#include "encoder.h"

#include "driver/pulse_cnt.h"
#include "esp_check.h"
#include "esp_log.h"
#include "esp_timer.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "pcf8574.h"

static const char *TAG = "encoder";

/*
 * Full quadrature decode counts 4 edges per mechanical detent on an EC28A.
 * PCNT counts in raw edges; we divide.
 */
#define COUNTS_PER_DETENT   4

#define PCNT_HIGH_LIMIT     1000
#define PCNT_LOW_LIMIT      (-1000)
#define GLITCH_FILTER_NS    1000

#define BUTTON_POLL_MS      20
#define BUTTON_DEBOUNCE_N   3
#define LONG_PRESS_MS       800

static pcnt_unit_handle_t s_unit;
static int s_residual;              /* raw counts not yet worth a detent */

static volatile encoder_button_event_t s_btn_event;
static volatile bool s_btn_down;

static void button_task(void *arg)
{
    (void)arg;

    int stable = 0;
    bool debounced = false;         /* true = pressed */
    int64_t pressed_at = 0;
    bool long_fired = false;

    while (1) {
        bool level = true;
        /* P5 is INPUT_PULLUP: low means pressed. */
        bool pressed = (pcf8574_read(PCF_PIN_ENCODER_SW, &level) == ESP_OK)
                       && !level;

        if (pressed == debounced) {
            stable = 0;
        } else if (++stable >= BUTTON_DEBOUNCE_N) {
            stable = 0;
            debounced = pressed;
            s_btn_down = pressed;

            if (pressed) {
                pressed_at = esp_timer_get_time();
                long_fired = false;
            } else if (!long_fired) {
                /* Click reported on release, so a long press never also
                 * produces a click. */
                s_btn_event = ENCODER_BTN_CLICK;
            }
        }

        if (debounced && !long_fired &&
            (esp_timer_get_time() - pressed_at) > (LONG_PRESS_MS * 1000)) {
            long_fired = true;
            s_btn_event = ENCODER_BTN_LONG_PRESS;
        }

        vTaskDelay(pdMS_TO_TICKS(BUTTON_POLL_MS));
    }
}

esp_err_t encoder_init(void)
{
    pcnt_unit_config_t unit_cfg = {
        .high_limit = PCNT_HIGH_LIMIT,
        .low_limit = PCNT_LOW_LIMIT,
    };
    ESP_RETURN_ON_ERROR(pcnt_new_unit(&unit_cfg, &s_unit), TAG, "pcnt unit");

    pcnt_glitch_filter_config_t filter = {
        .max_glitch_ns = GLITCH_FILTER_NS,
    };
    ESP_RETURN_ON_ERROR(pcnt_unit_set_glitch_filter(s_unit, &filter),
                        TAG, "glitch filter");

    /* Two channels, each watching one edge and using the other line as the
     * direction control — the standard full-quadrature setup. */
    pcnt_chan_config_t chan_a_cfg = {
        .edge_gpio_num = ENCODER_PIN_A,
        .level_gpio_num = ENCODER_PIN_B,
    };
    pcnt_channel_handle_t chan_a = NULL;
    ESP_RETURN_ON_ERROR(pcnt_new_channel(s_unit, &chan_a_cfg, &chan_a),
                        TAG, "chan a");

    pcnt_chan_config_t chan_b_cfg = {
        .edge_gpio_num = ENCODER_PIN_B,
        .level_gpio_num = ENCODER_PIN_A,
    };
    pcnt_channel_handle_t chan_b = NULL;
    ESP_RETURN_ON_ERROR(pcnt_new_channel(s_unit, &chan_b_cfg, &chan_b),
                        TAG, "chan b");

    ESP_RETURN_ON_ERROR(
        pcnt_channel_set_edge_action(chan_a,
                                     PCNT_CHANNEL_EDGE_ACTION_DECREASE,
                                     PCNT_CHANNEL_EDGE_ACTION_INCREASE),
        TAG, "chan a edge");
    ESP_RETURN_ON_ERROR(
        pcnt_channel_set_level_action(chan_a,
                                      PCNT_CHANNEL_LEVEL_ACTION_KEEP,
                                      PCNT_CHANNEL_LEVEL_ACTION_INVERSE),
        TAG, "chan a level");
    ESP_RETURN_ON_ERROR(
        pcnt_channel_set_edge_action(chan_b,
                                     PCNT_CHANNEL_EDGE_ACTION_INCREASE,
                                     PCNT_CHANNEL_EDGE_ACTION_DECREASE),
        TAG, "chan b edge");
    ESP_RETURN_ON_ERROR(
        pcnt_channel_set_level_action(chan_b,
                                      PCNT_CHANNEL_LEVEL_ACTION_KEEP,
                                      PCNT_CHANNEL_LEVEL_ACTION_INVERSE),
        TAG, "chan b level");

    ESP_RETURN_ON_ERROR(pcnt_unit_enable(s_unit), TAG, "enable");
    ESP_RETURN_ON_ERROR(pcnt_unit_clear_count(s_unit), TAG, "clear");
    ESP_RETURN_ON_ERROR(pcnt_unit_start(s_unit), TAG, "start");

    if (xTaskCreate(button_task, "enc_btn", 3072, NULL, 4, NULL) != pdPASS) {
        ESP_LOGE(TAG, "button task create failed");
        return ESP_ERR_NO_MEM;
    }

    ESP_LOGI(TAG, "ready: A=%d B=%d, button on expander P%d",
             ENCODER_PIN_A, ENCODER_PIN_B, PCF_PIN_ENCODER_SW);
    return ESP_OK;
}

int encoder_take_delta(void)
{
    if (!s_unit) {
        return 0;
    }

    int raw = 0;
    if (pcnt_unit_get_count(s_unit, &raw) != ESP_OK) {
        return 0;
    }
    pcnt_unit_clear_count(s_unit);

    /*
     * Carry the remainder rather than discarding it. Dropping it would lose a
     * detent whenever a turn straddles two polls, which shows up as a knob
     * that occasionally ignores you.
     */
    s_residual += raw;
    int detents = s_residual / COUNTS_PER_DETENT;
    s_residual -= detents * COUNTS_PER_DETENT;

    return detents;
}

encoder_button_event_t encoder_take_button_event(void)
{
    encoder_button_event_t e = s_btn_event;
    s_btn_event = ENCODER_BTN_NONE;
    return e;
}

bool encoder_button_is_down(void)
{
    return s_btn_down;
}