module Sprockets::SourceMapUtils

def decode_source_map(map)
  return nil unless map
  mappings, sources, names = [], [], []
  if map["sections"]
    map["sections"].each do |s|
      mappings += decode_source_map(s["map"])[:mappings].each do |m|
        m[:generated][0] += s["offset"]["line"]
        m[:generated][1] += s["offset"]["column"]
      end
      sources |= s["map"]["sources"]
      names   |= s["map"]["names"]
    end
  else
    mappings = decode_vlq_mappings(map["mappings"], sources: map["sources"], names: map["names"])
    sources  = map["sources"]
    names    = map["names"]
  end
  {
    version:  3,
    file:     map["file"],
    mappings: mappings,
    sources:  sources,
    names:    names
  }
end