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97 lines
3.6 KiB
Ruby
97 lines
3.6 KiB
Ruby
# frozen_string_literal: true
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module Service
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# Module to be included to provide steps DSL to any class. This allows to
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# create easy to understand services as the whole service cycle is visible
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# simply by reading the beginning of its class.
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#
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# Steps are executed in the order they’re defined. They will use their name
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# to execute the corresponding method defined in the service class.
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#
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# Currently, there are 5 types of steps:
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#
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# * +contract(name = :default)+: used to validate the input parameters,
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# typically provided by a user calling an endpoint. A special embedded
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# +Contract+ class has to be defined to holds the validations. If the
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# validations fail, the step will fail. Otherwise, the resulting contract
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# will be available in +context[:contract]+. When calling +step(name)+ or
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# +model(name = :model)+ methods after validating a contract, the contract
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# should be used as an argument instead of context attributes.
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# * +model(name = :model)+: used to instantiate a model (either by building
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# it or fetching it from the DB). If a falsy value is returned, then the
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# step will fail. Otherwise the resulting object will be assigned in
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# +context[name]+ (+context[:model]+ by default).
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# * +policy(name = :default)+: used to perform a check on the state of the
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# system. Typically used to run guardians. If a falsy value is returned,
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# the step will fail.
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# * +step(name)+: used to run small snippets of arbitrary code. The step
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# doesn’t care about its return value, so to mark the service as failed,
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# {#fail!} has to be called explicitly.
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# * +transaction+: used to wrap other steps inside a DB transaction.
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#
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# The methods defined on the service are automatically provided with
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# the whole context passed as keyword arguments. This allows to define in a
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# very explicit way what dependencies are used by the method. If for
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# whatever reason a key isn’t found in the current context, then Ruby will
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# raise an exception when the method is called.
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#
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# Regarding contract classes, they automatically have {ActiveModel} modules
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# included so all the {ActiveModel} API is available.
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#
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# @example An example from the {TrashChannel} service
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# class TrashChannel
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# include Base
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#
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# model :channel, :fetch_channel
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# policy :invalid_access
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# transaction do
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# step :prevents_slug_collision
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# step :soft_delete_channel
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# step :log_channel_deletion
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# end
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# step :enqueue_delete_channel_relations_job
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#
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# private
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#
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# def fetch_channel(channel_id:)
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# Chat::Channel.find_by(id: channel_id)
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# end
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#
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# def invalid_access(guardian:, channel:)
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# guardian.can_preview_chat_channel?(channel) && guardian.can_delete_chat_channel?
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# end
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#
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# def prevents_slug_collision(channel:)
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# …
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# end
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#
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# def soft_delete_channel(guardian:, channel:)
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# …
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# end
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#
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# def log_channel_deletion(guardian:, channel:)
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# …
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# end
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#
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# def enqueue_delete_channel_relations_job(channel:)
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# …
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# end
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# end
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# @example An example from the {UpdateChannelStatus} service which uses a contract
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# class UpdateChannelStatus
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# include Base
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#
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# model :channel, :fetch_channel
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# contract
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# policy :check_channel_permission
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# step :change_status
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#
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# class Contract
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# attribute :status
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# validates :status, inclusion: { in: Chat::Channel.editable_statuses.keys }
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# end
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#
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# …
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# end
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end
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