// Copyright 2019 The etcd Authors
//
// 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 quorum

// JointConfig is a configuration of two groups of (possibly overlapping)
// majority configurations. Decisions require the support of both majorities.
type JointConfig [2]MajorityConfig

func (c JointConfig) String() string {
	if len(c[1]) > 0 {
		return c[0].String() + "&&" + c[1].String()
	}
	return c[0].String()
}

// IDs returns a newly initialized map representing the set of voters present
// in the joint configuration.
func (c JointConfig) IDs() map[uint64]struct{} {
	m := map[uint64]struct{}{}
	for _, cc := range c {
		for id := range cc {
			m[id] = struct{}{}
		}
	}
	return m
}

// Describe returns a (multi-line) representation of the commit indexes for the
// given lookuper.
func (c JointConfig) Describe(l AckedIndexer) string {
	return MajorityConfig(c.IDs()).Describe(l)
}

// CommittedIndex returns the largest committed index for the given joint
// quorum. An index is jointly committed if it is committed in both constituent
// majorities.
func (c JointConfig) CommittedIndex(l AckedIndexer) Index {
	idx0 := c[0].CommittedIndex(l)
	idx1 := c[1].CommittedIndex(l)
	if idx0 < idx1 {
		return idx0
	}
	return idx1
}

// VoteResult takes a mapping of voters to yes/no (true/false) votes and returns
// a result indicating whether the vote is pending, lost, or won. A joint quorum
// requires both majority quorums to vote in favor.
func (c JointConfig) VoteResult(votes map[uint64]bool) VoteResult {
	r1 := c[0].VoteResult(votes)
	r2 := c[1].VoteResult(votes)

	if r1 == r2 {
		// If they agree, return the agreed state.
		return r1
	}
	if r1 == VoteLost || r2 == VoteLost {
		// If either config has lost, loss is the only possible outcome.
		return VoteLost
	}
	// One side won, the other one is pending, so the whole outcome is.
	return VotePending
}