csv/writer.hpp

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/*
 
Copyright 2025 Matthew Tolman
 
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.
 
*/
 
#ifndef MTCORE_CSV_WRITTER_HPP
#define MTCORE_CSV_WRITTER_HPP
 
#include "mtcore/csv/common.hpp"
#include "mtcore/io/writer.hpp"


namespace mtcore::csv {
  struct RowEnd {};
  struct ColEnd {};

  using Column = std::variant<i64, u64, Slice<const char>, f64>;
  using WriteElem = std::variant<i64, u64, Slice<const char>, f64, Slice<const Column>, RowEnd, ColEnd>;
 
  namespace impl {
    template<WriterImpl WI>
    struct Writer {
      static constexpr bool IsWriteThrough = true;
      using WriteElem                      = csv::WriteElem;
      using ErrType                        = typename io::Writer<WI>::ErrType;
      io::Writer<WI> &underlying;
      Options opts = {};
 
      Result<size_t, ErrType> operator()(Slice<const char> s) {
        size_t written = 0;
        if (auto r = underlying.write(opts.quote); r.is_error()) {
          return r.error();
        }
        ++written;
        if (slices::contains(opts.quote, s)) {
          auto splits = slices::split(opts.quote, s);
          Slice<const char> cur;
          bool first = true;
          while (splits.next().copy_if_present(cur)) {
            if (!first) {
              if (auto r = underlying.write_n_times(opts.quote, 2); r.is_error()) {
                return r.error();
              }
              written += 2;
            }
            else {
              first = false;
            }
            if (!cur.empty()) {
              if (auto r = underlying.write_all(cur); r.is_error()) {
                return r.error();
              }
              written += cur.size();
            }
          }
        }
        else if (!s.empty()) {
          if (auto r = underlying.write_all(s); r.is_error()) {
            return r.error();
          }
          written += s.size();
        }
 
        if (auto r = underlying.write(opts.quote); r.is_error()) {
          return r.error();
        }
 
        ++written;
        return success(written);
      }
      Result<size_t, ErrType> operator()(i64 i) { return print(underlying, "{}", i); }
      Result<size_t, ErrType> operator()(u64 i) { return print(underlying, "{}", i); }
      Result<size_t, ErrType> operator()(f64 i) { return print(underlying, "{}", i); }
      Result<size_t, ErrType> operator()(RowEnd) {
        if (opts.cr.has_value()) {
          return print(underlying, "{}{}", opts.cr.value(), opts.lf);
        }
        return print(underlying, "{}", opts.lf);
      }
      Result<size_t, ErrType> operator()(ColEnd) { return print(underlying, "{}", opts.sep); }
      Result<size_t, ErrType> operator()(Slice<const Column> col) {
        auto iter = col.iter();
        Column cur;
        auto first     = true;
        size_t written = 0;
        while (iter.next().copy_if_present(cur)) {
          if (!first) {
            if (auto r = (*this)(ColEnd{}); r.is_error()) {
              return r.error();
            }
            else {
              written += r.value();
            }
          }
          else {
            first = false;
          }
 
          auto pr = std::visit(*this, cur);
          if (pr.is_error()) {
            return pr.error();
          }
          written += pr.value();
        }
        auto leRes = (*this)(RowEnd{});
        if (leRes.is_error()) {
          return leRes.error();
        }
        written += leRes.value();
        return success(written);
      }
 
      Result<size_t, ErrType> write(WriteElem e) { return std::visit(*this, e); }
 
      Result<size_t, ErrType> write(Slice<const WriteElem> e) {
        auto iter = e.iter();
        WriteElem cur;
        size_t written = 0;
        while (iter.next().copy_if_present(cur)) {
          if (auto r = write(cur); r.is_error()) {
            return r.error();
          }
          else {
            written += r.value();
          }
        }
        return success(written);
      }
    };
  }  // namespace impl

  template<WriterImpl WI>
  io::Writer<csv::impl::Writer<WI>> writer(io::Writer<WI> &underlying, Options opts = {}) {
    return io::Writer<csv::impl::Writer<WI>>{.underlying = csv::impl::Writer<WI>{underlying, opts}};
  }
}  // namespace mtcore::csv
 
#endif  // MTCORE_CSV_WRITTER_HPP