/*
Copyright IBM Corp. 2016 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.
You may obtain a copy of the License at

                 http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License 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.
*/

package policies

import (
	"fmt"

	cb "github.com/hyperledger/fabric/protos/common"

	"github.com/golang/protobuf/proto"
)

type implicitMetaPolicy struct {
	conf        *cb.ImplicitMetaPolicy
	threshold   int
	subPolicies []Policy
}

// NewPolicy creates a new policy based on the policy bytes
func newImplicitMetaPolicy(data []byte) (*implicitMetaPolicy, error) {
	imp := &cb.ImplicitMetaPolicy{}
	if err := proto.Unmarshal(data, imp); err != nil {
		return nil, fmt.Errorf("Error unmarshaling to ImplicitMetaPolicy: %s", err)
	}

	return &implicitMetaPolicy{
		conf: imp,
	}, nil
}

func (imp *implicitMetaPolicy) initialize(config *policyConfig) {
	imp.subPolicies = make([]Policy, len(config.managers))
	i := 0
	for _, manager := range config.managers {
		imp.subPolicies[i], _ = manager.GetPolicy(imp.conf.SubPolicy)
		i++
	}

	switch imp.conf.Rule {
	case cb.ImplicitMetaPolicy_ANY:
		imp.threshold = 1
	case cb.ImplicitMetaPolicy_ALL:
		imp.threshold = len(imp.subPolicies)
	case cb.ImplicitMetaPolicy_MAJORITY:
		imp.threshold = len(imp.subPolicies)/2 + 1
	}

	// In the special case that there are no policies, consider 0 to be a majority or any
	if len(imp.subPolicies) == 0 {
		imp.threshold = 0
	}
}

// Evaluate takes a set of SignedData and evaluates whether this set of signatures satisfies the policy
func (imp *implicitMetaPolicy) Evaluate(signatureSet []*cb.SignedData) error {
	remaining := imp.threshold
	for _, policy := range imp.subPolicies {
		if policy.Evaluate(signatureSet) == nil {
			remaining--
			if remaining == 0 {
				return nil
			}
		}
	}
	if remaining == 0 {
		return nil
	}
	return fmt.Errorf("Failed to reach implicit threshold of %d sub-policies, required %d remaining", imp.threshold, remaining)
}