from machine import Pin
import time

# ---------- 引脚定义 ----------
LED_RED    = Pin(2, Pin.OUT)   # 红灯
LED_YELLOW = Pin(0, Pin.OUT)   # 黄灯
LED_GREEN  = Pin(4, Pin.OUT)   # 绿灯
BUTTON     = Pin(12, Pin.IN, Pin.PULL_UP)  # 按键，内部上拉

# ---------- 全局变量 ----------
running = False              # 交通灯是否运行
state = 0                    # 当前状态：0-红灯,1-绿灯,2-黄灯亮,3-黄灯灭
flash_count = 0              # 黄灯闪烁已完成的次数（一对亮灭算1次）
state_start = 0              # 进入当前状态时的 ticks_ms
last_button = 1              # 上一次读取的按键电平（1=未按）
DEBOUNCE_MS = 20             # 消抖时间（毫秒）
last_press_time = 0          # 上次有效按下的时间

# 时间参数（毫秒）
RED_TIME    = 5000           # 红灯亮 5 秒
GREEN_TIME  = 4000           # 绿灯亮 4 秒
YELLOW_ON   = 500            # 黄灯亮 0.5 秒
YELLOW_OFF  = 500            # 黄灯灭 0.5 秒
FLASH_TIMES = 3              # 闪烁次数

# 所有 LED 初始熄灭
LED_RED.value(0)
LED_YELLOW.value(0)
LED_GREEN.value(0)

def all_leds_off():
    """熄灭所有灯"""
    LED_RED.value(0)
    LED_YELLOW.value(0)
    LED_GREEN.value(0)

def set_leds(red, yellow, green):
    """便捷设置三灯状态"""
    LED_RED.value(red)
    LED_YELLOW.value(yellow)
    LED_GREEN.value(green)

def start_new_cycle():
    """开始一个新的交通灯循环，从红灯开始"""
    global state, flash_count, state_start
    state = 0
    flash_count = 0
    state_start = time.ticks_ms()
    set_leds(1, 0, 0)   # 红灯亮

# ---------- 主循环 ----------
while True:
    now = time.ticks_ms()

    # ----- 按键检测（下降沿触发，带消抖） -----
    btn_val = BUTTON.value()
    if btn_val == 0 and last_button == 1:          # 下降沿：从未按到按下
        if time.ticks_diff(now, last_press_time) > DEBOUNCE_MS:
            last_press_time = now
            running = not running                  # 切换运行状态
            if running:
                start_new_cycle()                  # 启动循环
            else:
                all_leds_off()                     # 停止：熄灭所有灯
    last_button = btn_val

    # ----- 交通灯状态机（仅在 running 状态下执行） -----
    if running:
        elapsed = time.ticks_diff(now, state_start)

        if state == 0:  # 红灯亮
            if elapsed >= RED_TIME:
                # 切换到绿灯
                state = 1
                state_start = now
                set_leds(0, 0, 1)   # 绿灯亮

        elif state == 1:  # 绿灯亮
            if elapsed >= GREEN_TIME:
                # 切换到黄灯闪烁序列，先进入黄灯亮状态
                state = 2
                flash_count = 0
                state_start = now
                set_leds(0, 1, 0)   # 黄灯亮

        elif state == 2:  # 黄灯亮
            if elapsed >= YELLOW_ON:
                # 黄灯灭
                state = 3
                state_start = now
                set_leds(0, 0, 0)   # 黄灯灭

        elif state == 3:  # 黄灯灭
            if elapsed >= YELLOW_OFF:
                flash_count += 1
                if flash_count < FLASH_TIMES:
                    # 继续下一次闪烁：黄灯亮
                    state = 2
                    state_start = now
                    set_leds(0, 1, 0)
                else:
                    # 闪烁完成，回到红灯，开始新循环
                    state = 0
                    flash_count = 0
                    state_start = now
                    set_leds(1, 0, 0)   # 红灯亮

    # 稍作休眠，降低 CPU 占用，同时不影响按键响应
    time.sleep_ms(10)