package main

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"math"
	"net/http"
	_ "net/http/pprof"
	"os"
	"runtime"
	"runtime/pprof"
	"sort"
	"time"

	"github.com/filecoin-project/lotus/api"
	"github.com/filecoin-project/lotus/chain/stmgr"
	"github.com/filecoin-project/lotus/chain/store"
	"github.com/filecoin-project/lotus/chain/types"
	"github.com/filecoin-project/lotus/chain/vm"
	_ "github.com/filecoin-project/lotus/lib/sigs/bls"
	_ "github.com/filecoin-project/lotus/lib/sigs/secp"
	"github.com/filecoin-project/sector-storage/ffiwrapper"
	"github.com/filecoin-project/specs-actors/actors/abi"
	"golang.org/x/xerrors"

	"github.com/ipfs/go-datastore"
	badger "github.com/ipfs/go-ds-badger2"
	blockstore "github.com/ipfs/go-ipfs-blockstore"
	"github.com/urfave/cli/v2"
)

type TipSetExec struct {
	TipSet   types.TipSetKey
	Trace    []*api.InvocResult
	Duration time.Duration
}

var importBenchCmd = &cli.Command{
	Name:  "import",
	Usage: "benchmark chain import and validation",
	Subcommands: []*cli.Command{
		importAnalyzeCmd,
	},
	Flags: []cli.Flag{
		&cli.Int64Flag{
			Name:  "height",
			Usage: "halt validation after given height",
		},
		&cli.IntFlag{
			Name:  "batch-seal-verify-threads",
			Usage: "set the parallelism factor for batch seal verification",
			Value: runtime.NumCPU(),
		},
	},
	Action: func(cctx *cli.Context) error {
		vm.BatchSealVerifyParallelism = cctx.Int("batch-seal-verify-threads")
		if !cctx.Args().Present() {
			fmt.Println("must pass car file of chain to benchmark importing")
			return nil
		}

		cfi, err := os.Open(cctx.Args().First())
		if err != nil {
			return err
		}
		defer cfi.Close() //nolint:errcheck // read only file

		tdir, err := ioutil.TempDir("", "lotus-import-bench")
		if err != nil {
			return err
		}

		bds, err := badger.NewDatastore(tdir, nil)
		if err != nil {
			return err
		}
		bs := blockstore.NewBlockstore(bds)
		cbs, err := blockstore.CachedBlockstore(context.TODO(), bs, blockstore.DefaultCacheOpts())
		if err != nil {
			return err
		}
		bs = cbs
		ds := datastore.NewMapDatastore()
		cs := store.NewChainStore(bs, ds, vm.Syscalls(ffiwrapper.ProofVerifier))
		stm := stmgr.NewStateManager(cs)

		prof, err := os.Create("import-bench.prof")
		if err != nil {
			return err
		}
		defer prof.Close() //nolint:errcheck

		if err := pprof.StartCPUProfile(prof); err != nil {
			return err
		}

		head, err := cs.Import(cfi)
		if err != nil {
			return err
		}

		if h := cctx.Int64("height"); h != 0 {
			tsh, err := cs.GetTipsetByHeight(context.TODO(), abi.ChainEpoch(h), head, true)
			if err != nil {
				return err
			}
			head = tsh
		}

		ts := head
		tschain := []*types.TipSet{ts}
		for ts.Height() != 0 {
			next, err := cs.LoadTipSet(ts.Parents())
			if err != nil {
				return err
			}

			tschain = append(tschain, next)
			ts = next
		}

		ibj, err := os.Create("import-bench.json")
		if err != nil {
			return err
		}
		defer ibj.Close() //nolint:errcheck

		enc := json.NewEncoder(ibj)

		var lastTse *TipSetExec

		lastState := tschain[len(tschain)-1].ParentState()
		for i := len(tschain) - 2; i >= 0; i-- {
			cur := tschain[i]
			log.Infof("computing state (height: %d, ts=%s)", cur.Height(), cur.Cids())
			if cur.ParentState() != lastState {
				lastTrace := lastTse.Trace
				d, err := json.MarshalIndent(lastTrace, "", "  ")
				if err != nil {
					panic(err)
				}
				fmt.Println("TRACE")
				fmt.Println(string(d))
				return xerrors.Errorf("tipset chain had state mismatch at height %d (%s != %s)", cur.Height(), cur.ParentState(), lastState)
			}
			start := time.Now()
			st, trace, err := stm.ExecutionTrace(context.TODO(), cur)
			if err != nil {
				return err
			}
			stripCallers(trace)

			lastTse = &TipSetExec{
				TipSet:   cur.Key(),
				Trace:    trace,
				Duration: time.Since(start),
			}
			lastState = st
			if err := enc.Encode(lastTse); err != nil {
				return xerrors.Errorf("failed to write out tipsetexec: %w", err)
			}
		}

		pprof.StopCPUProfile()

		return nil

	},
}

func walkExecutionTrace(et *types.ExecutionTrace) {
	for _, gc := range et.GasCharges {
		gc.Callers = nil
	}
	for _, sub := range et.Subcalls {
		walkExecutionTrace(&sub) //nolint:scopelint,gosec
	}
}

func stripCallers(trace []*api.InvocResult) {
	for _, t := range trace {
		walkExecutionTrace(&t.ExecutionTrace)
	}
}

type Invocation struct {
	TipSet types.TipSetKey
	Invoc  *api.InvocResult
}

const GasPerNs = 10

func countGasCosts(et *types.ExecutionTrace) (int64, int64) {
	var cgas, vgas int64

	for _, gc := range et.GasCharges {
		cgas += gc.ComputeGas
		vgas += gc.VirtualComputeGas
	}

	for _, sub := range et.Subcalls {
		c, v := countGasCosts(&sub)
		cgas += c
		vgas += v
	}

	return cgas, vgas
}

func compStats(vals []float64) (float64, float64) {
	var sum float64

	for _, v := range vals {
		sum += v
	}

	av := sum / float64(len(vals))

	var varsum float64
	for _, v := range vals {
		delta := av - v
		varsum += delta * delta
	}

	return av, float64(math.Sqrt(float64(varsum / float64(len(vals)))))
}

type stats struct {
	count float64
	mean  float64
	dSqr  float64
}

func (s *stats) AddPoint(value float64) {
	s.count++
	meanDiff := (value - s.mean) / s.count
	newMean := s.mean + meanDiff

	dSqrtInc := (value - newMean) * (value - s.mean)
	s.dSqr += dSqrtInc
	s.mean = newMean
}

func (s *stats) variance() float64 {
	return s.dSqr / (s.count - 1)
}

func (s1 *stats) Combine(s2 *stats) {
	if s1.count == 0 {
		*s1 = *s2
	}
	newCount := s1.count + s2.count
	newMean := s1.count*s1.mean + s2.count*s2.mean
	newMean /= newCount
	newVar := s1.count * (s1.variance() + (s1.mean-newMean)*(s1.mean-newMean))
	newVar += s2.count * (s2.variance() + (s2.mean-newMean)*(s2.mean-newMean))
	newVar /= newCount
	s1.count = newCount
	s1.mean = newMean
	s1.dSqr = newVar * (newCount - 1)
}

func tallyGasCharges(charges map[string]*stats, et types.ExecutionTrace) {
	for _, gc := range et.GasCharges {

		compGas := gc.ComputeGas + gc.VirtualComputeGas
		ratio := float64(compGas) / float64(gc.TimeTaken.Nanoseconds())

		s := charges[gc.Name]
		if s == nil {
			s = new(stats)
			charges[gc.Name] = s
		}

		s.AddPoint(1 / ratio)
		//fmt.Printf("%s: %d, %s: %0.2f\n", gc.Name, compGas, gc.TimeTaken, 1/(ratio/GasPerNs))
	}
	for _, sub := range et.Subcalls {
		tallyGasCharges(charges, sub)
	}
}

var importAnalyzeCmd = &cli.Command{
	Name: "analyze",
	Action: func(cctx *cli.Context) error {
		if !cctx.Args().Present() {
			fmt.Println("must pass bench file to analyze")
			return nil
		}

		go func() {
			http.ListenAndServe("localhost:6060", nil)
		}()

		fi, err := os.Open(cctx.Args().First())
		if err != nil {
			return err
		}

		const nWorkers = 16
		jsonIn := make(chan []byte, 2*nWorkers)
		type result struct {
			totalTime       time.Duration
			chargeStats     map[string]*stats
			expensiveInvocs []Invocation
		}

		results := make(chan result, nWorkers)

		for i := 0; i < nWorkers; i++ {
			go func() {
				chargeStats := make(map[string]*stats)
				var totalTime time.Duration
				const invocsKeep = 32
				var expensiveInvocs = make([]Invocation, 0, 8*invocsKeep)
				var leastExpensiveInvoc = time.Duration(0)

				for {
					b, ok := <-jsonIn
					var tse TipSetExec

					json.Unmarshal(b, &tse)
					if !ok {
						results <- result{
							totalTime:       totalTime,
							chargeStats:     chargeStats,
							expensiveInvocs: expensiveInvocs,
						}
						return
					}

					totalTime += tse.Duration
					for _, inv := range tse.Trace {
						if inv.Duration > leastExpensiveInvoc {
							expensiveInvocs = append(expensiveInvocs, Invocation{
								TipSet: tse.TipSet,
								Invoc:  inv,
							})
						}

						tallyGasCharges(chargeStats, inv.ExecutionTrace)
					}
					if len(expensiveInvocs) > 4*invocsKeep {
						sort.Slice(expensiveInvocs, func(i, j int) bool {
							return expensiveInvocs[i].Invoc.Duration > expensiveInvocs[j].Invoc.Duration
						})
						leastExpensiveInvoc = expensiveInvocs[len(expensiveInvocs)-1].Invoc.Duration
						n := 30
						if len(expensiveInvocs) < n {
							n = len(expensiveInvocs)
						}
						expensiveInvocs = expensiveInvocs[:n]
					}
				}
			}()
		}

		var totalTipsets int64
		reader := bufio.NewReader(fi)
		for {
			b, err := reader.ReadBytes('\n')
			if err != nil && err != io.EOF {
				if e, ok := err.(*json.SyntaxError); ok {
					log.Warnf("syntax error at byte offset %d", e.Offset)
				}
				return err
			}
			totalTipsets++
			jsonIn <- b
			fmt.Printf("\rProcessed %d tipsets", totalTipsets)
			if err == io.EOF {
				break
			}
		}
		close(jsonIn)
		fmt.Printf("\n")
		fmt.Printf("Collecting results\n")

		var invocs []Invocation
		var totalTime time.Duration
		var keys []string
		var charges = make(map[string]*stats)
		for i := 0; i < nWorkers; i++ {
			fmt.Printf("\rProcessing results from worker %d/%d", i+1, nWorkers)
			res := <-results
			invocs = append(invocs, res.expensiveInvocs...)
			for k, v := range res.chargeStats {
				s := charges[k]
				if s == nil {
					s = new(stats)
					charges[k] = s
				}
				s.Combine(v)
			}
			totalTime += res.totalTime
		}

		fmt.Printf("\nCollecting gas keys\n")
		for k := range charges {
			keys = append(keys, k)
		}

		fmt.Println("Gas Price Deltas")
		sort.Strings(keys)
		for _, k := range keys {
			s := charges[k]
			fmt.Printf("%s: incr by %f (%f)\n", k, s.mean, math.Sqrt(s.variance()))
		}

		sort.Slice(invocs, func(i, j int) bool {
			return invocs[i].Invoc.Duration > invocs[j].Invoc.Duration
		})

		fmt.Println("Total time: ", totalTime)
		fmt.Println("Average time per epoch: ", totalTime/time.Duration(totalTipsets))

		n := 30
		if len(invocs) < n {
			n = len(invocs)
		}
		fmt.Printf("Top %d most expensive calls:\n", n)
		for i := 0; i < n; i++ {
			inv := invocs[i].Invoc
			fmt.Printf("%s: %s %s %d %s\n", inv.Duration, inv.Msg.From, inv.Msg.To, inv.Msg.Method, invocs[i].TipSet)
		}
		return nil
	},
}