repository.rb

module Packages
  # Holds packages, calculates and validates a package dependency graph
  # Only one instance of each package may be present
  class Repository
    include Enumerable

    def initialize(*packages)
      @packages = packages
    end

    def query(name)
      package = find(name)
      raise OperationError, "Package does not exist in repository" if package.nil?
      package
    end

    def index(name, dependencies: [])
      return find(name) if find(name)

      dependencies.flatten! if dependencies.is_a? Array
      dependencies = [dependencies] if dependencies.is_a? String

      raise OperationError, "Package can't depend on itself" if dependencies.include?(name)
      raise OperationError, "Package depdency not yet indexed" unless dependencies_available? dependencies

      pkg = Package.new(name, dependencies)
      @packages << pkg
      pkg
    end

    def remove(name)
      pkg = find(name)
      raise OperationError, "remove failed, package depended on" if package_dependents(name).count > 0

      @packages.delete_if { |p| p == pkg }
      pkg
    end

    def each(&block)
      @packages.each(&block)
    end

    def list
      each.map(&:name)
    end

    private

    def find(name)
      find { |pkg| pkg.name == name }
    end

    # Find packages that depend
    def package_dependents(name)
      @packages.select { |p| p.dependencies.include?(name) }
    end

    def dependencies_available?(deps)
      (deps - list).empty?
    end
  end
end