Initial commit

Signed-off-by: Alex Vanin <a.vanin@yadro.com>
2023-09-27 14:05:46 +03:00 · 2023-09-27 14:05:46 +03:00 · db7464d2d3
commit db7464d2d3
12 changed files with 1823 additions and 0 deletions
--- a/.gitignore
+++ b/.gitignore
@ -0,0 +1 @@
+bin/*
--- a/21
+++ b/21
@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2023 TrueCloudLab
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
--- a/4
+++ b/4
@ -0,0 +1,4 @@
+.PHONY: build
+
+build:
+	CGO_ENABLED=0 go build -o ./bin/monza ./
--- a/README.md
+++ b/README.md
@ -0,0 +1,167 @@
+# Monza
+
+Find notifications in [Neo3](https://neo.org/) compatible chains and more.
+
+## Features
+
+- Stores chain blocks in the filesystem, so it will not fetch it again
+  at restart
+- Works with multiple chains by storing chain blocks based on magic number
+- Detailed notification output for NEP and FrostFS notifications
+- Use relative numbers for search interval
+- Use nice names for native contracts
+- Search multiple notifications at once
+
+## Examples
+
+```
+$ monza run -r http://localhost:30333 --from 22 --to 24 -n NewEpoch:* -n Transfer:gas
+syncing 100% [##################################################] (2/2, 3686 blocks/s)
+block:22 at:2023-09-27T13:50:03+03:00 name:Transfer from:56c989e76f9a2ca05bb5caa6c96f524d905accd8 to:nil amount:69915670
+block:22 at:2023-09-27T13:50:03+03:00 name:Transfer from:nil to:b248508f4ef7088e10c48f14d04be3272ca29eee amount:1219580
+block:22 at:2023-09-27T13:50:03+03:00 name:Transfer from:nil to:b248508f4ef7088e10c48f14d04be3272ca29eee amount:50000000
+block:22 at:2023-09-27T13:50:03+03:00 name:NewEpoch epoch:1
+block:23 at:2023-09-27T13:50:04+03:00 name:Transfer from:05195d17c8f013e258eb8dde1236c19d9a61b608 to:nil amount:33917200
+block:23 at:2023-09-27T13:50:04+03:00 name:Transfer from:6a131b2be19b7618dc22dbc8147015d947af67ce to:nil amount:12321080
+block:23 at:2023-09-27T13:50:04+03:00 name:Transfer from:b248508f4ef7088e10c48f14d04be3272ca29eee to:nil amount:12325080
+block:23 at:2023-09-27T13:50:04+03:00 name:Transfer from:nil to:b248508f4ef7088e10c48f14d04be3272ca29eee amount:8917170
+block:23 at:2023-09-27T13:50:04+03:00 name:Transfer from:nil to:b248508f4ef7088e10c48f14d04be3272ca29eee amount:20000000
+block:23 at:2023-09-27T13:50:04+03:00 name:Transfer from:nil to:b248508f4ef7088e10c48f14d04be3272ca29eee amount:50000000
+block:23 at:2023-09-27T13:50:04+03:00 name:Transfer from:6a131b2be19b7618dc22dbc8147015d947af67ce to:c1e14f19c3e60d0b9244d06dd7ba9b113135ec3b amount:243839460
+block:23 at:2023-09-27T13:50:04+03:00 name:Transfer from:b248508f4ef7088e10c48f14d04be3272ca29eee to:c1e14f19c3e60d0b9244d06dd7ba9b113135ec3b amount:250146763165
+```
+
+### Detailed output
+
+- NEP-17 `Transfer`
+
+```
+block:23 at:2023-09-27T13:50:04+03:00 name:Transfer from:6a131b2be19b7618dc22dbc8147015d947af67ce to:c1e14f19c3e60d0b9244d06dd7ba9b113135ec3b amount:243839460
+```
+
+- FrostFS `NewEpoch`
+
+```
+block:22 at:2023-09-27T13:50:03+03:00 name:NewEpoch epoch:1
+```
+
+- FrostFS `AddPeerSuccess`
+
+```
+block:21 at:2023-09-27T13:50:02+03:00 name:AddPeerSuccess pubkey:[..6a8131]
+```
+
+### Notifications
+
+Search notifications based on notification name and contract address.
+
+```
+monza run -r [endpoint] --from 110000 --to 110100 -n NewEpoch:ab8a83432af3cd32ce6ba3797f62b1ba330d7c3d
+```
+
+Use wildcard to search notifications from any contract.
+
+```
+monza run -r [endpoint] --from 110000 --to 110100 -n NewEpoch:*
+```
+
+Use native contract names such as `gas` and `neo`.
+
+```
+monza run -r [endpoint] --from 110000 --to 110100 -n Transfer:gas
+```
+
+Search for multiple notifications.
+
+```
+monza run -r [endpoint] --from 110000 --to 110100 -n Transfer:gas -n NewEpoch:*
+```
+
+### Intervals
+
+Define start and stop blocks.
+
+```
+monza run -r [endpoint] --from 110000 --to 110100 -n NewEpoch:*
+```
+
+Omit `--to` flag to search up to the latest block.
+
+```
+monza run -r [endpoint] --from 110000 -n NewEpoch:*
+```
+
+To look for `100` blocks before the latest block use prefix `m` (minus)
+
+```
+monza run -r [endpoint] --from m100 -n NewEpoch:*
+```
+
+To look for `100` blocks after specified `from` block, use prefix `p` (plus)
+
+```
+monza run -r [endpoint] --from 101230 --to p100 -n NewEpoch:*
+```
+
+### Other
+
+Blocks are stored in bolt databases. Specify database dir with `-c` flag
+(default path is `$HOME/.config/monza`)
+
+```
+monza run -r [endpoint] -c ./cache --from 110000 --to 110100 -n NewEpoch:*
+```
+
+To speed up block fetching from the RPC node, use more parallel workers with
+`-w` flag.
+
+```
+monza run -r [endpoint] -w 100 --from 110000 --to 110100 -n NewEpoch:*
+```
+
+To disable progress bar use `--disable-progress-bar` flag.
+
+### Stutter
+
+Stutter command searches for blocks that produced with threshold a delay
+or slower.
+
+```
+$ monza stutter -r [endpoint] --from 1159200 --to p30 --threshold 20s
+syncing 100% [##################################################] (30/30, 10 blocks/s)       
+block:1159201 at:2022-03-29T18:20:42+03:00
+block:1159202 at:2022-03-29T18:22:12+03:00 [<- stutter for 1m30s]
+-- skipped 5 blocks --
+block:1159208 at:2022-03-29T18:23:43+03:00
+block:1159209 at:2022-03-29T18:25:13+03:00 [<- stutter for 1m30s]
+-- skipped 5 blocks --
+block:1159215 at:2022-03-29T18:26:43+03:00
+block:1159216 at:2022-03-29T18:28:13+03:00 [<- stutter for 1m30s]
+-- skipped 5 blocks --
+block:1159222 at:2022-03-29T18:29:43+03:00
+block:1159223 at:2022-03-29T18:31:13+03:00 [<- stutter for 1m30s]
+```
+
+### Explorer
+
+Run monza in interactive mode to navigate through blocks, transactions and
+notifications with `explore` command.
+
+```
+$ monza explore -r [endpoint]
+```
+
+## Build
+
+Use `make build` command. Binary will be stored in `./bin/monza`.
+
+## To Do
+
+- [ ] `monza cache` command to manage bbolt instances: provide size and option to delete
+- [ ] Add verbose flag with for detailed view of notification body
+- [ ] Add more native contract hashes aliases
+- [ ] More NEP support (NEP-11?)
+
+## License
+
+Source code is available under the [MIT License](/LICENSE).
--- a/encoding.go
+++ b/encoding.go
@ -0,0 +1,194 @@
+package main
+
+import (
+	"encoding/hex"
+	"fmt"
+	"time"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/block"
+	"github.com/nspcc-dev/neo-go/pkg/core/state"
+	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
+)
+
+const nonCompatibleMsg = "not compatible with FrostFS"
+
+func PrintEvent(b *block.Block, n state.NotificationEvent, extra string) {
+	d := time.Unix(int64(b.Timestamp/1e3), 0)
+	s := fmt.Sprintf("block:%d at:%s name:%s",
+		b.Index, d.Format(time.RFC3339), n.Name,
+	)
+
+	if len(extra) != 0 {
+		s += fmt.Sprintf(" [%s]", extra)
+	}
+
+	fmt.Println(s)
+}
+
+func PrintTransfer(b *block.Block, n state.NotificationEvent) {
+	const nonCompatibleMsg = "not NEP-17 compatible"
+
+	items, ok := n.Item.Value().([]stackitem.Item)
+	if !ok {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	if len(items) != 3 {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	snd, err := items[0].TryBytes()
+	if err != nil {
+		snd = nil
+	}
+
+	rcv, err := items[1].TryBytes()
+	if err != nil {
+		rcv = nil
+	}
+
+	bigAmount, err := items[2].TryInteger()
+	if err != nil {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	var sndStr, rcvStr = "nil", "nil"
+	if snd != nil {
+		sndStr = hex.EncodeToString(revertBytes(snd))
+	}
+
+	if rcv != nil {
+		rcvStr = hex.EncodeToString(revertBytes(rcv))
+	}
+
+	d := time.Unix(int64(b.Timestamp/1e3), 0)
+
+	s := fmt.Sprintf("block:%d at:%s name:%s from:%s to:%s amount:%d",
+		b.Index, d.Format(time.RFC3339), n.Name,
+		sndStr, rcvStr, bigAmount.Int64(),
+	)
+
+	fmt.Println(s)
+}
+
+func PrintNewEpoch(b *block.Block, n state.NotificationEvent) {
+	items, ok := n.Item.Value().([]stackitem.Item)
+	if !ok {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	if len(items) != 1 {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	epoch, err := items[0].TryInteger()
+	if err != nil {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	d := time.Unix(int64(b.Timestamp/1e3), 0)
+
+	s := fmt.Sprintf("block:%d at:%s name:%s epoch:%d",
+		b.Index, d.Format(time.RFC3339), n.Name, epoch,
+	)
+
+	fmt.Println(s)
+}
+
+func PrintAddPeerSuccess(b *block.Block, n state.NotificationEvent) {
+	items, ok := n.Item.Value().([]stackitem.Item)
+	if !ok {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	if len(items) != 1 {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	data, err := items[0].TryBytes()
+	if err != nil {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	d := time.Unix(int64(b.Timestamp/1e3), 0)
+
+	s := fmt.Sprintf("block:%d at:%s name:%s pubkey:[..%s]",
+		b.Index, d.Format(time.RFC3339), n.Name,
+		hex.EncodeToString(data[len(data)-3:]),
+	)
+
+	fmt.Println(s)
+}
+
+func PrintUpdateState(b *block.Block, n state.NotificationEvent) {
+	items, ok := n.Item.Value().([]stackitem.Item)
+	if !ok {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	if len(items) != 2 {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	st, err := items[0].TryInteger()
+	if err != nil {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	var stateStr string
+	switch v := st.Uint64(); v {
+	case 1:
+		stateStr = "online"
+	case 2:
+		stateStr = "offline"
+	default:
+		stateStr = fmt.Sprintf("%d(unknown)", v)
+	}
+
+	pubkey, err := items[1].TryBytes()
+	if err != nil {
+		PrintEvent(b, n, nonCompatibleMsg)
+		return
+	}
+
+	d := time.Unix(int64(b.Timestamp/1e3), 0)
+
+	s := fmt.Sprintf("block:%d at:%s name:%s pubkey:[..%s] state:%s",
+		b.Index, d.Format(time.RFC3339), n.Name,
+		hex.EncodeToString(pubkey[len(pubkey)-3:]),
+		stateStr,
+	)
+
+	fmt.Println(s)
+}
+
+func PrintBlock(b *block.Block, extra string) {
+	d := time.Unix(int64(b.Timestamp/1e3), 0)
+	s := fmt.Sprintf("block:%d at:%s", b.Index, d.Format(time.RFC3339))
+
+	if len(extra) != 0 {
+		s += fmt.Sprintf(" [%s]", extra)
+	}
+
+	fmt.Println(s)
+}
+
+func revertBytes(data []byte) []byte {
+	ln := len(data)
+	for i := 0; i < ln/2; i++ {
+		data[i], data[ln-1-i] = data[ln-1-i], data[i]
+	}
+	return data
+}
--- a/explorer.go
+++ b/explorer.go
@ -0,0 +1,508 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/signal"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/monza/internal/chain"
+	"github.com/gdamore/tcell/v2"
+	"github.com/nspcc-dev/neo-go/pkg/core/block"
+	"github.com/nspcc-dev/neo-go/pkg/core/state"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/vm/stackitem"
+	"github.com/rivo/tview"
+	"github.com/urfave/cli/v2"
+)
+
+type (
+	Explorer struct {
+		ctx      context.Context
+		chain    *chain.Chain
+		endpoint string
+		app      *tview.Application
+
+		jobCh chan fetchTask
+		errCh chan error
+		wg    sync.WaitGroup
+
+		searchErrFlag bool
+	}
+
+	fetchTask struct {
+		txHash *util.Uint256
+		index  uint32
+	}
+)
+
+const defaultExploreWorkers = 100
+
+func explorer(c *cli.Context) (err error) {
+	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
+
+	// parse blockchain info
+	cacheDir := c.String(cacheFlagKey)
+	if len(cacheDir) == 0 {
+		cacheDir, err = defaultConfigDir()
+		if err != nil {
+			return err
+		}
+	}
+
+	endpoint := c.String(endpointFlagKey)
+	blockchain, err := chain.Open(ctx, cacheDir, endpoint)
+	if err != nil {
+		return fmt.Errorf("cannot initialize remote blockchain client: %w", err)
+	}
+	defer func() {
+		blockchain.Close()
+		cancel()
+	}()
+
+	e := Explorer{
+		ctx:      ctx,
+		chain:    blockchain,
+		endpoint: endpoint,
+		app:      tview.NewApplication(),
+		jobCh:    make(chan fetchTask),
+		errCh:    make(chan error),
+	}
+	e.startWorkers(defaultExploreWorkers)
+	return e.Run()
+}
+
+func (e *Explorer) Run() error {
+	// UI basic elements
+	blockList := tview.NewList()
+	searchInput := tview.NewInputField()
+	blockInfo := tview.NewTextView()
+	txCounter := tview.NewTextView()
+	txList := tview.NewList()
+	notifications := tview.NewTextView()
+
+	// UI containers
+	blockFlex := tview.NewFlex().
+		SetDirection(tview.FlexRow).
+		AddItem(blockInfo, 0, 1, false).
+		AddItem(txCounter, 2, 2, false).
+		AddItem(txList, 5, 3, false)
+	appGrid := tview.NewGrid().
+		SetRows(15, -1, 1).
+		SetColumns(-1, -2).
+		AddItem(blockList, 0, 0, 2, 1, 0, 0, false).
+		AddItem(searchInput, 2, 0, 1, 2, 0, 0, false).
+		AddItem(blockFlex, 0, 1, 1, 1, 0, 0, false).
+		AddItem(notifications, 1, 1, 1, 1, 0, 0, false)
+
+	// Initialize element style
+	blockList.ShowSecondaryText(false).SetWrapAround(false)
+	blockList.SetBorder(true).SetTitle("Blocks")
+	searchInput.SetFieldBackgroundColor(tcell.ColorBlack)
+	txList.ShowSecondaryText(false)
+	setFocusColorStyle(blockList.Box, blockList.Box)
+	setFocusColorStyle(blockFlex.Box, txList.Box)
+	setFocusColorStyle(notifications.Box, notifications.Box)
+
+	// Handle redrawing events
+	blockList.SetDrawFunc(func(_ tcell.Screen, _, _, _, _ int) (int, int, int, int) {
+		posX, posY, width, height := blockList.GetInnerRect()
+		e.redrawBlockList(blockList, height)
+		return posX, posY, width, height
+	})
+
+	// Handle non-default keyboard events
+	appGrid.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Rune() == '/' {
+			e.searchStatusBar(searchInput)
+			e.app.SetFocus(searchInput)
+			return nil
+		}
+		return event
+	})
+	blockList.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		switch event.Rune() {
+		case 'q':
+			e.app.Stop()
+			return nil
+		case 'r':
+			e.refillBlockList(blockList)
+			return nil
+		default:
+			return event
+		}
+	})
+	searchInput.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if !e.searchErrFlag {
+			return event
+		}
+		e.searchErrFlag = false
+		e.defaultStatusBar(searchInput, blockList.GetItemCount())
+		e.app.SetFocus(blockList)
+		return nil
+	})
+	txList.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyTAB || event.Key() == tcell.KeyEnter {
+			e.app.SetFocus(notifications)
+			return nil
+		}
+		if event.Rune() == 'q' {
+			e.hideBlockFlex(blockFlex, blockInfo, txCounter, notifications, txList)
+			e.app.SetFocus(blockList)
+			return nil
+		}
+		return event
+	})
+	notifications.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyTAB || event.Rune() == 'q' {
+			e.app.SetFocus(txList)
+			return nil
+		}
+		return event
+	})
+
+	// Handle search input logic
+	searchInput.SetDoneFunc(func(key tcell.Key) {
+		e.hideBlockFlex(blockFlex, blockInfo, txCounter, notifications, txList)
+		e.refillBlockList(blockList)
+
+		input := searchInput.GetText()
+		blockCount := blockList.GetItemCount()
+
+		// Try parse as lookingBlock index
+		lookingBlock, err := strconv.Atoi(input)
+		if err == nil {
+			if lookingBlock < 0 || lookingBlock >= blockCount {
+				e.errorStatusBar(searchInput, "invalid block number")
+				return
+			}
+			from, to := blockIndexRange(lookingBlock, blockCount, 50)
+			e.cacheBlocks(from, to)
+			e.defaultStatusBar(searchInput, blockCount)
+			blockList.SetCurrentItem(-lookingBlock - 1)
+			e.app.SetFocus(blockList)
+			return
+		}
+		// Try parse as transaction hash
+		h, err := util.Uint256DecodeStringLE(input)
+		if err == nil {
+			appLog, err := e.chain.Client.GetApplicationLog(h, nil)
+			if err != nil {
+				e.errorStatusBar(searchInput, "tx hash not found")
+				return
+			}
+			chainBlock, err := e.chain.BlockByHash(appLog.Container)
+			if err != nil {
+				e.errorStatusBar(searchInput, "can't get block of specified tx")
+				return
+			}
+			from, to := blockIndexRange(int(chainBlock.Index), blockCount, 50)
+			e.cacheBlocks(from, to)
+			e.defaultStatusBar(searchInput, blockCount)
+			blockList.SetCurrentItem(-int(chainBlock.Index) - 1)
+			e.app.SetFocus(blockList)
+			return
+		}
+		e.errorStatusBar(searchInput, "invalid input, expect valid block number or tx hash")
+	})
+
+	// Handle selecting block in block list
+	blockList.SetSelectedFunc(func(i int, s1, s2 string, r rune) {
+		chainBlock, err := e.chain.Block(uint32(blockList.GetItemCount() - i - 1))
+		if err != nil {
+			panic(err)
+		}
+		e.cacheNotifications(chainBlock)
+		e.displayBlockFlex(blockFlex, blockInfo, txCounter, notifications, txList, chainBlock)
+		e.app.SetFocus(txList)
+	})
+
+	// Handle select transaction in block flex
+	txList.SetChangedFunc(func(index int, mainText, secondaryText string, shortcut rune) {
+		txCounter.SetText(fmt.Sprintf("Transaction %d of %d\n---", index+1, txList.GetItemCount()))
+		txHash, err := util.Uint256DecodeStringLE(mainText)
+		if err != nil {
+			panic(err)
+		}
+		appLog, err := e.chain.ApplicationLog(txHash)
+		if err != nil {
+			panic(err)
+		}
+
+		events := make([]state.NotificationEvent, 0)
+		for _, execution := range appLog.Executions {
+			events = append(events, execution.Events...)
+		}
+
+		var res string
+		for _, event := range events {
+			v, err := formatNotification(event)
+			if err != nil {
+				continue
+			}
+			res += v
+		}
+		notifications.SetText(res)
+		notifications.ScrollToBeginning()
+	})
+
+	// Initialize element data
+	e.fillBlockList(blockList)
+	e.defaultStatusBar(searchInput, blockList.GetItemCount())
+
+	// Start UI
+	e.app.SetRoot(appGrid, true).SetFocus(blockList)
+	return e.app.Run()
+}
+
+func (e *Explorer) fillBlockList(list *tview.List) {
+	to, err := e.chain.Client.GetBlockCount()
+	if err != nil {
+		panic(err)
+	}
+
+	// adding is much faster than inserting
+	// so we reverse the order to use that
+	for i := int64(to) - 1; i >= 0; i-- {
+		line := fmt.Sprintf("#%d", i)
+		list.AddItem(line, "", 0, nil)
+	}
+
+	// cache some blocks upfront for smoother scrolling
+	var from uint32
+	if to > 100 {
+		from = to - 100
+	}
+	e.cacheBlocks(from, to-1)
+}
+
+func (e *Explorer) refillBlockList(list *tview.List) {
+	from := uint32(list.GetItemCount())
+
+	to, err := e.chain.Client.GetBlockCount()
+	if err != nil {
+		panic(err)
+	}
+
+	for i := from; i < to; i++ {
+		line := fmt.Sprintf("#%d", i)
+		list.InsertItem(0, line, "", 0, nil)
+	}
+
+	e.cacheBlocks(from, to-1)
+}
+
+func (e *Explorer) redrawBlockList(list *tview.List, height int) {
+	currentItemIndex := list.GetCurrentItem()
+	itemCount := list.GetItemCount()
+
+	// range of blocks for detailed info in listbox
+	// to avoid whole blockchain fetching, app works
+	// with small ranges of visible blocks on the screen
+	fromIndex := currentItemIndex - height
+	if fromIndex < 0 {
+		fromIndex = 0
+	}
+
+	toIndex := currentItemIndex + height
+	if toIndex > itemCount {
+		toIndex = itemCount
+	}
+
+	e.cacheBlocks(toBlockIndex(toIndex, itemCount), toBlockIndex(fromIndex, itemCount))
+	for i := fromIndex; i < toIndex; i++ {
+		elem, _ := list.GetItemText(i)
+		// ignore blocks that has been parsed
+		if strings.Contains(elem, "tx") {
+			continue
+		}
+		blockIndex := toBlockIndex(i, itemCount)
+		chainBlock, err := e.chain.Block(blockIndex)
+		if err != nil {
+			panic(err)
+		}
+		ts := time.Unix(int64(chainBlock.Timestamp/1e3), 0)
+		richText := fmt.Sprintf("#%d [%s] txs:%d", blockIndex, ts.Format(time.RFC3339), len(chainBlock.Transactions))
+		list.SetItemText(i, richText, "")
+	}
+}
+
+func (e *Explorer) startWorkers(amount int) {
+	worker := func(ctx context.Context, ch <-chan fetchTask, out chan<- error) {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case task, ok := <-ch:
+				if !ok {
+					return
+				}
+				var err error
+				if task.txHash != nil {
+					_, err = e.chain.ApplicationLog(*task.txHash)
+				} else {
+					_, err = e.chain.Block(task.index)
+				}
+				if err != nil {
+					out <- err
+					return
+				}
+				e.wg.Done()
+			}
+		}
+	}
+
+	for i := 0; i < amount; i++ {
+		go worker(e.ctx, e.jobCh, e.errCh)
+	}
+}
+
+func (e *Explorer) cacheBlocks(from, to uint32) {
+	for i := from; i <= to; i++ {
+		e.wg.Add(1)
+		select {
+		case <-e.ctx.Done():
+			return
+		case err := <-e.errCh:
+			panic(err)
+		case e.jobCh <- fetchTask{index: i}:
+		}
+	}
+
+	wgCh := make(chan struct{})
+
+	go func() {
+		e.wg.Wait()
+		close(wgCh)
+	}()
+
+	select {
+	case <-e.ctx.Done():
+		return
+	case err := <-e.errCh:
+		panic(err)
+	case <-wgCh:
+		return
+	}
+}
+
+func (e *Explorer) cacheNotifications(block *block.Block) {
+	for _, tx := range block.Transactions {
+		h := tx.Hash()
+		e.wg.Add(1)
+		select {
+		case <-e.ctx.Done():
+			return
+		case err := <-e.errCh:
+			panic(err)
+		case e.jobCh <- fetchTask{txHash: &h}:
+		}
+	}
+
+	wgCh := make(chan struct{})
+
+	go func() {
+		e.wg.Wait()
+		close(wgCh)
+	}()
+
+	select {
+	case <-e.ctx.Done():
+		return
+	case err := <-e.errCh:
+		panic(err)
+	case <-wgCh:
+		return
+	}
+}
+
+func (e *Explorer) defaultStatusBar(input *tview.InputField, blocks int) {
+	message := fmt.Sprintf("Endpoint: %s Blocks: %d | Press q to back, / to search, r to resync.",
+		e.endpoint,
+		blocks)
+	input.SetText("").
+		SetLabelColor(tcell.ColorWhite).
+		SetLabel(message)
+}
+
+func (e *Explorer) searchStatusBar(input *tview.InputField) {
+	input.SetText("").
+		SetLabelColor(tcell.ColorGreen).
+		SetLabel("Search block or transaction: ")
+}
+
+func (e *Explorer) errorStatusBar(input *tview.InputField, message string) {
+	e.searchErrFlag = true
+	input.SetText("").
+		SetLabelColor(tcell.ColorRed).
+		SetLabel(message)
+}
+
+func (e *Explorer) displayBlockFlex(f *tview.Flex, info, counter, notif *tview.TextView, list *tview.List, b *block.Block) {
+	ln := min(len(b.Transactions), 7)
+	for _, tx := range b.Transactions {
+		list.AddItem(tx.Hash().StringLE(), "", 0, nil)
+	}
+	info.SetText(fmt.Sprintf("Exploring block #%d", b.Index))
+	counter.SetText(fmt.Sprintf("Transaction %d of %d\n---", min(1, ln), list.GetItemCount()))
+	notif.SetBorder(true).SetTitle("Notifications")
+	f.Clear()
+	f.SetBorder(true)
+	f.AddItem(info, 0, 1, false)
+	f.AddItem(counter, 2, 2, false)
+	f.AddItem(list, ln, 3, false)
+}
+
+func (e *Explorer) hideBlockFlex(flex *tview.Flex, info, counter, notif *tview.TextView, list *tview.List) {
+	info.SetText("")
+	counter.SetText("")
+	list.Clear()
+	flex.SetBorder(false)
+	notif.SetText("").SetBorder(false).SetTitle("")
+}
+
+func toBlockIndex(index, length int) uint32 {
+	return uint32(length - index - 1)
+}
+
+func blockIndexRange(index, length, delta int) (uint32, uint32) {
+	from := index - delta
+	to := index + delta
+	if from < 0 {
+		from = 0
+	}
+	if to >= length {
+		to = length - 1
+	}
+	return uint32(from), uint32(to)
+}
+
+func formatNotification(event state.NotificationEvent) (string, error) {
+	data, err := stackitem.ToJSONWithTypes(event.Item)
+	if err != nil {
+		return "", err
+	}
+	var formatted bytes.Buffer
+	err = json.Indent(&formatted, data, "", "   ")
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%s\n---\n%s\n\n", event.Name, formatted.String()), nil
+}
+
+func setFocusColorStyle(target, focus *tview.Box) {
+	focus.SetFocusFunc(func() {
+		target.SetBorderColor(tcell.ColorGreen)
+		target.SetBorderAttributes(tcell.AttrBold)
+	})
+	focus.SetBlurFunc(func() {
+		target.SetBorderColor(tcell.ColorDefault)
+		target.SetBorderAttributes(tcell.AttrNone)
+	})
+}
--- a/flags.go
+++ b/flags.go
@ -0,0 +1,176 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/native/nativenames"
+	"github.com/nspcc-dev/neo-go/pkg/rpcclient"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/urfave/cli/v2"
+)
+
+const (
+	endpointFlagKey           = "rpc-endpoint"
+	fromFlagKey               = "from"
+	toFlagKey                 = "to"
+	notificationFlagKey       = "notification"
+	cacheFlagKey              = "cache"
+	workersFlagKey            = "workers"
+	disableProgressBarFlagKey = "disable-progress-bar"
+	stutterThresholdFlagKey   = "threshold"
+)
+
+var (
+	endpointFlag = &cli.StringFlag{
+		Name:     endpointFlagKey,
+		Aliases:  []string{"r"},
+		Usage:    "N3 RPC endpoint",
+		Required: true,
+	}
+
+	fromFlag = &cli.StringFlag{
+		Name:     fromFlagKey,
+		Usage:    "starting block (can be relative value with minus prefix, e.g. 'm100')",
+		Required: true,
+		Value:    "",
+	}
+
+	toFlag = &cli.StringFlag{
+		Name:     toFlagKey,
+		Usage:    "ending block (can be relative value with plus prefix, e.g. 'p100' or omitted for latest block in chain)",
+		Required: false,
+		Value:    "",
+	}
+
+	notificationFlag = &cli.StringSliceFlag{
+		Name:     notificationFlagKey,
+		Aliases:  []string{"n"},
+		Usage:    "'notification:contract' pair (specify LE script hash, '*' for any contract or 'gas' and 'neo' strings)",
+		Required: true,
+		Value:    nil,
+	}
+
+	cacheFlag = &cli.StringFlag{
+		Name:    cacheFlagKey,
+		Aliases: []string{"c"},
+		Usage:   "path to the blockchain cache (default: $HOME/.config/monza)",
+		Value:   "",
+	}
+
+	workersFlag = &cli.Uint64Flag{
+		Name:    workersFlagKey,
+		Aliases: []string{"w"},
+		Usage:   "amount of workers for parallel block fetch",
+		Value:   3,
+	}
+
+	disableProgressBarFlag = &cli.BoolFlag{
+		Name:  disableProgressBarFlagKey,
+		Usage: "disable progress bar output",
+	}
+
+	stutterThresholdFlag = &cli.DurationFlag{
+		Name:    stutterThresholdFlagKey,
+		Aliases: []string{"t"},
+		Usage:   "duration limit between block timestamps",
+		Value:   20 * time.Second,
+	}
+)
+
+func parseNotifications(notifications []string, cli *rpcclient.Client) (map[string]*util.Uint160, error) {
+	res := make(map[string]*util.Uint160, len(notifications))
+
+	for _, n := range notifications {
+		pair := strings.Split(n, ":")
+		if len(pair) != 2 {
+			return nil, fmt.Errorf("invalid notification %s", n)
+		}
+
+		name := pair[0]
+
+		switch contractName := strings.ToLower(pair[1]); contractName {
+		case "*":
+			res[name] = nil
+		case "gas":
+			state, err := cli.GetContractStateByAddressOrName(nativenames.Gas)
+			if err != nil {
+				return nil, fmt.Errorf("invalid contract name %s", contractName)
+			}
+			res[name] = &state.Hash
+		case "neo":
+			state, err := cli.GetContractStateByAddressOrName(nativenames.Neo)
+			if err != nil {
+				return nil, fmt.Errorf("invalid contract name %s", contractName)
+			}
+			res[name] = &state.Hash
+		default:
+			u160, err := util.Uint160DecodeStringLE(contractName)
+			if err != nil {
+				return nil, fmt.Errorf("invalid contract name %s", contractName)
+			}
+			res[name] = &u160
+		}
+	}
+
+	return res, nil
+}
+
+func parseInterval(fromStr, toStr string, cli *rpcclient.Client) (from, to uint32, err error) {
+	switch { // parse from value and return result if it is relative
+	case len(fromStr) == 0:
+		return 0, 0, ErrInvalidInterval(fromStr, toStr)
+	case fromStr[0] == 'm':
+		v, err := strconv.Atoi(fromStr[1:])
+		if err != nil || v <= 0 {
+			return 0, 0, ErrInvalidInterval(fromStr, toStr)
+		}
+		h, err := cli.GetBlockCount()
+		if err != nil {
+			return 0, 0, fmt.Errorf("latest block index unavailable: %w", err)
+		}
+		if uint32(v) >= h {
+			return 0, 0, fmt.Errorf("latest block is less than from value, from:%s, to:%d", fromStr, h)
+		}
+		return h - uint32(v), h, nil
+	default:
+		v, err := strconv.Atoi(fromStr)
+		if err != nil || v <= 0 {
+			return 0, 0, ErrInvalidInterval(fromStr, toStr)
+		}
+		from = uint32(v)
+	}
+
+	switch { // parse to value
+	case len(toStr) == 0:
+		h, err := cli.GetBlockCount()
+		if err != nil {
+			return 0, 0, fmt.Errorf("latest block index unavailable: %w", err)
+		}
+		if h <= from {
+			return 0, 0, fmt.Errorf("latest block is less than from value, from:%d, to:%d", from, h)
+		}
+		return from, h, nil
+	case toStr[0] == 'p':
+		v, err := strconv.Atoi(toStr[1:])
+		if err != nil || v <= 0 {
+			return 0, 0, ErrInvalidInterval(fromStr, toStr)
+		}
+		return from, from + uint32(v), nil
+	default:
+		v, err := strconv.Atoi(toStr)
+		if err != nil || v <= 0 {
+			return 0, 0, ErrInvalidInterval(fromStr, toStr)
+		}
+		if uint32(v) <= from {
+			return 0, 0, ErrInvalidInterval(fromStr, toStr)
+		}
+		return from, uint32(v), nil
+	}
+}
+
+func ErrInvalidInterval(from, to string) error {
+	return fmt.Errorf("invalid block interval from:%s to:%s", from, to)
+}
--- a/go.mod
+++ b/go.mod
@ -0,0 +1,39 @@
+module git.frostfs.info/TrueCloudLab/monza
+
+go 1.21
+
+require (
+	github.com/gdamore/tcell/v2 v2.5.1
+	github.com/nspcc-dev/neo-go v0.102.0
+	github.com/rivo/tview v0.0.0-20220307222120-9994674d60a8
+	github.com/schollz/progressbar/v3 v3.8.3
+	github.com/urfave/cli/v2 v2.3.0
+	go.etcd.io/bbolt v1.3.7
+)
+
+require (
+	github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d // indirect
+	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.0.1 // indirect
+	github.com/gdamore/encoding v1.0.0 // indirect
+	github.com/google/uuid v1.3.0 // indirect
+	github.com/gorilla/websocket v1.4.2 // indirect
+	github.com/hashicorp/golang-lru v0.6.0 // indirect
+	github.com/kr/pretty v0.1.0 // indirect
+	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
+	github.com/mattn/go-runewidth v0.0.13 // indirect
+	github.com/mitchellh/colorstring v0.0.0-20190213212951-d06e56a500db // indirect
+	github.com/mr-tron/base58 v1.2.0 // indirect
+	github.com/nspcc-dev/go-ordered-json v0.0.0-20220111165707-25110be27d22 // indirect
+	github.com/nspcc-dev/rfc6979 v0.2.0 // indirect
+	github.com/rivo/uniseg v0.2.0 // indirect
+	github.com/russross/blackfriday/v2 v2.0.1 // indirect
+	github.com/shurcooL/sanitized_anchor_name v1.0.0 // indirect
+	go.uber.org/atomic v1.10.0 // indirect
+	golang.org/x/crypto v0.4.0 // indirect
+	golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4 // indirect
+	golang.org/x/sys v0.8.0 // indirect
+	golang.org/x/term v0.5.0 // indirect
+	golang.org/x/text v0.7.0 // indirect
+	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
--- a/go.sum
+++ b/go.sum
@ -0,0 +1,103 @@
+github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d h1:U+s90UTSYgptZMwQh2aRr3LuazLJIa+Pg3Kc1ylSYVY=
+github.com/cpuguy83/go-md2man/v2 v2.0.0-20190314233015-f79a8a8ca69d/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/decred/dcrd/crypto/blake256 v1.0.0/go.mod h1:sQl2p6Y26YV+ZOcSTP6thNdn47hh8kt6rqSlvmrXFAc=
+github.com/decred/dcrd/dcrec/secp256k1/v4 v4.0.1 h1:YLtO71vCjJRCBcrPMtQ9nqBsqpA1m5sE92cU+pd5Mcc=
+github.com/decred/dcrd/dcrec/secp256k1/v4 v4.0.1/go.mod h1:hyedUtir6IdtD/7lIxGeCxkaw7y45JueMRL4DIyJDKs=
+github.com/gdamore/encoding v1.0.0 h1:+7OoQ1Bc6eTm5niUzBa0Ctsh6JbMW6Ra+YNuAtDBdko=
+github.com/gdamore/encoding v1.0.0/go.mod h1:alR0ol34c49FCSBLjhosxzcPHQbf2trDkoo5dl+VrEg=
+github.com/gdamore/tcell/v2 v2.4.1-0.20210905002822-f057f0a857a1/go.mod h1:Az6Jt+M5idSED2YPGtwnfJV0kXohgdCBPmHGSYc1r04=
+github.com/gdamore/tcell/v2 v2.5.1 h1:zc3LPdpK184lBW7syF2a5C6MV827KmErk9jGVnmsl/I=
+github.com/gdamore/tcell/v2 v2.5.1/go.mod h1:wSkrPaXoiIWZqW/g7Px4xc79di6FTcpB8tvaKJ6uGBo=
+github.com/golang/snappy v0.0.1 h1:Qgr9rKW7uDUkrbSmQeiDsGa8SjGyCOGtuasMWwvp2P4=
+github.com/golang/snappy v0.0.1/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
+github.com/google/uuid v1.3.0 h1:t6JiXgmwXMjEs8VusXIJk2BXHsn+wx8BZdTaoZ5fu7I=
+github.com/google/uuid v1.3.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/gorilla/websocket v1.4.2 h1:+/TMaTYc4QFitKJxsQ7Yye35DkWvkdLcvGKqM+x0Ufc=
+github.com/gorilla/websocket v1.4.2/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
+github.com/hashicorp/golang-lru v0.6.0 h1:uL2shRDx7RTrOrTCUZEGP/wJUFiUI8QT6E7z5o8jga4=
+github.com/hashicorp/golang-lru v0.6.0/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
+github.com/k0kubun/go-ansi v0.0.0-20180517002512-3bf9e2903213/go.mod h1:vNUNkEQ1e29fT/6vq2aBdFsgNPmy8qMdSay1npru+Sw=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
+github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
+github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
+github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
+github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69Aj6K7nkY=
+github.com/lucasb-eyer/go-colorful v1.2.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
+github.com/mattn/go-isatty v0.0.14/go.mod h1:7GGIvUiUoEMVVmxf/4nioHXj79iQHKdU27kJ6hsGG94=
+github.com/mattn/go-runewidth v0.0.13 h1:lTGmDsbAYt5DmK6OnoV7EuIF1wEIFAcxld6ypU4OSgU=
+github.com/mattn/go-runewidth v0.0.13/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
+github.com/mitchellh/colorstring v0.0.0-20190213212951-d06e56a500db h1:62I3jR2EmQ4l5rM/4FEfDWcRD+abF5XlKShorW5LRoQ=
+github.com/mitchellh/colorstring v0.0.0-20190213212951-d06e56a500db/go.mod h1:l0dey0ia/Uv7NcFFVbCLtqEBQbrT4OCwCSKTEv6enCw=
+github.com/mr-tron/base58 v1.2.0 h1:T/HDJBh4ZCPbU39/+c3rRvE0uKBQlU27+QI8LJ4t64o=
+github.com/mr-tron/base58 v1.2.0/go.mod h1:BinMc/sQntlIE1frQmRFPUoPA1Zkr8VRgBdjWI2mNwc=
+github.com/nspcc-dev/go-ordered-json v0.0.0-20220111165707-25110be27d22 h1:n4ZaFCKt1pQJd7PXoMJabZWK9ejjbLOVrkl/lOUmshg=
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--- a/internal/chain/chain.go
+++ b/internal/chain/chain.go
@ -0,0 +1,239 @@
+package chain
+
+import (
+	"context"
+	"encoding/binary"
+	"fmt"
+	"path"
+	"strconv"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/block"
+	"github.com/nspcc-dev/neo-go/pkg/core/state"
+	"github.com/nspcc-dev/neo-go/pkg/io"
+	"github.com/nspcc-dev/neo-go/pkg/neorpc/result"
+	"github.com/nspcc-dev/neo-go/pkg/rpcclient"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"go.etcd.io/bbolt"
+)
+
+type Chain struct {
+	db        *bbolt.DB
+	stateRoot bool
+	Client    *rpcclient.Client
+}
+
+var (
+	blocksBucket = []byte("blocks")
+	logsBucket   = []byte("logs")
+)
+
+func Open(ctx context.Context, dir, endpoint string) (*Chain, error) {
+	cli, err := rpcclient.New(ctx, endpoint, rpcclient.Options{})
+	if err != nil {
+		return nil, fmt.Errorf("rpc connection: %w", err)
+	}
+
+	err = cli.Init()
+	if err != nil {
+		return nil, fmt.Errorf("rpc client initialization: %w", err)
+	}
+
+	v, err := cli.GetVersion()
+	if err != nil {
+		return nil, fmt.Errorf("rpc get version: %w", err)
+	}
+
+	dbPath := path.Join(dir, strconv.Itoa(int(v.Protocol.Network))+".db")
+
+	db, err := bbolt.Open(dbPath, 0600, nil)
+	if err != nil {
+		return nil, fmt.Errorf("database [%s] init: %w", dbPath, err)
+	}
+
+	return &Chain{db, v.Protocol.StateRootInHeader, cli}, nil
+}
+
+func (d *Chain) Block(i uint32) (res *block.Block, err error) {
+	cached, err := d.block(i)
+	if err != nil {
+		return nil, err
+	}
+
+	if cached != nil {
+		return cached, nil
+	}
+
+	metaBlock, err := d.Client.GetBlockByIndexVerbose(i)
+	if err != nil {
+		return nil, fmt.Errorf("block %d fetch: %w", i, err)
+	}
+
+	return &metaBlock.Block, d.addBlock(&metaBlock.Block)
+}
+
+func (d *Chain) BlockByHash(h util.Uint256) (res *block.Block, err error) {
+	rev := h.Reverse()
+	metaBlock, err := d.Client.GetBlockByHashVerbose(rev)
+	if err != nil {
+		return nil, fmt.Errorf("block %s fetch: %w", h.StringLE(), err)
+	}
+
+	return &metaBlock.Block, d.addBlock(&metaBlock.Block)
+}
+
+func (d *Chain) block(i uint32) (res *block.Block, err error) {
+	err = d.db.View(func(tx *bbolt.Tx) error {
+		key := make([]byte, 4)
+		binary.LittleEndian.PutUint32(key, i)
+
+		bkt := tx.Bucket(blocksBucket)
+		if bkt == nil {
+			return nil
+		}
+
+		data := bkt.Get(key)
+		if len(data) == 0 {
+			return nil
+		}
+
+		res = block.New(d.stateRoot)
+		r := io.NewBinReaderFromBuf(data)
+		res.DecodeBinary(r)
+
+		return r.Err
+	})
+	if err != nil {
+		return nil, fmt.Errorf("cannot read block %d from cache: %w", i, err)
+	}
+
+	return res, nil
+}
+
+func (d *Chain) addBlock(block *block.Block) error {
+	err := d.db.Batch(func(tx *bbolt.Tx) error {
+		key := make([]byte, 4)
+		binary.LittleEndian.PutUint32(key, block.Index)
+
+		w := io.NewBufBinWriter()
+		block.EncodeBinary(w.BinWriter)
+		if w.Err != nil {
+			return w.Err
+		}
+
+		bkt, err := tx.CreateBucketIfNotExists(blocksBucket)
+		if err != nil {
+			return err
+		}
+
+		return bkt.Put(key, w.Bytes())
+	})
+	if err != nil {
+		return fmt.Errorf("cannot add block %d to cache: %w", block.Index, err)
+	}
+
+	return nil
+}
+
+func (d *Chain) ApplicationLog(txHash util.Uint256) (*result.ApplicationLog, error) {
+	cached, err := d.applicationLog(txHash)
+	if err != nil {
+		return nil, err
+	}
+
+	if cached != nil {
+		return cached, nil
+	}
+
+	appLog, err := d.Client.GetApplicationLog(txHash, nil)
+	if err != nil {
+		return nil, fmt.Errorf("app log of tx %s fetch: %w", txHash.StringLE(), err)
+	}
+
+	return appLog, d.addApplicationLog(txHash, appLog)
+}
+
+func (d *Chain) applicationLog(txHash util.Uint256) (res *result.ApplicationLog, err error) {
+	err = d.db.View(func(tx *bbolt.Tx) error {
+		bkt := tx.Bucket(logsBucket)
+		if bkt == nil {
+			return nil
+		}
+
+		data := bkt.Get(txHash.BytesLE())
+		if len(data) == 0 {
+			return nil
+		}
+
+		res = new(result.ApplicationLog)
+		return res.UnmarshalJSON(bkt.Get(txHash.BytesLE()))
+	})
+	if err != nil {
+		return nil, fmt.Errorf("cannot read tx %s from cache: %w", txHash.StringLE(), err)
+	}
+
+	return res, nil
+}
+
+func (d *Chain) addApplicationLog(txHash util.Uint256, appLog *result.ApplicationLog) error {
+	err := d.db.Batch(func(tx *bbolt.Tx) error {
+		val, err := appLog.MarshalJSON()
+		if err != nil {
+			return err
+		}
+
+		bkt, err := tx.CreateBucketIfNotExists(logsBucket)
+		if err != nil {
+			return err
+		}
+
+		return bkt.Put(txHash.BytesLE(), val)
+	})
+	if err != nil {
+		return fmt.Errorf("cannot add tx %s to cache: %w", txHash.StringLE(), err)
+	}
+
+	return nil
+}
+
+func (d *Chain) Notifications(txHash util.Uint256) ([]state.NotificationEvent, error) {
+	appLog, err := d.ApplicationLog(txHash)
+	if err != nil {
+		return nil, err
+	}
+
+	res := make([]state.NotificationEvent, 0)
+	for _, execution := range appLog.Executions {
+		res = append(res, execution.Events...)
+	}
+
+	return res, nil
+}
+
+func (d *Chain) AllNotifications(b *block.Block) ([]state.NotificationEvent, error) {
+	res := make([]state.NotificationEvent, 0)
+
+	appLog, err := d.ApplicationLog(b.Hash())
+	if err != nil {
+		return nil, err
+	}
+
+	for _, execution := range appLog.Executions {
+		res = append(res, execution.Events...)
+	}
+
+	for _, tx := range b.Transactions {
+		appLog, err = d.ApplicationLog(tx.Hash())
+		if err != nil {
+			return nil, err
+		}
+		for _, execution := range appLog.Executions {
+			res = append(res, execution.Events...)
+		}
+	}
+
+	return res, nil
+}
+
+func (d *Chain) Close() {
+	_ = d.db.Close()
+}
--- a/main.go
+++ b/main.go
@ -0,0 +1,273 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"os/signal"
+	"path"
+	"sync"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/monza/internal/chain"
+	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/schollz/progressbar/v3"
+	"github.com/urfave/cli/v2"
+)
+
+func main() {
+	app := &cli.App{
+		Name:  "monza",
+		Usage: "monitor notification events in N3 compatible chains",
+		Commands: []*cli.Command{
+			{
+				Name:      "run",
+				Usage:     "look up over subset of blocks to find notifications",
+				UsageText: "monza run -r [endpoint] --from 101000 --to p1000 -n \"Transfer:gas\" -n \"newEpoch:*\"",
+				Action:    monza,
+				Flags: []cli.Flag{
+					endpointFlag,
+					fromFlag,
+					toFlag,
+					notificationFlag,
+					cacheFlag,
+					workersFlag,
+					disableProgressBarFlag,
+				},
+			},
+			{
+				Name:      "stutter",
+				Usage:     "find stuttered blocks in subset",
+				UsageText: "monza stutter -r [endpoint] --from 101000 --to p1000 --threshold 20s",
+				Action:    stutter,
+				Flags: []cli.Flag{
+					endpointFlag,
+					fromFlag,
+					toFlag,
+					stutterThresholdFlag,
+					cacheFlag,
+					workersFlag,
+					disableProgressBarFlag,
+				},
+			},
+			{
+				Name:      "explore",
+				Usage:     "explore stuttered blocks in subset",
+				UsageText: "monza explore -r [endpoint]",
+				Action:    explorer,
+				Flags: []cli.Flag{
+					endpointFlag,
+					cacheFlag,
+				},
+			},
+		},
+	}
+
+	err := app.Run(os.Args)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+}
+
+func monza(c *cli.Context) (err error) {
+	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
+
+	// parse blockchain info
+	cacheDir := c.String(cacheFlagKey)
+	if len(cacheDir) == 0 {
+		cacheDir, err = defaultConfigDir()
+		if err != nil {
+			return err
+		}
+	}
+
+	blockchain, err := chain.Open(ctx, cacheDir, c.String(endpointFlagKey))
+	if err != nil {
+		return fmt.Errorf("cannot initialize remote blockchain client: %w", err)
+	}
+	defer func() {
+		blockchain.Close()
+		cancel()
+	}()
+
+	// parse block indices
+	from, to, err := parseInterval(c.String(fromFlagKey), c.String(toFlagKey), blockchain.Client)
+	if err != nil {
+		return err
+	}
+
+	// parse notifications
+	notifications, err := parseNotifications(c.StringSlice(notificationFlagKey), blockchain.Client)
+	if err != nil {
+		return err
+	}
+
+	// start monza
+	return run(ctx, &params{
+		from:          from,
+		to:            to,
+		blockchain:    blockchain,
+		notifications: notifications,
+		workers:       int(c.Uint64(workersFlagKey)),
+		disableBar:    c.Bool(disableProgressBarFlagKey),
+	})
+}
+
+type params struct {
+	from, to      uint32
+	blockchain    *chain.Chain
+	notifications map[string]*util.Uint160
+	workers       int
+	disableBar    bool
+}
+
+func run(ctx context.Context, p *params) error {
+	err := cacheBlocks(ctx, p)
+	if err != nil {
+		return err
+	}
+
+	for i := p.from; i < p.to; i++ {
+		b, err := p.blockchain.Block(i)
+		if err != nil {
+			return fmt.Errorf("cannot fetch block %d: %w", i, err)
+		}
+
+		notifications, err := p.blockchain.AllNotifications(b)
+		if err != nil {
+			return fmt.Errorf("cannot fetch notifications from block %d: %w", i, err)
+		}
+
+		for _, ev := range notifications {
+			contract, ok := p.notifications[ev.Name]
+			if !ok {
+				continue
+			}
+
+			if contract != nil && !contract.Equals(ev.ScriptHash) {
+				continue
+			}
+
+			switch ev.Name {
+			case "Transfer":
+				PrintTransfer(b, ev)
+			case "NewEpoch":
+				PrintNewEpoch(b, ev)
+			case "AddPeerSuccess":
+				PrintAddPeerSuccess(b, ev)
+			case "UpdateState":
+				PrintUpdateState(b, ev)
+			default:
+				PrintEvent(b, ev, "")
+			}
+		}
+	}
+
+	return nil
+}
+
+func cacheBlocks(ctx context.Context, p *params) error {
+	if p.workers <= 0 {
+		return fmt.Errorf("invalid amount of workers %d", p.workers)
+	}
+
+	var bar *progressbar.ProgressBar
+	if !p.disableBar {
+		bar = progressbar.NewOptions(int(p.to-p.from),
+			progressbar.OptionSetDescription("syncing"),
+			progressbar.OptionSetWriter(os.Stderr),
+			progressbar.OptionSetWidth(10),
+			progressbar.OptionThrottle(65*time.Millisecond),
+			progressbar.OptionShowCount(),
+			progressbar.OptionShowIts(),
+			progressbar.OptionSetItsString("blocks"),
+			progressbar.OptionOnCompletion(func() {
+				_, _ = fmt.Fprint(os.Stderr, "\n")
+			}),
+			progressbar.OptionSpinnerType(14),
+			progressbar.OptionSetWidth(50),
+			progressbar.OptionSetTheme(progressbar.Theme{
+				Saucer:        "#",
+				SaucerHead:    "#",
+				SaucerPadding: " ",
+				BarStart:      "[",
+				BarEnd:        "]",
+			}),
+		)
+	}
+
+	jobCh := make(chan uint32)
+	errCh := make(chan error)
+	wgCh := make(chan struct{})
+
+	wg := new(sync.WaitGroup)
+
+	for i := 0; i < p.workers; i++ {
+		go func(ctx context.Context, ch <-chan uint32, out chan<- error) {
+			for {
+				select {
+				case <-ctx.Done():
+					return
+				case block, ok := <-ch:
+					wg.Add(1)
+					if !ok {
+						return
+					}
+					b, err := p.blockchain.Block(block)
+					if err != nil {
+						out <- err
+						return
+					}
+					_, err = p.blockchain.AllNotifications(b)
+					if err != nil {
+						out <- err
+						return
+					}
+					if bar != nil {
+						_ = bar.Add(1)
+					}
+					wg.Done()
+				}
+			}
+		}(ctx, jobCh, errCh)
+	}
+
+	for i := p.from; i < p.to; i++ {
+		select {
+		case <-ctx.Done():
+			return errors.New("interrupted")
+		case err := <-errCh:
+			return err
+		case jobCh <- i:
+		}
+	}
+
+	go func() {
+		wg.Wait()
+		close(wgCh)
+	}()
+
+	select {
+	case <-ctx.Done():
+		return errors.New("interrupted")
+	case err := <-errCh:
+		return err
+	case <-wgCh:
+		return nil
+	}
+}
+
+func defaultConfigDir() (string, error) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		log.Fatalf("cannot determine home dir for default config path: %s", err)
+	}
+
+	p := path.Join(home, ".config")
+	p = path.Join(p, "monza")
+
+	return p, os.MkdirAll(p, os.ModePerm)
+}
--- a/stutter.go
+++ b/stutter.go
@ -0,0 +1,98 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"os/signal"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/monza/internal/chain"
+	"github.com/nspcc-dev/neo-go/pkg/core/block"
+	"github.com/urfave/cli/v2"
+)
+
+func stutter(c *cli.Context) (err error) {
+	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt)
+
+	// parse blockchain info
+	cacheDir := c.String(cacheFlagKey)
+	if len(cacheDir) == 0 {
+		cacheDir, err = defaultConfigDir()
+		if err != nil {
+			return err
+		}
+	}
+
+	blockchain, err := chain.Open(ctx, cacheDir, c.String(endpointFlagKey))
+	if err != nil {
+		return fmt.Errorf("cannot initialize remote blockchain client: %w", err)
+	}
+	defer func() {
+		blockchain.Close()
+		cancel()
+	}()
+
+	// parse block indices
+	from, to, err := parseInterval(c.String(fromFlagKey), c.String(toFlagKey), blockchain.Client)
+	if err != nil {
+		return err
+	}
+
+	threshold := c.Duration(stutterThresholdFlagKey)
+
+	// need at least two blocks
+	if to-from < 2 {
+		return errors.New("range must contain at least two blocks")
+	}
+
+	// fetch blocks
+	err = cacheBlocks(ctx, &params{
+		from:       from,
+		to:         to,
+		blockchain: blockchain,
+		workers:    int(c.Uint64(workersFlagKey)),
+		disableBar: c.Bool(disableProgressBarFlagKey),
+	})
+	if err != nil {
+		return err
+	}
+
+	// process blocks one by one
+	var (
+		prev, curr       *block.Block
+		prevTS, currTS   time.Time
+		lastStutterBlock uint32
+	)
+
+	for i := from; i < to; i++ {
+		b, err := blockchain.Block(i)
+		if err != nil {
+			return fmt.Errorf("cannot fetch block %d: %w", i, err)
+		}
+
+		prev, prevTS = curr, currTS
+		curr = b
+		currTS = time.Unix(int64(b.Timestamp/1e3), 0)
+		if prev == nil { // first block case
+			continue
+		}
+
+		blockDelta := currTS.Sub(prevTS)
+		if blockDelta <= threshold {
+			continue
+		}
+
+		skippedBlocks := prev.Index - lastStutterBlock
+		if lastStutterBlock > 0 && skippedBlocks > 1 {
+			fmt.Printf("-- skipped %d blocks --\n", skippedBlocks-1)
+		}
+
+		PrintBlock(prev, "")
+		PrintBlock(curr, fmt.Sprintf("<- stutter for %s", blockDelta))
+		lastStutterBlock = curr.Index
+	}
+
+	return nil
+}