-- PROTOTYPE (ticket "Can a script swap the positions of a follower and its leader?"): throwaway,
-- lives only on branch prototype/vehicle-probe.
-- Engine thread: every INTERVAL it logs every player-owned road vehicle (segment, lane, position, speed).
-- GUI thread: EXPERIMENT flipping the positions of a follower and its leader (see below).
-- Earlier experiments (timeToIgnore, engine-side jump, set-line, segment rebuild) are in git history and
-- docs/research/vehicle-probe.md; none moved a vehicle past another on a single-lane road.
-- ponytail: module-local timer, not GameScriptState; fine for a probe (state resets between calls anyway).

local TAG = "[overtake_probe] "
local INTERVAL = 2.0
local MAX_GAP = 40.0
local elapsed = 0.0
local ticks = 0

local function p(s : string)
	print(TAG .. s)
end

local function edgeAt(mp : Engine.Component.MovePath) : EdgeId, boolean
	-- path.edges is 1-based, elements are EdgeIdDir userdata (tealdef says {EdgeId, boolean})
	local e = (mp.path.edges as {any})[mp.dyn.pathPos.edgeIndex + 1] as UtilPathfinding.EdgeIdDir
	if e == nil then return nil, nil end
	return e.edgeId, e.dir
end

local function turnaround(edge : EdgeId) : integer
	local tn = api.engine.getComponent(edge.entity, api.type.ComponentType.TRANSPORT_NETWORK) as Engine.Component.TransportNetwork
	if tn == nil or tn.turnaroundEdges == nil then return nil end
	return tn.turnaroundEdges[edge.index + 1]
end

local record Car
	v : integer
	pos : number
	pos01 : number
	speed : number
	dir : boolean
end

local function dump(dt : number)
	local player = api.engine.util.getPlayer()
	local vehicles = api.engine.getEntitiesWithComponent(api.type.ComponentType.TRANSPORT_VEHICLE, { requireOwnedByPlayer = player })
	p(string.format("tick=%d dt=%s playerVehicles=%d", ticks, tostring(dt), #vehicles))
	for _, v in ipairs(vehicles) do
		local lv = api.engine.getComponent(v, api.type.ComponentType.LAND_VEHICLE) as Engine.Component.LandVehicle
		local mp = api.engine.getComponent(v, api.type.ComponentType.MOVE_PATH) as Engine.Component.MovePath
		local tv = api.engine.getComponent(v, api.type.ComponentType.TRANSPORT_VEHICLE) as Engine.Component.TransportVehicle
		if lv ~= nil and not lv.isTram and mp ~= nil then
			local edge, dir = edgeAt(mp)
			p(string.format(
				"veh=%d seg=%d lane=%s dir=%s turnaround=%s edgeIndex=%d/%d pos=%.1f speed=%.2f state=%s tvState=%s line=%s standing=%.1f",
				v, edge and edge.entity or -1, tostring(edge and edge.index), tostring(dir), tostring(edge and turnaround(edge)),
				mp.dyn.pathPos.edgeIndex, #(mp.path.edges as {any}), mp.dyn.pathPos.pos, mp.dyn.speed, tostring(mp.state),
				tostring(tv and tv.state), tostring(tv and tv.line), mp.dyn.timeStanding))
		end
	end
end

-- EXPERIMENT (GUI thread, where sendCommand callbacks work): flip the positions of a follower and its leader by
-- exchanging their MovePath components (route + position) with api.cmd.debug.makeComponentExchangeCmd.
local MAX_FLIPS = 2
local FLIP_SCAN_FRAMES = 60 -- scan for a pair about once per second
local FLIP_TRACE_FRAMES = 600 -- then log both vehicles every 10 frames for ~10 s

local record GuiState
	frames : integer
	flips : integer
	traceLeft : integer
	a : integer
	b : integer
end

local function movePathOf(v : integer) : Engine.Component.MovePath
	return api.engine.getComponent(v, api.type.ComponentType.MOVE_PATH) as Engine.Component.MovePath
end

local function flipLine(v : integer) : string
	local mp = movePathOf(v)
	if mp == nil then return "veh=" .. v .. " no MovePath" end
	local edge, _dir = edgeAt(mp)
	return string.format("veh=%d seg=%s lane=%s pos=%.1f v=%.2f", v, tostring(edge and edge.entity), tostring(edge and edge.index), mp.dyn.pathPos.pos, mp.dyn.speed)
end

local function sendFlip(gs : GuiState, follower : integer, leader : integer)
	local mpF, mpL = movePathOf(follower), movePathOf(leader)
	p("FLIP_TEST before " .. flipLine(follower) .. " | " .. flipLine(leader))
	local function done(label : string) : function(any, boolean)
		return function(res : any, success : boolean)
			p(string.format("FLIP_TEST result %s success=%s res=%s", label, tostring(success), tostring(res)))
		end
	end
	api.cmd.sendCommand(api.cmd.debug.makeComponentExchangeCmd(follower, mpL as Engine.Component), done("follower<-leader"))
	api.cmd.sendCommand(api.cmd.debug.makeComponentExchangeCmd(leader, mpF as Engine.Component), done("leader<-follower"))
	gs.flips = gs.flips + 1
	gs.traceLeft = FLIP_TRACE_FRAMES
	gs.a, gs.b = follower, leader
end

-- same pair rule as the engine-side probe: same segment + lane, follower < MAX_GAP behind a moving leader
local function findPair() : integer, integer
	local player = api.engine.util.getPlayer()
	local byLane : {string : {Car}} = {}
	for _, v in ipairs(api.engine.getEntitiesWithComponent(api.type.ComponentType.TRANSPORT_VEHICLE, { requireOwnedByPlayer = player })) do
		local lv = api.engine.getComponent(v, api.type.ComponentType.LAND_VEHICLE) as Engine.Component.LandVehicle
		local mp = movePathOf(v)
		if lv ~= nil and not lv.isTram and mp ~= nil then
			local edge, dir = edgeAt(mp)
			if edge ~= nil then
				local key = edge.entity .. ":" .. edge.index
				byLane[key] = byLane[key] or {}
				table.insert(byLane[key], { v = v, pos = mp.dyn.pathPos.pos, pos01 = mp.dyn.pathPos.pos01, speed = mp.dyn.speed, dir = dir })
			end
		end
	end
	for _, cars in pairs(byLane) do
		for i = 1, #cars do
			for j = 1, #cars do
				local a, b = cars[i], cars[j]
				local ahead = (a.dir and b.pos > a.pos) or (not a.dir and b.pos < a.pos)
				if i ~= j and ahead and math.abs(b.pos - a.pos) < MAX_GAP and b.speed > 1.0 then
					return a.v, b.v
				end
			end
		end
	end
	return nil, nil
end

local function guiStep(gsState : GameScriptState<GuiState>)
	local gs = gsState:get()
	gs.frames = (gs.frames or 0) + 1
	gs.flips = gs.flips or 0
	gs.traceLeft = gs.traceLeft or 0
	if gs.traceLeft > 0 then
		if gs.traceLeft % 10 == 0 then
			p(string.format("FLIP_TRACE f=%d %s | %s", FLIP_TRACE_FRAMES - gs.traceLeft, flipLine(gs.a), flipLine(gs.b)))
		end
		gs.traceLeft = gs.traceLeft - 1
	elseif gs.flips < MAX_FLIPS and gs.frames % FLIP_SCAN_FRAMES == 0 then
		local follower, leader = findPair()
		if follower ~= nil then sendFlip(gs, follower, leader) end
	end
	gsState:set(gs)
end

local ret : GameScriptWithGui<table, GuiState> = {
	update = function(_userParams : table, _state : GameScriptState<table>, dt : number) : nil
		ticks = ticks + 1
		elapsed = elapsed + dt
		if ticks == 1 then p("update running, first dt=" .. tostring(dt)) end
		if elapsed < INTERVAL then return end
		elapsed = 0.0
		xpcall(dump, function(err : any) p("ERROR " .. tostring(err)) end, dt)
	end,
	guiUpdate = function(_userParams : table, _state : GameScriptStateReadOnly<table>, guiState : GameScriptState<GuiState>)
		xpcall(guiStep, function(err : any) p("ERROR gui " .. tostring(err)) end, guiState)
	end,
}

return ret