fix: add pastParticipants to HistorySync with LID normalization and deduplication (#303)

Two bugs fixed compared to prior implementation:

1. history.ts — normalize userJid LID→PN
   pastParticipants[].userJid may arrive as a LID identifier (e.g. "46802258641027@lid").
   The consumer expects a phone number. After building the lidPnMap from conversations
   and phoneNumberToLidMappings, each userJid is resolved to its PN equivalent.
   If the mapping is not available the original value is preserved (no data loss).

2. event-buffer.ts — deduplicate by groupJid + userJid across chunks
   Multiple HistorySync chunks can contain the same group. The previous approach
   concatenated blindly, producing duplicate entries. Now a keyed map
   { [groupJid]: IPastParticipant[] } is used so each group appears once and
   each participant within a group appears at most once.

Types updated (Events.ts):
   - messaging-history.set event includes pastParticipants?: IPastParticipants[]
   - BufferedEventData.historySets.pastParticipants typed as keyed map

src/Types/Events.ts

@@ -27,6 +27,8 @@ export type BaileysEventMap = {
 		chats: Chat[]
 		contacts: Contact[]
 		messages: WAMessage[]
+		/** Past participants for group chats (people who left/were removed). userJid is always a phone number (PN), never a LID. */
+		pastParticipants?: proto.IPastParticipants[] | null
 		isLatest?: boolean
 		progress?: number | null
 		syncType?: proto.HistorySync.HistorySyncType | null
@@ -185,6 +187,8 @@ export type BufferedEventData = {
 		chats: { [jid: string]: Chat }
 		contacts: { [jid: string]: Contact }
 		messages: { [uqId: string]: WAMessage }
+		/** Keyed by groupJid for O(1) deduplication across chunks */
+		pastParticipants: { [groupJid: string]: proto.IPastParticipant[] }
 		empty: boolean
 		isLatest: boolean
 		progress?: number | null

src/Utils/event-buffer.ts

@@ -1,4 +1,5 @@
 import EventEmitter from 'events'
+import { proto } from '../../WAProto/index.js'
 import type {
 	BaileysEvent,
 	BaileysEventEmitter,
@@ -890,6 +891,7 @@ const makeBufferData = (): BufferedEventData => {
 			chats: {},
 			messages: {},
 			contacts: {},
+			pastParticipants: {},
 			isLatest: false,
 			empty: true
 		},
@@ -967,6 +969,28 @@ function append<E extends BufferableEvent>(
 				}
 			}
 
+			// Merge pastParticipants with deduplication by groupJid and by userJid within each group.
+			// Multiple HistorySync chunks can carry the same group -- we merge rather than concatenate
+			// to avoid duplicate entries in the final event delivered to the consumer.
+			for (const group of (eventData.pastParticipants ?? []) as proto.IPastParticipants[]) {
+				const groupJid = group.groupJid
+				if (!groupJid) continue
+
+				if (!data.historySets.pastParticipants[groupJid]) {
+					data.historySets.pastParticipants[groupJid] = []
+				}
+
+				const existing = data.historySets.pastParticipants[groupJid]
+				const seenJids = new Set(existing.map(p => p.userJid).filter(Boolean))
+
+				for (const participant of (group.pastParticipants ?? []) as proto.IPastParticipant[]) {
+					if (participant.userJid && !seenJids.has(participant.userJid)) {
+						existing.push(participant)
+						seenJids.add(participant.userJid)
+					}
+				}
+			}
+
 			data.historySets.empty = false
 			data.historySets.syncType = eventData.syncType
 			data.historySets.progress = eventData.progress
@@ -1292,6 +1316,10 @@ function consolidateEvents(data: BufferedEventData) {
 			chats: Object.values(data.historySets.chats),
 			messages: Object.values(data.historySets.messages),
 			contacts: Object.values(data.historySets.contacts),
+			// Convert dedup map back to array. Each entry has groupJid + participants (all unique userJids).
+			pastParticipants: Object.entries(data.historySets.pastParticipants).map(
+				([groupJid, participants]) => ({ groupJid, pastParticipants: participants })
+			),
 			syncType: data.historySets.syncType,
 			progress: data.historySets.progress,
 			isLatest: data.historySets.isLatest,

src/Utils/history.ts

@@ -374,10 +374,25 @@ export const processHistoryMessage = (item: proto.IHistorySync, logger?: ILogger
 	// Convert Map back to array for return
 	const lidPnMappings = Array.from(lidPnMap.values())
 
+	// Normalize pastParticipants: resolve LID userJids → PN so the consumer always
+	// receives a phone number, never an opaque LID identifier.
+	// Uses the lidPnMap built above (populated from phoneNumberToLidMappings + conversations).
+	// If a LID cannot be resolved, the original value is kept rather than dropping the participant.
+	const pastParticipants: proto.IPastParticipants[] = (item.pastParticipants ?? []).map(group => ({
+		groupJid: group.groupJid,
+		pastParticipants: (group.pastParticipants ?? []).map(participant => {
+			const userJid = participant.userJid
+			if (!userJid || !isAnyLidUser(userJid)) return participant
+			const mapping = lidPnMap.get(jidNormalizedUser(userJid))
+			return mapping?.pn ? { ...participant, userJid: mapping.pn } : participant
+		})
+	}))
+
 	return {
 		chats,
 		contacts,
 		messages,
+		pastParticipants,
 		lidPnMappings,
 		syncType: item.syncType,
 		progress: item.progress