class Sprockets::Rails::SourcemappingUrlProcessor

def call(input)
  env     = input[:environment]
  context = env.context_class.new(input)
  data    = input[:data].gsub(REGEX) do |_match|
    sourcemap_logical_path = combine_sourcemap_logical_path(sourcefile: input[:name], sourcemap: $1)
    begin
      resolved_sourcemap_comment(sourcemap_logical_path, context: context)
    rescue Sprockets::FileNotFound
      removed_sourcemap_comment(sourcemap_logical_path, filename: input[:filename], env: env)
    end
  end
  { data: data }
end

def combine_sourcemap_logical_path(sourcefile:, sourcemap:)
  if (parts = sourcefile.split("/")).many?
    parts[0..-2].append(sourcemap).join("/")
  else
    sourcemap
  end
end

def removed_sourcemap_comment(sourcemap_logical_path, filename:, env:)
  env.logger.warn "Removed sourceMappingURL comment for missing asset '#{sourcemap_logical_path}' from #{filename}"
  nil
end

def resolved_sourcemap_comment(sourcemap_logical_path, context:)
  "//# sourceMappingURL=#{sourcemap_asset_path(sourcemap_logical_path, context: context)}\n//!\n"
end

def sourcemap_asset_path(sourcemap_logical_path, context:)
  # FIXME: Work-around for bug where if the sourcemap is nested two levels deep, it'll resolve as the source file
  # that's being mapped, rather than the map itself. So context.resolve("a/b/c.js.map") will return "c.js?"
  if context.resolve(sourcemap_logical_path) =~ /\.map/
    context.asset_path(sourcemap_logical_path)
  else
    raise Sprockets::FileNotFound, "Failed to resolve source map asset due to nesting depth"
  end
end