extends Node
## Platform abstraction layer — D-138 §8. Central location for all OS queries.
## Owned by Stig (UI Developer). Registered FIRST in project.godot so other
## autoloads can read its properties in their own _ready().
##
## Sections:
##   Power:   PowerProfile enum, 30s poll timer, power_profile_changed signal.
##   Memory:  free_memory_mb / total_memory_mb, refresh_memory() on demand.
##   Paths:   Read-once OS path constants, populated in _ready().


# -- Power profile ------------------------------------------------------------

## High-level power classification. POWER_SAVER reserved for future OS API.
enum PowerProfile {
	FULL = 0,       # Plugged in (charged, charging, or no battery) — no restrictions
	BATTERY = 1,    # On battery — AI inference should be suspended per D-138 §8 Layer 3
	POWER_SAVER = 2 # System-level power-saver mode (future: no cross-platform API yet)
}

## Emitted when the detected power profile changes.
signal power_profile_changed(old_profile: int, new_profile: int)

## Current power profile. Updated by the 30-second poll timer.
var power_profile: PowerProfile = PowerProfile.FULL

## How often (seconds) to re-poll OS for power state changes.
const POWER_POLL_INTERVAL := 30.0

# OS power_state integer constants (Godot 4 — same values as POWERSTATE_* enum).
const _POWER_STATE_UNKNOWN    := 0
const _POWER_STATE_ON_BATTERY := 1
const _POWER_STATE_NO_BATTERY := 2
const _POWER_STATE_CHARGING   := 3
const _POWER_STATE_CHARGED    := 4


# -- Memory -------------------------------------------------------------------

## Free physical RAM in megabytes. Call refresh_memory() before reading if staleness matters.
var free_memory_mb: float = 0.0

## Total physical RAM in megabytes. Populated once in _ready(); doesn't change at runtime.
var total_memory_mb: float = 0.0


# -- File paths ---------------------------------------------------------------

## Base user data directory (user://).
var user_data_dir: String = ""

## Directory where settings.cfg is written. Same as user_data_dir in Godot 4.
var config_dir: String = ""

## Full path to AI benchmark cache (ai-dialogue-config.json).
var benchmark_cache_path: String = ""

## Directory where the game binary lives (install location).
var install_dir: String = ""

## Full path to the game executable.
var executable_path: String = ""

## OS-provided cache directory, or user_data_dir/cache as fallback.
var cache_dir: String = ""

## Directory where the bundled Gemma 2 model lives (derived from install_dir).
var model_dir: String = ""


# -- Lifecycle ----------------------------------------------------------------

func _ready() -> void:
	_init_paths()
	refresh_memory()
	_poll_power()

	var timer := Timer.new()
	timer.wait_time = POWER_POLL_INTERVAL
	timer.autostart = true
	timer.timeout.connect(_poll_power)
	add_child(timer)


func _init_paths() -> void:
	user_data_dir       = OS.get_user_data_dir()
	config_dir          = user_data_dir
	benchmark_cache_path = "user://ai-dialogue-config.json"
	executable_path     = OS.get_executable_path()
	install_dir         = executable_path.get_base_dir()
	model_dir           = install_dir + "/models"
	# get_cache_dir() may not exist on all Godot builds — use callv for safety.
	var os_cache: String = ""
	if OS.has_method("get_cache_dir"):
		var result: Variant = OS.callv("get_cache_dir", [])
		if result is String:
			os_cache = result
	cache_dir = os_cache if not os_cache.is_empty() else user_data_dir + "/cache"


# -- Memory API ---------------------------------------------------------------

## Refresh free/total memory readings from the OS. Call before read if freshness matters.
func refresh_memory() -> void:
	var mem := OS.get_memory_info()
	# "available" = Linux MemAvailable / Windows ullAvailPhys (includes reclaimable pages).
	# Fall back to "free" on platforms that don't provide "available".
	free_memory_mb  = float(mem.get("available", mem.get("free", 0))) / (1024.0 * 1024.0)
	total_memory_mb = float(mem.get("physical", 0)) / (1024.0 * 1024.0)


# -- Power API ----------------------------------------------------------------

## Classify an OS power_state integer into a human-readable string.
## Mirrors HardwareDetector.classify_power_state() for external consumers.
## 1 (ON_BATTERY) → "battery", 2/3/4 (plugged) → "plugged", 0 → "unknown".
static func classify_power_state(power_state: int) -> String:
	match power_state:
		_POWER_STATE_ON_BATTERY:
			return "battery"
		_POWER_STATE_NO_BATTERY, _POWER_STATE_CHARGING, _POWER_STATE_CHARGED:
			return "plugged"
		_:
			return "unknown"


## True only when the OS reports the device is on battery — used by Layer 3 suspend.
static func should_suspend_inference(power_state: int) -> bool:
	return power_state == _POWER_STATE_ON_BATTERY


## Read current OS power state integer. Returns 0 (UNKNOWN) if unavailable.
## Uses callv() to defer method resolution to runtime — avoids compile errors on builds
## where OS.get_power_info() or OS.get_power_state() are not available (e.g. headless).
func current_power_state() -> int:
	# Try Godot 4.x: OS.get_power_info() → {"power_state": int, "percent": int, ...}
	if OS.has_method("get_power_info"):
		var info: Variant = OS.callv("get_power_info", [])
		if info is Dictionary:
			return int(info.get("power_state", _POWER_STATE_UNKNOWN))
	# Fallback: unknown power state → treat as FULL (no inference suspension).
	return _POWER_STATE_UNKNOWN


func _poll_power() -> void:
	var state := current_power_state()
	var new_profile: PowerProfile = PowerProfile.BATTERY \
		if state == _POWER_STATE_ON_BATTERY \
		else PowerProfile.FULL
	if new_profile != power_profile:
		var old_profile := power_profile
		power_profile = new_profile
		power_profile_changed.emit(int(old_profile), int(new_profile))