# frozen_string_literal: true

module Analytics
  class SnapshotIngest
    MAX_BYTES = 1_800_000
    MIN_REFRESH = 12.hours
    RATE_LIMIT_PER_HOUR = 20

    Result = Struct.new(:ok, :skipped, :rate_limited, :error, keyword_init: true)

    def initialize(path:, device:, width:, height:, image:, remote_ip:)
      @path = path
      @device = device.to_s
      @width = width
      @height = height
      @image = image
      @remote_ip = remote_ip.to_s.presence || "unknown"
    end

    def call
      return Result.new(ok: false, skipped: false, rate_limited: true) if rate_limited?

      page_path = PathNormalizer.normalize(@path)
      return Result.new(ok: false, skipped: true, error: "path") if PathNormalizer.excluded?(page_path)
      return Result.new(ok: false, skipped: true, error: "device") unless AnalyticsEvent::DEVICES.include?(@device)
      return Result.new(ok: false, skipped: true, error: "image") unless valid_image?

      width = Integer(@width)
      height = Integer(@height)
      return Result.new(ok: false, skipped: true, error: "size") if width < 200 || height < 200 || width > 6000 || height > 20000

      snap = AnalyticsPageSnapshot.find_or_initialize_by(page_path: page_path, device: @device)
      if snap.persisted? && snap.captured_at.present? && snap.captured_at > MIN_REFRESH.ago && snap.image.attached?
        return Result.new(ok: true, skipped: true)
      end

      snap.width = width
      snap.height = height
      snap.captured_at = Time.current
      snap.save!
      snap.image.purge if snap.image.attached?
      snap.image.attach(
        io: image_io,
        filename: "analytics-#{Digest::SHA1.hexdigest(page_path)[0, 12]}-#{@device}.jpg",
        content_type: "image/jpeg"
      )

      Result.new(ok: true, skipped: false)
    rescue ArgumentError, TypeError, ActiveRecord::RecordInvalid => e
      Result.new(ok: false, skipped: true, error: e.class.name)
    end

    private

    def rate_limited?
      key = "analytics:snapshot:#{@remote_ip}"
      redis = Redis.new(url: ENV.fetch("REDIS_URL", "redis://localhost:6379/0"))
      count = redis.incr(key)
      redis.expire(key, 3600) if count == 1
      count > RATE_LIMIT_PER_HOUR
    rescue StandardError => e
      Rails.logger.warn("[analytics] snapshot rate limit unavailable: #{e.class}")
      false
    end

    def valid_image?
      return false if @image.blank?
      return false unless @image.respond_to?(:tempfile) || @image.respond_to?(:read)
      return false if @image.respond_to?(:size) && @image.size.to_i > MAX_BYTES

      content_type = @image.content_type.to_s if @image.respond_to?(:content_type)
      content_type.blank? || content_type.start_with?("image/")
    end

    def image_io
      if @image.respond_to?(:tempfile)
        @image.tempfile.rewind
        @image.tempfile
      else
        StringIO.new(@image.read)
      end
    end
  end
end