houdini/lib/json_resp.rb

# Provide a declarative json validation and error responses for the rails 'render' method in controllers
#
# The return value of the block you pass into #when_valid should look like {status: code, json: data}
#
# Concerns of this lib are:
# * Validate the params, only running a block when valid
# * Provide a declarative system for request parameter requirements
# * Respond with proper codes and error messages for everything

class JsonResp

  attr_accessor :errors

  def initialize(params, &block)
    @params = params
    validation = JsonResp::Validation.new(params)
    validation.instance_exec(params, &block)
    @errors = validation.errors
    return self
  end

  def when_valid(&block)
    return {status: 422, json: {errors: @errors}} if @errors.any?
    begin
      @response = block.call(@params)
    rescue Exception => e
      @response = {status: 500, json: {error: "We're sorry, but something went wrong. We've been notified about this issue."}}
      puts e
      puts e.backtrace.first(10)
    end
    return @response
  end


  # Validation of a set of request parameters
  class Validation

    attr_accessor :errors, :params

    def initialize(params)
      @params = params
      @errors = []
      return self
    end

    def requires(*keys)
      @errors.concat keys.select{|k| @params[k].blank? }.map{|k| "#{k} required"}
      return Param.new(keys, @errors, @params)
    end

    def requires_either(key1, key2)
      error_message = "#{key1} or #{key2} is required"
      if @params[key1].blank? && @params[key2].blank?
        @errors << error_message
      else
        @errors.concat [key1, key2].select{|k| @params[k].blank? }.map{|k| "#{k} required"}
      end
      return Param.new([key1, key2], @errors, @params)
    end

    def optional(*keys)
      keys_to_check = keys.select{|k| @params[k].present?}
      return Param.new(keys_to_check, @errors, @params)
    end

  end

  class Param
    # param validation methods
    # To make more validators, you can extend this class
    # All methods here are no-ops if the key was optional and is not present

    attr_accessor :keys, :errors, :params

    def initialize(keys, errors, params)
      @keys = keys.reject{|k| params[k].nil? }
      @errors = errors
      @params = params
    end

    def as_string
      @errors.concat @keys.reject{|k| @params[k].is_a?(String)}.map{|k| "#{k} must be a string"}
      return self
    end

    def as_int
      @errors.concat @keys
        .reject{|k| @params[k].is_a?(Integer) || @params[k].to_i.to_s == @params[k]}
        .map{|k| "#{k} must be an integer"}
      return self
    end

    def with_format(regex)
      @errors.concat @keys.reject{|k| @params[k] =~ regex}.map{|k| "#{k} must match: #{regex}"}
      return self
    end

    def one_of(*vals)
      @errors.concat @keys.reject{|k| vals.include?(@params[k])}.map{|k| "#{k} must be one of: #{vals.join(", ")}"}
      return self
    end

    def nested(&block)
      @errors.concat @keys.map{|k| Validation.new(@params[k]).instance_exec(@params, &block).errors}.flatten
      return self
    end

    def as_array
      @errors.concat @keys.reject{|k| @params[k].is_a?(Array)}.map{|k| "#{k} must be an array"}
    end

    def array_of(&block)
      @errors.concat @keys.reject{|k| @params[k].is_a?(Array)}.map{|k| "#{k} must be an array"}
      @errors.concat @keys.map{|k| @params[k].map{|h| Validation.new(h).instance_exec(@params, &block).errors}}.flatten
      return self
    end

    def as_date
      with_format /\d\d\d\d-\d\d-\d\d/
      @errors.concat @keys.map{|k| [k].concat @params[k].split('-').map(&:to_i)}
        .reject{|key, year, month, day| year.present? && year > 1000 && year < 3000 && month.present? && month > 0 && month < 13 && day.present? && day > 0 && day < 32}
        .map{|k, _,_,_| "#{k} must be a valid date"}
    end

    def min(n)
      @errors.concat @keys.reject{|k| @params[k] >= n}.map{|k| "#{k} must be at least #{n}"}
      return self
    end

    def max(n)
      @errors.concat @keys.reject{|k| @params[k] <= n}.map{|k| "#{k} must be less than #{n + 1}"}
      return self
    end

    # TODO min_len, max_len, as_float, as_currency, as_time, as_datetime
    # TODO return err resp on unrecognized params

  end
end