feat: add realm r/demo/keystore (#958)

This realm implements the `avl.Tree` as a user-addressable key-store. I
wanted to have this realm to possibly use `gno.land` as a database where
writes may cost gnots but reads are free because they can be performed
through `Render` (related discussion:
#947). As a nice additional feature
it provides a UI for the database (through `gno.land`).

Data can be set/removed if the caller is the same as the owner of the
key-store (i.e. only owner's have write-access). For example:

```bash
# Set key,value for user at YOURKEY (write-protected)
gnokey maketx call --pkgpath "gno.land/r/demo/keystore" \
--func "Set" --args "hello" --args "world" \
--gas-fee "1000000ugnot" --gas-wanted "8000000" \
--broadcast --chainid dev --remote localhost:26657 YOURKEY
```

```bash
# Remove key for user at YOURKEY (write-protected)
gnokey maketx call --pkgpath "gno.land/r/demo/keystore" \
--func "Remove" --args "hello"  \
--gas-fee "1000000ugnot" --gas-wanted "8000000" \
--broadcast --chainid dev --remote localhost:26657 YOURKEY
```

```bash
# Get key
gnokey maketx call --pkgpath "gno.land/r/demo/keystore" \
--func "Get" --args "hello"  \
--gas-fee "1000000ugnot" --gas-wanted "8000000" \
--broadcast --chainid dev --remote localhost:26657 YOURKEY
```

All data is public and accessible as read-only from any user, as well as
from gno.land.

The main page lists all the available databases by owner
(`/r/demo/keystore`):


![image](https://github.com/gnolang/gno/assets/6550035/3e21827c-0a22-47eb-bf42-53f6ee005a7e)

Clicking on a user will show all the keys in their key-store
(`/r/demo/keystore:USER`):


![image](https://github.com/gnolang/gno/assets/6550035/7d4b3d58-20ad-47fc-8e41-095e111f5f30)

And the key values are accessible as well
(`r/demo/keystore:USER:get:KEY`)


![image](https://github.com/gnolang/gno/assets/6550035/888a8ddf-6044-42d4-aed6-ffc3989def35)





## Contributors Checklist

- [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](../.benchmarks/README.md).

## Maintainers Checklist

- [ ] Checked that the author followed the guidelines in
`CONTRIBUTING.md`
- [ ] Checked the conventional-commit (especially PR title and verb,
presence of `BREAKING CHANGE:` in the body)
- [ ] Ensured that this PR is not a significant change or confirmed that
the review/consideration process was appropriate for the change

---------

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

examples/gno.land/r/demo/keystore/gno.mod

@@ -0,0 +1,6 @@
+module gno.land/r/demo/keystore
+
+require (
+        "gno.land/p/demo/ufmt" v0.0.0-latest
+        "gno.land/p/demo/avl" v0.0.0-latest
+)

examples/gno.land/r/demo/keystore/keystore.gno

@@ -0,0 +1,184 @@
+package keystore
+
+import (
+	"std"
+	"strings"
+
+	"gno.land/p/demo/avl"
+	"gno.land/p/demo/ufmt"
+)
+
+var data avl.Tree
+
+const (
+	BaseURL               = "/r/demo/keystore"
+	StatusOK              = "ok"
+	StatusNoUser          = "user not found"
+	StatusNotFound        = "key not found"
+	StatusNoWriteAccess   = "no write access"
+	StatusCouldNotExecute = "could not execute"
+	StatusNoDatabases     = "no databases"
+)
+
+func init() {
+	data = avl.Tree{} // user -> avl.Tree
+}
+
+// KeyStore stores the owner-specific avl.Tree
+type KeyStore struct {
+	Owner std.Address
+	Data  avl.Tree
+}
+
+// Set will set a value to a key
+// requires write-access (original caller must be caller)
+func Set(k, v string) string {
+	origOwner := std.GetOrigCaller()
+	return set(origOwner.String(), k, v)
+}
+
+// set (private) will set a key to value
+// requires write-access (original caller must be caller)
+func set(owner, k, v string) string {
+	origOwner := std.GetOrigCaller()
+	if origOwner.String() != owner {
+		return StatusNoWriteAccess
+	}
+	var keystore *KeyStore
+	keystoreInterface, exists := data.Get(owner)
+	if !exists {
+		keystore = &KeyStore{
+			Owner: origOwner,
+			Data:  avl.Tree{},
+		}
+		data.Set(owner, keystore)
+	} else {
+		keystore = keystoreInterface.(*KeyStore)
+	}
+	keystore.Data.Set(k, v)
+	return StatusOK
+}
+
+// Remove removes a key
+// requires write-access (original owner must be caller)
+func Remove(k string) string {
+	origOwner := std.GetOrigCaller()
+	return remove(origOwner.String(), k)
+}
+
+// remove (private) removes a key
+// requires write-access (original owner must be caller)
+func remove(owner, k string) string {
+	origOwner := std.GetOrigCaller()
+	if origOwner.String() != owner {
+		return StatusNoWriteAccess
+	}
+	var keystore *KeyStore
+	keystoreInterface, exists := data.Get(owner)
+	if !exists {
+		keystore = &KeyStore{
+			Owner: origOwner,
+			Data:  avl.Tree{},
+		}
+		data.Set(owner, keystore)
+	} else {
+		keystore = keystoreInterface.(*KeyStore)
+	}
+	_, removed := keystore.Data.Remove(k)
+	if !removed {
+		return StatusCouldNotExecute
+	}
+	return StatusOK
+}
+
+// Get returns a value for a key
+// read-only
+func Get(k string) string {
+	origOwner := std.GetOrigCaller()
+	return remove(origOwner.String(), k)
+}
+
+// get (private) returns a value for a key
+// read-only
+func get(owner, k string) string {
+	keystoreInterface, exists := data.Get(owner)
+	if !exists {
+		return StatusNoUser
+	}
+	keystore := keystoreInterface.(*KeyStore)
+	val, found := keystore.Data.Get(k)
+	if !found {
+		return StatusNotFound
+	}
+	return val.(string)
+}
+
+// Size returns size of database
+// read-only
+func Size() string {
+	origOwner := std.GetOrigCaller()
+	return size(origOwner.String())
+}
+
+func size(owner string) string {
+	keystoreInterface, exists := data.Get(owner)
+	if !exists {
+		return StatusNoUser
+	}
+	keystore := keystoreInterface.(*KeyStore)
+	return ufmt.Sprintf("%d", keystore.Data.Size())
+}
+
+// Render provides read-only url access to the functions of the keystore
+// "" -> show all keystores listed by owner
+// "owner" -> show all keys for that owner's keystore
+// "owner:size" -> returns size of owner's keystore
+// "owner:get:key" -> show value for that key in owner's keystore
+func Render(p string) string {
+	var response string
+	args := strings.Split(p, ":")
+	numArgs := len(args)
+	if p == "" {
+		numArgs = 0
+	}
+	switch numArgs {
+	case 0:
+		if data.Size() == 0 {
+			return StatusNoDatabases
+		}
+		data.Iterate("", "", func(key string, value interface{}) bool {
+			ks := value.(*KeyStore)
+			response += ufmt.Sprintf("- [%s](%s:%s) (%d keys)\n", ks.Owner, BaseURL, ks.Owner, ks.Data.Size())
+			return false
+		})
+	case 1:
+		owner := args[0]
+		keystoreInterface, exists := data.Get(owner)
+		if !exists {
+			return StatusNoUser
+		}
+		ks := keystoreInterface.(*KeyStore)
+		i := 0
+		response += ufmt.Sprintf("# %s database\n\n", ks.Owner)
+		ks.Data.Iterate("", "", func(key string, value interface{}) bool {
+			response += ufmt.Sprintf("- %d [%s](%s:%s:get:%s)\n", i, key, BaseURL, ks.Owner, key)
+			i++
+			return false
+		})
+	case 2:
+		owner := args[0]
+		cmd := args[1]
+		if cmd == "size" {
+			return size(owner)
+		}
+	case 3:
+		owner := args[0]
+		cmd := args[1]
+		key := args[2]
+		if cmd == "get" {
+			return get(owner, key)
+		}
+	}
+
+	return response
+}

examples/gno.land/r/demo/keystore/keystore_test.gno

@@ -0,0 +1,78 @@
+package keystore
+
+import (
+	"fmt"
+	"std"
+	"strings"
+	"testing"
+
+	"gno.land/p/demo/testutils"
+)
+
+func TestRender(t *testing.T) {
+	const (
+		author1 std.Address = testutils.TestAddress("author1")
+		author2 std.Address = testutils.TestAddress("author2")
+	)
+
+	tt := []struct {
+		caller std.Address
+		owner  std.Address
+		ps     []string
+		exp    string
+	}{
+		// can set database if the owner is the caller
+		{author1, author1, []string{"set", "hello", "gno"}, StatusOK},
+		{author1, author1, []string{"size"}, "1"},
+		{author1, author1, []string{"set", "hello", "world"}, StatusOK},
+		{author1, author1, []string{"size"}, "1"},
+		{author1, author1, []string{"set", "hi", "gno"}, StatusOK},
+		{author1, author1, []string{"size"}, "2"},
+		// only owner can remove
+		{author1, author1, []string{"remove", "hi"}, StatusOK},
+		{author1, author1, []string{"get", "hi"}, StatusNotFound},
+		{author1, author1, []string{"size"}, "1"},
+		// add back
+		{author1, author1, []string{"set", "hi", "gno"}, StatusOK},
+		{author1, author1, []string{"size"}, "2"},
+
+		// different owner has different database
+		{author2, author2, []string{"set", "hello", "universe"}, StatusOK},
+		// either author can get the other info
+		{author1, author2, []string{"get", "hello"}, "universe"},
+		// either author can get the other info
+		{author2, author1, []string{"get", "hello"}, "world"},
+		{author1, author2, []string{"get", "hello"}, "universe"},
+		// anyone can view the databases
+		{author1, author2, []string{}, `- [g1v96hg6r0wgc47h6lta047h6lta047h6lm33tq6](/r/demo/keystore:g1v96hg6r0wgc47h6lta047h6lta047h6lm33tq6) (2 keys)
+- [g1v96hg6r0wge97h6lta047h6lta047h6lyz7c00](/r/demo/keystore:g1v96hg6r0wge97h6lta047h6lta047h6lyz7c00) (1 keys)`},
+		// anyone can view the keys in a database
+		{author1, author2, []string{""}, `# g1v96hg6r0wge97h6lta047h6lta047h6lyz7c00 database
+
+- 0 [hello](/r/demo/keystore:g1v96hg6r0wge97h6lta047h6lta047h6lyz7c00:get:hello)`},
+	}
+	for _, tc := range tt {
+		p := ""
+		if len(tc.ps) > 0 {
+			p = tc.owner.String()
+			for i, psv := range tc.ps {
+				p += ":" + psv
+			}
+		}
+		p = strings.TrimSuffix(p, ":")
+		t.Run(p, func(t *testing.T) {
+			std.TestSetOrigCaller(tc.caller)
+			var act string
+			if len(tc.ps) > 0 && tc.ps[0] == "set" {
+				act = strings.TrimSpace(Set(tc.ps[1], tc.ps[2]))
+			} else if len(tc.ps) > 0 && tc.ps[0] == "remove" {
+				act = strings.TrimSpace(Remove(tc.ps[1]))
+			} else {
+				act = strings.TrimSpace(Render(p))
+			}
+			if act != tc.exp {
+				t.Errorf("%v -> '%s', got '%s', wanted '%s'", tc.ps, p, act, tc.exp)
+			}
+		})
+	}
+}