feat(examples): implement r/events, p/authorizable (gnolang#2372)

<!-- please provide a detailed description of the changes made in this
pull request. -->

## Description

This PR adds the r/gnoland/events realm. It handles events gno.land is
attending dynamically. An admin and modetators can add new events,
delete old ones, or make changes to existing ones.

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

- [x] Added new tests, or not needed, or not feasible
- [x] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [x] Updated the official documentation or not needed
- [x] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [x] Added references to related issues and PRs
- [x] Provided any useful hints for running manual tests
- [x] 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 <94029+moul@users.noreply.github.com>

examples/gno.land/p/demo/ownable/errors.gno

@@ -3,6 +3,6 @@ package ownable
 import "errors"
 
 var (
-	ErrUnauthorized   = errors.New("unauthorized; caller is not owner")
-	ErrInvalidAddress = errors.New("new owner address is invalid")
+	ErrUnauthorized   = errors.New("ownable: caller is not owner")
+	ErrInvalidAddress = errors.New("ownable: new owner address is invalid")
 )

examples/gno.land/p/demo/ownable/exts/authorizable/authorizable.gno

@@ -0,0 +1,90 @@
+// Package authorizable is an extension of p/demo/ownable;
+// It allows the user to instantiate an Authorizable struct, which extends
+// p/demo/ownable with a list of users that are authorized for something.
+// By using authorizable, you have a superuser (ownable), as well as another
+// authorization level, which can be used for adding moderators or similar to your realm.
+package authorizable
+
+import (
+	"std"
+
+	"gno.land/p/demo/avl"
+	"gno.land/p/demo/ownable"
+	"gno.land/p/demo/ufmt"
+)
+
+type Authorizable struct {
+	*ownable.Ownable           // owner in ownable is superuser
+	authorized       *avl.Tree // std.Addr > struct{}{}
+}
+
+func NewAuthorizable() *Authorizable {
+	a := &Authorizable{
+		ownable.New(),
+		avl.NewTree(),
+	}
+
+	// Add owner to auth list
+	a.authorized.Set(a.Owner().String(), struct{}{})
+	return a
+}
+
+func NewAuthorizableWithAddress(addr std.Address) *Authorizable {
+	a := &Authorizable{
+		ownable.NewWithAddress(addr),
+		avl.NewTree(),
+	}
+
+	// Add owner to auth list
+	a.authorized.Set(a.Owner().String(), struct{}{})
+	return a
+}
+
+func (a *Authorizable) AddToAuthList(addr std.Address) error {
+	if err := a.CallerIsOwner(); err != nil {
+		return ErrNotSuperuser
+	}
+
+	if _, exists := a.authorized.Get(addr.String()); exists {
+		return ErrAlreadyInList
+	}
+
+	a.authorized.Set(addr.String(), struct{}{})
+
+	return nil
+}
+
+func (a *Authorizable) DeleteFromAuthList(addr std.Address) error {
+	if err := a.CallerIsOwner(); err != nil {
+		return ErrNotSuperuser
+	}
+
+	if !a.authorized.Has(addr.String()) {
+		return ErrNotInAuthList
+	}
+
+	if _, removed := a.authorized.Remove(addr.String()); !removed {
+		str := ufmt.Sprintf("authorizable: could not remove %s from auth list", addr.String())
+		panic(str)
+	}
+
+	return nil
+}
+
+func (a Authorizable) CallerOnAuthList() error {
+	caller := std.PrevRealm().Addr()
+
+	if !a.authorized.Has(caller.String()) {
+		return ErrNotInAuthList
+	}
+
+	return nil
+}
+
+func (a Authorizable) AssertOnAuthList() {
+	caller := std.PrevRealm().Addr()
+
+	if !a.authorized.Has(caller.String()) {
+		panic(ErrNotInAuthList)
+	}
+}

examples/gno.land/p/demo/ownable/exts/authorizable/authorizable_test.gno

@@ -0,0 +1,116 @@
+package authorizable
+
+import (
+	"std"
+	"testing"
+
+	"gno.land/p/demo/testutils"
+	"gno.land/p/demo/uassert"
+)
+
+var (
+	alice   = testutils.TestAddress("alice")
+	bob     = testutils.TestAddress("bob")
+	charlie = testutils.TestAddress("charlie")
+)
+
+func TestNewAuthorizable(t *testing.T) {
+	std.TestSetRealm(std.NewUserRealm(alice))
+	std.TestSetOrigCaller(alice) // TODO(bug, issue #2371): should not be needed
+
+	a := NewAuthorizable()
+	got := a.Owner()
+
+	if alice != got {
+		t.Fatalf("Expected %s, got: %s", alice, got)
+	}
+}
+
+func TestNewAuthorizableWithAddress(t *testing.T) {
+	a := NewAuthorizableWithAddress(alice)
+
+	got := a.Owner()
+
+	if alice != got {
+		t.Fatalf("Expected %s, got: %s", alice, got)
+	}
+}
+
+func TestCallerOnAuthList(t *testing.T) {
+	a := NewAuthorizableWithAddress(alice)
+	std.TestSetRealm(std.NewUserRealm(alice))
+	std.TestSetOrigCaller(alice)
+
+	if err := a.CallerOnAuthList(); err == ErrNotInAuthList {
+		t.Fatalf("expected alice to be on the list")
+	}
+}
+
+func TestNotCallerOnAuthList(t *testing.T) {
+	a := NewAuthorizableWithAddress(alice)
+	std.TestSetRealm(std.NewUserRealm(bob))
+	std.TestSetOrigCaller(bob)
+
+	if err := a.CallerOnAuthList(); err == nil {
+		t.Fatalf("expected bob to not be on the list")
+	}
+}
+
+func TestAddToAuthList(t *testing.T) {
+	a := NewAuthorizableWithAddress(alice)
+	std.TestSetRealm(std.NewUserRealm(alice))
+	std.TestSetOrigCaller(alice)
+
+	if err := a.AddToAuthList(bob); err != nil {
+		t.Fatalf("Expected no error, got %v", err)
+	}
+
+	std.TestSetRealm(std.NewUserRealm(bob))
+	std.TestSetOrigCaller(bob)
+
+	if err := a.AddToAuthList(bob); err == nil {
+		t.Fatalf("Expected AddToAuth to error while bob called it, but it didn't")
+	}
+}
+
+func TestDeleteFromList(t *testing.T) {
+	a := NewAuthorizableWithAddress(alice)
+	std.TestSetRealm(std.NewUserRealm(alice))
+	std.TestSetOrigCaller(alice)
+
+	if err := a.AddToAuthList(bob); err != nil {
+		t.Fatalf("Expected no error, got %v", err)
+	}
+
+	if err := a.AddToAuthList(charlie); err != nil {
+		t.Fatalf("Expected no error, got %v", err)
+	}
+
+	std.TestSetRealm(std.NewUserRealm(bob))
+	std.TestSetOrigCaller(bob)
+
+	// Try an unauthorized deletion
+	if err := a.DeleteFromAuthList(alice); err == nil {
+		t.Fatalf("Expected DelFromAuth to error with %v", err)
+	}
+
+	std.TestSetRealm(std.NewUserRealm(alice))
+	std.TestSetOrigCaller(alice)
+
+	if err := a.DeleteFromAuthList(charlie); err != nil {
+		t.Fatalf("Expected no error, got %v", err)
+	}
+}
+
+func TestAssertOnList(t *testing.T) {
+	std.TestSetRealm(std.NewUserRealm(alice))
+	std.TestSetOrigCaller(alice)
+	a := NewAuthorizableWithAddress(alice)
+
+	std.TestSetRealm(std.NewUserRealm(bob))
+	std.TestSetOrigCaller(bob)
+
+	uassert.PanicsWithMessage(t, ErrNotInAuthList.Error(), func() {
+		a.AssertOnAuthList()
+	})
+}

examples/gno.land/p/demo/ownable/exts/authorizable/errors.gno

@@ -0,0 +1,9 @@
+package authorizable
+
+import "errors"
+
+var (
+	ErrNotInAuthList = errors.New("authorizable: caller is not in authorized list")
+	ErrNotSuperuser  = errors.New("authorizable: caller is not superuser")
+	ErrAlreadyInList = errors.New("authorizable: address is already in authorized list")
+)

examples/gno.land/p/demo/ownable/exts/authorizable/gno.mod

@@ -0,0 +1,9 @@
+module gno.land/p/demo/ownable/exts/authorizable
+
+require (
+	gno.land/p/demo/avl v0.0.0-latest
+	gno.land/p/demo/ownable 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
+)

examples/gno.land/p/demo/ownable/ownable.gno

@@ -1,8 +1,6 @@
 package ownable
 
-import (
-	"std"
-)
+import "std"
 
 const OwnershipTransferEvent = "OwnershipTransfer"
 
@@ -19,7 +17,9 @@ func New() *Ownable {
 }
 
 func NewWithAddress(addr std.Address) *Ownable {
-	return &Ownable{owner: addr}
+	return &Ownable{
+		owner: addr,
+	}
 }
 
 // TransferOwnership transfers ownership of the Ownable struct to a new address
@@ -40,6 +40,7 @@ func (o *Ownable) TransferOwnership(newOwner std.Address) error {
 		"from", string(prevOwner),
 		"to", string(newOwner),
 	)
+
 	return nil
 }
 
@@ -64,6 +65,7 @@ func (o *Ownable) DropOwnership() error {
 	return nil
 }
 
+// Owner returns the owner address from Ownable
 func (o Ownable) Owner() std.Address {
 	return o.owner
 }
@@ -73,9 +75,11 @@ func (o Ownable) CallerIsOwner() error {
 	if std.PrevRealm().Addr() == o.owner {
 		return nil
 	}
+
 	return ErrUnauthorized
 }
 
+// AssertCallerIsOwner panics if the caller is not the owner
 func (o Ownable) AssertCallerIsOwner() {
 	if std.PrevRealm().Addr() != o.owner {
 		panic(ErrUnauthorized)