# Copyright 2011-2012 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
#     http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.

require 'aws/core'
require 'aws/cloud_formation/config'

module AWS

  # = AWS::CloudFormation
  #
  # Provides an expressive, object-oriented interface to AWS CloudFormation.
  #
  # == Credentials
  #
  # You can setup default credentials for all AWS services via
  # AWS.config:
  #
  #   AWS.config(
  #     :access_key_id => 'YOUR_ACCESS_KEY_ID',
  #     :secret_access_key => 'YOUR_SECRET_ACCESS_KEY')
  #
  # Or you can set them directly on the CloudFormation interface:
  #
  #   cf = AWS::CloudFormation.new(
  #     :access_key_id => 'YOUR_ACCESS_KEY_ID',
  #     :secret_access_key => 'YOUR_SECRET_ACCESS_KEY')
  #
  # = Stacks
  #
  # This is the starting point for working with CloudFormation.
  #
  # == Creating a Stack
  #
  # You can create a CloudFormation stack with a name and a template.
  #
  #   template = <<-TEMPLATE
  #   {
  #     "AWSTemplateFormatVersion" : "2010-09-09",
  #     "Description": "A simple template",
  #     "Resources": {
  #       "web": {
  #         "Type": "AWS::EC2::Instance",
  #         "Properties": {
  #           "ImageId": "ami-41814f28"
  #         }
  #       }
  #     }
  #   }
  #   TEMPLATE
  #
  #   cfm = AWS::CloudFormation.new
  #   stack = cfm.stacks.create('stack-name', template)
  #
  # See {StackCollection#create} for more information on creating templates
  # with capabilities and parameters.
  #
  # == Getting a Stack
  # 
  # Given a name, you can fetch a {Stack}.
  #
  #   stack = cfm.stacks['stack-name']
  #
  # == Enumerating Stacks
  #
  # You can enumerate stacks in two ways.  You can enumerate {Stack}
  # objects or stack summaries (simple hashes).  You can filter the stack
  # summary collection by a status.
  #
  #   # enumerating all stack objects
  #   cfm.stacks.each do |stack|
  #     # ...
  #   end
  #
  #   # enumerating stack summaries (hashes)
  #   cfm.stack_summaries.each do |stack_summary|
  #     # ...
  #   end
  #
  #   # filtering stack summaries by status
  #   cfm.stack_summaries.with_status(:create_failed).each do |summary|
  #     puts summary.to_yaml
  #   end
  #
  # == Template
  #
  # You can fetch the template body for a stack as a JSON string.
  #
  #   cfm.stacks['stack-name'].template
  #   #=> "{...}"
  #
  # You can update the template for a {Stack} with the {Stack#update} method:
  #
  #   cfm.stacks['stack-name'].update(:template => new_template)
  #
  # == Stack Events
  #
  # You can enumerate events for a stack.
  #
  #   stack.events.each do |event|
  #     puts "#{event.physical_resource_id}: #{event.resource_status}"
  #   end
  #
  # See {StackEvent} for a complete list of event attributes.
  #
  # == Stack Resources
  #
  # You can enumerate stack resources or request a stack resource by its
  # logical resource id.
  #
  #   # enumerating stack resources
  #   stack.resources.each do |resource|
  #     # ...
  #   end
  #
  #   # getting a resource by its logical id
  #   res = stack.resources['logical-resource-id']
  #   puts res.physical_resource_id
  #
  # If you need a stack resource, but only have its physical resource 
  # id, then you can call {CloudFormation#stack_resource}.
  #
  #   stack_resource = cfm.stack_resource('physical-resource-id')
  #
  # == Stack Resource Summaries
  #
  # As an alternative to stack resources, you can enumerate stack
  # resource summaries (hashes).
  #
  #   # enumerate all resources, this collection can not be filtered
  #   stack.resource_summaries.each do |summary|
  #     # ...
  #   end
  #
  class CloudFormation

    AWS.register_autoloads(self, 'aws/cloud_formation') do
      autoload :Client, 'client'
      autoload :Errors, 'errors'
      autoload :Request, 'request'
      autoload :Stack, 'stack'
      autoload :StackCollection, 'stack_collection'
      autoload :StackEvent, 'stack_event'
      autoload :StackEventCollection, 'stack_event_collection'
      autoload :StackOptions, 'stack_options'
      autoload :StackOutput, 'stack_output'
      autoload :StackSummaryCollection, 'stack_summary_collection'
      autoload :StackResource, 'stack_resource'
      autoload :StackResourceCollection, 'stack_resource_collection'
      autoload :StackResourceSummaryCollection, 'stack_resource_summary_collection'
    end

    include Core::ServiceInterface
    include StackOptions

    # @return [StackCollection]
    def stacks
      StackCollection.new(:config => config)
    end

    # @return [StackSummaryCollection]
    def stack_summaries
      StackSummaryCollection.new(:config => config)
    end

    # Returns a stack resource with the given physical resource
    # id.  
    #
    #   resource = cfm.stack_resource('i-123456789')
    #
    # Alternatively, you may pass a stack name and logical resource id:
    #
    #   resource = cfm.stack_resource('stack-name', 'logical-resource-id')
    #
    # @overload stack_resource(physical_resource_id)
    #   @param [String] physical_resource_id The physical resource id
    #     of the stack resource you want returned.
    #
    # @overload stack_resource(stack_name, logical_resource_id)
    #   @param [String] stack_name
    #   @param [String] logical_resource_id
    #
    # @return [StackResource] Returns the stack resource with the
    #   given physical resource id.
    #
    def stack_resource *args

      client_opts = {}

      if args.size == 1
        client_opts[:physical_resource_id] = args.first
      else
        client_opts[:stack_name] = args[0]
        client_opts[:logical_resource_id] = args[1]
      end

      response = client.describe_stack_resources(client_opts)

      details = response.stack_resources.first

      StackResource.new_from(
        :describe_stack_resource, details,
        Stack.new(details.stack_name, :config => config),
        details.logical_resource_id)

    end

    # Validates the template and returns a hash.  If the template is valid,
    # the returned hash may/will contain the following keys (actual
    # key list depends on the template).
    #
    #   * +:description+
    #   * +:capabilities+
    #   * +:capabilities_reason+
    #   * +:parameters+
    #
    # If the template is not parseable, then a hash will the following
    # keys will be returned:
    #
    #   * +:code+
    #   * +:message+
    #
    # @return [Hash]
    # 
    def validate_template template
      begin

        client_opts = {}
        client_opts[:template] = template
        apply_template(client_opts)  
        resp = client.validate_template(client_opts)

        results = {}
        [
          :capabilities,
          :capabilities_reason,
          :description,
        ].each do |method|
          if resp.respond_to?(method)
            results[method] = resp.send(method)
          end
        end
        
        if resp.respond_to?(:parameters)
          results[:parameters] = resp.parameters.collect(&:to_hash)
        end

        results

      rescue CloudFormation::Errors::ValidationError => e

        results = {}  
        results[:code] = e.code
        results[:message] = e.message
        results

      end
    end

    # @param (see Stack#template=)
    #
    # @param [Hash] parameters A hash that specifies the input 
    #   parameters for the template.
    #
    # @return [String] Returns a URL to the AWS Simple Monthly Calculator 
    #   with a query string that describes the resources required to run 
    #   the template.
    #
    def estimate_template_cost template, parameters = {}
      client_opts = {}
      client_opts[:template] = template
      apply_template(client_opts)  
      apply_parameters(client_opts)  
      client.estimate_template_cost(client_opts).url
    end

  end
end