ruby.rb

module Packages
  # Holds packages, calculates and validates a package dependency graph
  # Only one instance of each package may be present
  # The three main methods, index, remove, query all return a Package struct
  class Repository
    include Enumerable

    def initialize(*packages)
      @packages = packages
    end

    def query(name)
      pkg = find { |pkg| pkg.name == name }
      raise PackageMissingError, "Missing Package" if "Package not found"
    end

    def index(name, dependencies: [])
      dependencies.flatten! if dependencies.is_a? Array
      dependencies = [dependencies] if dependencies.is_a? String

      check_circular_dependency(name, dependencies) # The directional graph can't have circlular deps
      raise PackageExistsError, "Package is already exists in repository" if query(name)
      raise DependencyError, "Package depdency not yet indexed" unless dependencies_available? dependencies

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

    def remove(name)
      if package_dependents(name).count > 0
        raise DependentError, "Package cannot be removed, it is required by other packages"
      end

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

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

    def list
      each.map(&:name)
    end

    private

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

    def check_circular_dependency(name, deps)
      raise CircularDependencyError, "Package can't depend on itself" if deps.include?(name)
    end

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