text: 
  // Copyright 2020 The Tint Authors.
  //
  // 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 SRC_SOURCE_H_
  #define SRC_SOURCE_H_
  
  #include <iostream>
  #include <string>
  #include <tuple>
  #include <vector>
  
  namespace tint {
  
  /// Source describes a range of characters within a source file.
  class Source {
   public:
    /// FileContent describes the content of a source file.
    class FileContent {
     public:
      /// Constructs the FileContent with the given file content.
      /// @param data the file contents
      explicit FileContent(const std::string& data);
  
      /// Destructor
      ~FileContent();
  
      /// un-split file content
      const std::string data;
      /// #data split by lines
      const std::vector<std::string> lines;
    };
  
    /// File describes a source file, including path and content.
    class File {
     public:
      /// Constructs the File with the given file path and content.
      /// @param p the path for this file
      /// @param c the file contents
      inline File(const std::string& p, const std::string& c)
          : path(p), content(c) {}
  
      ~File();
  
      /// file path (optional)
      const std::string path;
      /// file content
      const FileContent content;
    };
  
    /// Location holds a 1-based line and column index.
    class Location {
     public:
      /// the 1-based line number. 0 represents no line information.
      size_t line = 0;
      /// the 1-based column number. 0 represents no column information.
      size_t column = 0;
  
      /// Returns true of `this` location is lexicographically less than `rhs`
      /// @param rhs location to compare against
      /// @returns true if `this` < `rhs`
      inline bool operator<(const Source::Location& rhs) {
        return std::tie(line, column) < std::tie(rhs.line, rhs.column);
      }
  
      /// Returns true of `this` location is equal to `rhs`
      /// @param rhs location to compare against
      /// @returns true if `this` == `rhs`
      inline bool operator==(const Location& rhs) const {
        return line == rhs.line && column == rhs.column;
      }
  
      /// Returns true of `this` location is not equal to `rhs`
      /// @param rhs location to compare against
      /// @returns true if `this` != `rhs`
      inline bool operator!=(const Location& rhs) const {
        return !(*this == rhs);
      }
    };
  
    /// Range holds a Location interval described by [begin, end).
    class Range {
     public:
      /// Constructs a zero initialized Range.
      inline Range() = default;
  
      /// Constructs a zero-length Range starting at `loc`
      /// @param loc the start and end location for the range
      inline constexpr explicit Range(const Location& loc)
          : begin(loc), end(loc) {}
  
      /// Constructs the Range beginning at `b` and ending at `e`
      /// @param b the range start location
      /// @param e the range end location
      inline constexpr Range(const Location& b, const Location& e)
          : begin(b), end(e) {}
  
      /// Return a column-shifted Range
      /// @param n the number of characters to shift by
      /// @returns a Range with a #begin and #end column shifted by `n`
      inline Range operator+(size_t n) const {
        return Range{{begin.line, begin.column + n}, {end.line, end.column + n}};
      }
  
      /// Returns true of `this` range is not equal to `rhs`
      /// @param rhs range to compare against
      /// @returns true if `this` != `rhs`
      inline bool operator==(const Range& rhs) const {
        return begin == rhs.begin && end == rhs.end;
      }
  
      /// Returns true of `this` range is equal to `rhs`
      /// @param rhs range to compare against
      /// @returns true if `this` == `rhs`
      inline bool operator!=(const Range& rhs) const { return !(*this == rhs); }
  
      /// The location of the first character in the range.
      Location begin;
      /// The location of one-past the last character in the range.
      Location end;
    };
  
    /// Constructs the Source with an zero initialized Range and null File.
    inline Source() : range() {}
  
    /// Constructs the Source with the Range `rng` and a null File
    /// @param rng the source range
    inline explicit Source(const Range& rng) : range(rng) {}
  
    /// Constructs the Source with the Range `loc` and a null File
    /// @param loc the start and end location for the source range
    inline explicit Source(const Location& loc) : range(Range(loc)) {}
  
    /// Constructs the Source with the Range `rng` and File `file`
    /// @param rng the source range
    /// @param file the source file
    inline Source(const Range& rng, File const* file)
        : range(rng), file_path(file->path), file_content(&file->content) {}
  
    /// Constructs the Source with the Range `rng`, file path `path` and content
    /// `content`
    /// @param rng the source range
    /// @param path the source file path
    /// @param content the source file content
    inline Source(const Range& rng,
                  const std::string& path,
                  const FileContent* content = nullptr)
        : range(rng), file_path(path), file_content(content) {}
  
    /// @returns a Source that points to the begin range of this Source.
    inline Source Begin() const {
      return Source(Range{range.begin}, file_path, file_content);
    }
  
    /// @returns a Source that points to the end range of this Source.
    inline Source End() const {
      return Source(Range{range.end}, file_path, file_content);
    }
  
    /// Return a column-shifted Source
    /// @param n the number of characters to shift by
    /// @returns a Source with the range's columns shifted by `n`
    inline Source operator+(size_t n) const {
      return Source(range + n, file_path, file_content);
    }
  
    /// Returns true of `this` Source is lexicographically less than `rhs`
    /// @param rhs source to compare against
    /// @returns true if `this` < `rhs`
    inline bool operator<(const Source& rhs) {
      if (file_path != rhs.file_path) {
        return false;
      }
      if (file_content != rhs.file_content) {
        return false;
      }
      return range.begin < rhs.range.begin;
    }
  
    /// Helper function that returns the range union of two source locations. The
    /// `start` and `end` locations are assumed to refer to the same source file.
    /// @param start the start source of the range
    /// @param end the end source of the range
    /// @returns the combined source
    inline static Source Combine(const Source& start, const Source& end) {
      return Source(Source::Range(start.range.begin, end.range.end),
                    start.file_path, start.file_content);
    }
  
    /// range is the span of text this source refers to in #file_path
    Range range;
    /// file is the optional file path this source refers to
    std::string file_path;
    /// file is the optional source content this source refers to
    const FileContent* file_content = nullptr;
  };
  
  /// Writes the Source::Location to the std::ostream.
  /// @param out the std::ostream to write to
  /// @param loc the location to write
  /// @returns out so calls can be chained
  inline std::ostream& operator<<(std::ostream& out,
                                  const Source::Location& loc) {
    out << loc.line << ":" << loc.column;
    return out;
  }
  
  /// Writes the Source::Range to the std::ostream.
  /// @param out the std::ostream to write to
  /// @param range the range to write
  /// @returns out so calls can be chained
  inline std::ostream& operator<<(std::ostream& out, const Source::Range& range) {
    out << "[" << range.begin << ", " << range.end << "]";
    return out;
  }
  
  /// Writes the Source to the std::ostream.
  /// @param out the std::ostream to write to
  /// @param source the source to write
  /// @returns out so calls can be chained
  std::ostream& operator<<(std::ostream& out, const Source& source);
  
  /// Writes the Source::FileContent to the std::ostream.
  /// @param out the std::ostream to write to
  /// @param content the file content to write
  /// @returns out so calls can be chained
  inline std::ostream& operator<<(std::ostream& out,
                                  const Source::FileContent& content) {
    out << content.data;
    return out;
  }
  
  }  // namespace tint
  
  #endif  // SRC_SOURCE_H_
  