feat: add valset injection through r/sys/validators (gnolang#2229)

## Description

This PR introduces an `EndBlocker` system for applying validator set
changes protocol level, based on on-chain events (from the `/r/sys/vals`
realm).

I've utilized an already existing system:
- validator set changes still stay managed protocol-level in
`ConsensusState` -> refactoring this is not a small feat, and saying
this is an understatement
- event switch utilized by the node that dumps new block / new
transaction events

The way this flow essentially works is the following:
1. An on-chain event happens that indicates a change in the validator
set (added / removed)
2. These events (ABCI events) are parsed as soon as they end up in a
transaction result (are pushed to the event system of the SDK). The
top-level ABCI event type needs to be`EventTx` (indicating it's a new TX
result). The underlying tx GnoVM events (`GnoEvent`) need to be from the
`/r/sys/validators` Realm, and be a validator addition / removal (type
defined in the Realm)
4. Events are parsed down into `abci.ValidatorUpdates`, which are
returned as a result of `EndBlocker`
5. This `EndBlocker` result is later read by the `ConsensusState`, and
the validator set changes are applied for the upcoming block in a series
of existing callbacks. This also keeps proposer priority logic in check.

Blocked by gnolang#2130 
Closes gnolang#1823 

```mermaid
---
title: on-chain validator set injection flow
---
flowchart TD
    subgraph app.go
        nesvw(["Node event switch"]) -. pass all block events .-> collector(["event collector"])
        collector -. subscribes to .-> nesvw

        collector -. filter new events .-> collector

        EB["func EndBlocker(...)"] == 1: fetch relevant events ==> collector
        collector -. 2: return events, if any .-> EB
    end

    subgraph gno.land/r/sys/validators.gno
        GC["func GetChanges(from int64) []validators.Validator"]

        addVal["func addValidator(...)"]
        removeVal["func removeValidator(...)"]
        PE["func NewPropExecutor(changesFn) proposal.Executor"]

        PE -. calls internally .-> addVal
        PE -. calls internally .-> removeVal

        addVal -. std emits ValidatorAdded .-> nesvw
        removeVal -. std emits ValidatorRemoved .-> nesvw
    end

    subgraph gno.land/r/gov/dao.gno
        EP["func ExecuteProposal(...)"]
        

        EP == executes on-chain ==>PE
    end

    subgraph user_proposal.gno
        main("func main() {...}")
        PR["govdao.Propose(...)"]

        main -. contains .-> CB
        main -. contains .-> PR

        CB("changesFn func() []validators.Validator {...}")

        CB== creates ==>PE
        CB("changesFn func() []validators.Validator {...}")

        PE == passed into ==> PR
    end

    A[/fa:fa-user User\] == gnokey maketx run ==> main
    GDV[/fa:fa-people-group GOVDAO members\] == manually call ==> EP

    EB == 3: execute VM call to get changes since last block ==> GC
    GC -. 4: return changes .-> EB

    EB -. 5: return response with valset changes .-> EBR([abci.ResponseEndBlock]) -- applied in --> AB
    subgraph Cosmos SDK
        AB["func ApplyBlock(...) {...}"]
    end
```

Related: gnolang#1945

<details><summary>Contributors' checklist...</summary>

- [ ] Added new tests, or not needed, or not feasible
- [ ] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [ ] Updated the official documentation or not needed
- [ ] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [ ] Added references to related issues and PRs
- [ ] Provided any useful hints for running manual tests
- [ ] Added new benchmarks to [generated
graphs](https://gnoland.github.io/benchmarks), if any. More info
[here](https://github.com/gnolang/gno/blob/master/.benchmarks/README.md).
</details>

---------

Co-authored-by: Manfred Touron <[email protected]>

contribs/gnodev/pkg/dev/node.go

@@ -527,7 +527,7 @@ func buildNode(logger *slog.Logger, emitter emitter.Emitter, cfg *gnoland.InMemo
 func newNodeConfig(tmc *tmcfg.Config, chainid string, appstate gnoland.GnoGenesisState) *gnoland.InMemoryNodeConfig {
 	// Create Mocked Identity
 	pv := gnoland.NewMockedPrivValidator()
-	genesis := gnoland.NewDefaultGenesisConfig(pv.GetPubKey(), chainid)
+	genesis := gnoland.NewDefaultGenesisConfig(chainid)
 	genesis.AppState = appstate
 
 	// Add self as validator

examples/gno.land/r/gov/dao/prop1_filetest.gno

@@ -91,7 +91,7 @@ func main() {
 // Status: succeeded
 // Author: g1wymu47drhr0kuq2098m792lytgtj2nyx77yrsm
 // --
-// Valset changes to apply:
-// - g12345678 (10)
-// - g000000000 (10)
-// - g000000000 (0)
+// Valset changes:
+// - #123: g12345678 (10)
+// - #123: g000000000 (10)
+// - #123: g000000000 (0)

examples/gno.land/r/sys/validators/gno.mod

@@ -1,6 +1,11 @@
 module gno.land/r/sys/validators
 
 require (
+	gno.land/p/demo/avl v0.0.0-latest
+	gno.land/p/demo/seqid v0.0.0-latest
+	gno.land/p/demo/testutils v0.0.0-latest
+	gno.land/p/demo/uassert v0.0.0-latest
+	gno.land/p/demo/ufmt v0.0.0-latest
 	gno.land/p/gov/proposal v0.0.0-latest
 	gno.land/p/nt/poa v0.0.0-latest
 	gno.land/p/sys/validators v0.0.0-latest

examples/gno.land/r/sys/validators/gnosdk.gno

@@ -1,16 +1,24 @@
 package validators
 
-import "gno.land/p/sys/validators"
+import (
+	"gno.land/p/sys/validators"
+)
 
-// getChanges returns the validator changes stored on the realm.
-// This function is unexported and intended to be called by gno.land through the GnoSDK
-func getChanges() []validators.Validator {
-	// Construct the changes
-	valsetChanges := make([]validators.Validator, len(changes))
-	copy(valsetChanges, changes)
+// GetChanges returns the validator changes stored on the realm, since the given block number.
+// This function is intended to be called by gno.land through the GnoSDK
+func GetChanges(from int64) []validators.Validator {
+	valsetChanges := make([]validators.Validator, 0)
 
-	// Reset the changes set
-	changes = changes[:0]
+	// Gather the changes from the specified block
+	changes.Iterate(getBlockID(from), "", func(_ string, value interface{}) bool {
+		chs := value.([]change)
+
+		for _, ch := range chs {
+			valsetChanges = append(valsetChanges, ch.validator)
+		}
+
+		return false
+	})
 
 	return valsetChanges
 }

examples/gno.land/r/sys/validators/init.gno

@@ -1,14 +1,14 @@
 package validators
 
 import (
+	"gno.land/p/demo/avl"
 	"gno.land/p/nt/poa"
-	"gno.land/p/sys/validators"
 )
 
 func init() {
 	// The default valset protocol is PoA
 	vp = poa.NewPoA()
 
 	// No changes to apply initially
-	changes = make([]validators.Validator, 0)
+	changes = avl.NewTree()
 }

examples/gno.land/r/sys/validators/validators.gno

@@ -2,16 +2,24 @@ package validators
 
 import (
 	"std"
-	"strconv"
 
+	"gno.land/p/demo/avl"
+	"gno.land/p/demo/seqid"
+	"gno.land/p/demo/ufmt"
 	"gno.land/p/sys/validators"
 )
 
 var (
 	vp      validators.ValsetProtocol // p is the underlying validator set protocol
-	changes []validators.Validator    // changes are the set changes that happened between scrapes
+	changes *avl.Tree                 // changes holds any valset changes; seqid(block number) -> []change
 )
 
+// change represents a single valset change, tied to a specific block number
+type change struct {
+	blockNum  int64                // the block number associated with the valset change
+	validator validators.Validator // the validator update
+}
+
 // addValidator adds a new validator to the validator set.
 // If the validator is already present, the method errors out
 func addValidator(validator validators.Validator) {
@@ -21,7 +29,12 @@ func addValidator(validator validators.Validator) {
 	}
 
 	// Validator added, note the change
-	changes = append(changes, val)
+	ch := change{
+		blockNum:  std.GetHeight(),
+		validator: val,
+	}
+
+	saveChange(ch)
 
 	// Emit the validator set change
 	std.Emit(validators.ValidatorAddedEvent)
@@ -36,25 +49,69 @@ func removeValidator(address std.Address) {
 	}
 
 	// Validator removed, note the change
-	changes = append(changes, validators.Validator{
-		Address:     val.Address,
-		PubKey:      val.PubKey,
-		VotingPower: 0, // nullified the voting power indicates removal
-	})
+	ch := change{
+		blockNum: std.GetHeight(),
+		validator: validators.Validator{
+			Address:     val.Address,
+			PubKey:      val.PubKey,
+			VotingPower: 0, // nullified the voting power indicates removal
+		},
+	}
+
+	saveChange(ch)
 
 	// Emit the validator set change
 	std.Emit(validators.ValidatorRemovedEvent)
 }
 
+// saveChange saves the valset change
+func saveChange(ch change) {
+	id := getBlockID(ch.blockNum)
+
+	setRaw, exists := changes.Get(id)
+	if !exists {
+		changes.Set(id, []change{ch})
+
+		return
+	}
+
+	// Save the change
+	set := setRaw.([]change)
+	set = append(set, ch)
+
+	changes.Set(id, set)
+}
+
+// getBlockID converts the block number to a sequential ID
+func getBlockID(blockNum int64) string {
+	return seqid.ID(uint64(blockNum)).String()
+}
+
 func Render(_ string) string {
-	if len(changes) == 0 {
+	var (
+		size       = changes.Size()
+		maxDisplay = 10
+	)
+
+	if size == 0 {
 		return "No valset changes to apply."
 	}
 
-	output := "Valset changes to apply:\n"
-	for _, change := range changes {
-		output += "- " + string(change.Address) + " (" + strconv.FormatUint(change.VotingPower, 10) + ")\n"
-	}
+	output := "Valset changes:\n"
+	changes.ReverseIterateByOffset(size-maxDisplay, maxDisplay, func(_ string, value interface{}) bool {
+		chs := value.([]change)
+
+		for _, ch := range chs {
+			output += ufmt.Sprintf(
+				"- #%d: %s (%d)\n",
+				ch.blockNum,
+				ch.validator.Address.String(),
+				ch.validator.VotingPower,
+			)
+		}
+
+		return false
+	})
 
 	return output
 }

examples/gno.land/r/sys/validators/validators_test.gno

@@ -0,0 +1,102 @@
+package validators
+
+import (
+	"testing"
+
+	"std"
+
+	"gno.land/p/demo/avl"
+	"gno.land/p/demo/testutils"
+	"gno.land/p/demo/uassert"
+	"gno.land/p/demo/ufmt"
+	"gno.land/p/sys/validators"
+)
+
+// generateTestValidators generates a dummy validator set
+func generateTestValidators(count int) []validators.Validator {
+	vals := make([]validators.Validator, 0, count)
+
+	for i := 0; i < count; i++ {
+		val := validators.Validator{
+			Address:     testutils.TestAddress(ufmt.Sprintf("%d", i)),
+			PubKey:      "public-key",
+			VotingPower: 10,
+		}
+
+		vals = append(vals, val)
+	}
+
+	return vals
+}
+
+func TestValidators_AddRemove(t *testing.T) {
+	// Clear any changes
+	changes = avl.NewTree()
+
+	var (
+		vals          = generateTestValidators(100)
+		initialHeight = int64(123)
+	)
+
+	// Add in the validators
+	for _, val := range vals {
+		addValidator(val)
+
+		// Make sure the validator is added
+		uassert.True(t, vp.IsValidator(val.Address))
+
+		std.TestSkipHeights(1)
+	}
+
+	for i := initialHeight; i < initialHeight+int64(len(vals)); i++ {
+		// Make sure the changes are saved
+		chs := GetChanges(i)
+
+		// We use the funky index calculation to make sure
+		// changes are properly handled for each block span
+		uassert.Equal(t, initialHeight+int64(len(vals))-i, int64(len(chs)))
+
+		for index, val := range vals[i-initialHeight:] {
+			// Make sure the changes are equal to the additions
+			ch := chs[index]
+
+			uassert.Equal(t, val.Address, ch.Address)
+			uassert.Equal(t, val.PubKey, ch.PubKey)
+			uassert.Equal(t, val.VotingPower, ch.VotingPower)
+		}
+	}
+
+	// Save the beginning height for the removal
+	initialRemoveHeight := std.GetHeight()
+
+	// Clear any changes
+	changes = avl.NewTree()
+
+	// Remove the validators
+	for _, val := range vals {
+		removeValidator(val.Address)
+
+		// Make sure the validator is removed
+		uassert.False(t, vp.IsValidator(val.Address))
+
+		std.TestSkipHeights(1)
+	}
+
+	for i := initialRemoveHeight; i < initialRemoveHeight+int64(len(vals)); i++ {
+		// Make sure the changes are saved
+		chs := GetChanges(i)
+
+		// We use the funky index calculation to make sure
+		// changes are properly handled for each block span
+		uassert.Equal(t, initialRemoveHeight+int64(len(vals))-i, int64(len(chs)))
+
+		for index, val := range vals[i-initialRemoveHeight:] {
+			// Make sure the changes are equal to the additions
+			ch := chs[index]
+
+			uassert.Equal(t, val.Address, ch.Address)
+			uassert.Equal(t, val.PubKey, ch.PubKey)
+			uassert.Equal(t, uint64(0), ch.VotingPower)
+		}
+	}
+}

gno.land/cmd/gnoland/start.go

@@ -23,6 +23,7 @@ import (
 	bft "github.com/gnolang/gno/tm2/pkg/bft/types"
 	"github.com/gnolang/gno/tm2/pkg/commands"
 	"github.com/gnolang/gno/tm2/pkg/crypto"
+	"github.com/gnolang/gno/tm2/pkg/events"
 	osm "github.com/gnolang/gno/tm2/pkg/os"
 	"github.com/gnolang/gno/tm2/pkg/telemetry"
 	"go.uber.org/zap"
@@ -239,14 +240,17 @@ func execStart(ctx context.Context, c *startCfg, io commands.IO) error {
 		io.Println(startGraphic)
 	}
 
+	// Create a top-level shared event switch
+	evsw := events.NewEventSwitch()
+
 	// Create application and node
-	cfg.LocalApp, err = gnoland.NewApp(nodeDir, c.skipFailingGenesisTxs, logger, c.genesisMaxVMCycles)
+	cfg.LocalApp, err = gnoland.NewApp(nodeDir, c.skipFailingGenesisTxs, evsw, logger)
 	if err != nil {
 		return fmt.Errorf("unable to create the Gnoland app, %w", err)
 	}
 
 	// Create a default node, with the given setup
-	gnoNode, err := node.DefaultNewNode(cfg, genesisPath, logger)
+	gnoNode, err := node.DefaultNewNode(cfg, genesisPath, evsw, logger)
 	if err != nil {
 		return fmt.Errorf("unable to create the Gnoland node, %w", err)
 	}