Init

.editorconfig

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+root = true
+
+[*.cr]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+indent_style = space
+indent_size = 2
+trim_trailing_whitespace = true

.gitignore

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+/docs/
+/lib/
+/bin/
+/.shards/
+*.dwarf
+
+# Libraries don't need dependency lock
+# Dependencies will be locked in applications that use them
+/shard.lock

LICENSE

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+MIT License
+
+Copyright (c) 2022 Dominic Grimm <dominic.grimm@gmail.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# service
+
+TODO: Write a description here
+
+## Installation
+
+1. Add the dependency to your `shard.yml`:
+
+   ```yaml
+   dependencies:
+     service:
+       git: https://git.dergrimm.net/dergrimm/service.git
+   ```
+
+2. Run `shards install`
+
+## Usage
+
+```crystal
+require "service"
+```
+
+TODO: Write usage instructions here
+
+## Development
+
+TODO: Write development instructions here
+
+## Contributing
+
+1. Fork it
+2. Create your feature branch (`git checkout -b my-new-feature`)
+3. Commit your changes (`git commit -am 'Add some feature'`)
+4. Push to the branch (`git push origin my-new-feature`)
+5. Create a new Pull Request
+
+## Contributors
+
+- [Dominic Grimm](https://git.dergrimm.net/dergrimm) - creator and maintainer

examples/example.cr

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+require "../src/service"
+require "log"
+
+class MessageService < Service
+  Log = ::Log.for(self)
+
+  @@i = 0
+
+  getter message
+  getter delay
+  getter times
+
+  def initialize(@message : String, @delay : Int32, @times : Int32)
+  end
+
+  def run(_unit : Unit) : Service::Unit?
+    puts @message
+    @@i += 1
+    Log.info { @@i }
+    sleep @delay
+
+    if @@i < @times
+      Service::Unit.new(self)
+    else
+      Log.info { "Done." }
+
+      nil
+    end
+  end
+end
+
+class Runner < Service::Runner
+  def starters : Array(Service::Starter)
+    [
+      Service::AsynchronousStarter.new([
+        MessageService.new("Hello world from AsynchronousStarter!", delay: 1, times: 5).as(Service),
+      ]).as(Service::Starter),
+    ]
+  end
+end
+
+Runner.new.run

shard.yml

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+name: service
+version: 0.1.0
+
+authors:
+  - Dominic Grimm <dominic.grimm@gmail.com>
+
+crystal: 1.3.2
+
+license: MIT
+
+dependencies:
+  version_from_shard:
+    github: hugopl/version_from_shard

src/service.cr

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+require "version_from_shard"
+
+abstract class Service
+  VersionFromShard.declare
+
+  abstract def run(unit : Unit) : Unit?
+
+  def handle(unit : Unit?) : Unit?
+    if unit
+      unit.handle(self)
+    end
+  end
+
+  class Unit
+    property service
+    property handler_proc
+
+    alias Handler = (self, Service) -> Unit?
+
+    DEFAULT_HANLDER    = ->(unit : self, service : Service) { service.run(unit).as(Unit?) }
+    NO_RESTART_HANDLER = ->(_unit : self, _service : Service) { nil }
+
+    def initialize(@service : Service, @handler_proc : Handler = DEFAULT_HANLDER)
+    end
+
+    def initialize(service : Service, &handler_proc : Handler)
+      initialize(service, handler_proc)
+    end
+
+    def handle(service : Service) : Unit?
+      handler_proc.call(self, service)
+    end
+  end
+
+  abstract class Starter
+    abstract def logic : Array(Service)
+
+    abstract def start : self
+
+    def self.handle(service : Service) : Nil
+      unit = service.run(Unit.new(service))
+
+      if unit
+        while unit = service.handle(unit.not_nil!)
+        end
+      end
+    end
+  end
+
+  abstract class ArrayStarter < Starter
+    getter services
+
+    def initialize(@services : Array(Service))
+    end
+
+    def logic : Array(Service)
+      @services
+    end
+  end
+
+  class SynchronousStarter < ArrayStarter
+    def start : self
+      l = logic
+
+      channel = Channel(Nil).new(l.size)
+      logic.each do |service|
+        spawn do
+          Starter.handle(service)
+          channel.send(nil)
+        end
+      end
+      l.size.times do
+        channel.receive
+      end
+      Fiber.yield
+
+      self
+    end
+  end
+
+  class AsynchronousStarter < ArrayStarter
+    def start : self
+      logic.each do |service|
+        Starter.handle(service)
+      end
+
+      self
+    end
+  end
+
+  abstract class Runner
+    Log = Log.for(self)
+
+    abstract def starters : Array(Starter)
+
+    def run : self
+      s = starters
+
+      channel = Channel(Nil).new(s.size)
+      s.each do |starter|
+        spawn do
+          starter.start
+          channel.send(nil)
+        end
+      end
+      s.size.times do
+        channel.receive
+      end
+      Fiber.yield
+
+      self
+    end
+  end
+end