#include "LiquidCrystal.h"
#include "nrf_gpio.h"
#include "app_timer.h"

/*
 * Arduino | LCD | nrf51
 *      D4 | DB4 | P0.16
 *      D5 | DB5 | P0.17
 *      D6 | DB6 | P0.18
 *      D7 | DB7 | P0.10
 *      D8 |  RS | P0.20, register select. 0=instruction (write), 0=busy (read), 1=data
 *      D9 |  EN | P0.23, clock, data is clocked in/out on falling edge
 *     D10 | DB4 | P0.24
 */

enum liquid_crystal_cmd {
    LIQUID_CRYSTAL_CMD_CLEAR = 0x01,
    LIQUID_CRYSTAL_CMD_RETURN_HOME = 0x02,
    LIQUID_CRYSTAL_CMD_ENTRY_MODE_SET = 0x04,
    LIQUID_CRYSTAL_CMD_DISPLAY = 0x08,
    LIQUID_CRYSTAL_CMD_SHIFT = 0x10,
    LIQUID_CRYSTAL_CMD_FUNCTION_SET = 0x20,
    LIQUID_CRYSTAL_CMD_SET_CGRAM_ADDDRESS = 0x40,
    LIQUID_CRYSTAL_CMD_SET_DDRAM_ADDDRESS = 0x80,
};

static struct {
    uint8_t pin_db4;
    uint8_t pin_db5;
    uint8_t pin_db6;
    uint8_t pin_db7;
    uint8_t pin_rs;
    uint8_t pin_en;

    app_gpiote_user_id_t gpio_user_id;
} data = { .pin_db4 = 16, .pin_db5 = 17, .pin_db6 = 18, .pin_db7 = 19, .pin_rs =
        20, .pin_en = 23, };

static uint32_t ticks_per_ms;

static void event_handler() {
}

static void wait_ms(uint32_t ms) {
    uint32_t ticks;

    app_timer_cnt_get(&ticks);

    const uint32_t end_ticks = ticks + ms * ticks_per_ms;

    do {
        app_timer_cnt_get(&ticks);
    } while (ticks < end_ticks);
}

static void write_4(uint8_t value) {
    nrf_gpio_pin_write(data.pin_db4, value & 0x01);
    nrf_gpio_pin_write(data.pin_db5, value & 0x02);
    nrf_gpio_pin_write(data.pin_db6, value & 0x04);
    nrf_gpio_pin_write(data.pin_db7, value & 0x08);

    nrf_gpio_pin_set(data.pin_en);
    nrf_gpio_pin_clear(data.pin_en);
}

static void write_value(uint8_t value, bool is_data) {
    nrf_gpio_pin_write(data.pin_rs, is_data);

    write_4(value >> 4);
    write_4(value);
}

static void begin() {
    nrf_gpio_pin_clear(data.pin_rs);
    nrf_gpio_pin_clear(data.pin_en);

    // SEE PAGE 45/46 FOR INITIALIZATION SPECIFICATION!
    // according to datasheet, we need at least 40ms after power rises above 2.7V
    // before sending commands. Arduino can turn on way before 4.5V so we'll wait 50
    wait_ms(50);

    write_4(0x03);
    wait_ms(5); // 4.5ms

    write_4(0x03);
    wait_ms(5); // 4.5ms

    write_4(0x03);
    wait_ms(5); // 4.5ms

    write_4(0x02);

    write_value(LIQUID_CRYSTAL_CMD_DISPLAY, false);

//	_displaycontrol = LCD_DISPLAYON | LCD_CURSOROFF | LCD_BLINKOFF;
    liquid_crystal_display(true, true, true);
}

void liquid_crystal_write_char(char chr) {
    write_value(chr, true);
}

void liquid_crystal_write_string(char *chr) {
    while (*chr != '\0') {
        liquid_crystal_write_char(*chr);
    }
}

uint32_t liquid_crystal_display(bool display_on, bool cursor_on, bool blink) {
    uint8_t value = LIQUID_CRYSTAL_CMD_DISPLAY;

    value |= display_on ? 0x04 : 0x00;
    value |= cursor_on ? 0x02 : 0x00;
    value |= blink ? 0x01 : 0x00;

    write_value(value, false);

    return NRF_SUCCESS;
}

uint32_t liquid_crystal_init(uint32_t _ticks_per_ms) {
    ticks_per_ms = _ticks_per_ms;

    uint32_t err_code = app_gpiote_user_register(&data.gpio_user_id, 0x0000,
            0x0000, event_handler);

    if (err_code != NRF_SUCCESS) {
        return err_code;
    }

    nrf_gpio_cfg_output(data.pin_db4);
    nrf_gpio_cfg_output(data.pin_db5);
    nrf_gpio_cfg_output(data.pin_db6);
    nrf_gpio_cfg_output(data.pin_db7);
    nrf_gpio_cfg_output(data.pin_rs);
    nrf_gpio_cfg_output(data.pin_en);

    begin(data);

    return NRF_SUCCESS;
}