Repo created

libs/coding/csv_reader.hpp

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+#pragma once
+
+#include "coding/reader.hpp"
+
+#include <fstream>
+#include <functional>
+#include <optional>
+#include <string>
+#include <vector>
+
+namespace coding
+{
+class CSVReader
+{
+public:
+  using Row = std::vector<std::string>;
+  using Rows = std::vector<Row>;
+
+  explicit CSVReader(std::string const & filename, bool hasHeader = false, char delimiter = ',');
+  explicit CSVReader(std::istream & stream, bool hasHeader = false, char delimiter = ',');
+  explicit CSVReader(Reader const & reader, bool hasHeader = false, char delimiter = ',');
+
+  bool HasHeader() const;
+  char GetDelimiter() const;
+
+  Row const & GetHeader() const;
+  std::optional<Row> ReadRow();
+  Rows ReadAll();
+
+  template <typename Fn>
+  void ForEachRow(Fn && fn)
+  {
+    while (auto const optRow = ReadRow())
+      fn(*optRow);
+  }
+
+  // The total number of lines read including the header. Count starts at 0.
+  size_t GetCurrentLineNumber() const;
+
+private:
+  class ReaderInterface
+  {
+  public:
+    virtual ~ReaderInterface() = default;
+
+    virtual std::optional<std::string> ReadLine() = 0;
+  };
+
+  class IstreamWrapper : public ReaderInterface
+  {
+  public:
+    explicit IstreamWrapper(std::istream & stream);
+
+    // ReaderInterface overrides:
+    std::optional<std::string> ReadLine() override;
+
+  private:
+    std::istream & m_stream;
+  };
+
+  class ReaderWrapper : public ReaderInterface
+  {
+  public:
+    explicit ReaderWrapper(Reader const & reader);
+
+    // ReaderInterface overrides:
+    std::optional<std::string> ReadLine() override;
+
+  private:
+    size_t m_pos = 0;
+    Reader const & m_reader;
+  };
+
+  class DefaultReader : public ReaderInterface
+  {
+  public:
+    explicit DefaultReader(std::string const & filename);
+
+    // ReaderInterface overrides:
+    std::optional<std::string> ReadLine() override;
+
+  private:
+    std::ifstream m_stream;
+  };
+
+  explicit CSVReader(std::unique_ptr<ReaderInterface> reader, bool hasHeader, char delimiter);
+
+  std::unique_ptr<ReaderInterface> m_reader;
+  size_t m_currentLine = 0;
+  bool m_hasHeader = false;
+  char m_delimiter = ',';
+  Row m_header;
+};
+
+class CSVRunner
+{
+public:
+  explicit CSVRunner(CSVReader && reader);
+
+  class Iterator
+  {
+  public:
+    using iterator_category = std::input_iterator_tag;
+    using value_type = CSVReader::Row;
+
+    explicit Iterator(CSVReader & reader, bool isEnd = false);
+    Iterator(Iterator const & other);
+    Iterator & operator++();
+    Iterator operator++(int);
+    // Checks whether both this and other are equal. Two CSVReader iterators are equal if both of
+    // them are end-of-file iterators or not and both of them refer to the same CSVReader.
+    bool operator==(Iterator const & other) const;
+    bool operator!=(Iterator const & other) const;
+    CSVReader::Row & operator*();
+
+  private:
+    CSVReader & m_reader;
+    std::optional<CSVReader::Row> m_current;
+  };
+
+  // Warning: It reads first line.
+  Iterator begin();
+  Iterator end();
+
+private:
+  CSVReader m_reader;
+};
+}  // namespace coding