class_name LogisticsRequest
extends RefCounted

enum State {
	OPEN,
	RESERVED,
	ASSIGNED,
	PICKING_UP,
	DELIVERING,
	COMPLETED,
	BLOCKED,
	CANCELLED,
}

const MAX_PRIORITY := 100

var request_id: StringName = &""
var source_inventory_id: StringName = &""
var destination_inventory_id: StringName = &""
var item_requirements: Dictionary = {}
var priority := 0
var created_at := 0
var deadline := -1
var total_weight := 0
var reserved_stack_ids: Array[StringName] = []
var reservation_ids: Array[StringName] = []
var assigned_carrier_id: StringName = &""
var state: State = State.OPEN
var retry_count := 0
var state_reason := ""
var state_changed_at := 0


func configure(
	p_request_id: StringName,
	p_source_inventory_id: StringName,
	p_destination_inventory_id: StringName,
	p_item_requirements: Dictionary,
	p_priority: int,
	p_created_at: int,
	p_deadline: int,
	p_total_weight: int
) -> LogisticsRequest:
	request_id = p_request_id
	source_inventory_id = p_source_inventory_id
	destination_inventory_id = p_destination_inventory_id
	item_requirements = _normalize_requirements(p_item_requirements)
	priority = clampi(p_priority, 0, MAX_PRIORITY)
	created_at = maxi(p_created_at, 0)
	deadline = p_deadline
	total_weight = maxi(p_total_weight, 0)
	state_changed_at = created_at
	return self


func mark_reserved(
	p_reservation_ids: Array[StringName],
	p_reserved_stack_ids: Array[StringName] = [],
	absolute_minute: int = -1
) -> bool:
	if state != State.OPEN and state != State.BLOCKED:
		return false
	if p_reservation_ids.is_empty():
		return false
	reservation_ids.assign(p_reservation_ids)
	reserved_stack_ids.assign(p_reserved_stack_ids)
	assigned_carrier_id = &""
	return transition_to(State.RESERVED, "", absolute_minute)


func assign(carrier_id: StringName, absolute_minute: int = -1) -> bool:
	if carrier_id == &"" or state != State.RESERVED:
		return false
	assigned_carrier_id = carrier_id
	if transition_to(State.ASSIGNED, "", absolute_minute):
		return true
	assigned_carrier_id = &""
	return false


func unassign(absolute_minute: int = -1) -> bool:
	if state != State.ASSIGNED:
		return false
	assigned_carrier_id = &""
	return transition_to(State.RESERVED, "", absolute_minute)


func mark_blocked(reason: String, absolute_minute: int = -1) -> bool:
	if state == State.COMPLETED or state == State.CANCELLED:
		return false
	retry_count += 1
	assigned_carrier_id = &""
	return transition_to(State.BLOCKED, reason, absolute_minute)


func cancel(reason: String = "", absolute_minute: int = -1) -> bool:
	return transition_to(State.CANCELLED, reason, absolute_minute)


func transition_to(next_state: State, reason: String = "", absolute_minute: int = -1) -> bool:
	if state == next_state:
		return true
	if not _can_transition(state, next_state):
		return false
	state = next_state
	state_reason = reason
	state_changed_at = created_at if absolute_minute < 0 else absolute_minute
	if state == State.COMPLETED or state == State.CANCELLED:
		assigned_carrier_id = &""
	return true


func is_terminal() -> bool:
	return state == State.COMPLETED or state == State.CANCELLED


func is_dispatchable() -> bool:
	return state == State.RESERVED and assigned_carrier_id == &"" and total_weight > 0


func create_snapshot() -> Dictionary:
	return {
		&"request_id": String(request_id),
		&"source_inventory_id": String(source_inventory_id),
		&"destination_inventory_id": String(destination_inventory_id),
		&"item_requirements": item_requirements.duplicate(true),
		&"priority": priority,
		&"created_at": created_at,
		&"deadline": deadline,
		&"total_weight": total_weight,
		&"reserved_stack_ids": _names_to_strings(reserved_stack_ids),
		&"reservation_ids": _names_to_strings(reservation_ids),
		&"assigned_carrier_id": String(assigned_carrier_id),
		&"state": State.keys()[state],
		&"retry_count": retry_count,
		&"state_reason": state_reason,
		&"state_changed_at": state_changed_at,
	}


static func from_snapshot(snapshot: Dictionary) -> LogisticsRequest:
	if not _is_valid_snapshot(snapshot):
		return null
	var state_index := State.keys().find(String(snapshot.get(&"state", "OPEN")))
	if state_index < 0:
		return null
	var request := LogisticsRequest.new().configure(
		StringName(snapshot.get(&"request_id", "")),
		StringName(snapshot.get(&"source_inventory_id", "")),
		StringName(snapshot.get(&"destination_inventory_id", "")),
		snapshot.get(&"item_requirements", {}),
		int(snapshot.get(&"priority", 0)),
		int(snapshot.get(&"created_at", 0)),
		int(snapshot.get(&"deadline", -1)),
		int(snapshot.get(&"total_weight", 0))
	)
	request.reserved_stack_ids = _parse_names(snapshot.get(&"reserved_stack_ids", []))
	request.reservation_ids = _parse_names(snapshot.get(&"reservation_ids", []))
	request.assigned_carrier_id = StringName(snapshot.get(&"assigned_carrier_id", ""))
	request.state = state_index as State
	request.retry_count = maxi(int(snapshot.get(&"retry_count", 0)), 0)
	request.state_reason = String(snapshot.get(&"state_reason", ""))
	request.state_changed_at = int(snapshot.get(&"state_changed_at", request.created_at))
	if request.state == State.ASSIGNED and request.assigned_carrier_id == &"":
		return null
	return request


static func _can_transition(from_state: State, to_state: State) -> bool:
	match from_state:
		State.OPEN:
			return to_state in [State.RESERVED, State.BLOCKED, State.CANCELLED]
		State.RESERVED:
			return to_state in [State.OPEN, State.ASSIGNED, State.BLOCKED, State.CANCELLED]
		State.ASSIGNED:
			return to_state in [State.RESERVED, State.PICKING_UP, State.BLOCKED, State.CANCELLED]
		State.PICKING_UP:
			return to_state in [State.DELIVERING, State.BLOCKED, State.CANCELLED]
		State.DELIVERING:
			return to_state in [State.COMPLETED, State.BLOCKED, State.CANCELLED]
		State.BLOCKED:
			return to_state in [State.OPEN, State.RESERVED, State.CANCELLED]
		_:
			return false


static func _normalize_requirements(source: Variant) -> Dictionary:
	var normalized: Dictionary = {}
	if not source is Dictionary:
		return normalized
	for raw_item_id: Variant in source:
		var item_id := StringName(raw_item_id)
		var quantity := int(source[raw_item_id])
		if item_id != &"" and quantity > 0:
			normalized[item_id] = quantity
	return normalized


static func _is_valid_snapshot(snapshot: Dictionary) -> bool:
	return (
		not String(snapshot.get(&"request_id", "")).is_empty()
		and not String(snapshot.get(&"source_inventory_id", "")).is_empty()
		and not String(snapshot.get(&"destination_inventory_id", "")).is_empty()
		and snapshot.get(&"item_requirements", null) is Dictionary
		and int(snapshot.get(&"total_weight", -1)) >= 0
	)


static func _parse_names(source: Variant) -> Array[StringName]:
	var result: Array[StringName] = []
	if not source is Array:
		return result
	for value: Variant in source:
		result.append(StringName(value))
	return result


static func _names_to_strings(source: Array[StringName]) -> Array[String]:
	var result: Array[String] = []
	for value: StringName in source:
		result.append(String(value))
	return result