module Streams
  # Assicura che la slate MP4 custom sia sul nodo assegnato (home/lab locale, CPX via agent).
  class SlateDistributor
    class Error < StandardError; end

    def self.slate_path_for_session(session)
      new(session).mediamtx_slate_path
    end

    def self.ensure_for!(session)
      new(session).ensure!
    end

    def initialize(session)
      @session = session
      @match = session.match
      @node = session.stream_node
      @resolver = CoverResolver.new(@match)
    end

    def mediamtx_slate_path
      ensure! unless defined?(@mediamtx_path)
      @mediamtx_path
    end

    def ensure!
      result = @resolver.resolve
      unless result
        @mediamtx_path = default_slate_path
        return @mediamtx_path
      end

      host_path = result.slate_local_path
      filename = File.basename(host_path)
      mediamtx_path = "#{CoverSlatePaths.slates_custom_root}/#{filename}"

      if cloud_node?
        push_to_agent!(filename, result.record, host_path)
      else
        verify_local_slate!(host_path)
      end

      @mediamtx_path = mediamtx_path
    rescue Error => e
      Rails.logger.warn("[SlateDistributor] session=#{@session.id} #{e.message}")
      @mediamtx_path = default_slate_path
    end

    private

    def cloud_node?
      @node&.role == "cloud" && agent_url.present?
    end

    def agent_url
      ENV["STREAM_NODE_RELAY_AGENT_URL"].presence || @node&.relay_agent_url
    end

    def agent_secret
      ENV["STREAM_NODE_AGENT_SECRET"].presence || "mediamtx_webhook_dev_secret"
    end

    def push_to_agent!(filename, record, host_path)
      bytes = read_slate_bytes(record, host_path)
      raise Error, "slate bytes missing for #{filename}" if bytes.blank?

      uri = URI.parse("#{agent_url.chomp('/')}/slates/#{CGI.escape(filename)}")
      http = Net::HTTP.new(uri.host, uri.port)
      http.open_timeout = 5
      http.read_timeout = 120
      req = Net::HTTP::Put.new(uri)
      req["Authorization"] = "Bearer #{agent_secret}" if agent_secret.present?
      req["Content-Type"] = "video/mp4"
      req.body = bytes
      res = http.request(req)
      return if res.is_a?(Net::HTTPSuccess)

      raise Error, "agent PUT /slates/#{filename} HTTP #{res.code} #{res.body.to_s.truncate(200)}"
    end

    def read_slate_bytes(record, host_path)
      return File.binread(host_path) if host_path.present? && File.exist?(host_path)

      return unless record.cover_slate.attached?

      record.cover_slate.blob.open(tmpdir: Dir.tmpdir) do |file|
        return File.binread(file.path)
      end
    end

    def verify_local_slate!(host_path)
      return if host_path.present? && File.exist?(host_path)

      raise Error, "slate missing on disk: #{host_path}"
    end

    def default_slate_path
      ENV.fetch("MEDIAMTX_SLATE_FILE", "/slates/offline.mp4")
    end
  end
end