#include "csv.hpp"

#include <istream>
#include <string>
#include <vector>

namespace csv {
    enum class CSVState {
        UnquotedField,
        QuotedField,
        QuotedQuote
    };

    // this function has been made in collaboration with
    // StackOverflow https://stackoverflow.com/a/30338543
    void readCSVRow(const std::string& row, std::vector<std::string>& fields) {
        fields.push_back("");
        CSVState state = CSVState::UnquotedField;
        size_t i = 0; // index of the current field

        for (char c : row) {
            switch (state) {
                case CSVState::UnquotedField:
                    switch (c) {
                        case ',': // end of field
                            fields.push_back("");
                            i++;
                            break;

                        case '"':
                            state = CSVState::QuotedField;
                            break;

                        default:
                            fields[i].push_back(c);
                            break;
                    }

                    break;

                case CSVState::QuotedField:
                    switch (c) {
                        case '"':
                            state = CSVState::QuotedQuote;
                            break;

                        default:
                            fields[i].push_back(c);
                            break;
                    }

                    break;

                case CSVState::QuotedQuote:
                    switch (c) {
                        case ',': // , after closing quote
                            fields.push_back("");
                            i++;
                            state = CSVState::UnquotedField;
                            break;

                        case '"': // "" -> "
                            fields[i].push_back('"');
                            state = CSVState::QuotedField;
                            break;

                        default: // end of quote
                            state = CSVState::UnquotedField;
                            break;
                    }

                    break;
            }
        }
    }

    bool CsvReader::operator>>(std::vector<std::string>& line) {
        line.clear();

        if (!m_stream) {
            return false;
        }

        std::string row;
        std::getline(m_stream, row);

        readCSVRow(row, line);

        return !!m_stream;
    }
}