require 'yaml'

module Dbcp
  class DatabaseYamlEnvironmentProvider
    def initialize(database_yaml_path)
      @database_yaml_path = database_yaml_path
    end

    # @return [Environment, nil]
    def find(environment_name)
      begin
        environment_hash = read_file[environment_name]
        if environment_hash
          build_environment environment_name, environment_hash
        else
          nil
        end
      rescue Errno::ENOENT
        return nil
      end
    end

   private

    def read_file
      YAML.load_file @database_yaml_path
    end

    def build_environment(environment_name, environment_hash)
      execution_host = ExecutionHost.build(environment_hash)

      begin
        database = Database.build(environment_hash)
      rescue Database::BlankDatabaseDefinition => e
        if execution_host.remote?
          database = Database.build fetch_remote_environment_hash(execution_host)[environment_name]
        else
          raise e
        end
      end

      Environment.new({
        environment_name: environment_name,
        database:         database,
        execution_host:   execution_host
      })
    end

    def fetch_remote_environment_hash(execution_host)
      YAML.load execution_host.download "#{execution_host.path}/#{@database_yaml_path}"
    end

  end
end