csv/slice.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_SLICE_HPP
#define MTCORE_CSV_SLICE_HPP
 
#include "mtcore/colls/slice.hpp"
#include "mtcore/csv/common.hpp"
#include "mtcore/csv/writer.hpp"
#include "mtcore/io/reader.hpp"
 
namespace mtcore::csv {
  struct SliceParser {
    Slice<const char> slice;
    Options options;
 
    struct Field {
      Slice<const char> data;
      Options options;
 
      template<WriterImpl WI>
      Result<size_t, typename io::Writer<WI>::ErrType> decode(io::Writer<WI> &writer) const {
        return mtcore::csv::common::decode(writer, data, options);
      }
 
      [[nodiscard]] Result<Slice<char>, AllocationError> copy(Allocator alloc) const;
    };
 
    struct RowField {
      Field field = {};
      bool rowEnd = false;
    };
 
    struct FieldParser {
      using IterElem = RowField;
 
      Slice<const char> data;
      Options opts;
      Optional<ReadError> error = nullopt;
      struct {
        u64 prevQuote       = 0;
        u64 prevCr          = 0;
        u64 prevQuoteEnds   = 0;
        u64 prevFieldSeps   = static_cast<u64>(1) << (chunkSize - 1);
        u64 fieldSeparators = 0;
        u64 startChunk      = 0;
        u64 startChunkPos   = 0;
        u64 endChunk        = 0;
        u64 nextChunk       = 0;
        bool fieldStart     = true;
        bool skip           = false;
      } state = {};
 
      FieldParser(const Slice<const char> &data, const Options &opts);
 
      [[nodiscard]] size_t start_pos() const;
 
      [[nodiscard]] bool done() const;
 
      [[nodiscard]] bool has_next_chunk() const;
 
      Optional<RowField> next();
    };
    static_assert(is_iterator<FieldParser>, "Not an iterator");
 
    struct Row {
      Slice<const char> data;
      Options opts;
      size_t len = 0;
 
      struct Iter {
        FieldParser fieldParser;
        using IterElem = Field;
 
        Optional<Field> next();
      };
      static_assert(is_iterator<Iter>, "Not an iterator");
 
      [[nodiscard]] Iter iter() const;
 
      [[nodiscard]] size_t size() const;
 
      Field operator[](size_t i) const;
    };
 
    using IterElem = Row;
 
    struct Iter {
      FieldParser parser;
 
      using IterElem = Row;
 
      Optional<Row> next();
      [[nodiscard]] Optional<ReadError> error() const { return parser.error; };
    };
 
    static_assert(is_iterator<Iter>, "Not an iterator");
 
    [[nodiscard]] Iter iter() const;
 
    struct RowReader {
      using ReadElem = Row;
      using ErrType  = ReadError;
      Iter iter;
 
      Result<Slice<const ReadElem>, ErrType> read(Slice<ReadElem> out) {
        Row cur;
        size_t read = 0;
        while (read < out.len && iter.next().copy_if_present(cur)) {
          out[read++] = cur;
        }
        if (iter.parser.error.has_value()) {
          return error(iter.parser.error.value());
        }
        return success(out.sub(0, read).to_const());
      }
    };
 
    [[nodiscard]] io::Reader<RowReader> rows() const { return {RowReader{iter()}}; }
 
    struct FieldReader {
      using ReadElem = std::variant<RowEnd, Field>;
      using ErrType  = ReadError;
      FieldParser iter;
      bool rowEnd = false;
 
      Result<Slice<const ReadElem>, ErrType> read(Slice<ReadElem> out) {
        RowField cur;
        size_t read = 0;
        if (!out.empty() && rowEnd) {
          out[read++] = RowEnd{};
          rowEnd      = false;
        }
 
        while (read < out.len && iter.next().copy_if_present(cur)) {
          out[read++] = cur.field;
          if (cur.rowEnd) {
            if (read < out.len) {
              out[read++] = RowEnd{};
            }
            else {
              rowEnd = true;
            }
          }
        }
 
        if (iter.error.has_value()) {
          return error(iter.error.value());
        }
        return success(out.sub(0, read).to_const());
      }
    };
 
    [[nodiscard]] io::Reader<FieldReader> fields() const { return {FieldReader{iter().parser}}; }
  };
}  // namespace mtcore::csv
 
#endif  // MTCORE_CSV_SLICE_HPP