extends Node

# Autoload singleton - the one thing that survives change_scene_to_file()
# scene swaps between space (Main.tscn) and a planet's surface
# (PlanetSurface.tscn). Everything else in either scene gets torn down
# and rebuilt from scratch on each swap, so anything that needs to
# survive the trip has to live here instead.

var has_return_position: bool = false
var surviving_ship_count: int = 5
var return_world_position: Vector2 = Vector2.ZERO
var return_camera_zoom: float = 1.0

var planet_name: String = ""
var planet_type: String = ""

# Explored-chunk history for the world map's fog-of-war reveal. Lives
# here (not on ExplorationTracker, which gets destroyed and recreated on
# every scene swap) so exploration progress isn't lost every time the
# player lands on and leaves a planet.
var explored_chunks: Dictionary = {}

# --- Resources -------------------------------------------------------------

# Ore that has been BANKED at the mothership. This is the only pool anything
# can be bought with.
# Starts stocked for play-testing so buildings can be tried without mining
# first - drop this back to 0 for a real playthrough.
var rocks: int = 500

# Ore the fleet is physically carrying and has not delivered yet (#14). Mining
# fills this, not `rocks`: ore is cargo until the fleet brings it home, so a
# long mining run is a real trip with something to lose rather than instant
# income from anywhere on the map.
#
# Lives here, like everything else that has to survive Main.tscn being torn
# down and rebuilt on every trip to a planet's surface - and cargo mined ON a
# surface would otherwise be dropped the moment the player took off.
var fleet_cargo: int = 0

signal cargo_delivered(amount: int)


func collect_cargo(amount: int = 1) -> void:
	fleet_cargo += amount


# One press of "load ore" at the mothership. A batch rather than the whole
# bank: the hold is the part that can be lost, and emptying the bank in one
# tap would also strand research, which still spends from it.
const CARGO_LOAD_BATCH: int = 25


func withdraw_to_fleet(amount: int = CARGO_LOAD_BATCH) -> int:
	# Banked ore back into the hold, so the fleet can carry it to a building
	# that is waiting on it (#17).
	var taken: int = mini(amount, rocks)
	if taken <= 0:
		return 0
	rocks -= taken
	fleet_cargo += taken
	return taken


func unload_into_building(id: int) -> int:
	# Everything the fleet is carrying, into this building's stock. Returns
	# how much moved so a caller can tell the player something happened.
	if fleet_cargo <= 0:
		return 0
	var moved: int = fleet_cargo
	if deposit_to_building(id, moved) <= 0:
		return 0
	fleet_cargo = 0
	return moved


func deliver_cargo() -> int:
	# Everything the fleet is carrying, banked at once. Returns how much moved
	# so a caller can react to a delivery actually having happened rather than
	# to merely being in range.
	if fleet_cargo <= 0:
		return 0
	var delivered: int = fleet_cargo
	rocks += delivered
	fleet_cargo = 0
	cargo_delivered.emit(delivered)
	return delivered

const MOTHERSHIP_COST: int = 20
const SHIP_CRAFTER_COST: int = 12
const SHIP_COST: int = 6

# --- Buildings -------------------------------------------------------------

# Player-placed structures, as [{"type": String, "position": Vector2}].
# Buildings exist only in space (Main.tscn) but are stored here so they
# survive the scene swap to a planet's surface and back.
const BUILDING_MOTHERSHIP: String = "mothership"
const BUILDING_SHIP_CRAFTER: String = "ship_crafter"
const BUILDING_COMMAND_CENTER: String = "command_center"
# Extractors are not placed in space like the others - they are built ON a
# planet's surface and tracked separately (see `extractors`).
const BUILDING_EXTRACTOR: String = "extractor"

const COMMAND_CENTER_COST: int = 15
const EXTRACTOR_COST: int = 25

var buildings: Array = []

# --- Skill tree ------------------------------------------------------------

# Researched at the mothership. Two things hang off it: which structures the
# player is allowed to build at all, and permanent upgrades that have no
# building of their own. The mothership itself is deliberately NOT in the
# tree - it is the thing you research AT, so gating it behind research would
# be a deadlock.
#
# `x` is a horizontal position on a 0..1 grid; the vertical position is NOT
# stored, it is derived from how many prerequisites deep the node is, so the
# tree always reads root-at-the-bottom and cannot drift out of step with the
# dependencies when nodes are added. `requires` is a single prerequisite id
# ("" for a root).
const SKILL_TREE: Array = [
	{
		"id": "shipyards", "name": "Shipyards", "cost": 15, "requires": "",
		"x": 0.5, "unlocks": BUILDING_SHIP_CRAFTER,
		"desc": "Build ship crafters, and buy extra vessels at them.",
	},
	{
		"id": "logistics", "name": "Logistics", "cost": 25, "requires": "shipyards",
		"x": 0.18, "unlocks": BUILDING_EXTRACTOR,
		"desc": "Build extractors on planets. They mine ore whether or not you are nearby.",
	},
	{
		"id": "coordination", "name": "Coordination", "cost": 20, "requires": "shipyards",
		"x": 0.82, "unlocks": BUILDING_COMMAND_CENTER,
		"desc": "Build command centers, where the fleet formation is arranged.",
	},
	{
		"id": "wing", "name": "Wing Doctrine", "cost": 30, "requires": "coordination",
		"x": 0.82, "fleet_bonus": 1,
		"desc": "Permanent: +1 vessel in the fleet.",
	},
	{
		"id": "squadron", "name": "Squadron Doctrine", "cost": 70, "requires": "wing",
		"x": 0.65, "fleet_bonus": 1,
		"desc": "Permanent: +1 vessel in the fleet.",
	},
	{
		"id": "armada", "name": "Armada Doctrine", "cost": 150, "requires": "squadron",
		"x": 0.3, "fleet_bonus": 1,
		"desc": "Permanent: +1 vessel in the fleet.",
	},
]

const BASE_FLEET_SIZE: int = 5

var unlocked: Array = []


func skill_node(id: String) -> Dictionary:
	for node in SKILL_TREE:
		if node.id == id:
			return node
	return {}


func skill_depth(id: String) -> int:
	# How many prerequisites deep this node sits. Drives its height in the
	# tree view: roots at the bottom, everything that depends on something
	# above it.
	var depth: int = 0
	var node: Dictionary = skill_node(id)
	while not node.is_empty() and node.requires != "":
		depth += 1
		node = skill_node(node.requires)
		if depth > SKILL_TREE.size():
			break  # a cycle in the data would otherwise hang here
	return depth


func max_skill_depth() -> int:
	var deepest: int = 0
	for node in SKILL_TREE:
		deepest = maxi(deepest, skill_depth(node.id))
	return deepest


func is_unlocked(id: String) -> bool:
	return id in unlocked


func prerequisite_met(id: String) -> bool:
	var node: Dictionary = skill_node(id)
	if node.is_empty():
		return false
	return node.requires == "" or is_unlocked(node.requires)


func can_unlock(id: String) -> bool:
	return not is_unlocked(id) and prerequisite_met(id) and can_afford(int(skill_node(id).cost))


func unlock(id: String) -> bool:
	if not can_unlock(id):
		return false
	if not spend(int(skill_node(id).cost)):
		return false
	unlocked.append(id)
	return true


func is_building_unlocked(type: String) -> bool:
	# The mothership is always buildable: it is where research happens, so
	# locking it would leave a player with no mothership unable to ever get
	# one.
	if type == BUILDING_MOTHERSHIP:
		return true
	for node in SKILL_TREE:
		if node.get("unlocks", "") == type:
			return is_unlocked(node.id)
	return true


func research_for_building(type: String) -> String:
	for node in SKILL_TREE:
		if node.get("unlocks", "") == type:
			return node.name
	return ""


func max_fleet_size() -> int:
	var n: int = BASE_FLEET_SIZE
	for id in unlocked:
		n += int(skill_node(id).get("fleet_bonus", 0))
	return mini(n, DEFAULT_FORMATION.size())


func reset_progression() -> void:
	unlocked.clear()


# --- building stock and production queue (#16) -----------------------------

# Since #12, a building cannot just deduct from the bank at the moment of
# purchase: what it produces has to be paid for out of resources physically
# delivered to it. So each building carries its own `stock`, and an order it
# cannot afford yet is QUEUED rather than refused, and completes by itself
# once the stock turns up.
#
# `id` exists because a building has to be referable across the space <->
# planet-surface scene swap, when every Building NODE has been destroyed and
# rebuilt. Position would nearly work and then fail on two buildings placed
# on the same spot.
var next_building_id: int = 1

# Ships that have been paid for and built but not yet handed to the fleet.
# Production is simulated here, in the autoload, the same way extractor
# haulers are - so an order can complete while the player is down on a
# planet's surface, where there is no Fleet node to hand a ship to. The fleet
# claims them when it next can.
var ships_owed: int = 0

signal order_completed(building_id: int, type: String)


func add_building(type: String, at_position: Vector2) -> int:
	var id: int = next_building_id
	next_building_id += 1
	buildings.append({
		"id": id, "type": type, "position": at_position, "stock": 0, "queued": 0,
	})
	return id


func find_building(id: int) -> Dictionary:
	for b in buildings:
		if b.get("id", 0) == id:
			return b
	return {}


func production_cost(type: String) -> int:
	# What one order out of this building costs it. 0 means it produces
	# nothing and cannot be ordered from.
	if type == BUILDING_SHIP_CRAFTER:
		return SHIP_COST
	return 0


func building_stock(id: int) -> int:
	var b: Dictionary = find_building(id)
	return 0 if b.is_empty() else int(b.get("stock", 0))


func pending_orders(id: int) -> int:
	var b: Dictionary = find_building(id)
	return 0 if b.is_empty() else int(b.get("queued", 0))


func deposit_to_building(id: int, amount: int) -> int:
	if amount <= 0:
		return 0
	var b: Dictionary = find_building(id)
	if b.is_empty():
		return 0
	b.stock = int(b.get("stock", 0)) + amount
	return amount


func queue_order(id: int) -> bool:
	var b: Dictionary = find_building(id)
	if b.is_empty() or production_cost(b.type) <= 0:
		return false
	b.queued = int(b.get("queued", 0)) + 1
	return true


func _advance_production() -> void:
	for b in buildings:
		var cost: int = production_cost(b.type)
		if cost <= 0:
			continue
		# `while`, not `if`: a delivery big enough to cover several queued
		# orders should clear them all rather than dribbling one out per
		# frame.
		while int(b.get("queued", 0)) > 0 and int(b.get("stock", 0)) >= cost:
			b.stock = int(b.stock) - cost
			b.queued = int(b.queued) - 1
			if b.type == BUILDING_SHIP_CRAFTER:
				ships_owed += 1
			order_completed.emit(int(b.id), String(b.type))


func has_mothership() -> bool:
	return get_mothership_position() != null


func remove_buildings_of_type(type: String) -> int:
	var kept: Array = []
	var removed: int = 0
	for b in buildings:
		if b.type == type:
			removed += 1
		else:
			kept.append(b)
	buildings = kept
	return removed


func get_mothership_position() -> Variant:
	# Where a wiped-out fleet gets rebuilt. Returns null when no mothership
	# has been built yet, so the caller can fall back to the world origin.
	for b in buildings:
		if b.type == BUILDING_MOTHERSHIP:
			return b.position
	return null


# --- Fleet formation -------------------------------------------------------

# Where each vessel sits relative to the fleet centre, editable at a command
# centre. Lives here (not as a const on Fleet) so a layout the player has
# arranged survives the trip to a planet's surface and back, and so a
# rebuilt fleet keeps their arrangement.
# Slots beyond BASE_FLEET_SIZE only become usable once the matching fleet
# capacity upgrade is researched, but they are defined up front so the wedge
# keeps a deliberate shape as it grows rather than having positions invented
# at unlock time.
const DEFAULT_FORMATION: Array = [
	Vector2(0, -48), Vector2(-30, -8), Vector2(30, -8), Vector2(-60, 32), Vector2(60, 32),
	Vector2(-90, 72), Vector2(90, 72), Vector2(0, 56),
]

var formation: Array = DEFAULT_FORMATION.duplicate()


func reset_formation() -> void:
	formation = DEFAULT_FORMATION.duplicate()


func rotate_formation(radians: float) -> void:
	# Pivots every slot about the fleet centre, keeping the shape intact
	# and only changing which way it faces.
	for i in range(formation.size()):
		formation[i] = formation[i].rotated(radians)


# --- Extractors and their haulers -----------------------------------------

# An extractor sits on a planet and runs a single automated hauler back and
# forth to the mothership, delivering ore on each arrival.
#
# The round trip is SIMULATED HERE, in the autoload, rather than by any
# node: it advances whether the player is in space, on a planet's surface,
# or far enough away that nothing about the route is loaded. `progress` is
# a fraction of one full there-and-back cycle, so a hauler's drawn position
# is derived from the same number that decides when ore is delivered - the
# visual arrival and the payout cannot drift apart, because they are the
# same event.
#
# Entries are {"position": Vector2 (the planet's position in SPACE),
# "planet_name": String, "progress": float}.
const HAULER_SPEED: float = 260.0
const HAULER_YIELD: int = 4
# Progress value at which the hauler reaches the mothership: exactly half
# way through the cycle, the outbound leg being the first half.
const HAULER_ARRIVAL: float = 0.5

var extractors: Array = []


func has_extractor_at(planet_name: String) -> bool:
	for e in extractors:
		if e.planet_name == planet_name:
			return true
	return false


signal extractor_added(planet_name: String)


func add_extractor(planet_name: String, at_position: Vector2) -> void:
	extractors.append({
		"position": at_position,
		"planet_name": planet_name,
		"progress": 0.0,
	})
	# An extractor is built from SPACE, with the fleet parked on the planet -
	# so the Planet node is already in the tree with its _ready() long since
	# run. Without this it kept showing no derrick until it happened to
	# despawn and respawn, which reads as the build having done nothing.
	extractor_added.emit(planet_name)


func get_hauler_route_time(extractor: Dictionary) -> float:
	# Full cycle: out to the mothership and back again.
	var mothership: Variant = get_mothership_position()
	if mothership == null:
		return 0.0
	var distance: float = extractor.position.distance_to(mothership)
	if distance < 1.0:
		return 0.0
	return (distance * 2.0) / HAULER_SPEED


func get_hauler_position(extractor: Dictionary) -> Variant:
	# Where the hauler is right now, derived purely from `progress`. Returns
	# null when there is no route (no mothership built yet).
	var mothership: Variant = get_mothership_position()
	if mothership == null:
		return null
	var t: float = extractor.progress
	if t <= HAULER_ARRIVAL:
		return extractor.position.lerp(mothership, t / HAULER_ARRIVAL)
	return mothership.lerp(extractor.position, (t - HAULER_ARRIVAL) / (1.0 - HAULER_ARRIVAL))


func _process(delta: float) -> void:
	# Runs in the autoload, so extraction keeps earning - and queued orders
	# keep completing - while the player is on a planet's surface or nowhere
	# near either.
	_advance_production()
	if extractors.is_empty():
		return
	for e in extractors:
		var cycle: float = get_hauler_route_time(e)
		if cycle <= 0.0:
			continue  # nothing to deliver to yet
		var before: float = e.progress
		e.progress += delta / cycle
		# Ore lands the instant the hauler reaches the mothership - the same
		# instant get_hauler_position() puts it there.
		if before < HAULER_ARRIVAL and e.progress >= HAULER_ARRIVAL:
			rocks += HAULER_YIELD
		while e.progress >= 1.0:
			e.progress -= 1.0


func can_afford(cost: int) -> bool:
	return rocks >= cost


func spend(cost: int) -> bool:
	if not can_afford(cost):
		return false
	rocks -= cost
	return true