module Sprockets::SourceMapUtils

def encode_vlq_mappings(mappings, sources: nil, names: nil)
  sources ||= mappings.map { |m| m[:source] }.uniq.compact
  names   ||= mappings.map { |m| m[:name] }.uniq.compact
  sources_index = Hash[sources.each_with_index.to_a]
  names_index   = Hash[names.each_with_index.to_a]
  source_id     = 0
  source_line   = 1
  source_column = 0
  name_id       = 0
  by_lines = mappings.group_by { |m| m[:generated][0] }
  ary = (1..(by_lines.keys.max || 1)).map do |line|
    generated_column = 0
    (by_lines[line] || []).map do |mapping|
      group = []
      group << mapping[:generated][1] - generated_column
      group << sources_index[mapping[:source]] - source_id
      group << mapping[:original][0] - source_line
      group << mapping[:original][1] - source_column
      group << names_index[mapping[:name]] - name_id if mapping[:name]
      generated_column = mapping[:generated][1]
      source_id        = sources_index[mapping[:source]]
      source_line      = mapping[:original][0]
      source_column    = mapping[:original][1]
      name_id          = names_index[mapping[:name]] if mapping[:name]
      group
    end
  end
  vlq_encode_mappings(ary)
end