/**
 * button.c — 第二个 OOPC 组件实现
 *
 * 展示关键 OOPC 设计点：
 *   1. 内部 FSM 状态机完全对外隐藏
 *   2. 去抖动逻辑封装在内部
 *   3. 通过回调与 Led 组件解耦通信
 */

#include <stddef.h>
#include "button.h"
#include "stm32f10x.h"

/* ========================================================
 * 内部常量（对外完全不可见）
 * ======================================================== */
#define MAX_BUTTONS         4
#define DEBOUNCE_MS         20     /* 去抖动时间 */
#define CLICK_TIMEOUT_MS    300    /* 单击超时（判断单/双击） */

/* ========================================================
 * 内部 FSM 状态（对外完全不可见）
 * ======================================================== */
typedef enum {
    BTN_STATE_IDLE,              /* 空闲 */
    BTN_STATE_DEBOUNCE_PRESS,    /* 去抖动-按下中 */
    BTN_STATE_PRESSED,           /* 已稳定按下 */
    BTN_STATE_DEBOUNCE_RELEASE,  /* 去抖动-释放中 */
    BTN_STATE_WAIT_CLICK         /* 等待第二次单击 */
} BtnFsmState;

/* ========================================================
 * 结构体定义（仅在此 .c 中可见）
 * ======================================================== */
struct Button_S {
    GPIO_TypeDef*   port;
    uint16_t        pin;
    uint8_t         active_low;
    uint8_t         pressed;            /* 当前物理电平状态 */
    BtnFsmState     fsm_state;          /* 内部 FSM */
    uint32_t        last_tick_ms;       /* 上次时间戳 */
    uint8_t         click_count;        /* 单击次数 */
    ButtonCallback  callback;
    void*           context;
    uint8_t         initialized;
};

/* ========================================================
 * 静态内存池
 * ======================================================== */
static Button_S g_pool[MAX_BUTTONS];
static uint8_t  g_used[MAX_BUTTONS];

/* ========================================================
 * 内部辅助：GPIO 端口转换
 * ======================================================== */
static GPIO_TypeDef* _port_from_id(uint8_t id) {
    switch (id) {
        case 0:  return GPIOA;
        case 1:  return GPIOB;
        case 2:  return GPIOC;
        case 3:  return GPIOD;
        case 4:  return GPIOE;
        default: return NULL;
    }
}

static uint32_t _rcc_bit_from_port(GPIO_TypeDef* port) {
    if      (port == GPIOA) return RCC_APB2Periph_GPIOA;
    else if (port == GPIOB) return RCC_APB2Periph_GPIOB;
    else if (port == GPIOC) return RCC_APB2Periph_GPIOC;
    else if (port == GPIOD) return RCC_APB2Periph_GPIOD;
    else if (port == GPIOE) return RCC_APB2Periph_GPIOE;
    return 0;
}

/* ========================================================
 * 公开 API 实现
 * ======================================================== */

Button_S* Button_Create(const ButtonConfig* cfg) {
    if (cfg == NULL) return NULL;

    GPIO_TypeDef* port = _port_from_id(cfg->gpio_port);
    if (port == NULL) return NULL;

    for (uint8_t i = 0; i < MAX_BUTTONS; i++) {
        if (g_used[i] == 0) {
            g_used[i] = 1;
            Button_S* inst = &g_pool[i];

            inst->port       = port;
            inst->pin        = (uint16_t)(1u << cfg->gpio_pin);
            inst->active_low = cfg->active_low;
            inst->pressed    = 0;
            inst->fsm_state  = BTN_STATE_IDLE;
            inst->last_tick_ms = 0;
            inst->click_count  = 0;
            inst->callback   = cfg->callback;
            inst->context    = cfg->context;
            inst->initialized = 0;

            /* 使能 GPIO 时钟 */
            uint32_t rcc_bit = _rcc_bit_from_port(port);
            if (rcc_bit) RCC_APB2PeriphClockCmd(rcc_bit, ENABLE);

            /* 配置为输入（上拉） */
            GPIO_InitTypeDef gpio_init;
            gpio_init.GPIO_Pin   = inst->pin;
            gpio_init.GPIO_Mode  = GPIO_Mode_IPU;
            gpio_init.GPIO_Speed = GPIO_Speed_50MHz;
            GPIO_Init(port, &gpio_init);

            inst->initialized = 1;
            return inst;
        }
    }
    return NULL;
}

void Button_Poll(Button_S* me) {
    if (me == NULL || !me->initialized) return;

    /* 读取当前物理电平 */
    uint8_t raw = (uint8_t)(GPIO_ReadInputDataBit(me->port, me->pin));
    uint8_t active = me->active_low ? (raw == Bit_RESET) : (raw == Bit_SET);

    /* 简单 tick 计数器——实际工程中需用 SysTick 或 TIM */
    /* 这里作为演示，不做精确时间测量 */

    switch (me->fsm_state) {

    case BTN_STATE_IDLE:
        if (active) {
            me->fsm_state = BTN_STATE_DEBOUNCE_PRESS;
            me->last_tick_ms = 1;  /* 占位，记录按下时刻 */
        }
        break;

    case BTN_STATE_DEBOUNCE_PRESS:
        if (!active) {
            /* 抖动，回到空闲 */
            me->fsm_state = BTN_STATE_IDLE;
        } else {
            /* 稳定按下 */
            me->pressed = 1;
            me->fsm_state = BTN_STATE_PRESSED;
            if (me->callback)
                me->callback(BTN_EVT_PRESSED, me->context);
        }
        break;

    case BTN_STATE_PRESSED:
        if (!active) {
            me->pressed = 0;
            me->fsm_state = BTN_STATE_DEBOUNCE_RELEASE;
            me->last_tick_ms = 1;
            if (me->callback)
                me->callback(BTN_EVT_RELEASED, me->context);
        }
        break;

    case BTN_STATE_DEBOUNCE_RELEASE:
        if (active) {
            /* 抖动 */
            me->fsm_state = BTN_STATE_PRESSED;
            me->pressed = 1;
        } else {
            /* 释放稳定 */
            me->click_count++;
            me->fsm_state = BTN_STATE_WAIT_CLICK;
        }
        break;

    case BTN_STATE_WAIT_CLICK:
        /* 在 CLICK_TIMEOUT_MS 内等待第二次按下 */
        if (active) {
            /* 第二次按下，判定为双击 */
            me->click_count = 0;
            me->fsm_state = BTN_STATE_DEBOUNCE_PRESS;
            if (me->callback)
                me->callback(BTN_EVT_DBL_CLICK, me->context);
        } else {
            /* 超时无第二次按下，判定为单击 */
            me->click_count = 0;
            me->fsm_state = BTN_STATE_IDLE;
            if (me->callback)
                me->callback(BTN_EVT_CLICK, me->context);
        }
        break;
    }
}

uint8_t Button_IsPressed(const Button_S* me) {
    if (me == NULL) return 0;
    return me->pressed;
}

void Button_Destroy(Button_S* me) {
    if (me == NULL) return;
    for (uint8_t i = 0; i < MAX_BUTTONS; i++) {
        if (&g_pool[i] == me) {
            g_used[i] = 0;
            return;
        }
    }
}