module forum

abstract sig Subforum{
	name: one String
}

//post type with either link or text data
abstract sig PostType{
	content: one String
}

sig PostTypeLink extends PostType {
}

sig PostTypeText extends PostType {
}

abstract sig Account{
	username: one String,
	password: one String,
}

sig Admin extends Account{
	domain: Subforum
}

sig Moderator extends Account{
	domain: one Subforum
}

sig User extends Account{
}

sig Post{
	subforum: one Subforum,
	title: String,
	//upvotes: Int,
	//downvotes: Int,
	Vote: all User,
	Type: one PostType,
	poster: one User
}

sig Reply extends Post{
	parent: lone Post
}

//facts
fact commentMustHavePost{
}

fact oneRolePerAccount{
	disj[User, Moderator, Admin]
}

fact uniqueUsernames{
	all a, a': Account | a.username != a'.username
}

pred onVotePerUserForPost[p: Post, a: Account]{
	one v: a | {
    	all u
	}
}

pred oneAccountPerPost[p: Post, a: Account]{
	all p: Post | #p.poster = 1
}

assert oneAccountPerPost{
	all p: Post | one a: Account | oneAccountPerPost[p, a]
}

pred demo {
	//for running in Alloy
	//This is just for testing, but we can fill it in with something meaningful if we want
}

run demo for 3 Account, 2 Post, 5 Reply, 3 Subforum, 3 PostType