module Sprockets::Loader

def asset_from_cache(key)
  asset = cache.get(key, true)
  if asset
    asset[:uri]       = expand_from_root(asset[:uri])
    asset[:load_path] = expand_from_root(asset[:load_path])
    asset[:filename]  = expand_from_root(asset[:filename])
    asset[:metadata][:included].map!          { |uri| expand_from_root(uri) } if asset[:metadata][:included]
    asset[:metadata][:links].map!             { |uri| expand_from_root(uri) } if asset[:metadata][:links]
    asset[:metadata][:stubbed].map!           { |uri| expand_from_root(uri) } if asset[:metadata][:stubbed]
    asset[:metadata][:required].map!          { |uri| expand_from_root(uri) } if asset[:metadata][:required]
    asset[:metadata][:dependencies].map!      { |uri| uri.start_with?("file-digest://") ? expand_from_root(uri) : uri } if asset[:metadata][:dependencies]
    asset[:metadata].each_key do |k|
      next unless k =~ /_dependencies\z/
      asset[:metadata][k].map! { |uri| expand_from_root(uri) }
    end
  end
  asset
end

def fetch_asset_from_dependency_cache(unloaded, limit = 3)
  key = unloaded.dependency_history_key
  history = cache.get(key) || []
  history.each_with_index do |deps, index|
    expanded_deps = deps.map do |path|
      path.start_with?("file-digest://") ? expand_from_root(path) : path
    end
    if asset = yield(expanded_deps)
      cache.set(key, history.rotate!(index)) if index > 0
      return asset
    end
  end
  asset = yield
  deps  = asset[:metadata][:dependencies].dup.map! do |uri|
    uri.start_with?("file-digest://") ? compress_from_root(uri) : uri
  end
  cache.set(key, history.unshift(deps).take(limit))
  asset
end

def load(uri)
  unloaded = UnloadedAsset.new(uri, self)
  if unloaded.params.key?(:id)
    unless asset = asset_from_cache(unloaded.asset_key)
      id = unloaded.params.delete(:id)
      uri_without_id = build_asset_uri(unloaded.filename, unloaded.params)
      asset = load_from_unloaded(UnloadedAsset.new(uri_without_id, self))
      if asset[:id] != id
        @logger.warn "Sprockets load error: Tried to find #{uri}, but latest was id #{asset[:id]}"
      end
    end
  else
    asset = fetch_asset_from_dependency_cache(unloaded) do |paths|
      # When asset is previously generated, its "dependencies" are stored in the cache.
      # The presence of `paths` indicates dependencies were stored.
      # We can check to see if the dependencies have not changed by "resolving" them and
      # generating a digest key from the resolved entries. If this digest key has not
      # changed the asset will be pulled from cache.
      #
      # If this `paths` is present but the cache returns nothing then `fetch_asset_from_dependency_cache`
      # will confusingly be called again with `paths` set to nil where the asset will be
      # loaded from disk.
      if paths
        digest = DigestUtils.digest(resolve_dependencies(paths))
        if uri_from_cache = cache.get(unloaded.digest_key(digest), true)
          asset_from_cache(UnloadedAsset.new(uri_from_cache, self).asset_key)
        end
      else
        load_from_unloaded(unloaded)
      end
    end
  end
  Asset.new(self, asset)
end

def load_from_unloaded(unloaded)
  unless file?(unloaded.filename)
    raise FileNotFound, "could not find file: #{unloaded.filename}"
  end
  load_path, logical_path = paths_split(config[:paths], unloaded.filename)
  unless load_path
    raise FileOutsidePaths, "#{unloaded.filename} is no longer under a load path: #{self.paths.join(', ')}"
  end
  logical_path, file_type, engine_extnames, _ = parse_path_extnames(logical_path)
  name = logical_path
  if pipeline = unloaded.params[:pipeline]
    logical_path += ".#{pipeline}"
  end
  if type = unloaded.params[:type]
    logical_path += config[:mime_types][type][:extensions].first
  end
  if type != file_type && !config[:transformers][file_type][type]
    raise ConversionError, "could not convert #{file_type.inspect} to #{type.inspect}"
  end
  processors = processors_for(type, file_type, engine_extnames, pipeline)
  processors_dep_uri = build_processors_uri(type, file_type, engine_extnames, pipeline)
  dependencies = config[:dependencies] + [processors_dep_uri]
  # Read into memory and process if theres a processor pipeline
  if processors.any?
    result = call_processors(processors, {
      environment: self,
      cache: self.cache,
      uri: unloaded.uri,
      filename: unloaded.filename,
      load_path: load_path,
      name: name,
      content_type: type,
      metadata: { dependencies: dependencies }
    })
    validate_processor_result!(result)
    source = result.delete(:data)
    metadata = result.merge!(
      charset: source.encoding.name.downcase,
      digest: digest(source),
      length: source.bytesize
    )
  else
    dependencies << build_file_digest_uri(unloaded.filename)
    metadata = {
      digest: file_digest(unloaded.filename),
      length: self.stat(unloaded.filename).size,
      dependencies: dependencies
    }
  end
  asset = {
    uri: unloaded.uri,
    load_path: load_path,
    filename: unloaded.filename,
    name: name,
    logical_path: logical_path,
    content_type: type,
    source: source,
    metadata: metadata,
    dependencies_digest: DigestUtils.digest(resolve_dependencies(metadata[:dependencies]))
  }
  asset[:id]  = pack_hexdigest(digest(asset))
  asset[:uri] = build_asset_uri(unloaded.filename, unloaded.params.merge(id: asset[:id]))
  # Deprecated: Avoid tracking Asset mtime
  asset[:mtime] = metadata[:dependencies].map { |u|
    if u.start_with?("file-digest:")
      s = self.stat(parse_file_digest_uri(u))
      s ? s.mtime.to_i : nil
    else
      nil
    end
  }.compact.max
  asset[:mtime] ||= self.stat(unloaded.filename).mtime.to_i
  store_asset(asset, unloaded)
  asset
end

def resolve_dependencies(uris)
  uris.map { |uri| resolve_dependency(uri) }
end

def store_asset(asset, unloaded)
  # Save the asset in the cache under the new URI
  cached_asset             = asset.dup
  cached_asset[:uri]       = compress_from_root(asset[:uri])
  cached_asset[:filename]  = compress_from_root(asset[:filename])
  cached_asset[:load_path] = compress_from_root(asset[:load_path])
  if cached_asset[:metadata]
    # Deep dup to avoid modifying `asset`
    cached_asset[:metadata] = cached_asset[:metadata].dup
    if cached_asset[:metadata][:included] && !cached_asset[:metadata][:included].empty?
      cached_asset[:metadata][:included] = cached_asset[:metadata][:included].dup
      cached_asset[:metadata][:included].map! { |uri| compress_from_root(uri) }
    end
    if cached_asset[:metadata][:links] && !cached_asset[:metadata][:links].empty?
      cached_asset[:metadata][:links] = cached_asset[:metadata][:links].dup
      cached_asset[:metadata][:links].map! { |uri| compress_from_root(uri) }
    end
    if cached_asset[:metadata][:stubbed] && !cached_asset[:metadata][:stubbed].empty?
      cached_asset[:metadata][:stubbed] = cached_asset[:metadata][:stubbed].dup
      cached_asset[:metadata][:stubbed].map! { |uri| compress_from_root(uri) }
    end
    if cached_asset[:metadata][:required] && !cached_asset[:metadata][:required].empty?
      cached_asset[:metadata][:required] = cached_asset[:metadata][:required].dup
      cached_asset[:metadata][:required].map! { |uri| compress_from_root(uri) }
    end
    if cached_asset[:metadata][:dependencies] && !cached_asset[:metadata][:dependencies].empty?
      cached_asset[:metadata][:dependencies] = cached_asset[:metadata][:dependencies].dup
      cached_asset[:metadata][:dependencies].map! do |uri|
        uri.start_with?("file-digest://".freeze) ? compress_from_root(uri) : uri
      end
    end
    # compress all _dependencies in metadata like `sass_dependencies`
    cached_asset[:metadata].each do |key, value|
      next unless key =~ /_dependencies\z/
      cached_asset[:metadata][key] = value.dup
      cached_asset[:metadata][key].map! {|uri| compress_from_root(uri) }
    end
  end
  # Unloaded asset and stored_asset now have a different URI
  stored_asset = UnloadedAsset.new(asset[:uri], self)
  cache.set(stored_asset.asset_key, cached_asset, true)
  # Save the new relative path for the digest key of the unloaded asset
  cache.set(unloaded.digest_key(asset[:dependencies_digest]), stored_asset.compressed_path, true)
end