"""Short APA102 activity flashes for the T-Dongle-S3's onboard RGB LED."""

import time
from machine import Pin

# Verified against LILYGO's T-Dongle-S3 pin map. The APA102 uses BGR order.
_DATA_PIN = 40
_CLOCK_PIN = 39
_PULSE_MS = 90
_BRIGHTNESS = 1 # APA102 global brightness: 1 (dim) through 31 (full).

class ActivityLed:
    """Drive the single onboard APA102 LED without delaying the main loop."""

    def __init__(self):
        self._available = True
        self._off_at = None
        try:
            self._data = Pin(_DATA_PIN, Pin.OUT, value=0)
            self._clock = Pin(_CLOCK_PIN, Pin.OUT, value=0)
            self._write(0, 0, 0)
        except (OSError, ValueError):
            # Keep display-less or alternate ESP32-S3 development boards usable.
            self._available = False

    def pulse(self, red, green, blue, now):
        """Show one colour briefly; a later event simply extends the flash."""
        if not self._available:
            return
        self._write(red, green, blue)
        self._off_at = time.ticks_add(now, _PULSE_MS)

    def tick(self, now):
        """Turn the LED off after its scheduled pulse without sleeping."""
        if (self._available and self._off_at is not None and
                time.ticks_diff(now, self._off_at) >= 0):
            self._write(0, 0, 0)
            self._off_at = None

    def _write(self, red, green, blue):
        # APA102: start frame, global-brightness pixel frame, end frame.
        self._send_byte(0)
        self._send_byte(0)
        self._send_byte(0)
        self._send_byte(0)
        self._send_byte(0xE0 | _BRIGHTNESS)
        self._send_byte(blue)
        self._send_byte(green)
        self._send_byte(red)
        self._send_byte(0xFF)
        self._send_byte(0xFF)
        self._send_byte(0xFF)
        self._send_byte(0xFF)

    def _send_byte(self, value):
        for bit in range(7, -1, -1):
            self._data.value((value >> bit) & 1)
            self._clock.on()
            self._clock.off()