package evidence

import (
	"fmt"
	"sync"

	dbm "github.com/tendermint/tmlibs/db"
	"github.com/tendermint/tmlibs/log"

	sm "github.com/tendermint/tendermint/state"
	"github.com/tendermint/tendermint/types"
)

// EvidencePool maintains a pool of valid evidence
// in an EvidenceStore.
type EvidencePool struct {
	logger log.Logger

	evidenceStore *EvidenceStore

	// needed to load validators to verify evidence
	stateDB dbm.DB

	// latest state
	mtx   sync.Mutex
	state sm.State

	// never close
	evidenceChan chan types.Evidence
}

func NewEvidencePool(stateDB dbm.DB, evidenceStore *EvidenceStore) *EvidencePool {
	evpool := &EvidencePool{
		stateDB:       stateDB,
		state:         sm.LoadState(stateDB),
		logger:        log.NewNopLogger(),
		evidenceStore: evidenceStore,
		evidenceChan:  make(chan types.Evidence),
	}
	return evpool
}

// SetLogger sets the Logger.
func (evpool *EvidencePool) SetLogger(l log.Logger) {
	evpool.logger = l
}

// EvidenceChan returns an unbuffered channel on which new evidence can be received.
func (evpool *EvidencePool) EvidenceChan() <-chan types.Evidence {
	return evpool.evidenceChan
}

// PriorityEvidence returns the priority evidence.
func (evpool *EvidencePool) PriorityEvidence() []types.Evidence {
	return evpool.evidenceStore.PriorityEvidence()
}

// PendingEvidence returns all uncommitted evidence.
func (evpool *EvidencePool) PendingEvidence() []types.Evidence {
	return evpool.evidenceStore.PendingEvidence()
}

// State returns the current state of the evpool.
func (evpool *EvidencePool) State() sm.State {
	evpool.mtx.Lock()
	defer evpool.mtx.Unlock()
	return evpool.state
}

// Update loads the latest
func (evpool *EvidencePool) Update(block *types.Block) {
	evpool.mtx.Lock()
	defer evpool.mtx.Unlock()

	state := sm.LoadState(evpool.stateDB)
	if state.LastBlockHeight != block.Height {
		panic(fmt.Sprintf("EvidencePool.Update: loaded state with height %d when block.Height=%d", state.LastBlockHeight, block.Height))
	}
	evpool.state = state

	// NOTE: shouldn't need the mutex
	evpool.MarkEvidenceAsCommitted(block.Evidence.Evidence)
}

// AddEvidence checks the evidence is valid and adds it to the pool.
// Blocks on the EvidenceChan.
func (evpool *EvidencePool) AddEvidence(evidence types.Evidence) (err error) {

	// TODO: check if we already have evidence for this
	// validator at this height so we dont get spammed

	if err := sm.VerifyEvidence(evpool.stateDB, evpool.State(), evidence); err != nil {
		return err
	}

	// fetch the validator and return its voting power as its priority
	// TODO: something better ?
	valset, _ := sm.LoadValidators(evpool.stateDB, evidence.Height())
	_, val := valset.GetByAddress(evidence.Address())
	priority := val.VotingPower

	added := evpool.evidenceStore.AddNewEvidence(evidence, priority)
	if !added {
		// evidence already known, just ignore
		return
	}

	evpool.logger.Info("Verified new evidence of byzantine behaviour", "evidence", evidence)

	// never closes. always safe to send on
	evpool.evidenceChan <- evidence
	return nil
}

// MarkEvidenceAsCommitted marks all the evidence as committed.
func (evpool *EvidencePool) MarkEvidenceAsCommitted(evidence []types.Evidence) {
	for _, ev := range evidence {
		evpool.evidenceStore.MarkEvidenceAsCommitted(ev)
	}
}