feat(boards2): add core flagging logic

examples/gno.land/r/demo/boards2/flag.gno

@@ -0,0 +1,47 @@
+package boards2
+
+import (
+	"std"
+	"strconv"
+)
+
+var flagThreshold = 3
+
+type Flag struct {
+	User   std.Address
+	Reason string
+}
+
+func NewFlag(creator std.Address, reason string) Flag {
+	return Flag{
+		User:   creator,
+		Reason: reason,
+	}
+}
+
+type Flaggable interface {
+	// AddFlag adds a new flag to an entry.
+	//
+	// Returns false if item was already flagged by user.
+	AddFlag(flag Flag) bool
+
+	// FlagsCount returns number of times entry was flagged.
+	FlagsCount() int
+}
+
+// flagItem adds a flag to a flaggable item (post, thread, etc).
+//
+// Returns whether flag count threshold is reached and item can be hidden.
+//
+// Panics if flag count threshold was already reached.
+func flagItem(item Flaggable, flag Flag) bool {
+	if item.FlagsCount() >= flagThreshold {
+		panic("item flag count threshold exceeded: " + strconv.Itoa(flagThreshold))
+	}
+
+	if !item.AddFlag(flag) {
+		panic("item has been already flagged by a user")
+	}
+
+	return item.FlagsCount() == flagThreshold
+}

examples/gno.land/r/demo/boards2/permission.gno

@@ -7,8 +7,10 @@ const (
 	PermissionThreadCreate            = "thread:create"
 	PermissionThreadEdit              = "thread:edit"
 	PermissionThreadDelete            = "thread:delete"
+	PermissionThreadFlag              = "thread:flag"
 	PermissionThreadRepost            = "thread:repost"
 	PermissionReplyDelete             = "reply:delete"
+	PermissionReplyFlag               = "reply:flag"
 	PermissionMemberInvite            = "member:invite"
 	PermissionMemberRemove            = "member:remove"
 )

examples/gno.land/r/demo/boards2/post.gno

@@ -30,12 +30,14 @@ type Post struct {
 	creator       std.Address
 	title         string // optional
 	body          string
+	isHidden      bool
 	replies       avl.Tree // Post.id -> *Post
 	repliesAll    avl.Tree // Post.id -> *Post (all replies, for top-level posts)
 	reposts       avl.Tree // Board.id -> Post.id
-	threadID      PostID   // original Post.id
-	parentID      PostID   // parent Post.id (if reply or repost)
-	repostBoardID BoardID  // original Board.id (if repost)
+	flags         []Flag
+	threadID      PostID  // original Post.id
+	parentID      PostID  // parent Post.id (if reply or repost)
+	repostBoardID BoardID // original Board.id (if repost)
 	createdAt     time.Time
 	updatedAt     time.Time
 }
@@ -97,6 +99,30 @@ func (post *Post) GetUpdatedAt() time.Time {
 	return post.updatedAt
 }
 
+func (post *Post) AddFlag(flag Flag) bool {
+	// TODO: sort flags for fast search in case of big thresholds
+	for _, v := range post.flags {
+		if v.User == flag.User {
+			return false
+		}
+	}
+
+	post.flags = append(post.flags, flag)
+	return true
+}
+
+func (post *Post) FlagsCount() int {
+	return len(post.flags)
+}
+
+func (post *Post) SetVisibility(isVisible bool) {
+	post.isHidden = !isVisible
+}
+
+func (post *Post) Hidden() bool {
+	return post.isHidden
+}
+
 func (post *Post) AddReply(creator std.Address, body string) *Post {
 	board := post.board
 	pid := board.incGetPostID()

examples/gno.land/r/demo/boards2/public.gno

@@ -39,6 +39,21 @@ func CreateBoard(name string) BoardID {
 	return id
 }
 
+func FlagThread(bid BoardID, postID PostID, reason string) {
+	caller := std.GetOrigCaller()
+	assertHasPermission(caller, PermissionThreadFlag)
+
+	board := mustGetBoard(bid)
+	t, ok := board.GetThread(postID)
+	if !ok {
+		panic("post doesn't exist")
+	}
+
+	if flagItem(t, NewFlag(caller, reason)) {
+		t.SetVisibility(false)
+	}
+}
+
 func CreateThread(bid BoardID, title, body string) PostID {
 	assertIsUserCall()
 
@@ -75,6 +90,19 @@ func CreateReply(bid BoardID, threadID, replyID PostID, body string) PostID {
 	return reply.id
 }
 
+func FlagReply(bid BoardID, threadID, replyID PostID, reason string) {
+	caller := std.GetOrigCaller()
+	assertHasPermission(caller, PermissionThreadFlag)
+
+	board := mustGetBoard(bid)
+	thread := mustGetThread(board, threadID)
+	reply := mustGetReply(thread, replyID)
+
+	if flagItem(reply, NewFlag(caller, reason)) {
+		reply.SetVisibility(false)
+	}
+}
+
 func CreateRepost(bid BoardID, threadID PostID, title, body string, dstBoardID BoardID) PostID {
 	assertIsUserCall()