class Webpacker::Compiler

def compilation_digest_path
  config.cache_path.join(".last-compilation-digest-#{Webpacker.env}")
end

def compile
  if stale?
    record_compilation_digest
    run_webpack.tap do |success|
      remove_compilation_digest if !success
    end
  else
    true
  end
end

def default_watched_paths
  [
    *config.resolved_paths_globbed,
    "#{config.source_path.relative_path_from(Rails.root)}/**/*",
    "yarn.lock", "package.json",
    "config/webpack/**/*"
  ].freeze
end

def fresh?
  watched_files_digest == last_compilation_digest
end

def initialize(webpacker)
  @webpacker = webpacker
end

def last_compilation_digest
  compilation_digest_path.read if compilation_digest_path.exist? && config.public_manifest_path.exist?
end

def record_compilation_digest
  config.cache_path.mkpath
  compilation_digest_path.write(watched_files_digest)
end

def remove_compilation_digest
  compilation_digest_path.delete if compilation_digest_path.exist?
end

def run_webpack
  logger.info "Compiling…"
  stdout, sterr , status = Open3.capture3(webpack_env, "#{RbConfig.ruby} ./bin/webpack")
  if status.success?
    logger.info "Compiled all packs in #{config.public_output_path}"
  else
    logger.error "Compilation failed:\n#{sterr}\n#{stdout}"
  end
  status.success?
end

def stale?
  !fresh?
end

def watched_files_digest
  files = Dir[*default_watched_paths, *watched_paths].reject { |f| File.directory?(f) }
  Digest::SHA1.hexdigest(files.map { |f| "#{File.basename(f)}/#{File.mtime(f).utc.to_i}" }.join("/"))
end

def webpack_env
  env.merge("WEBPACKER_ASSET_HOST"        => ActionController::Base.helpers.compute_asset_host,
            "WEBPACKER_RELATIVE_URL_ROOT" => ActionController::Base.relative_url_root)
end