require 'ezid-client'

module Ddr::Models
  class PermanentId

    class Error < Ddr::Models::Error; end
    class AssignmentFailed < Error; end
    class RepoObjectNotPersisted < Error; end
    class AlreadyAssigned < AssignmentFailed; end
    class IdentifierNotAssigned < Error; end
    class IdentifierNotFound < Error; end

    PERMANENT_URL_BASE = "https://idn.duke.edu/".freeze
    DEFAULT_STATUS     = Ezid::Status::RESERVED
    DEFAULT_EXPORT     = "no".freeze
    DEFAULT_PROFILE    = "dc".freeze
    DEFAULT_TARGET     = "https://repository.duke.edu/id/%s"
    FCREPO3_PID        = "fcrepo3.pid".freeze
    DELETED            = "deleted".freeze
    DEACCESSIONED      = "deaccessioned".freeze

    class_attribute :identifier_class, :identifier_repo_id_field

    self.identifier_class = Ezid::Identifier
    self.identifier_class.defaults = {
      profile: DEFAULT_PROFILE,
      export:  DEFAULT_EXPORT,
      status:  DEFAULT_STATUS,
    }

    self.identifier_repo_id_field = FCREPO3_PID

    # ActiveSupport::Notifications event handler
    def self.call(*args)
      event = ActiveSupport::Notifications::Event.new(*args)
      repo_id, identifier_id, reason = event.payload.values_at(:pid, :permanent_id, :reason)
      case event.name
      when /workflow/
        update!(repo_id) if auto_update?
      when /^deaccession/
        if auto_update? && identifier_id
          deaccession!(repo_id, identifier_id, reason)
        end
      when /^destroy/
        if auto_update? && identifier_id
          delete!(repo_id, identifier_id, reason)
        end
      end
    end

    def self.auto_update?
      Ddr::Models.auto_update_permanent_id
    end

    def self.deaccession!(repo_object_or_id, identifier_or_id, reason = nil)
      new(repo_object_or_id, identifier_or_id).deaccession!(reason)
    end

    def self.delete!(repo_object_or_id, identifier_or_id, reason = nil)
      new(repo_object_or_id, identifier_or_id).delete!(reason)
    end

    def self.update!(repo_object_or_id)
      perm_id = new(repo_object_or_id)
      perm_id.update! if perm_id.assigned?
    end

    def self.assign!(repo_object_or_id, identifier_or_id = nil)
      new(repo_object_or_id, identifier_or_id).assign!
    end

    def self.assigned(repo_object_or_id)
      perm_id = new(repo_object_or_id)
      perm_id.assigned? ? perm_id : nil
    end

    def initialize(repo_object_or_id, identifier_or_id = nil)
      case repo_object_or_id
      when ActiveFedora::Base
        raise RepoObjectNotPersisted, "Repository object must be persisted." if repo_object_or_id.new_record?
        @repo_object = repo_object_or_id
      when String, nil
        @repo_id = repo_object_or_id
      else
        raise TypeError, "#{repo_object_or_id.class} is not expected as the first argument."
      end

      case identifier_or_id
      when identifier_class
        @identifier = identifier_or_id
      when String, nil
        @identifier_id = identifier_or_id
      else
        raise TypeError, "#{identifier_or_id.class} is not expected as the second argument."
      end
    end

    def repo_object
      @repo_object ||= ActiveFedora::Base.find(repo_id)
    end

    def repo_id
      @repo_id ||= @repo_object && @repo_object.id
    end

    def assign!(id = nil)
      ActiveSupport::Notifications.instrument("assign.permanent_id", pid: repo_object.id) do |payload|
        assign(id)
        software = [ "ddr-models #{Ddr::Models::VERSION}", Ezid::Client.version ].join("; ")
        detail = <<-EOS
Permanent ID:  #{repo_object.permanent_id}
Permanent URL: #{repo_object.permanent_url}

EZID Metadata:
#{identifier.metadata}
      EOS
        payload.merge!(summary: "Permanent ID assignment",
                       detail: detail,
                       software: software,
                       permanent_id: identifier.id)
      end
    end

    def assigned?
      repo_object.permanent_id
    end

    def update!
      ActiveSupport::Notifications.instrument("update.permanent_id", pid: repo_object.id) do |payload|
        update
        payload.merge!(permanent_id: identifier.id)
      end
    end

    def deaccession!(reason = nil)
      delete_or_make_unavailable(reason || DEACCESSIONED)
    end

    def delete!(reason = nil)
      delete_or_make_unavailable(reason || DELETED)
    end

    def identifier
      if @identifier.nil?
        if identifier_id
          @identifier = find_identifier(identifier_id)
        elsif assigned?
          @identifier = find_identifier(repo_object.permanent_id)
        end
      end
      @identifier
    end

    def identifier_id
      @identifier_id ||= @identifier && @identifier.id
    end

    def set_permanent_url
      repo_object.permanent_url = PERMANENT_URL_BASE + identifier.id
    end

    def set_metadata!
      set_metadata
      save
      self
    end

    def set_metadata
      set_target
      set_status
      set_identifier_repo_id
    end

    def set_target
      self.target = DEFAULT_TARGET % id
    end

    def set_identifier_repo_id
      self.identifier_repo_id = repo_object.id
    end

    def identifier_repo_id=(val)
      if identifier_repo_id
        raise Error, "Identifier repository id already set to \"#{identifier_repo_id}\"; cannot change."
      end
      self[identifier_repo_id_field] = val
    end

    def identifier_repo_id
      self[identifier_repo_id_field]
    end

    def set_status!
      save if set_status
    end

    def set_status
      if repo_object.published? && !public?
        public!
      elsif repo_object.unpublished? && public?
        unavailable!("not published")
      end
    end

    protected

    def method_missing(name, *args, &block)
      identifier.send(name, *args, &block)
    end

    private

    def find_identifier(ark)
      identifier_class.find(ark)
    rescue Ezid::IdentifierNotFoundError => e
      raise IdentifierNotFound, e.message
    end

    def mint_identifier(*args)
      identifier_class.mint(*args)
    end

    def update
      if !assigned?
        raise IdentifierNotAssigned,
              "Cannot update identifier for repository object \"#{repo_object.id}\"; not assigned."
      end
      set_status!
    end

    def assign(id = nil)
      if assigned?
        raise AlreadyAssigned,
              "Repository object \"#{repo_object.id}\" has already been assigned permanent id \"#{repo_object.permanent_id}\"."
      end
      @identifier = case id
                    when identifier_class
                      id
                    when String
                      find_identifier(id)
                    when nil
                      mint_identifier
                    end
      repo_object.reload
      repo_object.permanent_id = identifier.id
      repo_object.permanent_url = PERMANENT_URL_BASE + identifier.id
      repo_object.save(validate: false)
      set_metadata!
    end

    def delete_or_make_unavailable(reason)
      if repo_id && identifier_repo_id && ( identifier_repo_id != repo_id )
        raise Error, "Identifier \"#{identifier_id}\" is assigned to a different repository object \"#{repo_id}\"."
      end
      if reserved?
        delete
      else
        unavailable!(reason) && save
      end
    end

  end
end