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42.13/media/lua/client/Landtrain/LandtrainTowbarChainsRebuild.lua

@@ -12,6 +12,13 @@ local MAX_DIST_SQ = 3.25
 local MAX_DZ = 0.9
 local tmpA = Vector3f.new()
 local tmpB = Vector3f.new()
+local PERSIST_FRONT_SQL_KEY = "landtrainFrontTowSqlId"
+local PERSIST_FRONT_ID_KEY = "landtrainFrontTowId"
+local PERSIST_ATTACHMENT_A_KEY = "landtrainFrontTowAttachmentA"
+local PERSIST_ATTACHMENT_B_KEY = "landtrainFrontTowAttachmentB"
+local PERSIST_CHAIN_HEAD_SQL_KEY = "landtrainChainHeadSql"
+local PERSIST_CHAIN_ORDER_KEY = "landtrainChainOrder"
+local PERSIST_CHAIN_TOKEN_KEY = "landtrainChainToken"
 
 local function log(msg)
     print("[Landtrain] " .. tostring(msg))
@@ -177,12 +184,258 @@ local function refreshAround(vehicle)
     refreshTowBarState(vehicle:getVehicleTowing())
 end
 
+local function clearPersistedFrontLinkData(rearVehicle)
+    if not rearVehicle then return end
+    local md = rearVehicle:getModData()
+    if not md then return end
+
+    local changed = false
+    if md[PERSIST_FRONT_SQL_KEY] ~= nil then
+        md[PERSIST_FRONT_SQL_KEY] = nil
+        changed = true
+    end
+    if md[PERSIST_FRONT_ID_KEY] ~= nil then
+        md[PERSIST_FRONT_ID_KEY] = nil
+        changed = true
+    end
+    if md[PERSIST_ATTACHMENT_A_KEY] ~= nil then
+        md[PERSIST_ATTACHMENT_A_KEY] = nil
+        changed = true
+    end
+    if md[PERSIST_ATTACHMENT_B_KEY] ~= nil then
+        md[PERSIST_ATTACHMENT_B_KEY] = nil
+        changed = true
+    end
+
+    if changed then
+        rearVehicle:transmitModData()
+    end
+end
+
+local function storePersistedFrontLinkData(frontVehicle, rearVehicle, attachmentA, attachmentB)
+    if not frontVehicle or not rearVehicle then return end
+    local md = rearVehicle:getModData()
+    if not md then return end
+
+    local frontSql = frontVehicle.getSqlId and tonumber(frontVehicle:getSqlId()) or nil
+    local frontId = frontVehicle:getId()
+    local resolvedAttachmentA = attachmentA or "trailer"
+    local resolvedAttachmentB = attachmentB or "trailerfront"
+    local changed = false
+
+    if frontSql and frontSql > 0 then
+        if tonumber(md[PERSIST_FRONT_SQL_KEY]) ~= frontSql then
+            md[PERSIST_FRONT_SQL_KEY] = frontSql
+            changed = true
+        end
+    end
+
+    if tonumber(md[PERSIST_FRONT_ID_KEY]) ~= frontId then
+        md[PERSIST_FRONT_ID_KEY] = frontId
+        changed = true
+    end
+    if md[PERSIST_ATTACHMENT_A_KEY] ~= resolvedAttachmentA then
+        md[PERSIST_ATTACHMENT_A_KEY] = resolvedAttachmentA
+        changed = true
+    end
+    if md[PERSIST_ATTACHMENT_B_KEY] ~= resolvedAttachmentB then
+        md[PERSIST_ATTACHMENT_B_KEY] = resolvedAttachmentB
+        changed = true
+    end
+
+    if changed then
+        rearVehicle:transmitModData()
+    end
+end
+
+local function storePersistedChainOrderData(vehicle, headSql, orderIndex, chainToken)
+    if not vehicle then return end
+    local md = vehicle:getModData()
+    if not md then return end
+
+    local resolvedHeadSql = headSql and tonumber(headSql) or nil
+    local resolvedOrder = orderIndex and tonumber(orderIndex) or nil
+    local resolvedToken = chainToken and tostring(chainToken) or nil
+    if resolvedToken == "" then resolvedToken = nil end
+    local changed = false
+
+    if resolvedHeadSql and resolvedHeadSql > 0 then
+        if tonumber(md[PERSIST_CHAIN_HEAD_SQL_KEY]) ~= resolvedHeadSql then
+            md[PERSIST_CHAIN_HEAD_SQL_KEY] = resolvedHeadSql
+            changed = true
+        end
+    elseif md[PERSIST_CHAIN_HEAD_SQL_KEY] ~= nil then
+        md[PERSIST_CHAIN_HEAD_SQL_KEY] = nil
+        changed = true
+    end
+
+    if resolvedOrder and resolvedOrder > 0 then
+        if tonumber(md[PERSIST_CHAIN_ORDER_KEY]) ~= resolvedOrder then
+            md[PERSIST_CHAIN_ORDER_KEY] = resolvedOrder
+            changed = true
+        end
+    elseif md[PERSIST_CHAIN_ORDER_KEY] ~= nil then
+        md[PERSIST_CHAIN_ORDER_KEY] = nil
+        changed = true
+    end
+
+    if resolvedToken then
+        if tostring(md[PERSIST_CHAIN_TOKEN_KEY]) ~= resolvedToken then
+            md[PERSIST_CHAIN_TOKEN_KEY] = resolvedToken
+            changed = true
+        end
+    elseif md[PERSIST_CHAIN_TOKEN_KEY] ~= nil then
+        md[PERSIST_CHAIN_TOKEN_KEY] = nil
+        changed = true
+    end
+
+    if changed then
+        vehicle:transmitModData()
+    end
+end
+
+local function clearPersistedChainOrderData(vehicle)
+    if not vehicle then return end
+    local md = vehicle:getModData()
+    if not md then return end
+
+    local changed = false
+    if md[PERSIST_CHAIN_HEAD_SQL_KEY] ~= nil then
+        md[PERSIST_CHAIN_HEAD_SQL_KEY] = nil
+        changed = true
+    end
+    if md[PERSIST_CHAIN_ORDER_KEY] ~= nil then
+        md[PERSIST_CHAIN_ORDER_KEY] = nil
+        changed = true
+    end
+    if md[PERSIST_CHAIN_TOKEN_KEY] ~= nil then
+        md[PERSIST_CHAIN_TOKEN_KEY] = nil
+        changed = true
+    end
+
+    if changed then
+        vehicle:transmitModData()
+    end
+end
+
+local function getLoadedVehicles()
+    local results = {}
+    local cell = getCell()
+    if not cell then return results end
+    local list = cell:getVehicles()
+    if not list then return results end
+
+    for i = 0, list:size() - 1 do
+        local vehicle = list:get(i)
+        if vehicle then
+            table.insert(results, vehicle)
+        end
+    end
+    return results
+end
+
+local function indexVehiclesBySql(vehicles)
+    local bySql = {}
+    for _, vehicle in ipairs(vehicles) do
+        local sqlId = vehicle and vehicle.getSqlId and tonumber(vehicle:getSqlId()) or nil
+        if sqlId and sqlId > 0 then
+            bySql[sqlId] = vehicle
+        end
+    end
+    return bySql
+end
+
+local function hasValidTowLink(vehicle)
+    if not vehicle then return false end
+    local rear = vehicle:getVehicleTowing()
+    if rear and rear:getVehicleTowedBy() == vehicle then
+        return true
+    end
+    local front = vehicle:getVehicleTowedBy()
+    if front and front:getVehicleTowing() == vehicle then
+        return true
+    end
+    return false
+end
+
+local function snapshotChainFromHead(headVehicle, visitedIds)
+    if not headVehicle then return end
+
+    local headSql = headVehicle.getSqlId and tonumber(headVehicle:getSqlId()) or nil
+    if not (headSql and headSql > 0) then
+        headSql = nil
+    end
+    local headMd = headVehicle:getModData()
+    local chainToken = headMd and tostring(headMd[PERSIST_CHAIN_TOKEN_KEY] or "") or ""
+    if chainToken == "" then
+        if headSql then
+            chainToken = "sql:" .. tostring(headSql)
+        else
+            chainToken = "veh:" .. tostring(headVehicle:getId())
+        end
+    end
+    if headVehicle:getVehicleTowedBy() == nil then
+        clearPersistedFrontLinkData(headVehicle)
+    end
+
+    local cursor = headVehicle
+    local order = 1
+    local localVisited = {}
+    while cursor do
+        local cursorId = cursor:getId()
+        if visitedIds[cursorId] or localVisited[cursorId] then
+            break
+        end
+
+        visitedIds[cursorId] = true
+        localVisited[cursorId] = true
+        storePersistedChainOrderData(cursor, headSql, order, chainToken)
+
+        local rearVehicle = cursor:getVehicleTowing()
+        if rearVehicle and rearVehicle:getVehicleTowedBy() == cursor then
+            local attachmentA, attachmentB = resolvePair(cursor, rearVehicle)
+            storePersistedFrontLinkData(cursor, rearVehicle, attachmentA, attachmentB)
+        end
+
+        cursor = rearVehicle
+        order = order + 1
+    end
+end
+
+local function snapshotActiveTowLinks()
+    local vehicles = getLoadedVehicles()
+    if #vehicles == 0 then return end
+
+    local visitedIds = {}
+
+    for _, vehicle in ipairs(vehicles) do
+        local vehicleId = vehicle and vehicle:getId() or nil
+        if vehicleId and not visitedIds[vehicleId] and vehicle:getVehicleTowedBy() == nil then
+            local rearVehicle = vehicle:getVehicleTowing()
+            if rearVehicle and rearVehicle:getVehicleTowedBy() == vehicle then
+                snapshotChainFromHead(vehicle, visitedIds)
+            end
+        end
+    end
+
+    for _, vehicle in ipairs(vehicles) do
+        local vehicleId = vehicle and vehicle:getId() or nil
+        if vehicleId and not visitedIds[vehicleId] and hasValidTowLink(vehicle) then
+            snapshotChainFromHead(vehicle, visitedIds)
+        end
+    end
+end
+
 local function restoreDefaultsIfLeadLost(vehicle)
     if not vehicle then return end
     if vehicle:getVehicleTowedBy() ~= nil then return end
 
     clearChangedOffset(vehicle)
     restoreTowBarDefaults(vehicle)
+    clearPersistedFrontLinkData(vehicle)
+    if vehicle:getVehicleTowing() == nil then
+        clearPersistedChainOrderData(vehicle)
+    end
 
     local md = vehicle:getModData()
     if md then
@@ -234,24 +487,42 @@ local function markTowBarPair(towingVehicle, towedVehicle)
     local towedMd = towedVehicle and towedVehicle:getModData() or nil
 
     if towingMd then
+        local towingChanged = false
+        if towingMd["isTowingByTowBar"] ~= true then
             towingMd["isTowingByTowBar"] = true
+            towingChanged = true
+        end
+        if towingChanged then
             towingVehicle:transmitModData()
         end
+    end
     if towedMd then
+        local towedChanged = false
         local currentScript = towedVehicle and towedVehicle:getScriptName() or nil
         if towedMd.towBarOriginalScriptName == nil and currentScript ~= "notTowingA_Trailer" then
             towedMd.towBarOriginalScriptName = currentScript
+            towedChanged = true
         end
         if towedMd.towBarOriginalMass == nil and towedVehicle then
             towedMd.towBarOriginalMass = towedVehicle:getMass()
+            towedChanged = true
         end
         if towedMd.towBarOriginalBrakingForce == nil and towedVehicle then
             towedMd.towBarOriginalBrakingForce = towedVehicle:getBrakingForce()
+            towedChanged = true
         end
+        if towedMd["isTowingByTowBar"] ~= true then
             towedMd["isTowingByTowBar"] = true
+            towedChanged = true
+        end
+        if towedMd["towed"] ~= true then
             towedMd["towed"] = true
+            towedChanged = true
+        end
+        if towedChanged then
             towedVehicle:transmitModData()
         end
+    end
 end
 
 local function ensurePairAttached(playerObj, towingVehicle, towedVehicle, preferredA, preferredB, alwaysSend)
@@ -278,6 +549,7 @@ local function ensurePairAttached(playerObj, towingVehicle, towedVehicle, prefer
     applyRigidTow(towingVehicle, towedVehicle, attachmentA, attachmentB)
     towedVehicle:setScriptName("notTowingA_Trailer")
     markTowBarPair(towingVehicle, towedVehicle)
+    storePersistedFrontLinkData(towingVehicle, towedVehicle, attachmentA, attachmentB)
 
     local linked = isLinkedPair(towingVehicle, towedVehicle)
     log("ensurePairAttached pair=" .. tostring(vehicleId(towingVehicle)) .. "->" .. tostring(vehicleId(towedVehicle))
@@ -297,6 +569,7 @@ local function ensurePairAttached(playerObj, towingVehicle, towedVehicle, prefer
     setTowBarModelVisible(towedVehicle, true)
     refreshAround(towingVehicle)
     refreshAround(towedVehicle)
+    snapshotActiveTowLinks()
     return true
 end
 
@@ -564,6 +837,7 @@ LT.performDetachWrapper = function(playerObj, towingVehicle, towedVehicle)
     queueAction(playerObj, 12, function(_, v) restoreDefaultsIfLeadLost(v); refreshAround(v) end, resolvedTowed)
 
     setTowBarModelVisible(resolvedTowed, false)
+    snapshotActiveTowLinks()
 end
 
 LT.showRadialWrapper = function(playerObj)
@@ -611,6 +885,319 @@ LT.onDetachTrailerWrapper = function(playerObj, vehicle, ...)
     end
 end
 
+local function collectPersistedLinks(vehicles)
+    local links = {}
+
+    for _, rearVehicle in ipairs(vehicles) do
+        local md = rearVehicle and rearVehicle:getModData() or nil
+        local frontSql = md and tonumber(md[PERSIST_FRONT_SQL_KEY]) or nil
+        local headSql = md and tonumber(md[PERSIST_CHAIN_HEAD_SQL_KEY]) or nil
+        local rearOrder = md and tonumber(md[PERSIST_CHAIN_ORDER_KEY]) or nil
+        local chainToken = md and tostring(md[PERSIST_CHAIN_TOKEN_KEY] or "") or ""
+        if not (headSql and headSql > 0) then headSql = nil end
+        if not (rearOrder and rearOrder >= 2) then rearOrder = nil end
+        if chainToken == "" then chainToken = nil end
+        if (frontSql and frontSql > 0) or ((headSql or chainToken) and rearOrder) then
+            local rearSql = rearVehicle.getSqlId and tonumber(rearVehicle:getSqlId()) or nil
+            local link = {
+                rear = rearVehicle,
+                rearSql = rearSql,
+                frontSql = (frontSql and frontSql > 0) and frontSql or nil,
+                headSql = headSql,
+                rearOrder = rearOrder,
+                chainToken = chainToken,
+                attachmentA = md[PERSIST_ATTACHMENT_A_KEY] or "trailer",
+                attachmentB = md[PERSIST_ATTACHMENT_B_KEY] or "trailerfront"
+            }
+            table.insert(links, link)
+        end
+    end
+
+    return links
+end
+
+local function computePersistedDepth(link, byRearSql, visitedSql)
+    if not link or not link.frontSql then return 0 end
+    visitedSql = visitedSql or {}
+    if visitedSql[link.frontSql] then return 0 end
+
+    local frontLink = byRearSql[link.frontSql]
+    if not frontLink then return 0 end
+
+    visitedSql[link.frontSql] = true
+    return 1 + computePersistedDepth(frontLink, byRearSql, visitedSql)
+end
+
+local function filterAmbiguousPersistedLinks(links)
+    if #links <= 1 then return links end
+
+    local frontCounts = {}
+    for _, link in ipairs(links) do
+        if link.frontSql then
+            frontCounts[link.frontSql] = (frontCounts[link.frontSql] or 0) + 1
+        end
+    end
+
+    local filtered = {}
+    local dropped = 0
+    for _, link in ipairs(links) do
+        if link.frontSql and frontCounts[link.frontSql] and frontCounts[link.frontSql] > 1 then
+            dropped = dropped + 1
+        else
+            table.insert(filtered, link)
+        end
+    end
+
+    if dropped > 0 then
+        log("load rebuild skipped ambiguous links dropped=" .. tostring(dropped))
+    end
+
+    return filtered
+end
+
+local function linkOrderKey(link)
+    if not link then return nil end
+    if link.headSql and link.headSql > 0 then
+        return "sql:" .. tostring(link.headSql)
+    end
+    if link.chainToken and tostring(link.chainToken) ~= "" then
+        return "tok:" .. tostring(link.chainToken)
+    end
+    return nil
+end
+
+local function filterConflictingOrderedLinks(links)
+    if #links <= 1 then return links end
+
+    local orderSlots = {}
+    for _, link in ipairs(links) do
+        local orderKey = linkOrderKey(link)
+        if orderKey and link.rearOrder and link.rearOrder >= 2 then
+            local key = orderKey .. ":" .. tostring(link.rearOrder)
+            orderSlots[key] = (orderSlots[key] or 0) + 1
+        end
+    end
+
+    local filtered = {}
+    local dropped = 0
+    for _, link in ipairs(links) do
+        local orderKey = linkOrderKey(link)
+        if orderKey and link.rearOrder and link.rearOrder >= 2 then
+            local key = orderKey .. ":" .. tostring(link.rearOrder)
+            if (orderSlots[key] or 0) > 1 then
+                dropped = dropped + 1
+            else
+                table.insert(filtered, link)
+            end
+        else
+            table.insert(filtered, link)
+        end
+    end
+
+    if dropped > 0 then
+        log("load rebuild skipped conflicting ordered links dropped=" .. tostring(dropped))
+    end
+
+    return filtered
+end
+
+local function indexPersistedLinksByRearSql(links)
+    local byRearSql = {}
+    for _, link in ipairs(links) do
+        if link.rearSql and link.rearSql > 0 then
+            byRearSql[link.rearSql] = link
+        end
+    end
+    return byRearSql
+end
+
+local function indexVehiclesByHeadAndOrder(vehicles)
+    local byHead = {}
+    for _, vehicle in ipairs(vehicles) do
+        local md = vehicle and vehicle:getModData() or nil
+        local headSql = md and tonumber(md[PERSIST_CHAIN_HEAD_SQL_KEY]) or nil
+        local order = md and tonumber(md[PERSIST_CHAIN_ORDER_KEY]) or nil
+        local chainToken = md and tostring(md[PERSIST_CHAIN_TOKEN_KEY] or "") or ""
+        if chainToken == "" then chainToken = nil end
+        local key = nil
+        if headSql and headSql > 0 then
+            key = "sql:" .. tostring(headSql)
+        elseif chainToken then
+            key = "tok:" .. tostring(chainToken)
+        end
+        if key and order and order > 0 then
+            byHead[key] = byHead[key] or {}
+            if byHead[key][order] == nil then
+                byHead[key][order] = vehicle
+            else
+                byHead[key][order] = false
+            end
+        end
+    end
+    return byHead
+end
+
+local function sortPersistedLinks(links, byRearSql)
+    table.sort(links, function(a, b)
+        local orderKeyA = linkOrderKey(a)
+        local orderKeyB = linkOrderKey(b)
+        if orderKeyA and orderKeyB then
+            if orderKeyA ~= orderKeyB then
+                return orderKeyA < orderKeyB
+            end
+            if a.rearOrder and b.rearOrder and a.rearOrder ~= b.rearOrder then
+                return a.rearOrder < b.rearOrder
+            end
+        end
+
+        local depthA = computePersistedDepth(a, byRearSql, {})
+        local depthB = computePersistedDepth(b, byRearSql, {})
+        if depthA == depthB then
+            return vehicleId(a.rear) < vehicleId(b.rear)
+        end
+        return depthA < depthB
+    end)
+end
+
+local function isTowbarPairStateComplete(frontVehicle, rearVehicle)
+    if not isLinkedPair(frontVehicle, rearVehicle) then return false end
+    return rearVehicle:getScriptName() == "notTowingA_Trailer"
+end
+
+local function restoreViaAttachWrapper(playerObj, frontVehicle, rearVehicle, attachmentA, attachmentB)
+    if not playerObj or not frontVehicle or not rearVehicle then return false end
+    if not LT.performAttachWrapper then return false end
+    if not TowBarMod or not TowBarMod.Hook or TowBarMod.Hook._ltOriginalPerformAttach == nil then
+        return false
+    end
+
+    local ok, err = pcall(LT.performAttachWrapper, playerObj, frontVehicle, rearVehicle, attachmentA, attachmentB)
+    if not ok then
+        log("load rebuild wrapper attach failed pair=" .. tostring(vehicleId(frontVehicle)) .. "->" .. tostring(vehicleId(rearVehicle))
+            .. " err=" .. tostring(err))
+        return false
+    end
+    return true
+end
+
+local function restorePersistedLink(playerObj, link, bySql, byHeadOrder)
+    if not playerObj or not link then return false end
+
+    local rearVehicle = link.rear
+    local frontVehicle = nil
+    if link.frontSql and bySql then
+        frontVehicle = bySql[link.frontSql]
+    end
+    local orderKey = linkOrderKey(link)
+    if not frontVehicle and orderKey and link.rearOrder and link.rearOrder >= 2 and byHeadOrder then
+        local byOrder = byHeadOrder[orderKey]
+        if byOrder then
+            local candidate = byOrder[link.rearOrder - 1]
+            if candidate and candidate ~= false then
+                frontVehicle = candidate
+            end
+        end
+    end
+    if not rearVehicle or not frontVehicle then return false end
+    if rearVehicle == frontVehicle or rearVehicle:getId() == frontVehicle:getId() then return false end
+
+    if isTowbarPairStateComplete(frontVehicle, rearVehicle) then
+        return false
+    end
+
+    if rearVehicle:getVehicleTowedBy() ~= nil and rearVehicle:getVehicleTowedBy() ~= frontVehicle then
+        return false
+    end
+    if frontVehicle:getVehicleTowing() ~= nil and frontVehicle:getVehicleTowing() ~= rearVehicle then
+        return false
+    end
+    if orderKey and link.rearOrder and link.rearOrder >= 2 then
+        local frontMd = frontVehicle and frontVehicle:getModData() or nil
+        local frontHeadSql = frontMd and tonumber(frontMd[PERSIST_CHAIN_HEAD_SQL_KEY]) or nil
+        local frontOrder = frontMd and tonumber(frontMd[PERSIST_CHAIN_ORDER_KEY]) or nil
+        local frontChainToken = frontMd and tostring(frontMd[PERSIST_CHAIN_TOKEN_KEY] or "") or ""
+        if frontChainToken == "" then frontChainToken = nil end
+        local frontOrderKey = nil
+        if frontHeadSql and frontHeadSql > 0 then
+            frontOrderKey = "sql:" .. tostring(frontHeadSql)
+        elseif frontChainToken then
+            frontOrderKey = "tok:" .. tostring(frontChainToken)
+        end
+        if frontOrderKey ~= orderKey or frontOrder ~= (link.rearOrder - 1) then
+            return false
+        end
+    end
+    if wouldCreateTowLoop(frontVehicle, rearVehicle) then return false end
+
+    if not isLinkedPair(frontVehicle, rearVehicle) then
+        if not canTowByLandtrain(frontVehicle, rearVehicle, link.attachmentA, link.attachmentB, true) then
+            return false
+        end
+        if restoreViaAttachWrapper(playerObj, frontVehicle, rearVehicle, link.attachmentA, link.attachmentB) then
+            return true
+        end
+    end
+
+    return ensurePairAttached(playerObj, frontVehicle, rearVehicle, link.attachmentA, link.attachmentB, true)
+end
+
+local function runPersistedLoadRebuildPass()
+    if not TowBarMod or not TowBarMod.Hook or TowBarMod.Hook._ltOriginalPerformAttach == nil then
+        return
+    end
+
+    local playerObj = getPlayer() or getSpecificPlayer(0)
+    if not playerObj then return end
+
+    local vehicles = getLoadedVehicles()
+    if #vehicles == 0 then return end
+
+    local bySql = indexVehiclesBySql(vehicles)
+    local byHeadOrder = indexVehiclesByHeadAndOrder(vehicles)
+    local links = collectPersistedLinks(vehicles)
+    links = filterAmbiguousPersistedLinks(links)
+    links = filterConflictingOrderedLinks(links)
+    if #links == 0 then return end
+    local byRearSql = indexPersistedLinksByRearSql(links)
+    sortPersistedLinks(links, byRearSql)
+
+    local attempted = 0
+    local restored = 0
+    for _, link in ipairs(links) do
+        attempted = attempted + 1
+        if restorePersistedLink(playerObj, link, bySql, byHeadOrder) then
+            restored = restored + 1
+        end
+    end
+
+    if restored > 0 then
+        log("load rebuild pass restored=" .. tostring(restored) .. "/" .. tostring(attempted))
+    end
+end
+
+local loadRebuildWarmupTicks = 0
+local loadRebuildIntervalTicks = 0
+
+local function loadRebuildTick()
+    if loadRebuildWarmupTicks > 0 then
+        loadRebuildWarmupTicks = loadRebuildWarmupTicks - 1
+        return
+    end
+
+    loadRebuildIntervalTicks = loadRebuildIntervalTicks + 1
+    if loadRebuildIntervalTicks < 180 then return end
+    loadRebuildIntervalTicks = 0
+
+    runPersistedLoadRebuildPass()
+end
+
+local function startLoadRebuildWatch()
+    loadRebuildWarmupTicks = 120
+    loadRebuildIntervalTicks = 0
+    Events.OnTick.Remove(loadRebuildTick)
+    Events.OnTick.Add(loadRebuildTick)
+end
+
 local function ensureTrailerAttachments()
     local sm = getScriptManager()
     if sm == nil then return end
@@ -708,6 +1295,7 @@ local function startWatchdog()
     Events.OnTick.Remove(watchdogTick)
     Events.OnTick.Add(watchdogTick)
     installPatch()
+    startLoadRebuildWatch()
 end
 
 Events.OnGameBoot.Add(ensureTrailerAttachments)

42.13/media/lua/server/Landtrain/LandtrainTowSyncServer.lua

@@ -6,12 +6,193 @@ if TowBarMod.Landtrain._towSyncServerLoaded then return end
 TowBarMod.Landtrain._towSyncServerLoaded = true
 
 local SYNC_DELAY_TICKS = 2
+local SNAPSHOT_INTERVAL_TICKS = 120
 local pending = {}
+local snapshotTickCounter = 0
+local PERSIST_FRONT_SQL_KEY = "landtrainFrontTowSqlId"
+local PERSIST_FRONT_ID_KEY = "landtrainFrontTowId"
+local PERSIST_ATTACHMENT_A_KEY = "landtrainFrontTowAttachmentA"
+local PERSIST_ATTACHMENT_B_KEY = "landtrainFrontTowAttachmentB"
+local PERSIST_CHAIN_HEAD_SQL_KEY = "landtrainChainHeadSql"
+local PERSIST_CHAIN_ORDER_KEY = "landtrainChainOrder"
+local PERSIST_CHAIN_TOKEN_KEY = "landtrainChainToken"
 
 local function log(msg)
     print("[Landtrain][TowSyncServer] " .. tostring(msg))
 end
 
+local function storePersistedFrontLinkData(frontVehicle, rearVehicle, attachmentA, attachmentB)
+    if not frontVehicle or not rearVehicle then return end
+    local md = rearVehicle:getModData()
+    if not md then return end
+
+    local frontSql = frontVehicle.getSqlId and tonumber(frontVehicle:getSqlId()) or nil
+    local frontId = frontVehicle:getId()
+    local resolvedAttachmentA = attachmentA or "trailer"
+    local resolvedAttachmentB = attachmentB or "trailerfront"
+    local changed = false
+
+    if frontSql and frontSql > 0 then
+        if tonumber(md[PERSIST_FRONT_SQL_KEY]) ~= frontSql then
+            md[PERSIST_FRONT_SQL_KEY] = frontSql
+            changed = true
+        end
+    end
+
+    if tonumber(md[PERSIST_FRONT_ID_KEY]) ~= frontId then
+        md[PERSIST_FRONT_ID_KEY] = frontId
+        changed = true
+    end
+    if md[PERSIST_ATTACHMENT_A_KEY] ~= resolvedAttachmentA then
+        md[PERSIST_ATTACHMENT_A_KEY] = resolvedAttachmentA
+        changed = true
+    end
+    if md[PERSIST_ATTACHMENT_B_KEY] ~= resolvedAttachmentB then
+        md[PERSIST_ATTACHMENT_B_KEY] = resolvedAttachmentB
+        changed = true
+    end
+
+    if changed then
+        rearVehicle:transmitModData()
+    end
+end
+
+local function storePersistedChainOrderData(vehicle, headSql, orderIndex, chainToken)
+    if not vehicle then return end
+    local md = vehicle:getModData()
+    if not md then return end
+
+    local resolvedHeadSql = headSql and tonumber(headSql) or nil
+    local resolvedOrder = orderIndex and tonumber(orderIndex) or nil
+    local resolvedToken = chainToken and tostring(chainToken) or nil
+    if resolvedToken == "" then resolvedToken = nil end
+    local changed = false
+
+    if resolvedHeadSql and resolvedHeadSql > 0 then
+        if tonumber(md[PERSIST_CHAIN_HEAD_SQL_KEY]) ~= resolvedHeadSql then
+            md[PERSIST_CHAIN_HEAD_SQL_KEY] = resolvedHeadSql
+            changed = true
+        end
+    elseif md[PERSIST_CHAIN_HEAD_SQL_KEY] ~= nil then
+        md[PERSIST_CHAIN_HEAD_SQL_KEY] = nil
+        changed = true
+    end
+
+    if resolvedOrder and resolvedOrder > 0 then
+        if tonumber(md[PERSIST_CHAIN_ORDER_KEY]) ~= resolvedOrder then
+            md[PERSIST_CHAIN_ORDER_KEY] = resolvedOrder
+            changed = true
+        end
+    elseif md[PERSIST_CHAIN_ORDER_KEY] ~= nil then
+        md[PERSIST_CHAIN_ORDER_KEY] = nil
+        changed = true
+    end
+
+    if resolvedToken then
+        if tostring(md[PERSIST_CHAIN_TOKEN_KEY]) ~= resolvedToken then
+            md[PERSIST_CHAIN_TOKEN_KEY] = resolvedToken
+            changed = true
+        end
+    elseif md[PERSIST_CHAIN_TOKEN_KEY] ~= nil then
+        md[PERSIST_CHAIN_TOKEN_KEY] = nil
+        changed = true
+    end
+
+    if changed then
+        vehicle:transmitModData()
+    end
+end
+
+local function clearPersistedChainOrderData(vehicle)
+    if not vehicle then return end
+    local md = vehicle:getModData()
+    if not md then return end
+
+    local changed = false
+    if md[PERSIST_CHAIN_HEAD_SQL_KEY] ~= nil then
+        md[PERSIST_CHAIN_HEAD_SQL_KEY] = nil
+        changed = true
+    end
+    if md[PERSIST_CHAIN_ORDER_KEY] ~= nil then
+        md[PERSIST_CHAIN_ORDER_KEY] = nil
+        changed = true
+    end
+    if md[PERSIST_CHAIN_TOKEN_KEY] ~= nil then
+        md[PERSIST_CHAIN_TOKEN_KEY] = nil
+        changed = true
+    end
+
+    if changed then
+        vehicle:transmitModData()
+    end
+end
+
+local function clearPersistedFrontLinkData(rearVehicle)
+    if not rearVehicle then return end
+    local md = rearVehicle:getModData()
+    if not md then return end
+
+    local changed = false
+    if md[PERSIST_FRONT_SQL_KEY] ~= nil then
+        md[PERSIST_FRONT_SQL_KEY] = nil
+        changed = true
+    end
+    if md[PERSIST_FRONT_ID_KEY] ~= nil then
+        md[PERSIST_FRONT_ID_KEY] = nil
+        changed = true
+    end
+    if md[PERSIST_ATTACHMENT_A_KEY] ~= nil then
+        md[PERSIST_ATTACHMENT_A_KEY] = nil
+        changed = true
+    end
+    if md[PERSIST_ATTACHMENT_B_KEY] ~= nil then
+        md[PERSIST_ATTACHMENT_B_KEY] = nil
+        changed = true
+    end
+
+    if changed then
+        rearVehicle:transmitModData()
+    end
+end
+
+local function resolveDetachPair(vehicleA, vehicleB)
+    local front = vehicleA
+    local rear = vehicleB
+
+    if front and rear then
+        if front:getVehicleTowing() == rear and rear:getVehicleTowedBy() == front then
+            return front, rear
+        end
+        if rear:getVehicleTowing() == front and front:getVehicleTowedBy() == rear then
+            return rear, front
+        end
+    end
+
+    if front and not rear then
+        local directRear = front:getVehicleTowing()
+        if directRear and directRear:getVehicleTowedBy() == front then
+            return front, directRear
+        end
+        local directFront = front:getVehicleTowedBy()
+        if directFront and directFront:getVehicleTowing() == front then
+            return directFront, front
+        end
+    end
+
+    if rear and not front then
+        local directFront = rear:getVehicleTowedBy()
+        if directFront and directFront:getVehicleTowing() == rear then
+            return directFront, rear
+        end
+        local directRear = rear:getVehicleTowing()
+        if directRear and directRear:getVehicleTowedBy() == rear then
+            return rear, directRear
+        end
+    end
+
+    return nil, nil
+end
+
 local function queueSync(kind, player, args)
     if not args then return end
     table.insert(pending, {
@@ -33,6 +214,19 @@ local function isLinked(vehicleA, vehicleB)
     return vehicleA:getVehicleTowing() == vehicleB and vehicleB:getVehicleTowedBy() == vehicleA
 end
 
+local function hasValidTowLink(vehicle)
+    if not vehicle then return false end
+    local rear = vehicle:getVehicleTowing()
+    if rear and rear:getVehicleTowedBy() == vehicle then
+        return true
+    end
+    local front = vehicle:getVehicleTowedBy()
+    if front and front:getVehicleTowing() == vehicle then
+        return true
+    end
+    return false
+end
+
 local function resolveAttachmentA(args, vehicleA)
     if args and args.attachmentA then return args.attachmentA end
     if vehicleA and vehicleA:getTowAttachmentSelf() then return vehicleA:getTowAttachmentSelf() end
@@ -45,6 +239,99 @@ local function resolveAttachmentB(args, vehicleB)
     return "trailerfront"
 end
 
+local function resolveSnapshotAttachmentPair(vehicleA, vehicleB)
+    local selfA = vehicleA and vehicleA:getTowAttachmentSelf() or nil
+    local selfB = vehicleB and vehicleB:getTowAttachmentSelf() or nil
+    local candidates = {
+        { selfA, selfB },
+        { "trailer", "trailerfront" },
+        { "trailerfront", "trailer" }
+    }
+
+    for _, pair in ipairs(candidates) do
+        local attachmentA = pair[1]
+        local attachmentB = pair[2]
+        if attachmentA and attachmentB and attachmentA ~= attachmentB
+            and vehicleHasAttachment(vehicleA, attachmentA) and vehicleHasAttachment(vehicleB, attachmentB) then
+            return attachmentA, attachmentB
+        end
+    end
+
+    return "trailer", "trailerfront"
+end
+
+local function snapshotChainFromHead(headVehicle, visitedIds)
+    if not headVehicle then return end
+
+    local headSql = headVehicle.getSqlId and tonumber(headVehicle:getSqlId()) or nil
+    if not (headSql and headSql > 0) then
+        headSql = nil
+    end
+    local headMd = headVehicle:getModData()
+    local chainToken = headMd and tostring(headMd[PERSIST_CHAIN_TOKEN_KEY] or "") or ""
+    if chainToken == "" then
+        if headSql then
+            chainToken = "sql:" .. tostring(headSql)
+        else
+            chainToken = "veh:" .. tostring(headVehicle:getId())
+        end
+    end
+    if headVehicle:getVehicleTowedBy() == nil then
+        clearPersistedFrontLinkData(headVehicle)
+    end
+
+    local cursor = headVehicle
+    local order = 1
+    local localVisited = {}
+    while cursor do
+        local cursorId = cursor:getId()
+        if visitedIds[cursorId] or localVisited[cursorId] then
+            break
+        end
+
+        visitedIds[cursorId] = true
+        localVisited[cursorId] = true
+        storePersistedChainOrderData(cursor, headSql, order, chainToken)
+
+        local rearVehicle = cursor:getVehicleTowing()
+        if rearVehicle and rearVehicle:getVehicleTowedBy() == cursor then
+            local attachmentA, attachmentB = resolveSnapshotAttachmentPair(cursor, rearVehicle)
+            storePersistedFrontLinkData(cursor, rearVehicle, attachmentA, attachmentB)
+        end
+
+        cursor = rearVehicle
+        order = order + 1
+    end
+end
+
+local function snapshotActiveTowLinksServer()
+    local cell = getCell()
+    if not cell then return end
+    local list = cell:getVehicles()
+    if not list then return end
+
+    local visitedIds = {}
+
+    for i = 0, list:size() - 1 do
+        local vehicle = list:get(i)
+        local vehicleId = vehicle and vehicle:getId() or nil
+        if vehicleId and not visitedIds[vehicleId] and vehicle:getVehicleTowedBy() == nil then
+            local rearVehicle = vehicle:getVehicleTowing()
+            if rearVehicle and rearVehicle:getVehicleTowedBy() == vehicle then
+                snapshotChainFromHead(vehicle, visitedIds)
+            end
+        end
+    end
+
+    for i = 0, list:size() - 1 do
+        local vehicle = list:get(i)
+        local vehicleId = vehicle and vehicle:getId() or nil
+        if vehicleId and not visitedIds[vehicleId] and hasValidTowLink(vehicle) then
+            snapshotChainFromHead(vehicle, visitedIds)
+        end
+    end
+end
+
 local function processAttach(item)
     local args = item.args or {}
     local vehicleA = args.vehicleA and getVehicleById(args.vehicleA) or nil
@@ -74,6 +361,9 @@ local function processAttach(item)
         log("attach sync already linked A=" .. tostring(vehicleA:getId()) .. " B=" .. tostring(vehicleB:getId()))
     end
 
+    storePersistedFrontLinkData(vehicleA, vehicleB, attachmentA, attachmentB)
+    snapshotActiveTowLinksServer()
+
     log("attach sync broadcast A=" .. tostring(vehicleA:getId()) .. " B=" .. tostring(vehicleB:getId())
         .. " attachmentA=" .. tostring(attachmentA) .. " attachmentB=" .. tostring(attachmentB))
     sendServerCommand("landtrain", "forceAttachSync", {
@@ -88,14 +378,31 @@ local function processDetach(item)
     local args = item.args or {}
     local vehicleAId = args.towingVehicle or args.vehicleA or args.vehicle
     local vehicleBId = args.vehicleB
+    local vehicleA = vehicleAId and getVehicleById(vehicleAId) or nil
+    local vehicleB = vehicleBId and getVehicleById(vehicleBId) or nil
+    local _, resolvedRear = resolveDetachPair(vehicleA, vehicleB)
+    if resolvedRear then
+        clearPersistedFrontLinkData(resolvedRear)
+        clearPersistedChainOrderData(resolvedRear)
+    elseif vehicleB then
+        clearPersistedFrontLinkData(vehicleB)
+        clearPersistedChainOrderData(vehicleB)
+    end
 
     sendServerCommand("landtrain", "forceDetachSync", {
         vehicleA = vehicleAId,
         vehicleB = vehicleBId
     })
+    snapshotActiveTowLinksServer()
 end
 
 local function processPending()
+    snapshotTickCounter = snapshotTickCounter + 1
+    if snapshotTickCounter >= SNAPSHOT_INTERVAL_TICKS then
+        snapshotTickCounter = 0
+        snapshotActiveTowLinksServer()
+    end
+
     if #pending == 0 then return end
 
     local remaining = {}