/*
 * Single-File-Header for SSD1306 emulated I2C interface
 * 02-12-2025 cnlohr
 */

#ifndef _SSD1306_I2C_BITBANG_H
#define _SSD1306_I2C_BITBANG_H

#include <string.h>

// SSD1306 I2C address
#ifndef SSD1306_I2C_ADDR
#define SSD1306_I2C_ADDR 0x3c
#endif

#ifndef SSD1306_I2C_BITBANG_SDA
#define SSD1306_I2C_BITBANG_SDA PC1
#endif

#ifndef SSD1306_I2C_BITBANG_SCL
#define SSD1306_I2C_BITBANG_SCL PC2
#endif

/*
 * init just I2C
 */
void ssd1306_i2c_setup(void)
{
    funGpioInitAll();
    funPinMode(SSD1306_I2C_BITBANG_SDA, GPIO_CFGLR_OUT_10Mhz_PP);
    funDigitalWrite(SSD1306_I2C_BITBANG_SDA, 1);
    funPinMode(SSD1306_I2C_BITBANG_SCL, GPIO_CFGLR_OUT_10Mhz_PP);
    funDigitalWrite(SSD1306_I2C_BITBANG_SCL, 1);
}

#define SDA_HIGH funDigitalWrite(SSD1306_I2C_BITBANG_SDA, 1);
#define SCL_HIGH funDigitalWrite(SSD1306_I2C_BITBANG_SCL, 1);
#define SDA_LOW funDigitalWrite(SSD1306_I2C_BITBANG_SDA, 0);
#define SCL_LOW funDigitalWrite(SSD1306_I2C_BITBANG_SCL, 0);
#define SDA_IN funDigitalRead(SSD1306_I2C_BITBANG_SDA);
#define I2CSPEEDBASE 1
#define I2CDELAY_FUNC(x) ADD_N_NOPS(x * 1)
// Delay_Us(x*1);

static void ssd1306_i2c_sendstart()
{
    SCL_HIGH
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    SDA_LOW
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    SCL_LOW
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
}

void ssd1306_i2c_sendstop()
{
    SDA_LOW
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    SCL_LOW
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    SCL_HIGH
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    SDA_HIGH
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
}

// Return nonzero on failure.
unsigned char ssd1306_i2c_sendbyte(unsigned char data)
{
    unsigned int i;
    for (i = 0; i < 8; i++)
    {
        I2CDELAY_FUNC(1 * I2CSPEEDBASE);
        if (data & 0x80)
        {
            SDA_HIGH;
        }
        else
        {
            SDA_LOW;
        }
        data <<= 1;
        I2CDELAY_FUNC(1 * I2CSPEEDBASE);
        SCL_HIGH
        I2CDELAY_FUNC(2 * I2CSPEEDBASE);
        SCL_LOW
    }

    // Immediately after sending last bit, open up DDDR for control.
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    funPinMode(SSD1306_I2C_BITBANG_SDA, GPIO_CFGLR_IN_PUPD);
    SDA_HIGH
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    SCL_HIGH
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    i = SDA_IN;
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    SCL_LOW
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    SDA_HIGH // Maybe?
        funPinMode(SSD1306_I2C_BITBANG_SDA, GPIO_CFGLR_OUT_10Mhz_PP);
    I2CDELAY_FUNC(1 * I2CSPEEDBASE);
    return !!i;
}

uint8_t ssd1306_pkt_send(const uint8_t *data, int sz, uint8_t cmd)
{
    ssd1306_i2c_sendstart();
    int r = ssd1306_i2c_sendbyte(SSD1306_I2C_ADDR << 1);
    if (r) return r;
    // ssd1306_i2c_sendstart(); For some reason displays don't want repeated start
    if (cmd)
    {
        if (ssd1306_i2c_sendbyte(0x00))
            return 1; // Control
    }
    else
    {
        if (ssd1306_i2c_sendbyte(0x40))
            return 1; // Data
    }
    for (int i = 0; i < sz; i++)
    {
        if (ssd1306_i2c_sendbyte(data[i]))
            return 1;
    }
    ssd1306_i2c_sendstop();
    return 0;
}

void ssd1306_rst(void)
{
    funPinMode(SSD1306_RST_PIN, GPIO_CFGLR_OUT_10Mhz_PP);
    funDigitalWrite(SSD1306_RST_PIN, 0);
    Delay_Ms(10);
    funDigitalWrite(SSD1306_RST_PIN, 1);
    Delay_Us(10);
}

#endif