module SnippetsHelper
  def reliable_snippet_path(snippet)
    if snippet.project_id?
      namespace_project_snippet_path(snippet.project.namespace,
                                     snippet.project, snippet)
    else
      snippet_path(snippet)
    end
  end

  # Get an array of line numbers surrounding a matching
  # line, bounded by min/max.
  #
  # @returns Array of line numbers
  def bounded_line_numbers(line, min, max, surrounding_lines)
    lower = line - surrounding_lines > min ? line - surrounding_lines : min
    upper = line + surrounding_lines < max ? line + surrounding_lines : max
    (lower..upper).to_a
  end

  # Returns a sorted set of lines to be included in a snippet preview.
  # This ensures matching adjacent lines do not display duplicated
  # surrounding code.
  #
  # @returns Array, unique and sorted.
  def matching_lines(lined_content, surrounding_lines, query)
    used_lines = []
    lined_content.each_with_index do |line, line_number|
      used_lines.concat bounded_line_numbers(
        line_number,
        0,
        lined_content.size,
        surrounding_lines
      ) if line.include?(query)
    end

    used_lines.uniq.sort
  end

  # 'Chunkify' entire snippet.  Splits the snippet data into matching lines +
  # surrounding_lines() worth of unmatching lines.
  #
  # @returns a hash with {snippet_object, snippet_chunks:{data,start_line}}
  def chunk_snippet(snippet, query, surrounding_lines = 3)
    lined_content = snippet.content.split("\n")
    used_lines = matching_lines(lined_content, surrounding_lines, query)

    snippet_chunk = []
    snippet_chunks = []
    snippet_start_line = 0
    last_line = -1

    # Go through each used line, and add consecutive lines as a single chunk
    # to the snippet chunk array.
    used_lines.each do |line_number|
      if last_line < 0
        # Start a new chunk.
        snippet_start_line = line_number
        snippet_chunk << lined_content[line_number]
      elsif last_line == line_number - 1
        # Consecutive line, continue chunk.
        snippet_chunk << lined_content[line_number]
      else
        # Non-consecutive line, add chunk to chunk array.
        snippet_chunks << {
          data: snippet_chunk.join("\n"),
          start_line: snippet_start_line + 1
        }

        # Start a new chunk.
        snippet_chunk = [lined_content[line_number]]
        snippet_start_line = line_number
      end
      last_line = line_number
    end
    # Add final chunk to chunk array
    snippet_chunks << {
      data: snippet_chunk.join("\n"),
      start_line: snippet_start_line + 1
    }

    # Return snippet with chunk array
    { snippet_object: snippet, snippet_chunks: snippet_chunks }
  end
end
