class_name MatchmakingState
extends RefCounted

# Client-side projection of the authenticated control-plane lifecycle. The
# server remains authoritative; this object only decides what the UI may show
# and refuses stale, gapped, or conflicting revisions instead of guessing.

signal changed(snapshot: Dictionary)
signal resync_required(resource_id: String)

const IDLE := "IDLE"
const QUEUED := "QUEUED"
const PROPOSED := "PROPOSED"
const ACCEPTED := "ACCEPTED"
const ALLOCATING := "ALLOCATING"
const PROCESS_READY := "PROCESS_READY"
const ASSIGNMENT_READY := "ASSIGNMENT_READY"
const CONNECTING := "CONNECTING"
const LIVE := "LIVE"
const ASSIGNED := "ASSIGNED"
const RESULT_PENDING := "RESULT_PENDING"
const COMPLETED := "COMPLETED"
const CANCELLED := "CANCELLED"
const EXPIRED := "EXPIRED"
const FAILED := "FAILED"

var phase := IDLE
var ticket_id := ""
var playlist := ""
var revision := 0
var enqueued_at_unix := 0
var expires_at_unix := 0
var proposal_id := ""
var proposal_revision := 0
var proposal_state := ""
var message := ""
var needs_resync := false


func begin_queue(new_ticket_id: String, new_playlist: String) -> bool:
	if new_ticket_id.is_empty() or (new_playlist != "casual" and new_playlist != "ranked"):
		return false
	_reset()
	ticket_id = new_ticket_id
	playlist = new_playlist
	phase = QUEUED
	_emit_changed()
	return true


func apply_ticket_update(update: Dictionary) -> bool:
	if not _has_string(update, "ticket_id") or not update.has("revision") or not _valid_revision(update["revision"]) or not update.has("state"):
		return _request_resync(self.ticket_id)
	if update.has("playlist") and not _valid_playlist(String(update["playlist"])):
		return _request_resync(self.ticket_id)
	if ticket_id.is_empty() or String(update["ticket_id"]) != ticket_id:
		return _request_resync(self.ticket_id)
	var incoming_revision := int(update["revision"])
	if incoming_revision < revision:
		return false
	if incoming_revision == revision:
		if _ticket_differs(update):
			return _request_resync(self.ticket_id)
		# expires_at_unix is deliberately not part of _ticket_differs' conflict
		# check (see its own comment) but is still adopted here: begin_queue()
		# has no way to know the server-assigned expiry in advance, so the
		# very first same-revision confirmation is the only place a freshly
		# queued ticket's expiry is ever set at all.
		if update.has("expires_at_unix"):
			expires_at_unix = int(update["expires_at_unix"])
		if update.has("enqueued_at_unix"):
			enqueued_at_unix = maxi(0, int(update["enqueued_at_unix"]))
		return true
	if incoming_revision > revision + 1:
		return _request_resync(self.ticket_id)
	var incoming_state := String(update["state"])
	if not _is_ticket_state(incoming_state):
		return _request_resync(self.ticket_id)
	if not _is_legal_ticket_transition(phase, incoming_state):
		return _request_resync(self.ticket_id)
	revision = incoming_revision
	phase = incoming_state
	if update.has("playlist"):
		playlist = String(update["playlist"])
	if update.has("expires_at_unix"):
		expires_at_unix = int(update["expires_at_unix"])
	if update.has("enqueued_at_unix"):
		enqueued_at_unix = maxi(0, int(update["enqueued_at_unix"]))
	if update.has("message"):
		message = String(update["message"])
	else:
		message = ""
	needs_resync = false
	_emit_changed()
	return true


func apply_proposal_update(update: Dictionary) -> bool:
	if not _has_string(update, "proposal_id") or not update.has("revision") or not _valid_revision(update["revision"]) or not update.has("state"):
		return _request_resync(proposal_id)
	var incoming_id := String(update["proposal_id"])
	if proposal_id.is_empty():
		proposal_id = incoming_id
	elif proposal_id != incoming_id:
		return _request_resync(proposal_id)
	var incoming_revision := int(update["revision"])
	if incoming_revision < proposal_revision:
		return false
	if incoming_revision == proposal_revision and not proposal_state.is_empty():
		if String(update["state"]) != proposal_state:
			return _request_resync(proposal_id)
		return true
	if not proposal_state.is_empty() and incoming_revision > proposal_revision + 1:
		return _request_resync(proposal_id)
	var incoming_proposal_state := String(update["state"])
	if incoming_proposal_state == "OPEN":
		if not _is_legal_proposal_transition(proposal_state, incoming_proposal_state):
			return _request_resync(proposal_id)
		phase = PROPOSED
	elif incoming_proposal_state == "ACCEPTED":
		if not _is_legal_proposal_transition(proposal_state, incoming_proposal_state):
			return _request_resync(proposal_id)
		phase = ALLOCATING
	elif incoming_proposal_state == "DECLINED":
		if not _is_legal_proposal_transition(proposal_state, incoming_proposal_state):
			return _request_resync(proposal_id)
		phase = FAILED
		message = "A player declined the match proposal"
	elif incoming_proposal_state == "EXPIRED":
		if not _is_legal_proposal_transition(proposal_state, incoming_proposal_state):
			return _request_resync(proposal_id)
		phase = EXPIRED
		message = "The match proposal expired"
	elif incoming_proposal_state == "CANCELLED":
		if not _is_legal_proposal_transition(proposal_state, incoming_proposal_state):
			return _request_resync(proposal_id)
		phase = CANCELLED
		message = "The match proposal was cancelled"
	else:
		return _request_resync(proposal_id)
	proposal_revision = incoming_revision
	proposal_state = incoming_proposal_state
	needs_resync = false
	if incoming_proposal_state == "OPEN" or incoming_proposal_state == "ACCEPTED":
		message = ""
	if update.has("expires_at_unix"):
		expires_at_unix = int(update["expires_at_unix"])
	_emit_changed()
	return true


func mark_assignment_ready() -> void:
	phase = ASSIGNMENT_READY
	message = "Match server is ready"
	_emit_changed()


func mark_connecting() -> void:
	phase = CONNECTING
	message = "Connecting to match server"
	_emit_changed()


func mark_live() -> void:
	phase = LIVE
	message = "Match in progress"
	_emit_changed()


func fail(reason: String) -> void:
	phase = FAILED
	message = reason if not reason.is_empty() else "Matchmaking failed"
	_emit_changed()


func expire(reason: String = "Matchmaking expired") -> void:
	phase = EXPIRED
	message = reason
	_emit_changed()


func set_notice(notice: String) -> void:
	message = notice
	_emit_changed()


func restore_snapshot(saved: Dictionary) -> bool:
	_reset()
	if saved.is_empty():
		return true
	var saved_phase := String(saved.get("phase", IDLE))
	var saved_ticket_id := String(saved.get("ticket_id", ""))
	if saved_ticket_id.is_empty() or not _is_ticket_state(saved_phase):
		return false
	var saved_playlist := String(saved.get("playlist", ""))
	if saved_playlist != "casual" and saved_playlist != "ranked":
		return false
	ticket_id = saved_ticket_id
	playlist = saved_playlist
	phase = saved_phase
	revision = maxi(0, int(saved.get("revision", 0)))
	enqueued_at_unix = maxi(0, int(saved.get("enqueued_at_unix", 0)))
	expires_at_unix = maxi(0, int(saved.get("expires_at_unix", 0)))
	proposal_id = String(saved.get("proposal_id", ""))
	proposal_revision = maxi(0, int(saved.get("proposal_revision", 0)))
	proposal_state = String(saved.get("proposal_state", ""))
	message = "Recovering authoritative matchmaking state"
	needs_resync = phase != CANCELLED and phase != EXPIRED and phase != FAILED and phase != COMPLETED
	_emit_changed()
	return true


func can_cancel() -> bool:
	return phase == QUEUED or phase == PROPOSED or phase == ALLOCATING


func waited_seconds(now_unix: int) -> int:
	if enqueued_at_unix <= 0:
		return 0
	return maxi(0, now_unix - enqueued_at_unix)


func snapshot() -> Dictionary:
	return {"phase": phase, "ticket_id": ticket_id, "playlist": playlist, "revision": revision, "enqueued_at_unix": enqueued_at_unix, "expires_at_unix": expires_at_unix, "proposal_id": proposal_id, "proposal_revision": proposal_revision, "proposal_state": proposal_state, "message": message, "needs_resync": needs_resync}


func _ticket_differs(update: Dictionary) -> bool:
	# expires_at_unix is excluded on purpose: begin_queue()'s optimistic local
	# state has no way to know the server-assigned expiry before the first
	# real response arrives, so comparing it here made the very first
	# same-revision confirmation after every begin_queue() look like a
	# conflict, unconditionally -- found by an actual client hitting a real
	# server: apply_ticket_update() kept requesting a resync, whose own
	# response hit exactly the same false mismatch, forever, which
	# control_plane_smoke.gd (a live end-to-end test, not a mock) surfaced as
	# a request that legitimately never terminates. It's still kept current
	# via the direct assignment below, just not treated as a conflict signal.
	return String(update["state"]) != phase or (update.has("playlist") and String(update["playlist"]) != playlist)


func _request_resync(resource_id: String) -> bool:
	needs_resync = true
	resync_required.emit(resource_id)
	return false


func _emit_changed() -> void:
	changed.emit(snapshot())


func _reset() -> void:
	phase = IDLE
	playlist = ""
	revision = 0
	enqueued_at_unix = 0
	expires_at_unix = 0
	proposal_id = ""
	proposal_revision = 0
	proposal_state = ""
	message = ""
	needs_resync = false


func _is_ticket_state(value: String) -> bool:
	return value in [QUEUED, PROPOSED, ACCEPTED, ALLOCATING, PROCESS_READY, ASSIGNMENT_READY, ASSIGNED, CONNECTING, LIVE, RESULT_PENDING, COMPLETED, CANCELLED, EXPIRED, FAILED]


func _is_legal_ticket_transition(from: String, to: String) -> bool:
	if from == to:
		return true
	var transitions := {
		QUEUED: [PROPOSED, CANCELLED, EXPIRED],
		PROPOSED: [QUEUED, ACCEPTED, CANCELLED, EXPIRED],
		ACCEPTED: [QUEUED, ALLOCATING, CANCELLED, FAILED],
		ALLOCATING: [PROCESS_READY, FAILED, CANCELLED],
		PROCESS_READY: [ASSIGNMENT_READY, FAILED, CANCELLED],
		ASSIGNMENT_READY: [ASSIGNED, FAILED, CANCELLED],
		ASSIGNED: [CONNECTING, FAILED, CANCELLED],
		CONNECTING: [LIVE, FAILED, EXPIRED],
		LIVE: [RESULT_PENDING, FAILED],
		RESULT_PENDING: [COMPLETED, FAILED],
	}
	return transitions.has(from) and to in transitions[from]


func _is_legal_proposal_transition(from: String, to: String) -> bool:
	if from.is_empty():
		return to == "OPEN"
	if from == to:
		return true
	return from == "OPEN" and to in ["ACCEPTED", "DECLINED", "EXPIRED", "CANCELLED"]


func _has_string(value: Dictionary, key: String) -> bool:
	return value.has(key) and value[key] is String and not String(value[key]).is_empty()


func _valid_revision(value: Variant) -> bool:
	if value is int:
		return int(value) >= 0
	if value is float:
		return is_finite(float(value)) and float(value) >= 0.0 and float(value) == floor(float(value))
	return false


func _valid_playlist(value: String) -> bool:
	return value == "casual" or value == "ranked"