Source code for server_side.controls.serializers

""" JSON serializers for database models.
Classes here parses python objects into JSON formats to be transmitted with HTTP requests to the Pi
or to client Javascript code.

Jin Cheng, 02/12/16
"""

from django.utils import timezone
from rest_framework import serializers

from server_side.controls.models import Calorimeter, Run, DataPoint


class CalorimeterSerializer(serializers.ModelSerializer):
    """JSON representation of calorimetry settings."""
    is_active = serializers.SerializerMethodField('is_calorimeter_active')
    has_active_runs = serializers.SerializerMethodField('check_active_runs')

    class Meta:
        model = Calorimeter
        fields = ('id', 'serial', 'access_code', 'name', 'creation_time',
                  'current_sample_temp', 'current_ref_temp',
                  'K_p', 'K_i', 'K_d', 'idle_loop_interval',
                  'max_ramp_rate', 'temp_tolerance_range', 'temp_tolerance_duration',
                  'active_loop_interval', 'web_api_min_upload_length',
                  'last_changed_time', 'last_comm_time',
                  'is_active', 'has_active_runs',
                  )
        read_only_fields = ('access_code', )

    def __init__(self, *args, **kwargs):
        super(CalorimeterSerializer, self).__init__(*args, **kwargs)
        self.from_device = False
        if 'from_device' in kwargs:
            if kwargs['from_device']:
                self.from_device = True

    def is_calorimeter_active(self, instance):
        time_delta = instance.last_comm_time - timezone.now()
        return abs(time_delta.total_seconds()) < 60

    def check_active_runs(self, instance):
        kwargs = {'calorimeter': instance, 'is_finished': False}
        if Run.objects.filter(**kwargs).exists():
            active_run = Run.objects.filter(**kwargs).order_by('-start_time')[0]
            return RunSerializer(active_run).data
        return False

    def update(self, instance, validated_data):
        instance.last_comm_time = timezone.now()
        super(CalorimeterSerializer, self).update(instance, validated_data)
        return instance


class DataPointSerializer(serializers.ModelSerializer):
    """JSON representation of measurements made at a certain point in time."""
    measured_at = serializers.DateTimeField(input_formats=['iso-8601'])
    run = serializers.PrimaryKeyRelatedField(queryset=Run.objects.all(), validators=[])

    class Meta:
        model = DataPoint
        fields = ('measured_at', 'received_at',
                  'temp_ref', 'temp_sample',
                  'heat_ref', 'heat_sample',
                  'run',
                  )


class RunSerializer(serializers.ModelSerializer):
    """JSON representation of a calorimetry job."""
    calorimeter = serializers.PrimaryKeyRelatedField(queryset=Calorimeter.objects.all(), validators=[])
    data_point_count = serializers.SerializerMethodField('count_data_points')

    class Meta:
        model = Run
        fields = ('id', 'name', 'creation_time', 'start_time', 'finish_time',
                  'stabilized_at_start', 'is_ready', 'is_running', 'is_finished', 'email',
                  'start_temp', 'target_temp', 'ramp_rate',
                  'calorimeter', 'data_point_count',
                  )

    def count_data_points(self, instance):
        return instance.datapoint_set.count()