# frozen_string_literal: true
require 'set'

module Sprockets

  # The purpose of this class is to generate a source map file
  # that can be read and understood by browsers.
  #
  # When a file is passed in it will have a `application/js-sourcemap+json`
  # or `application/css-sourcemap+json` mime type. The filename will be
  # match the original asset. The original asset is loaded. As it
  # gets processed by Sprockets it will aquire all information
  # needed to build a source map file in the `asset.to_hash[:metadata][:map]`
  # key.
  #
  # The output is an asset with a properly formatted source map file:
  #
  #   {
  #     "version": 3,
  #     "sources": ["foo.js"],
  #     "names":   [ ],
  #     "mappings": "AAAA,GAAIA"
  #   }
  #
  class SourceMapProcessor
    def self.call(input)
      links = Set.new(input[:metadata][:links])
      env = input[:environment]

      uri, _ = env.resolve!(input[:filename], accept: self.original_content_type(input[:content_type]))
      asset  = env.load(uri)
      map    = asset.metadata[:map]

      # TODO: Because of the default piplene hack we have to apply dependencies
      #       from compiled asset to the source map, otherwise the source map cache
      #       will never detect the changes from directives
      dependencies = Set.new(input[:metadata][:dependencies])
      dependencies.merge(asset.metadata[:dependencies])

      map["file"] = PathUtils.split_subpath(input[:load_path], input[:filename])
      sources = map["sections"] ? map["sections"].map { |s| s["map"]["sources"] }.flatten : map["sources"]

      sources.each do |source|
        source = PathUtils.join(File.dirname(map["file"]), source)
        uri, _ = env.resolve!(source)
        links << uri
      end

      json = JSON.generate(map)

      { data: json, links: links, dependencies: dependencies }
    end

    def self.original_content_type(source_map_content_type, error_when_not_found: true)
      case source_map_content_type
      when "application/js-sourcemap+json"
        "application/javascript"
      when "application/css-sourcemap+json"
        "text/css"
      else
        fail(source_map_content_type) if error_when_not_found
        source_map_content_type
      end
    end
  end
end