client/src/comments/model.ts

import * as Y from 'yjs'

// Comment threads live inside the shared Yjs doc, so they sync in real time and persist
// with the deck. Each thread is anchored to a text range via Yjs *relative positions*,
// which survive concurrent edits.

export interface ReplySnap {
  id: string
  author: string
  color: string
  text: string
  ts: number
}

export interface ThreadSnap {
  id: string
  from: number | null // absolute position in the current doc (null if the anchor was deleted)
  to: number | null
  quote: string
  resolved: boolean
  replies: ReplySnap[]
}

export interface CommentRange {
  id: string
  from: number | null
  to: number | null
  resolved: boolean
}

export interface ReplyInput {
  author: string
  color: string
  text: string
}

const uid = () => Math.random().toString(36).slice(2) + Date.now().toString(36)

function commentsArray(doc: Y.Doc): Y.Array<Y.Map<unknown>> {
  return doc.getArray<Y.Map<unknown>>('comments')
}

function makeReply(input: ReplyInput): Y.Map<unknown> {
  const r = new Y.Map<unknown>()
  r.set('id', uid())
  r.set('author', input.author)
  r.set('color', input.color)
  r.set('text', input.text)
  r.set('ts', Date.now())
  return r
}

export function createThread(
  doc: Y.Doc,
  ytext: Y.Text,
  from: number,
  to: number,
  quote: string,
  reply: ReplyInput,
): void {
  const anchor = Y.relativePositionToJSON(Y.createRelativePositionFromTypeIndex(ytext, from))
  const anchorEnd = Y.relativePositionToJSON(Y.createRelativePositionFromTypeIndex(ytext, to))
  doc.transact(() => {
    const t = new Y.Map<unknown>()
    t.set('id', uid())
    t.set('anchor', JSON.stringify(anchor))
    t.set('anchorEnd', JSON.stringify(anchorEnd))
    t.set('quote', quote.slice(0, 240))
    t.set('resolved', false)
    const replies = new Y.Array<Y.Map<unknown>>()
    replies.push([makeReply(reply)])
    t.set('replies', replies)
    commentsArray(doc).push([t])
  })
}

export function addReply(doc: Y.Doc, threadId: string, reply: ReplyInput): void {
  for (const t of commentsArray(doc)) {
    if (t.get('id') === threadId) {
      ;(t.get('replies') as Y.Array<Y.Map<unknown>>).push([makeReply(reply)])
      return
    }
  }
}

export function setResolved(doc: Y.Doc, threadId: string, resolved: boolean): void {
  for (const t of commentsArray(doc)) {
    if (t.get('id') === threadId) {
      t.set('resolved', resolved)
      return
    }
  }
}

export function deleteThread(doc: Y.Doc, threadId: string): void {
  const arr = commentsArray(doc)
  for (let i = 0; i < arr.length; i++) {
    if (arr.get(i).get('id') === threadId) {
      arr.delete(i, 1)
      return
    }
  }
}

function absFromJSON(doc: Y.Doc, json: unknown): number | null {
  try {
    const rel = Y.createRelativePositionFromJSON(JSON.parse(json as string))
    const abs = Y.createAbsolutePositionFromRelativePosition(rel, doc)
    return abs ? abs.index : null
  } catch {
    return null
  }
}

export function snapshotThreads(doc: Y.Doc, _ytext: Y.Text): ThreadSnap[] {
  const out: ThreadSnap[] = []
  for (const t of commentsArray(doc)) {
    const replies = (t.get('replies') as Y.Array<Y.Map<unknown>>).map((r) => ({
      id: r.get('id') as string,
      author: r.get('author') as string,
      color: r.get('color') as string,
      text: r.get('text') as string,
      ts: r.get('ts') as number,
    }))
    out.push({
      id: t.get('id') as string,
      from: absFromJSON(doc, t.get('anchor')),
      to: absFromJSON(doc, t.get('anchorEnd')),
      quote: t.get('quote') as string,
      resolved: Boolean(t.get('resolved')),
      replies,
    })
  }
  return out
}