//
//  tokenizer.cxx
//  string-utils
//
//  Created by Sam Jaffe on 10/8/20.
//  Copyright © 2020 Sam Jaffe. All rights reserved.
//

#include "string_utils/tokenizer.h"

namespace {
bool is_escaped(std::string_view str, std::size_t p) {
  if (p == 0 || str[p - 1] != '\\') { return false; }
  return ((p - str.find_last_not_of('\\', p - 1) - 1) & 1) == 1;
}

auto promote(std::vector<std::string_view> input) {
  return std::vector<std::string>(input.cbegin(), input.cend());
}

bool current_token_is(std::string_view token, size_t offset,
                      std::string_view find) {
  return find.size() > 0 and token.compare(offset, find.size(), find) == 0;
};
}

namespace string_utils {

Tokenizer::Tokenizer(std::string_view divider) : divider_(divider) {}

Tokenizer & Tokenizer::max_outputs(size_t new_max_outputs) {
  max_outputs_ = new_max_outputs;
  return *this;
}

Tokenizer & Tokenizer::truncate(bool new_truncate) {
  truncate_ = new_truncate;
  return *this;
}

Tokenizer & Tokenizer::ignore_empty_tokens(bool new_ignore_empty_tokens) {
  ignore_empty_tokens_ = new_ignore_empty_tokens;
  return *this;
}

Tokenizer & Tokenizer::reverse_search(bool new_reverse) {
  reverse_search_ = new_reverse;
  return *this;
}

EscapedTokenizer::EscapedTokenizer(std::string_view divider, Quote quote)
    : EscapedTokenizer(Tokenizer(divider), quote) {}

EscapedTokenizer::EscapedTokenizer(Tokenizer tok, Quote quote)
    : Tokenizer(tok) {
  this->quote(quote);
}

EscapedTokenizer & EscapedTokenizer::max_outputs(size_t new_max_outputs) {
  Tokenizer::max_outputs(new_max_outputs);
  return *this;
}

EscapedTokenizer & EscapedTokenizer::truncate(bool new_truncate) {
  Tokenizer::truncate(new_truncate);
  return *this;
}

EscapedTokenizer &
EscapedTokenizer::ignore_empty_tokens(bool new_ignore_empty_tokens) {
  Tokenizer::ignore_empty_tokens(new_ignore_empty_tokens);
  return *this;
}

EscapedTokenizer & EscapedTokenizer::reverse_search(bool new_reverse) {
  Tokenizer::reverse_search(new_reverse);
  return *this;
}

Tokenizer & Tokenizer::quote(Quote quote) {
  quote_ = quote;
  escapable_ = true;
  return *this;
}

EscapedTokenizer Tokenizer::escapable(Quote quote) const {
  return EscapedTokenizer(*this, quote);
}

std::vector<std::string_view>
Tokenizer::operator()(std::string_view input) const {
  std::vector<std::string_view> rval;
  // If max_outputs_ == infinite_outputs, this will be infinite enough to work
  // since we'll hit overflow on the string itself before this.
  std::size_t const max = max_outputs_ - !truncate_;
  std::size_t const qsz = quote_.escaped.size();
  size_t span = 0;
  auto index = [this, &input, &span]() {
    return reverse_search_ ? input.size() - span - 1 : span;
  };
  bool in_quote{false};
  while (not input.empty() and rval.size() < max and span == 0) {
    for (span = 0; span < input.size(); ++span) {
      // We check for escaped-quotes before we check for quotes to minimise
      // complexity. Once in a quote, we simply append everything without
      // checking for the divider until the end quote is encountered (escaped
      // quotes are processed normally).
      if (not quote_.escaped.empty() and
          current_token_is(input, index(), quote_.escaped)) {
        span += qsz - 1;
      } else if (input[index()] == quote_.on) {
        in_quote = !in_quote;
      } else if (in_quote or not current_token_is(input, index(), divider_)) {
        continue;
      } else if (escapable_ and is_escaped(input, index())) {
        continue;
      } else if (reverse_search_) {
        if (not ignore_empty_tokens_ or span > 0) {
          rval.push_back(input.substr(index() + 1, span));
        }
        input.remove_suffix(span + divider_.size());
        span = 0;
        break;
      } else {
        if (not ignore_empty_tokens_ or span > 0) {
          rval.push_back(input.substr(0, span));
        }
        input.remove_prefix(span + divider_.size());
        span = 0;
        break;
      }
    }
  }
  // Due to the special handling rules of the truncate feature, we need
  // to add an additional layer of handling around empty tokens and buffer
  if (ignore_empty_tokens_ and current_token_is(input, span, divider_)) {
    input.remove_prefix(divider_.size());
  }
  // Additionally, we do not want to include the final element if there is
  // actually no data remaining in the buffer/input string, even when we permit
  // empty tokens in our output.
  if (rval.size() < max_outputs_ and not input.empty()) {
    rval.push_back(input);
  }
  if (reverse_search_) { std::reverse(rval.begin(), rval.end()); }
  return rval;
}

std::string Tokenizer::unescape(std::string_view token) const {
  std::string rval;
  rval.reserve(token.size());
  for (size_t i = 0; i < token.size(); ++i) {
    /*if (current_token_is(token, i, "\\\\")) {
      rval.append(1, '\\');
      ++i;
    } else */
    // The order of these tests is important!
    // First we check if the current token is an escaped-quote - if so,
    // replace it with the regular quote.
    if (current_token_is(token, i, quote_.escaped)) {
      rval.append(1, quote_.on);
    } else if (token[i] == '\\' and current_token_is(token, i + 1, divider_)) {
      // Then we check if we're looking at an escaped divider
      rval.append(divider_);
      i += divider_.size();
    } else if (token[i] != quote_.on) {
      // Lastly - we remote unescaped quotes
      rval.append(1, token[i]);
    }
  }
  return rval;
}

std::vector<std::string> Tokenizer::operator()(std::string && input) const {
  return promote(operator()(std::string_view(input)));
}

std::vector<std::string>
EscapedTokenizer::operator()(std::string_view input) const {
  auto rval = promote(Tokenizer::operator()(std::string_view(input)));
  for (auto & token : rval) {
    token = unescape(token);
  }
  return rval;
}

std::vector<std::string>
EscapedTokenizer::operator()(std::string && input) const {
  return operator()(std::string_view(input));
}

}