class Hashr < Hash
  autoload :EnvDefaults, 'hashr/env_defaults'

  TEMPLATE = new

  class << self
    attr_accessor :raise_missing_keys

    def define(definition)
      @definition = definition
    end

    def definition
      @definition ||= {}
    end
  end

  def initialize(data = {})
    include_modules(data.delete(:_include)) if data
    replace(deep_hasherize(deep_merge(self.class.definition, data)))
  end

  def []=(key, value)
    super(key, value.is_a?(Hash) ? self.class.new(value) : value)
  end

  def respond_to?(name)
    true
  end

  def method_missing(name, *args, &block)
    case name.to_s[-1, 1]
    when '?'
      !!self[name.to_s[0..-2].to_sym]
    when '='
      self[name.to_s[0..-2].to_sym] = args.first
    else
      read(name)
    end
  end

  protected

    def read(key)
      raise(IndexError.new("Key #{key.inspect} is not defined.")) if !key?(key) && self.class.raise_missing_keys
      self[key]
    end

    def include_modules(modules)
      Array(modules).each { |mod| meta_class.send(:include, mod) } if modules
    end

    def meta_class
      class << self; self end
    end

    def deep_merge(left, right)
      merger = proc { |key, v1, v2| v1.is_a?(Hash) && v2.is_a?(Hash) ? self.class.new(v1.merge(v2, &merger)) : v2 }
      left.merge(right || {}, &merger)
    end

    def deep_hasherize(hash)
      hash.inject(TEMPLATE.dup) do |result, (key, value)|
        result[key.to_sym] = value.is_a?(Hash) ? deep_hasherize(value) : value
        result
      end
    end
end