// Copyright 2018 The dexon-consensus-core Authors
// This file is part of the dexon-consensus-core library.
//
// The dexon-consensus-core library is free software: you can redistribute it
// and/or modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// The dexon-consensus-core library is distributed in the hope that it will be
// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
// General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the dexon-consensus-core library. If not, see
// <http://www.gnu.org/licenses/>.

package core

import (
	"fmt"
	"sync"

	"github.com/dexon-foundation/dexon-consensus-core/common"
	"github.com/dexon-foundation/dexon-consensus-core/core/crypto"
	"github.com/dexon-foundation/dexon-consensus-core/core/types"
)

// Errors for compaction chain module.
var (
	ErrBlockNotRegistered = fmt.Errorf(
		"block not registered")
	ErrNotInitiazlied = fmt.Errorf(
		"not initialized")
)

type compactionChain struct {
	gov                    Governance
	blocks                 map[common.Hash]*types.Block
	pendingBlocks          []*types.Block
	pendingFinalizedBlocks []*types.Block
	blocksLock             sync.RWMutex
	prevBlockLock          sync.RWMutex
	prevBlock              *types.Block
}

func newCompactionChain(gov Governance) *compactionChain {
	return &compactionChain{
		gov:    gov,
		blocks: make(map[common.Hash]*types.Block),
	}
}

func (cc *compactionChain) init(initBlock *types.Block) {
	cc.prevBlockLock.Lock()
	defer cc.prevBlockLock.Unlock()
	cc.prevBlock = initBlock
}

func (cc *compactionChain) registerBlock(block *types.Block) {
	if cc.blockRegistered(block.Hash) {
		return
	}
	cc.blocksLock.Lock()
	defer cc.blocksLock.Unlock()
	cc.blocks[block.Hash] = block
}

func (cc *compactionChain) blockRegistered(hash common.Hash) (exist bool) {
	cc.blocksLock.RLock()
	defer cc.blocksLock.RUnlock()
	_, exist = cc.blocks[hash]
	return
}

func (cc *compactionChain) processBlock(block *types.Block) error {
	prevBlock := cc.lastBlock()
	if prevBlock == nil {
		return ErrNotInitiazlied
	}
	block.Finalization.Height = prevBlock.Finalization.Height + 1
	cc.prevBlockLock.Lock()
	defer cc.prevBlockLock.Unlock()
	cc.prevBlock = block
	cc.blocksLock.Lock()
	defer cc.blocksLock.Unlock()
	cc.pendingBlocks = append(cc.pendingBlocks, block)
	return nil
}

func (cc *compactionChain) processFinalizedBlock(block *types.Block) (
	[]*types.Block, error) {
	blocks := func() []*types.Block {
		cc.blocksLock.Lock()
		defer cc.blocksLock.Unlock()
		blocks := cc.pendingFinalizedBlocks
		cc.pendingFinalizedBlocks = []*types.Block{}
		return blocks
	}()
	threshold := make(map[uint64]int)
	gpks := make(map[uint64]*DKGGroupPublicKey)
	toPending := []*types.Block{}
	confirmed := []*types.Block{}
	blocks = append(blocks, block)
	for _, b := range blocks {
		if !cc.gov.IsDKGFinal(b.Position.Round) {
			toPending = append(toPending, b)
			continue
		}
		round := b.Position.Round
		if _, exist := gpks[round]; !exist {
			threshold[round] = int(cc.gov.Configuration(round).DKGSetSize)/3 + 1
			var err error
			gpks[round], err = NewDKGGroupPublicKey(
				round,
				cc.gov.DKGMasterPublicKeys(round), cc.gov.DKGComplaints(round),
				threshold[round])
			if err != nil {
				continue
			}
		}
		gpk := gpks[round]
		if ok := gpk.VerifySignature(b.Hash, crypto.Signature{
			Type:      "bls",
			Signature: b.Finalization.Randomness}); !ok {
			continue
		}
		confirmed = append(confirmed, b)
	}
	cc.blocksLock.Lock()
	defer cc.blocksLock.Unlock()
	cc.pendingFinalizedBlocks = append(cc.pendingFinalizedBlocks, toPending...)
	return confirmed, nil
}

func (cc *compactionChain) extractBlocks() []*types.Block {
	deliveringBlocks := make([]*types.Block, 0)
	cc.blocksLock.Lock()
	defer cc.blocksLock.Unlock()
	for len(cc.pendingBlocks) != 0 &&
		(len(cc.pendingBlocks[0].Finalization.Randomness) != 0 ||
			cc.pendingBlocks[0].Position.Round == 0) {
		var block *types.Block
		block, cc.pendingBlocks = cc.pendingBlocks[0], cc.pendingBlocks[1:]
		delete(cc.blocks, block.Hash)
		deliveringBlocks = append(deliveringBlocks, block)
	}
	return deliveringBlocks
}

func (cc *compactionChain) processBlockRandomnessResult(
	rand *types.BlockRandomnessResult) error {
	if !cc.blockRegistered(rand.BlockHash) {
		return ErrBlockNotRegistered
	}
	cc.blocksLock.Lock()
	defer cc.blocksLock.Unlock()
	cc.blocks[rand.BlockHash].Finalization.Randomness = rand.Randomness
	return nil
}

func (cc *compactionChain) lastBlock() *types.Block {
	cc.prevBlockLock.RLock()
	defer cc.prevBlockLock.RUnlock()
	return cc.prevBlock
}