#include "java_tokens.hh"

#include "errors.hh"
#include "java_tokens_java-8.hh"
#include "java_uescape.hh"
#include "str.hh"
#include "u8.hh"
#include "uline.hh"

#include <cassert>
#include <charconv>
#include <cstddef>
#include <expected>
#include <format>
#include <limits>
#include <memory>
#include <optional>
#include <string>
#include <string_view>
#include <system_error>
#include <utility>

namespace java {

namespace {

template <typename TokenMatcher, typename MatchToken>
class TokensImpl : public Tokens {
 public:
  TokensImpl(std::unique_ptr<io::Reader> reader,
             std::unique_ptr<src::Errors> errors, TokensConfig config)
      : reader_(u8::line::open(u8::java::open(std::move(reader)))),
        errors_(std::move(errors)),
        config_(config) {}

  std::expected<Token, io::ReadError> read() override {
    while (true) {
      while (line_.empty()) {
        auto maybe_line = reader_->read();
        if (!maybe_line.has_value())
          return std::unexpected(maybe_line.error());
        line_ = maybe_line.value();
        location_.line = reader_->number();
        location_.column = 0;
      }

      Token token;
      token.loc = location_;

      auto maybe_token_pair = matcher_.matchNext(line_);

      while (matcher_.line_end_reached_) {
        // Matcher wants more lines.
        matcher_.line_end_reached_ = false;

        bool got_any = false;
        line_tmp_ = line_;
        line_tmp_.push_back('\n');
        while (true) {
          auto maybe_line = reader_->read();
          if (!maybe_line.has_value())
            break;
          line_tmp_.append(maybe_line.value());
          got_any = true;
          // Simple check, it might not actually end the comment but if so tokenizer will complain
          // about reaching line_end again.
          if (maybe_line->contains("*/"))
            break;
          line_tmp_.push_back('\n');
        }
        line_ = line_tmp_;
        maybe_token_pair = matcher_.matchNext(line_);

        if (!got_any)
          break;
      }

      if (maybe_token_pair.has_value()) {
        token.str = line_.substr(0, maybe_token_pair->second);
        location_.column += u8len(token.str);
        line_ = line_.substr(maybe_token_pair->second);
        switch (maybe_token_pair->first) {
          case MatchToken::kBinaryIntegerLiteral:
            handle_int_literal(token, /* base */ 2);
            break;
          case MatchToken::kBooleanLiteral:
            token.type = Token::Type::kLiteralBoolean;
            token.int_value = token.str != "false";
            break;
          case MatchToken::kCharacterLiteral:
            token.type = Token::Type::kLiteralCharacter;
            if (token.str[1] == '\\') {
              token.int_value =
                  unescape(token.str.substr(1, token.str.size() - 2)).first;
            } else {
              auto* ptr =
                  reinterpret_cast<uint8_t const*>(token.str.data() + 1);
              auto* end = ptr + token.str.size() - 2;
              token.int_value = u8::read(ptr, end).value();
            }
            break;
          case MatchToken::kDecimalFloatingPointLiteral:
            handle_float_literal(token);
            break;
          case MatchToken::kDecimalIntegerLiteral:
            handle_int_literal(token);
            break;
          case MatchToken::kEndOfLineComment:
            token.type = Token::Type::kComment;
            token.str = str::trim(token.str.substr(2));
            break;
          case MatchToken::kHexIntegerLiteral:
            handle_int_literal(token, /* base */ 16);
            break;
          case MatchToken::kHexadecimalFloatingPointLiteral:
            handle_float_literal(token, /* base */ 16);
            break;
          case MatchToken::kIdentifier:
            token.type = Token::Type::kIdentifier;
            break;
          case MatchToken::kKeyword:
            token.type = Token::Type::kKeyword;
            break;
          case MatchToken::kNullLiteral:
            token.type = Token::Type::kLiteralNull;
            break;
          case MatchToken::kOctalIntegerLiteral:
            handle_int_literal(token, /* base */ 8);
            break;
          case MatchToken::kOperator:
            token.type = Token::Type::kOperator;
            break;
          case MatchToken::kSeparator:
            token.type = Token::Type::kSeparator;
            break;
          case MatchToken::kStringLiteral:
            token.type = Token::Type::kLiteralString;
            token.str =
                unescape_if_needed(token.str.substr(1, token.str.size() - 2));
            break;
          case MatchToken::kTraditionalComment: {
            token.type = Token::Type::kComment;
            size_t s = 2;
            while (s < token.str.size() && token.str[s] == '*')
              ++s;
            token.str =
                str::trim(token.str.substr(s, token.str.size() - 2 - s));
            token.int_value = static_cast<int64_t>(s - 1);
            break;
          }
          case MatchToken::kWhiteSpace:
            continue;
        }
      } else {
        errors_->err(location_, std::format("Invalid token: {}", line_));
        token.type = Token::Type::kError;
        token.str = line_;
      }
      return token;
    }
  }

 private:
  void handle_int_literal_error(Token& token, std::string_view str,
                                std::errc err, int base) {
    if (err == std::errc::result_out_of_range) {
      // Java assumes two completent (so 0xffff_ffff is -1) and also, negative literals
      // are read as positive (because the operator '-' is a separate token)
      uint64_t tmp;
      auto ret =
          std::from_chars(str.data(), str.data() + str.size(), tmp, base);
      if (ret.ec == std::errc()) {
        token.type = ret.ptr < str.data() + str.size()
                         ? Token::Type::kLiteralLong
                         : Token::Type::kLiteralInt;
        token.int_value = static_cast<int64_t>(tmp);
        return;
      }
    }
    errors_->err(location_,
                 std::format("Invalid integer literal: {}", token.str));
    token.type = Token::Type::kError;
  }

  void handle_int_literal(Token& token, int base = 10) {
    size_t prefix;
    switch (base) {
      case 16:  // 0x
      case 2:   // 0b
        prefix = 2;
        break;
      case 8:  // 0
        prefix = 1;
        break;
      default:
        prefix = 0;
        break;
    }
    std::optional<char> suffix;
    if (token.str.find('_') == std::string_view::npos) {
      auto ret = std::from_chars(token.str.data() + prefix,
                                 token.str.data() + token.str.size(),
                                 token.int_value, base);
      if (ret.ec != std::errc()) {
        handle_int_literal_error(token, token.str.substr(prefix), ret.ec, base);
        return;
      }
      if (ret.ptr < token.str.data() + token.str.size())
        suffix = *ret.ptr;
    } else {
      std::string tmp;
      tmp.reserve(token.str.size() - prefix);
      for (size_t i = prefix; i < token.str.size(); ++i) {
        if (token.str[i] != '_') {
          tmp.push_back(token.str[i]);
        }
      }
      auto ret = std::from_chars(tmp.data(), tmp.data() + tmp.size(),
                                 token.int_value, base);
      if (ret.ec != std::errc()) {
        handle_int_literal_error(token, tmp, ret.ec, base);
        return;
      }
      if (ret.ptr < tmp.data() + tmp.size())
        suffix = *ret.ptr;
    }
    if (suffix.has_value() &&
        (suffix.value() == 'l' || suffix.value() == 'L')) {
      token.type = Token::Type::kLiteralLong;
    } else {
      if (base == 10 &&
          token.int_value >
              static_cast<int64_t>(1) + std::numeric_limits<int32_t>::max()) {
        errors_->err(location_,
                     std::format("Invalid integer literal: {}", token.str));
        token.type = Token::Type::kError;
        return;
      }
      if (std::cmp_greater(token.int_value,
                           std::numeric_limits<uint32_t>::max())) {
        errors_->err(location_,
                     std::format("Invalid integer literal: {}", token.str));
        token.type = Token::Type::kError;
        return;
      }
      token.type = Token::Type::kLiteralInt;
      token.int_value = static_cast<int32_t>(token.int_value);
    }
  }

  void handle_float_literal(Token& token, int base = 10) {
    size_t prefix;
    std::chars_format fmt;
    switch (base) {
      case 16:  // 0x
        fmt = std::chars_format::general | std::chars_format::hex;
        prefix = 2;
        break;
      default:
        fmt = std::chars_format::general;
        prefix = 0;
        break;
    }

    std::from_chars_result ret;
    if (token.str.ends_with("f") || token.str.ends_with("F")) {
      // float and double do not parse exactly the same, so use a float parser for float.
      float tmp;
      ret = std::from_chars(token.str.data() + prefix,
                            token.str.data() + token.str.size(), tmp, fmt);
      token.type = Token::Type::kLiteralFloatingPoint;
      token.float_value = tmp;
    } else {
      ret = std::from_chars(token.str.data() + prefix,
                            token.str.data() + token.str.size(),
                            token.float_value, fmt);
      token.type = Token::Type::kLiteralDoubleFloatingPoint;
    }

    if (ret.ec != std::errc()) {
      // Java allows 0 with just a suffix, std::from_chars does not.
      if (token.str == "0f" || token.str == "0F") {
        token.type = Token::Type::kLiteralFloatingPoint;
        token.float_value = 0;
        return;
      }
      if (token.str == "0d" || token.str == "0D") {
        token.type = Token::Type::kLiteralDoubleFloatingPoint;
        token.float_value = 0;
        return;
      }
      errors_->err(location_,
                   std::format("Invalid float literal: {}", token.str));
      token.type = Token::Type::kError;
    }
  }

  std::string_view unescape_if_needed(std::string_view str) {
    auto back_slash = str.find('\\');
    if (back_slash == std::string_view::npos)
      return str;
    unescape_tmp_.clear();
    unescape_tmp_.reserve(str.size());
    size_t last = 0;
    uint8_t tmp[4];
    while (true) {
      unescape_tmp_.append(str, last, back_slash - last);
      auto ret = unescape(str.substr(back_slash));
      auto* ptr = tmp;
      u8::write(ptr, tmp + sizeof(tmp), ret.first);
      unescape_tmp_.append(
          std::string_view(reinterpret_cast<char*>(tmp), ptr - tmp));
      last = back_slash + ret.second;
      back_slash = str.find('\\', last);
      if (back_slash == std::string::npos) {
        unescape_tmp_.append(str, last);
        break;
      }
    }
    return unescape_tmp_;
  }

  // Strings coming here have already been validated by the tokenizer
  static std::pair<uint16_t, size_t> unescape(std::string_view in) {
    assert(in.front() == '\\');
    assert(in.size() > 1);
    switch (in[1]) {
      case 'b':
        return std::make_pair(8, 2);
      case 't':
        return std::make_pair(9, 2);
      case 'n':
        return std::make_pair(10, 2);
      case 'f':
        return std::make_pair(12, 2);
      case 'r':
        return std::make_pair(13, 2);
      case '"':
        return std::make_pair(34, 2);
      case '\'':
        return std::make_pair(39, 2);
      case '\\':
        return std::make_pair(92, 2);
      case '0':
      case '1':
      case '2':
      case '3':
      case '4':
      case '5':
      case '6':
      case '7': {
        uint8_t tmp;
        auto ret = std::from_chars(in.data() + 1, in.data() + in.size(), tmp,
                                   /* base */ 8);
        return std::make_pair(tmp, ret.ptr - in.data());
      }
      default:
        std::unreachable();
    }
  }

  static size_t u8len(std::string_view str) {
    auto* ptr = reinterpret_cast<uint8_t const*>(str.data());
    auto* const end = ptr + str.size();
    size_t count = 0;
    while (u8::skip(ptr, end))
      ++count;
    return count;
  }

  std::unique_ptr<u8::line::Reader> reader_;
  std::unique_ptr<src::Errors> errors_;
  TokensConfig const config_;
  TokenMatcher matcher_;
  std::string_view line_;
  std::string line_tmp_;
  Location location_;
  std::string unescape_tmp_;
};

}  // namespace

std::unique_ptr<Tokens> open(std::unique_ptr<io::Reader> reader,
                             std::unique_ptr<src::Errors> errors,
                             TokensConfig config) {
  switch (config.version) {
    case Version::kJava8:
      return std::make_unique<TokensImpl<java_8::TokenMatcher, java_8::Token>>(
          std::move(reader), std::move(errors), config);
  }
  std::unreachable();
}

}  // namespace java