require 'multi_json'

module Slackify
  class Payload

    def initialize(context, status)
      @context = context
      @status = status
    end

    def self.build(context, status)
      new(context, status).build
    end

    def build
      "'payload=#{payload}'"
    end

    def payload
      fields_map = {
        'status' => {
          title: 'Status',
          value: @status,
          short: true
        },
        'stage' => {
          title: 'Stage',
          value: fetch(:stage),
          short: true
        },
        'branch' => {
          title: 'Branch',
          value: fetch(:branch),
          short: true
        },
        'revision' => {
          title: 'Revision',
          value: fetch(:current_revision),
          short: true
        },
        'hosts' => {
          title: 'Hosts',
          value: fetch(:slack_hosts),
          short: true
        }
      }

      fields = []

      fetch(:slack_fields).each { |field|
        fields.push(fields_map[field])
      }

      MultiJson.dump(
        {
          channel: fetch(:slack_channel),
          username: fetch(:slack_username),
          icon_emoji: fetch(:slack_emoji),
          parse: fetch(:slack_parse),
          attachments: [
            {
              fallback: text,
              color: color,
              text: text,
              fields: fields,
              mrkdwn_in: fetch(:slack_mrkdwn_in),
            }
          ]
        }
      )
    end

    def fetch(*args, &block)
      @context.fetch(*args, &block)
    end

    def text
      @text ||= case @status
      when :starting
        fetch(:slack_deploy_starting_text)
      when :success
        fetch(:slack_text)
      when :failed
        fetch(:slack_deploy_failed_text)
      end
    end

    def color
      case @status
      when :starting
        fetch(:slack_deploy_starting_color)
      when :success
        fetch(:slack_deploy_finished_color)
      when :failed
        fetch(:slack_deploy_failed_color)
      end
    end
  end
end