def rig_participant(event):
"""
Rig the specified wheel for the specified participant. Default behavior is comical rigging (hidden == False)
but hidden can be specified to indicate deceptive rigging (hidden == True)
:param event: Lambda event containing the API Gateway request path parameters wheel_id and participant_id
{
"pathParameters":
{
"wheel_id": string ID of the wheel to rig (DDB Hash Key)
"participant_id": string ID of the participant to rig (DDB Hash Key)
},
"body":
{
"hidden": boolean indicates deceptive rigging if True, comical if False
}
}
:return: response dictionary
"""
# By default, rigging the wheel isn't hidden but they can be
wheel_id = event['pathParameters']['wheel_id']
participant_id = event['pathParameters']['participant_id']
hidden = bool(event['body'].get('hidden', False))
update = {'rigging': {'participant_id': participant_id, 'hidden': hidden}}
Wheel.update_item(Key={'id': wheel_id}, **to_update_kwargs(update))
def select_participant(event):
"""
Indicates selection of a participant by the wheel. This will cause updates to the weights for all participants
or removal of rigging if the wheel is rigged.
:param event: Lambda event containing the API Gateway request path parameters wheel_id and participant_id
{
"pathParameters":
{
"wheel_id": string ID of the wheel to rig (DDB Hash Key)
"participant_id": string ID of the participant to rig (DDB Hash Key)
},
}
:return: response dictionary
"""
wheel_id = event['pathParameters']['wheel_id']
participant_id = event['pathParameters']['participant_id']
wheel = Wheel.get_existing_item(Key={'id': wheel_id})
participant = WheelParticipant.get_existing_item(Key={
'id': participant_id,
'wheel_id': wheel_id
})
choice_algorithm.select_participant(wheel, participant)
# Undo any rigging that has been set up
Wheel.update_item(Key={'id': wheel['id']},
UpdateExpression='remove rigging')
def wrap_participant_creation(wheel, participant):
participant['weight'] = 1
yield
Wheel.update_item(Key={'id': wheel['id']},
**to_update_kwargs({
'participant_count':
wheel['participant_count'] + 1
}))
def wrap_participant_creation(wheel, participant):
participant['weight'] = 1
yield
count = 0
with WheelParticipant.batch_writer() as batch:
for p in WheelParticipant.iter_query(
KeyConditionExpression=Key('wheel_id').eq(wheel['id'])):
count += 1
Wheel.update_item(Key={'id': wheel['id']},
**to_update_kwargs({'participant_count': count}))
def on_participant_deletion(wheel, participant):
"""
Normalize the remaining participant weights to account for participant removal.
The ratio is based on the following:
1) The participant should be at weight=1 when it leaves the system (which is the same as it arrived)
2) That difference should be split by the remaining participants proportional by weight
This ensures that 'weight=0' participants are still at weight=0 and that the sum of all
weights is equal to the number of participants, so new additions are treated fairly
:param wheel: Wheel dictionary:
{
"id": string ID of the wheel (DDB Hash Key),
"name": string name of the wheel,
"participant_count": number of participants in the wheel,
}
:param participant: Participant dictionary:
{
"id": string ID of the wheel (DDB Hash Key),
"name": string name of the wheel,
"url": Participant's URL,
"wheel_id": string ID of the wheel the participant belongs to,
}
:return: None
"""
total_weight = participant['weight']
for p in WheelParticipant.iter_query(
KeyConditionExpression=Key('wheel_id').eq(wheel['id'])):
total_weight += p['weight']
weight = participant['weight']
remaining_weight = total_weight - weight # <-- no longer presumes existing weight balance via 'int(participant_count)'
ratio = (1 + ((weight - 1) / remaining_weight)) if (
remaining_weight != 0) else 1
num_participants = Decimal(0)
with WheelParticipant.batch_writer() as batch:
for p in WheelParticipant.iter_query(
KeyConditionExpression=Key('wheel_id').eq(wheel['id'])):
if p['id'] != participant['id']:
# This is cast to a string before turning into a decimal because of rounding/inexact guards in boto3
p['weight'] = Decimal(
str(float(p['weight']) *
float(ratio))) if (remaining_weight != 0) else 1
batch.put_item(Item=p)
num_participants = num_participants + 1
Wheel.update_item(Key={'id': wheel['id']},
**to_update_kwargs(
{'participant_count': num_participants}))
def unrig_participant(event):
"""
Remove rigging for the specified wheel
:param event: Lambda event containing the API Gateway request path parameter wheel_id
{
"pathParameters":
{
"wheel_id": string ID of the wheel (DDB Hash Key)
}
}
:return: response dictionary
"""
# By default, rigging the wheel isn't hidden but they can be
wheel_id = event['pathParameters']['wheel_id']
Wheel.update_item(Key={'id': wheel_id}, UpdateExpression='remove rigging')
def select_participant(wheel, participant):
"""
Register the selection of a participant by updating the weights of all participants for a given wheel
:param wheel: Wheel dictionary:
{
"id": string ID of the wheel (DDB Hash Key),
"name": string name of the wheel,
"participant_count": number of participants in the wheel,
}
:param participant: Participant dictionary:
{
"id": string ID of the participant (DDB Hash Key),
"name": string name of the participant,
"url": Participant's URL,
"wheel_id": string ID of the wheel the participant belongs to,
"weight": participant's weight in the selection algorithm
}
:return: None
"""
num_participants = 0
total_weight = Decimal(0)
for p in WheelParticipant.iter_query(
KeyConditionExpression=Key('wheel_id').eq(wheel['id'])):
num_participants = num_participants + 1
total_weight += p['weight']
# Factor is the number by which all weights must be multiplied
# so total weight will be equal to the number of participants.
factor = Decimal(num_participants) / total_weight
if num_participants > 1:
weight_share = participant['weight'] / Decimal(num_participants - 1)
with WheelParticipant.batch_writer() as batch:
# Redistribute and normalize the weights.
for p in WheelParticipant.iter_query(
KeyConditionExpression=Key('wheel_id').eq(wheel['id'])):
if p['id'] == participant['id']:
p['weight'] = 0
else:
p['weight'] += Decimal(weight_share)
p['weight'] *= factor
batch.put_item(Item=p)
Wheel.update_item(Key={'id': wheel['id']},
**to_update_kwargs(
{'participant_count': num_participants}))
def reset_wheel(wheel):
"""
Resets the weights of all participants in the wheel and updates the wheel's participant count
:param wheel: Wheel dictionary:
{
"id": string ID of the wheel (DDB Hash Key),
"name": string name of the wheel,
"participant_count": number of participants in the wheel,
}
:return: None
"""
count = 0
with WheelParticipant.batch_writer() as batch:
for p in WheelParticipant.iter_query(KeyConditionExpression=Key('wheel_id').eq(wheel['id'])):
p['weight'] = get_sub_wheel_size(p['name'])
batch.put_item(Item=p)
count += 1
Wheel.update_item(Key={'id': wheel['id']}, **to_update_kwargs({'participant_count': count}))
def update_wheel(event):
"""
Update the name of the wheel and/or refresh its participant count
:param event: Lambda event containing the API Gateway request path parameter wheel_id
{
"pathParameters":
{
"wheel_id": string ID of the wheel (DDB Hash Key)
},
"body":
{
"id": string ID of the wheel (DDB Hash Key),
"name": string name of the wheel,
}
}
:return: response dictionary containing the updated wheel object if successful
{
"body":
{
"id": string ID of the wheel (DDB Hash Key),
"name": string name of the wheel,
"participant_count": number of participants in the wheel,
"created_at": creation timestamp,
"updated_at": updated timestamp,
}
}
"""
wheel_id = event['pathParameters']['wheel_id']
key = {'id': wheel_id}
# Make sure wheel exists
wheel = Wheel.get_existing_item(Key=key)
name = event['body'].get('name', None)
if not check_string(name):
raise base.BadRequestError(
"Updating a wheel requires a new name of at least 1 character in length"
)
update = {'name': name, 'updated_at': get_utc_timestamp()}
Wheel.update_item(Key=key, **to_update_kwargs(update))
# Represent the change locally for successful responses
wheel.update(update)
return wheel