Tusker/Tusker/Screens/Conversation/ConversationTree.swift

//
//  ConversationTree.swift
//  Tusker
//
//  Created by Shadowfacts on 2/4/23.
//  Copyright © 2023 Shadowfacts. All rights reserved.
//

import Foundation
import Pachyderm

class ConversationNode {
    let status: StatusMO
    var children: [ConversationNode]
    
    init(status: StatusMO) {
        self.status = status
        self.children = []
    }
}
struct ConversationTree {
    let ancestors: [String]
    let descendants: [ConversationNode]
    
    static func build(from context: ConversationContext, mainStatus: StatusMO, descendants: [StatusMO]) -> ConversationTree {
        let ancestors = getDirectParents(inReplyTo: mainStatus.inReplyToID, from: context)
        let childThreads = getDescendantThreads(mainStatus: mainStatus, descendants: descendants)
        return ConversationTree(ancestors: ancestors, descendants: childThreads)
    }
    
    private static func getDirectParents(inReplyTo inReplyToID: String?, from context: ConversationContext) -> [String] {
        var statuses = context.ancestors
        var parents = [String]()
        
        var parentID: String? = inReplyToID
        
        while let currentParentID = parentID,
              let parentIndex = statuses.firstIndex(where: { $0.id == currentParentID }) {
            let parentStatus = statuses.remove(at: parentIndex)
            parents.insert(parentStatus.id, at: 0)
            parentID = parentStatus.inReplyToID
        }
        
        return parents
    }
    
    private static func getDescendantThreads(mainStatus: StatusMO, descendants: [StatusMO]) -> [ConversationNode] {
        var descendants = descendants
        
        func removeAllInReplyTo(id: String) -> [StatusMO] {
            let statuses = descendants.filter { $0.inReplyToID == id }
            descendants.removeAll { $0.inReplyToID == id }
            return statuses
        }
        
        let mainStatusNode = ConversationNode(status: mainStatus)
        var nodes: [String: ConversationNode] = [
            mainStatus.id: mainStatusNode
        ]
        
        var idsToCheck = [mainStatus.id]
        
        while !idsToCheck.isEmpty {
            let inReplyToID = idsToCheck.removeFirst()
            let nodeForID = nodes[inReplyToID]!
            
            let inReply = removeAllInReplyTo(id: inReplyToID)
            for reply in inReply {
                idsToCheck.append(reply.id)
                
                let replyNode = ConversationNode(status: reply)
                nodes[reply.id] = replyNode
                
                nodeForID.children.append(replyNode)
            }
        }
        
        return mainStatusNode.children
    }
}