#include "cst826.h"

#include "display.h"
#include "esp_log.h"
#include "i2c_bus.h"

static const char *TAG = "cst826";

#define REG_NUM_TOUCHES     0x02
#define REG_TOUCH_DATA      0x03
#define REG_CHIP_TYPE       0xAA

static i2c_master_dev_handle_t s_dev;
static bool s_ready;

static esp_err_t read_reg(uint8_t reg, uint8_t *buf, size_t len)
{
    return i2c_master_transmit_receive(s_dev, &reg, 1, buf, len, 100);
}

esp_err_t cst826_init(void)
{
    if (s_ready) {
        return ESP_OK;
    }

    esp_err_t err = i2c_bus_add_device(CST826_I2C_ADDR, &s_dev);
    if (err != ESP_OK) {
        ESP_LOGE(TAG, "add device 0x%02X failed: %s",
                 CST826_I2C_ADDR, esp_err_to_name(err));
        return err;
    }

    uint8_t id = 0;
    err = read_reg(REG_CHIP_TYPE, &id, 1);
    if (err != ESP_OK) {
        ESP_LOGE(TAG, "no response at 0x%02X: %s",
                 CST826_I2C_ADDR, esp_err_to_name(err));
        return err;
    }

    if (id != CST826_CHIP_ID) {
        /* Not fatal — the thermostat is fully usable from the encoder alone,
         * and refusing to boot over a touch panel would be a poor trade for
         * something that controls heat. */
        ESP_LOGW(TAG, "unexpected chip id 0x%02X (expected 0x%02X) — "
                      "continuing with touch disabled", id, CST826_CHIP_ID);
        return ESP_ERR_NOT_FOUND;
    }

    s_ready = true;
    ESP_LOGI(TAG, "ready at 0x%02X, chip id 0x%02X", CST826_I2C_ADDR, id);
    return ESP_OK;
}

bool cst826_is_ready(void)
{
    return s_ready;
}

void cst826_read(cst826_touch_t *out)
{
    if (!out) {
        return;
    }
    out->pressed = false;
    out->x = 0;
    out->y = 0;

    if (!s_ready) {
        return;
    }

    uint8_t n = 0;
    if (read_reg(REG_NUM_TOUCHES, &n, 1) != ESP_OK || n == 0 || n > 2) {
        return;
    }

    uint8_t d[6];
    if (read_reg(REG_TOUCH_DATA, d, sizeof(d)) != ESP_OK) {
        return;
    }

    uint16_t x = (uint16_t)((d[0] & 0x0F) << 8 | d[1]);
    uint16_t y = (uint16_t)((d[2] & 0x0F) << 8 | d[3]);

    /* A garbage read past the panel edge means a bad transfer, not a touch at
     * the corner. Drop it rather than sending LVGL a bogus press. */
    if (x >= DISPLAY_H_RES || y >= DISPLAY_V_RES) {
        return;
    }

    out->x = x;
    out->y = y;
    out->pressed = true;
}