? VarargSize<long long>() : VarargSize<long>();

  }

  if (length[0] == 'j') {

    return VarargSize<intmax_t>();

  }

  if (length[0] == 'z') {

    return VarargSize<size_t>();

  }

  if (length[0] == 't') {

    return VarargSize<ptrdiff_t>();

  }

  return VarargSize<int>();

}

DecodedArg StringSegment::DecodeString(

    const span<const uint8_t>& arguments) const {

  if (arguments.empty()) {

    return DecodedArg(ArgStatus::kMissing, text_);

  }

  ArgStatus status =

      (arguments[0] & 0x80u) == 0u ? ArgStatus::kOk : ArgStatus::kTruncated;

  const uint_fast8_t size = arguments[0] & 0x7Fu;

  if (arguments.size() - 1 < size) {

    status.Update(ArgStatus::kDecodeError);

    span<const uint8_t> arg_val = arguments.subspan(1);

    return DecodedArg(

        status,

        text_,

        arguments.size(),

        {reinterpret_cast<const char*>(arg_val.data()), arg_val.size()});

  }

  std::string value(reinterpret_cast<const char*>(arguments.data() + 1), size);

  if (status.HasError(ArgStatus::kTruncated)) {

    value.append("[...]");

  }

  return DecodedArg::FromValue(text_.c_str(), value.c_str(), 1 + size, status);

}

DecodedArg StringSegment::DecodeInteger(

    const span<const uint8_t>& arguments) const {

  if (arguments.empty()) {

    return DecodedArg(ArgStatus::kMissing, text_);

  }

  int64_t value;

  const size_t bytes = varint::Decode(as_bytes(arguments), &value);

  if (bytes == 0u) {

    return DecodedArg(ArgStatus::kDecodeError,

                      text_,

                      std::min(varint::kMaxVarint64SizeBytes,

                               static_cast<size_t>(arguments.size())));

  }

  // Unsigned ints need to be masked to their bit width due to sign extension.

  if (type_ == kUnsigned32) {

    value &= 0xFFFFFFFFu;

  }

  if (local_size_ == k32Bit) {

    return DecodedArg::FromValue(

        text_.c_str(), static_cast<uint32_t>(value), bytes);

  }

  return DecodedArg::FromValue(text_.c_str(), value, bytes);

}

DecodedArg StringSegment::DecodeFloatingPoint(

    const span<const uint8_t>& arguments) const {

  static_assert(sizeof(float) == 4u);

  if (arguments.size() < sizeof(float)) {

    return DecodedArg(ArgStatus::kMissing, text_);

  }

  float value;

  std::memcpy(&value, arguments.data(), sizeof(value));

  return DecodedArg::FromValue(text_.c_str(), value, sizeof(value));

}

DecodedArg StringSegment::Decode(const span<const uint8_t>& arguments) const {

  switch (type_) {

    case kLiteral:

      return DecodedArg(text_);

    case kPercent:

      return DecodedArg("%");

    case kString:

      return DecodeString(arguments);

    case kSignedInt:

    case kUnsigned32:

    case kUnsigned64:

      return DecodeInteger(arguments);

    case kFloatingPoint:

      return DecodeFloatingPoint(arguments);

  }

  return DecodedArg(ArgStatus::kDecodeError, text_);

}

DecodedArg StringSegment::Skip() const {

  switch (type_) {

    case kLiteral:

      return DecodedArg(text_);

    case kPercent:

      return DecodedArg("%");

    case kString:

    case kSignedInt:

    case kUnsigned32:

    case kUnsigned64:

    case kFloatingPoint:

    default:

      return DecodedArg(ArgStatus::kSkipped, text_);

  }

}

std::string DecodedFormatString::value() const {

  std::string output;

  for (const DecodedArg& arg : segments_) {

    output.append(arg.ok() ? arg.value() : arg.spec());

  }

  return output;

}

std::string DecodedFormatString::value_with_errors() const {

  std::string output;

  for (const DecodedArg& arg : segments_) {

    output.append(arg.value());

  }

  return output;

}

size_t DecodedFormatString::argument_count() const {

  return std::count_if(segments_.begin(), segments_.end(), [](const auto& arg) {

    return !arg.spec().empty();

  });

}

size_t DecodedFormatString::decoding_errors() const {

  return std::count_if(segments_.begin(), segments_.end(), [](const auto& arg) {

    return !arg.ok();

  });

}

FormatString::FormatString(const char* format) {

  const char* text_start = format;

  while (format[0] != '\0') {

    if (StringSegment spec = StringSegment::ParseFormatSpec(format);

        !spec.empty()) {

      // Add the text segment seen so far (if any).

      if (text_start < format) {

        segments_.emplace_back(

            std::string_view(text_start, format - text_start));

      }

      // Move along the index and text segment start.

      format += spec.text().size();

      text_start = format;

      // Add the format specifier that was just found.

      segments_.push_back(std::move(spec));

    } else {

      format += 1;

    }

  }

  if (text_start < format) {

    segments_.emplace_back(std::string_view(text_start, format - text_start));

  }

}

DecodedFormatString FormatString::Format(span<const uint8_t> arguments) const {

  std::vector<DecodedArg> results;

  bool skip = false;

  for (const auto& segment : segments_) {

    if (skip) {

      results.push_back(segment.Skip());

    } else {

      results.push_back(segment.Decode(arguments));

      arguments = arguments.subspan(results.back().raw_size_bytes());

      // If an error occurred, skip decoding the remaining arguments.

      if (!results.back().ok()) {

        skip = true;

      }

    }

  }

  return DecodedFormatString(std::move(results), arguments.size());

}

}  // namespace pw::tokenizer