/**
 * @file lcd1602_display.c
 * @brief Minimal SPLC780D/HD44780-compatible LCD1602 driver in 4-bit mode.
 *
 * Architectural note:
 * The chosen wiring keeps the whole standalone UI on GPIOG. This driver uses
 * write-only transfers with fixed delays, which keeps the implementation
 * compact and avoids a bidirectional R/W pin or extra state.
 */

#include "lcd1602_display.h"

#include <stdbool.h>
#include <stddef.h>

#include "main.h"

#define LCD1602_COLUMNS 16u
#define LCD1602_LINE_1_ADDRESS 0x00u
#define LCD1602_LINE_2_ADDRESS 0x40u
#define LCD1602_COMMAND_DELAY_US 50u
#define LCD1602_CLEAR_DELAY_US 2000u
#define LCD1602_ENABLE_PULSE_US 1u
#define LCD1602_POWER_ON_DELAY_US 50000u

#define LCD1602_DATA_MASK (UI_LCD_D4_Pin | UI_LCD_D5_Pin | UI_LCD_D6_Pin | UI_LCD_D7_Pin)

static uint8_t g_cycle_counter_available = 0u;

static void lcd1602_enable_cycle_counter(void);
static void lcd1602_delay_us(uint32_t delay_us);
static void lcd1602_write_nibble(uint8_t nibble);
static void lcd1602_pulse_enable(void);
static void lcd1602_write_byte(bool is_data, uint8_t value);
static void lcd1602_write_command(uint8_t command);
static void lcd1602_write_data(uint8_t value);
static void lcd1602_set_cursor(uint8_t address);
static void lcd1602_write_padded_line(const char *text);

void lcd1602_display_init(void)
{
    lcd1602_enable_cycle_counter();

    HAL_GPIO_WritePin(UI_LCD_RS_GPIO_Port, UI_LCD_RS_Pin, GPIO_PIN_RESET);
    HAL_GPIO_WritePin(UI_LCD_E_GPIO_Port, UI_LCD_E_Pin, GPIO_PIN_RESET);
    UI_LCD_D4_GPIO_Port->BSRR = ((uint32_t)LCD1602_DATA_MASK) << 16u;

    lcd1602_delay_us(LCD1602_POWER_ON_DELAY_US);

    lcd1602_write_nibble(0x03u);
    lcd1602_delay_us(5000u);
    lcd1602_write_nibble(0x03u);
    lcd1602_delay_us(150u);
    lcd1602_write_nibble(0x03u);
    lcd1602_delay_us(150u);
    lcd1602_write_nibble(0x02u);
    lcd1602_delay_us(LCD1602_COMMAND_DELAY_US);

    lcd1602_write_command(0x28u);
    lcd1602_write_command(0x08u);
    lcd1602_write_command(0x01u);
    lcd1602_write_command(0x06u);
    lcd1602_write_command(0x0Cu);
}

void lcd1602_display_set_lines(const char *line1, const char *line2)
{
    lcd1602_set_cursor(LCD1602_LINE_1_ADDRESS);
    lcd1602_write_padded_line(line1);
    lcd1602_set_cursor(LCD1602_LINE_2_ADDRESS);
    lcd1602_write_padded_line(line2);
}

static void lcd1602_enable_cycle_counter(void)
{
    uint32_t start_cycles;
    uint32_t spin;

    CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
    DWT->CYCCNT = 0u;
    DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;

    start_cycles = DWT->CYCCNT;
    for (spin = 0u; spin < 64u; ++spin)
    {
        __NOP();
    }

    /*
     * DWT-based microsecond delays are convenient, but they are not
     * guaranteed to be available in every production boot/debug state.
     * Falling back to HAL_Delay() keeps the LCD optional rather than
     * letting the standalone UI block the whole firmware startup.
     */
    g_cycle_counter_available = (DWT->CYCCNT != start_cycles) ? 1u : 0u;
}

static void lcd1602_delay_us(uint32_t delay_us)
{
    if (delay_us == 0u)
    {
        return;
    }

    if (g_cycle_counter_available != 0u)
    {
        uint32_t start_cycles = DWT->CYCCNT;
        uint32_t target_cycles = delay_us * (SystemCoreClock / 1000000u);

        while ((DWT->CYCCNT - start_cycles) < target_cycles)
        {
        }
        return;
    }

    while (delay_us > 1000u)
    {
        HAL_Delay(1u);
        delay_us -= 1000u;
    }

    HAL_Delay(1u);
}

static void lcd1602_write_nibble(uint8_t nibble)
{
    uint32_t bsrr = ((uint32_t)LCD1602_DATA_MASK) << 16u;

    if ((nibble & 0x01u) != 0u)
    {
        bsrr |= UI_LCD_D4_Pin;
    }
    if ((nibble & 0x02u) != 0u)
    {
        bsrr |= UI_LCD_D5_Pin;
    }
    if ((nibble & 0x04u) != 0u)
    {
        bsrr |= UI_LCD_D6_Pin;
    }
    if ((nibble & 0x08u) != 0u)
    {
        bsrr |= UI_LCD_D7_Pin;
    }

    UI_LCD_D4_GPIO_Port->BSRR = bsrr;
    lcd1602_pulse_enable();
}

static void lcd1602_pulse_enable(void)
{
    HAL_GPIO_WritePin(UI_LCD_E_GPIO_Port, UI_LCD_E_Pin, GPIO_PIN_SET);
    lcd1602_delay_us(LCD1602_ENABLE_PULSE_US);
    HAL_GPIO_WritePin(UI_LCD_E_GPIO_Port, UI_LCD_E_Pin, GPIO_PIN_RESET);
    lcd1602_delay_us(LCD1602_COMMAND_DELAY_US);
}

static void lcd1602_write_byte(bool is_data, uint8_t value)
{
    HAL_GPIO_WritePin(UI_LCD_RS_GPIO_Port, UI_LCD_RS_Pin, is_data ? GPIO_PIN_SET : GPIO_PIN_RESET);
    lcd1602_write_nibble((uint8_t)(value >> 4u));
    lcd1602_write_nibble((uint8_t)(value & 0x0Fu));
}

static void lcd1602_write_command(uint8_t command)
{
    lcd1602_write_byte(false, command);

    if ((command == 0x01u) || (command == 0x02u))
    {
        lcd1602_delay_us(LCD1602_CLEAR_DELAY_US);
    }
}

static void lcd1602_write_data(uint8_t value)
{
    lcd1602_write_byte(true, value);
}

static void lcd1602_set_cursor(uint8_t address)
{
    lcd1602_write_command((uint8_t)(0x80u | address));
}

static void lcd1602_write_padded_line(const char *text)
{
    uint8_t index;
    uint8_t value;

    for (index = 0u; index < LCD1602_COLUMNS; ++index)
    {
        value = ' ';
        if ((text != NULL) && (text[index] != '\0'))
        {
            value = (uint8_t)text[index];
        }
        lcd1602_write_data(value);
    }
}