require "digest/sha1"
require_dependency "file_helper"
require_dependency "url_helper"
require_dependency "db_helper"
require_dependency "validators/upload_validator"
require_dependency "file_store/local_store"
require_dependency "base62"

class Upload < ActiveRecord::Base
  include ActionView::Helpers::NumberHelper
  include HasUrl

  SHA1_LENGTH = 40
  SEEDED_ID_THRESHOLD = 0
  URL_REGEX ||= /(\/original\/\dX[\/\.\w]*\/([a-zA-Z0-9]+)[\.\w]*)/

  belongs_to :user

  has_many :post_uploads, dependent: :destroy
  has_many :posts, through: :post_uploads

  has_many :optimized_images, dependent: :destroy
  has_many :user_uploads, dependent: :destroy

  attr_accessor :for_group_message
  attr_accessor :for_theme
  attr_accessor :for_private_message
  attr_accessor :for_export
  attr_accessor :for_site_setting

  validates_presence_of :filesize
  validates_presence_of :original_filename

  validates_with ::Validators::UploadValidator

  after_destroy do
    User.where(uploaded_avatar_id: self.id).update_all(uploaded_avatar_id: nil)
    UserAvatar.where(gravatar_upload_id: self.id).update_all(gravatar_upload_id: nil)
    UserAvatar.where(custom_upload_id: self.id).update_all(custom_upload_id: nil)
  end

  scope :by_users, -> { where("uploads.id > ?", SEEDED_ID_THRESHOLD) }

  def to_s
    self.url
  end

  def thumbnail(width = self.thumbnail_width, height = self.thumbnail_height)
    optimized_images.find_by(width: width, height: height)
  end

  def has_thumbnail?(width, height)
    thumbnail(width, height).present?
  end

  def create_thumbnail!(width, height, opts = nil)
    return unless SiteSetting.create_thumbnails?
    opts ||= {}
    opts[:allow_animation] = SiteSetting.allow_animated_thumbnails

    if get_optimized_image(width, height, opts)
      save(validate: false)
    end
  end

  # this method attempts to correct old incorrect extensions
  def get_optimized_image(width, height, opts)
    if (!extension || extension.length == 0)
      fix_image_extension
    end

    opts = opts.merge(raise_on_error: true)
    begin
      OptimizedImage.create_for(self, width, height, opts)
    rescue => ex
      Rails.logger.info ex if Rails.env.development?
      opts = opts.merge(raise_on_error: false)
      if fix_image_extension
        OptimizedImage.create_for(self, width, height, opts)
      else
        nil
      end
    end
  end

  def fix_image_extension
    return false if extension == "unknown"

    begin
      # this is relatively cheap once cached
      original_path = Discourse.store.path_for(self)
      if original_path.blank?
        external_copy = Discourse.store.download(self) rescue nil
        original_path = external_copy.try(:path)
      end

      image_info = FastImage.new(original_path) rescue nil
      new_extension = image_info&.type&.to_s || "unknown"

      if new_extension != self.extension
        self.update_columns(extension: new_extension)
        true
      end
    rescue
      self.update_columns(extension: "unknown")
      true
    end
  end

  def destroy
    Upload.transaction do
      Discourse.store.remove_upload(self)
      super
    end
  end

  def short_url
    "upload://#{Base62.encode(sha1.hex)}.#{extension}"
  end

  def local?
    !(url =~ /^(https?:)?\/\//)
  end

  def fix_dimensions!
    return if !FileHelper.is_supported_image?("image.#{extension}")

    path =
      if local?
        Discourse.store.path_for(self)
      else
        Discourse.store.download(self).path
      end

    begin
      w, h = FastImage.new(path, raise_on_failure: true).size

      self.width = w || 0
      self.height = h || 0

      self.thumbnail_width, self.thumbnail_height = ImageSizer.resize(w, h)

      self.update_columns(
        width: width,
        height: height,
        thumbnail_width: thumbnail_width,
        thumbnail_height: thumbnail_height
      )
    rescue => e
      Discourse.warn_exception(e, message: "Error getting image dimensions")
    end
    nil
  end

  # on demand image size calculation, this allows us to null out image sizes
  # and still handle as needed
  def get_dimension(key)
    if v = read_attribute(key)
      return v
    end
    fix_dimensions!
    read_attribute(key)
  end

  def width
    get_dimension(:width)
  end

  def height
    get_dimension(:height)
  end

  def thumbnail_width
    get_dimension(:thumbnail_width)
  end

  def thumbnail_height
    get_dimension(:thumbnail_height)
  end

  def self.sha1_from_short_url(url)
    if url =~ /(upload:\/\/)?([a-zA-Z0-9]+)(\..*)?/
      sha1 = Base62.decode($2).to_s(16)

      if sha1.length > SHA1_LENGTH
        nil
      else
        sha1.rjust(SHA1_LENGTH, '0')
      end
    end
  end

  def self.generate_digest(path)
    Digest::SHA1.file(path).hexdigest
  end

  def human_filesize
    number_to_human_size(self.filesize)
  end

  def rebake_posts_on_old_scheme
    self.posts.where("cooked LIKE '%/_optimized/%'").find_each(&:rebake!)
  end

  def self.migrate_to_new_scheme(limit: nil)
    problems = []

    DistributedMutex.synchronize("migrate_upload_to_new_scheme") do
      if SiteSetting.migrate_to_new_scheme
        max_file_size_kb = [
          SiteSetting.max_image_size_kb,
          SiteSetting.max_attachment_size_kb
        ].max.kilobytes

        local_store = FileStore::LocalStore.new
        db = RailsMultisite::ConnectionManagement.current_db

        scope = Upload.by_users
          .where("url NOT LIKE '%/original/_X/%' AND url LIKE '%/uploads/#{db}%'")
          .order(id: :desc)

        scope = scope.limit(limit) if limit

        if scope.count == 0
          SiteSetting.migrate_to_new_scheme = false
          return problems
        end

        remap_scope = nil

        scope.each do |upload|
          begin
            # keep track of the url
            previous_url = upload.url.dup
            # where is the file currently stored?
            external = previous_url =~ /^\/\//
            # download if external
            if external
              url = SiteSetting.scheme + ":" + previous_url

              begin
                retries ||= 0

                file = FileHelper.download(
                  url,
                  max_file_size: max_file_size_kb,
                  tmp_file_name: "discourse",
                  follow_redirect: true
                )
              rescue OpenURI::HTTPError
                retry if (retires += 1) < 1
                next
              end

              path = file.path
            else
              path = local_store.path_for(upload)
            end
            # compute SHA if missing
            if upload.sha1.blank?
              upload.sha1 = Upload.generate_digest(path)
            end

            # store to new location & update the filesize
            File.open(path) do |f|
              upload.url = Discourse.store.store_upload(f, upload)
              upload.filesize = f.size
              upload.save!(validate: false)
            end
            # remap the URLs
            DbHelper.remap(UrlHelper.absolute(previous_url), upload.url) unless external

            DbHelper.remap(
              previous_url,
              upload.url,
              excluded_tables: %w{
                posts
                post_search_data
                incoming_emails
                notifications
                single_sign_on_records
                stylesheet_cache
                topic_search_data
                users
                user_emails
                draft_sequences
                optimized_images
              }
            )

            remap_scope ||= begin
              Post.with_deleted
                .where("raw ~ '/uploads/#{db}/\\d+/' OR raw ~ '/uploads/#{db}/original/(\\d|[a-z])/'")
                .select(:id, :raw, :cooked)
                .all
            end

            remap_scope.each do |post|
              post.raw.gsub!(previous_url, upload.url)
              post.cooked.gsub!(previous_url, upload.url)
              Post.with_deleted.where(id: post.id).update_all(raw: post.raw, cooked: post.cooked) if post.changed?
            end

            upload.optimized_images.find_each(&:destroy!)
            upload.rebake_posts_on_old_scheme
            # remove the old file (when local)
            unless external
              FileUtils.rm(path, force: true)
            end
          rescue => e
            problems << { upload: upload, ex: e }
          ensure
            file&.unlink
            file&.close
          end
        end
      end
    end

    problems
  end

end

# == Schema Information
#
# Table name: uploads
#
#  id                :integer          not null, primary key
#  user_id           :integer          not null
#  original_filename :string           not null
#  filesize          :integer          not null
#  width             :integer
#  height            :integer
#  url               :string           not null
#  created_at        :datetime         not null
#  updated_at        :datetime         not null
#  sha1              :string(40)
#  origin            :string(1000)
#  retain_hours      :integer
#  extension         :string(10)
#  thumbnail_width   :integer
#  thumbnail_height  :integer
#  etag              :string
#
# Indexes
#
#  index_uploads_on_etag        (etag)
#  index_uploads_on_extension   (lower((extension)::text))
#  index_uploads_on_id_and_url  (id,url)
#  index_uploads_on_sha1        (sha1) UNIQUE
#  index_uploads_on_url         (url)
#  index_uploads_on_user_id     (user_id)
#