#!/usr/bin/python

DOCUMENTATION = """
---
module:ec2_scaling_policy
short_description: Create or delete AWS scaling policies for Autoscaling groups
description:
  - Can create or delete scaling policies for autoscaling groups
  - Referenced autoscaling groups must already exist
version_added: "1.6"
requirements: [ "boto" ]
author: Zacharie Eakin
options:
  state:
    description:
      - register or deregister the policy
    required: true
    choices: ['present', 'absent']
  name:
    description:
      - Unique name for the scaling policy
    required: true
  asg_name:
    description:
      - Name of the associated autoscaling group
    required: true
  adjustment_type:
    desciption: 
      - The type of change in capacity of the autoscaling group
    required: false
    choices: ['ChangeInCapacity','ExactCapacity','PercentChangeInCapacity']
  scaling_adjustment:
    description:
      - The amount by which the autoscaling group is adjusted by the policy
    required: false
  min_adjustment_step:
    description:
      - Minimum amount of adjustment when policy is triggered
    required: false
  cooldown:
    description:
      - The minimum period of time between which autoscaling actions can take place
    required: false
"""

EXAMPLES = '''
- ec2_scaling_policy:
    state: present
    region: US-XXX
    name: "scaledown-policy"
    adjustment_type: "ChangeInCapacity"
    asg_name: "slave-pool"
    scaling_adjustment: -1
    min_adjustment_step: 1
    cooldown: 300
'''


import sys

from ansible.module_utils.basic import *
from ansible.module_utils.ec2 import *

try: 
    import boto.ec2.autoscale
    from boto.ec2.autoscale import ScalingPolicy
    from boto.exception import BotoServerError

except ImportError:
    print "failed=True msg='boto required for this module'"
    sys.exit(1)


def create_scaling_policy(connection, module):
    sp_name = module.params.get('name')
    adjustment_type = module.params.get('adjustment_type')
    asg_name = module.params.get('asg_name')
    scaling_adjustment = module.params.get('scaling_adjustment')
    min_adjustment_step = module.params.get('min_adjustment_step')
    cooldown = module.params.get('cooldown')
 
    scalingPolicies = connection.get_all_policies(as_group=asg_name,policy_names=[sp_name])
    
    if not scalingPolicies:
        sp = ScalingPolicy(
            name=sp_name,
            adjustment_type=adjustment_type,
            as_name=asg_name,
            scaling_adjustment=scaling_adjustment,
            min_adjustment_step=min_adjustment_step,
            cooldown=cooldown)

        try:
            connection.create_scaling_policy(sp)
            module.exit_json(changed=True)
        except BotoServerError, e:
            module.fail_json(msg=str(e))
    else:
        policy = scalingPolicies[0]
        changed = False

        #min_adjustment_step attribute is only relevant if the adjustment_type
        #is set to percentage change in capacity, so it is a special case
        if getattr(policy, 'adjustment_type') == 'PercentChangeInCapacity':
            if getattr(policy, 'min_adjustment_step') != module.params.get('min_adjustment_step'):
                changed = True
        
        #set the min adjustment step incase the user decided to change their adjustment type to percentage
        setattr(policy, 'min_adjustment_step', module.params.get('min_adjustment_step'))

        #check the remaining attributes
        for attr in ('adjustment_type','scaling_adjustment','cooldown'):
            if getattr(policy, attr) != module.params.get(attr):
                changed = True
                setattr(policy, attr, module.params.get(attr))

        try:
            if changed:
                connection.create_scaling_policy(policy)
                policy = connection.get_all_policies(policy_names=[sp_name])[0]
                module.exit_json(changed=changed, name=policy.name, arn=policy.policy_arn, as_name=policy.as_name, scaling_adjustment=policy.scaling_adjustment, cooldown=policy.cooldown, adjustment_type=policy.adjustment_type, min_adjustment_step=policy.min_adjustment_step)
            module.exit_json(changed=changed)
        except BotoServerError, e:
            module.fail_json(msg=str(e))


def delete_scaling_policy(connection, module):
    sp_name = module.params.get('name')
    asg_name = module.params.get('asg_name')

    scalingPolicies = connection.get_all_policies(as_group=asg_name,policy_names=[sp_name])

    if scalingPolicies:
        try:
            connection.delete_policy(sp_name, asg_name)
            module.exit_json(changed=True)
        except BotoServerError, e:
            module.exit_json(changed=False, msg=str(e))
    else:
        module.exit_json(changed=False)


def main():
    argument_spec = ec2_argument_spec()
    argument_spec.update(
        dict(
            name = dict(required=True, type='str'),
            adjustment_type = dict(type='str', choices=['ChangeInCapacity','ExactCapacity','PercentChangeInCapacity']),
            asg_name = dict(required=True, type='str'),
            scaling_adjustment = dict(type='int'),
            min_adjustment_step = dict(type='int'),
            cooldown = dict(type='int'),
            region = dict(aliases=['aws_region', 'ec2_region'], choices=AWS_REGIONS),
            state=dict(default='present', choices=['present', 'absent']),
        )    
    )
    
    module = AnsibleModule(argument_spec=argument_spec)

    region, ec2_url, aws_connect_params = get_aws_connection_info(module)
    
    state = module.params.get('state')

    try:
        connection = connect_to_aws(boto.ec2.autoscale, region, **aws_connect_params)
    except boto.exception.NoAuthHandlerFound, e:
        module.fail_json(msg = str(e))

    if state == 'present':
        create_scaling_policy(connection, module)
    elif state == 'absent':
        delete_scaling_policy(connection, module)


main()