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 -------------------------------------------------------------

# Rocks mined from asteroid-planet surfaces, spent on buildings and ships.
# 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

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()


func add_building(type: String, at_position: Vector2) -> void:
	buildings.append({"type": type, "position": at_position})


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


func add_extractor(planet_name: String, at_position: Vector2) -> void:
	extractors.append({
		"position": at_position,
		"planet_name": planet_name,
		"progress": 0.0,
	})


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 while the player is
	# on a planet's surface or nowhere near the route.
	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