package main

import (
	nativeerrors "errors"
	"math/rand"
	"sync/atomic"
	"time"

	"github.com/kaspanet/kaspad/cmd/kaspaminer/templatemanager"
	"github.com/kaspanet/kaspad/domain/consensus/model/pow"
	"github.com/kaspanet/kaspad/util/difficulty"

	"github.com/kaspanet/kaspad/domain/consensus/utils/consensushashing"

	"github.com/kaspanet/kaspad/domain/consensus/model/externalapi"

	"github.com/kaspanet/kaspad/app/appmessage"
	"github.com/kaspanet/kaspad/infrastructure/network/netadapter/router"

	"github.com/kaspanet/kaspad/util"
	"github.com/pkg/errors"
)

var hashesTried uint64

const logHashRateInterval = 10 * time.Second

func mineLoop(client *minerClient, numberOfBlocks uint64, targetBlocksPerSecond float64, mineWhenNotSynced bool,
	miningAddr util.Address) error {
	rand.Seed(time.Now().UnixNano()) // Seed the global concurrent-safe random source.

	errChan := make(chan error)
	doneChan := make(chan struct{})

	// We don't want to send router.DefaultMaxMessages blocks at once because there's
	// a high chance we'll get disconnected from the node, so we make the channel
	// capacity router.DefaultMaxMessages/2 (we give some slack for getBlockTemplate
	// requests)
	foundBlockChan := make(chan *externalapi.DomainBlock, router.DefaultMaxMessages/2)

	spawn("templatesLoop", func() {
		templatesLoop(client, miningAddr, errChan)
	})

	spawn("blocksLoop", func() {
		const windowSize = 10
		var expectedDurationForWindow time.Duration
		var windowExpectedEndTime time.Time
		hasBlockRateTarget := targetBlocksPerSecond != 0
		if hasBlockRateTarget {
			expectedDurationForWindow = time.Duration(float64(windowSize)/targetBlocksPerSecond) * time.Second
			windowExpectedEndTime = time.Now().Add(expectedDurationForWindow)
		}
		blockInWindowIndex := 0

		for {
			foundBlockChan <- mineNextBlock(mineWhenNotSynced)

			if hasBlockRateTarget {
				blockInWindowIndex++
				if blockInWindowIndex == windowSize-1 {
					deviation := windowExpectedEndTime.Sub(time.Now())
					if deviation > 0 {
						log.Infof("Finished to mine %d blocks %s earlier than expected. Sleeping %s to compensate",
							windowSize, deviation, deviation)
						time.Sleep(deviation)
					}
					blockInWindowIndex = 0
					windowExpectedEndTime = time.Now().Add(expectedDurationForWindow)
				}
			}

		}
	})

	spawn("handleFoundBlock", func() {
		for i := uint64(0); numberOfBlocks == 0 || i < numberOfBlocks; i++ {
			block := <-foundBlockChan
			err := handleFoundBlock(client, block)
			if err != nil {
				errChan <- err
				return
			}
		}
		doneChan <- struct{}{}
	})

	logHashRate()

	select {
	case err := <-errChan:
		return err
	case <-doneChan:
		return nil
	}
}

func logHashRate() {
	spawn("logHashRate", func() {
		lastCheck := time.Now()
		for range time.Tick(logHashRateInterval) {
			currentHashesTried := atomic.LoadUint64(&hashesTried)
			currentTime := time.Now()
			kiloHashesTried := float64(currentHashesTried) / 1000.0
			hashRate := kiloHashesTried / currentTime.Sub(lastCheck).Seconds()
			log.Infof("Current hash rate is %.2f Khash/s", hashRate)
			lastCheck = currentTime
			// subtract from hashesTried the hashes we already sampled
			atomic.AddUint64(&hashesTried, -currentHashesTried)
		}
	})
}

func handleFoundBlock(client *minerClient, block *externalapi.DomainBlock) error {
	blockHash := consensushashing.BlockHash(block)
	log.Infof("Submitting block %s to %s", blockHash, client.safeRPCClient().Address())

	rejectReason, err := client.safeRPCClient().SubmitBlock(block)
	if err != nil {
		if nativeerrors.Is(err, router.ErrTimeout) {
			log.Warnf("Got timeout while submitting block %s to %s: %s", blockHash, client.safeRPCClient().Address(), err)
			client.reconnect()
			return nil
		}
		if rejectReason == appmessage.RejectReasonIsInIBD {
			const waitTime = 1 * time.Second
			log.Warnf("Block %s was rejected because the node is in IBD. Waiting for %s", blockHash, waitTime)
			time.Sleep(waitTime)
			return nil
		}
		return errors.Wrapf(err, "Error submitting block %s to %s", blockHash, client.safeRPCClient().Address())
	}
	return nil
}

func mineNextBlock(mineWhenNotSynced bool) *externalapi.DomainBlock {
	nonce := rand.Uint64() // Use the global concurrent-safe random source.
	for {
		nonce++
		// For each nonce we try to build a block from the most up to date
		// block template.
		// In the rare case where the nonce space is exhausted for a specific
		// block, it'll keep looping the nonce until a new block template
		// is discovered.
		block := getBlockForMining(mineWhenNotSynced)
		targetDifficulty := difficulty.CompactToBig(block.Header.Bits())
		headerForMining := block.Header.ToMutable()
		headerForMining.SetNonce(nonce)
		atomic.AddUint64(&hashesTried, 1)
		if pow.CheckProofOfWorkWithTarget(headerForMining, targetDifficulty) {
			block.Header = headerForMining.ToImmutable()
			log.Infof("Found block %s with parents %s", consensushashing.BlockHash(block), block.Header.ParentHashes())
			return block
		}
	}
}

func getBlockForMining(mineWhenNotSynced bool) *externalapi.DomainBlock {
	tryCount := 0

	const sleepTime = 500 * time.Millisecond
	const sleepTimeWhenNotSynced = 5 * time.Second

	for {
		tryCount++

		shouldLog := (tryCount-1)%10 == 0
		template, isSynced := templatemanager.Get()
		if template == nil {
			if shouldLog {
				log.Info("Waiting for the initial template")
			}
			time.Sleep(sleepTime)
			continue
		}
		if !isSynced && !mineWhenNotSynced {
			if shouldLog {
				log.Warnf("Kaspad is not synced. Skipping current block template")
			}
			time.Sleep(sleepTimeWhenNotSynced)
			continue
		}

		return template
	}
}

func templatesLoop(client *minerClient, miningAddr util.Address, errChan chan error) {
	getBlockTemplate := func() {
		template, err := client.safeRPCClient().GetBlockTemplate(miningAddr.String())
		if nativeerrors.Is(err, router.ErrTimeout) {
			log.Warnf("Got timeout while requesting block template from %s: %s", client.safeRPCClient().Address(), err)
			client.reconnect()
			return
		}
		if err != nil {
			errChan <- errors.Wrapf(err, "Error getting block template from %s", client.safeRPCClient().Address())
			return
		}
		templatemanager.Set(template)
	}

	getBlockTemplate()
	const tickerTime = 500 * time.Millisecond
	ticker := time.NewTicker(tickerTime)
	for {
		select {
		case <-client.blockAddedNotificationChan:
			getBlockTemplate()
			ticker.Reset(tickerTime)
		case <-ticker.C:
			getBlockTemplate()
		}
	}
}