/*
 * STC8H1K28 board controller, CrowPanel 7" Advance v1.3.
 *
 * A small 8051-class MCU sitting on the I2C bus at 0x30. It drives the LCD
 * backlight and, critically, the GT911 reset line -- there is no ESP32 GPIO
 * for touch reset on this board, so the GT911 stays mute until the sequence
 * below has run.
 *
 * Protocol is single raw bytes, no register addressing:
 *   0x19          wake
 *   0x10, 0x18    configure / release GT911 from reset
 *   0x00 - 0xF5   brightness, INVERTED (0x00 = full, 0xF5 = off)
 *
 * v1.2 boards use a different, narrower range (0x05 = off .. 0x10 = max).
 */

#include "esp_check.h"
#include "esp_log.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"

#include "backlight.h"
#include "i2c_bus.h"

static const char *TAG = "backlight";

#define STC8_ADDR        0x30
#define STC8_I2C_HZ      100000
#define STC8_TIMEOUT_MS  100

#define STC8_CMD_WAKE    0x19
#define STC8_CMD_CFG1    0x10
#define STC8_CMD_CFG2    0x18

/* Inverted brightness range. */
#define STC8_DUTY_MAX_ON  0x00
#define STC8_DUTY_OFF     0xF5

static i2c_master_dev_handle_t dev = NULL;

static esp_err_t stc8_cmd(uint8_t cmd)
{
    return i2c_master_transmit(dev, &cmd, 1, STC8_TIMEOUT_MS);
}

esp_err_t backlight_init(void)
{
    const i2c_device_config_t cfg = {
        .dev_addr_length = I2C_ADDR_BIT_LEN_7,
        .device_address = STC8_ADDR,
        .scl_speed_hz = STC8_I2C_HZ,
    };
    ESP_RETURN_ON_ERROR(i2c_master_bus_add_device(i2c_bus_get(), &cfg, &dev), TAG,
                        "could not add STC8H1K28 at 0x%02X", STC8_ADDR);

    ESP_RETURN_ON_ERROR(stc8_cmd(STC8_CMD_WAKE), TAG, "wake failed");
    vTaskDelay(pdMS_TO_TICKS(10));

    /* These two also release the GT911 from reset. */
    ESP_RETURN_ON_ERROR(stc8_cmd(STC8_CMD_CFG1), TAG, "config 1 failed");
    vTaskDelay(pdMS_TO_TICKS(10));

    ESP_RETURN_ON_ERROR(stc8_cmd(STC8_CMD_CFG2), TAG, "config 2 failed");
    vTaskDelay(pdMS_TO_TICKS(100));

    ESP_LOGI(TAG, "STC8H1K28 initialized (GT911 released from reset)");
    return ESP_OK;
}

esp_err_t backlight_set(uint8_t brightness)
{
    if (dev == NULL) {
        return ESP_ERR_INVALID_STATE;
    }

    /* Map 0..255 (intuitive) onto 0xF5..0x00 (wire, inverted). */
    const uint8_t duty = (uint8_t)(STC8_DUTY_OFF -
                                   ((uint32_t)brightness * STC8_DUTY_OFF) / 255);
    return stc8_cmd(duty);
}