/**
 * Copyright (c) 2017-2018 Tara Keeling
 *				 2020 Philippe G.
 * 
 * This software is released under the MIT License.
 * https://opensource.org/licenses/MIT
 */

#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <esp_heap_caps.h>
#include <esp_log.h>

#include "gds.h"
#include "gds_private.h"

#define SHADOW_BUFFER
#define USE_IRAM

static char TAG[] = "SSD1306";

struct PrivateSpace {
    uint8_t* Shadowbuffer;
};

// Functions are not declared to minimize # of lines

static void SetColumnAddress(struct GDS_Device* Device, uint8_t Start, uint8_t End) {
    Device->WriteCommand(Device, 0x21);
    Device->WriteCommand(Device, Start);
    Device->WriteCommand(Device, End);
}
static void SetPageAddress(struct GDS_Device* Device, uint8_t Start, uint8_t End) {
    Device->WriteCommand(Device, 0x22);
    Device->WriteCommand(Device, Start);
    Device->WriteCommand(Device, End);
}

static void Update(struct GDS_Device* Device) {
#ifdef SHADOW_BUFFER
    struct PrivateSpace* Private = (struct PrivateSpace*)Device->Private;
    // not sure the compiler does not have to redo all calculation in for loops, so local it is
    int width = Device->Width, pages = Device->Height / 8;
    uint8_t *optr = Private->Shadowbuffer, *iptr = Device->Framebuffer;
    int CurrentPage = -1, FirstCol = -1, LastCol = -1;

    // by row, find first and last columns that have been updated
    for(int p = 0; p < pages; p++) {
        uint8_t first = 0, last;
        for(int c = 0; c < width; c++) {
            if(*iptr != *optr) {
                if(!first) first = c + 1;
                last = c;
            }
            *optr++ = *iptr++;
        }

        // now update the display by "byte rows"
        if(first--) {
            // only set column when useful, saves a fair bit of CPU
            if(first > FirstCol && first <= FirstCol + 4 && last < LastCol && last >= LastCol - 4) {
                first = FirstCol;
                last = LastCol;
            } else {
                SetColumnAddress(Device, first, last);
                FirstCol = first;
                LastCol = last;
            }

            // Set row only when needed, otherwise let auto-increment work
            if(p != CurrentPage) SetPageAddress(Device, p, Device->Height / 8 - 1);
            CurrentPage = p + 1;

            // actual write
            Device->WriteData(Device, Private->Shadowbuffer + p * width + first, last - first + 1);
        }
    }
#else
    // automatic counter and end Page/Column (we assume Height % 8 == 0)
    SetColumnAddress(Device, 0, Device->Width - 1);
    SetPageAddress(Device, 0, Device->Height / 8 - 1);
    Device->WriteData(Device, Device->Framebuffer, Device->FramebufferSize);
#endif
}

static void SetLayout(struct GDS_Device* Device, struct GDS_Layout* Layout) {
    Device->WriteCommand(Device, Layout->HFlip ? 0xA1 : 0xA0);
    Device->WriteCommand(Device, Layout->VFlip ? 0xC8 : 0xC0);
    Device->WriteCommand(Device, Layout->Invert ? 0xA7 : 0xA6);
}

static void DisplayOn(struct GDS_Device* Device) { Device->WriteCommand(Device, 0xAF); }
static void DisplayOff(struct GDS_Device* Device) { Device->WriteCommand(Device, 0xAE); }

static void SetContrast(struct GDS_Device* Device, uint8_t Contrast) {
    Device->WriteCommand(Device, 0x81);
    Device->WriteCommand(Device, Contrast);
}

static bool Init(struct GDS_Device* Device) {
#ifdef SHADOW_BUFFER
    struct PrivateSpace* Private = (struct PrivateSpace*)Device->Private;
#ifdef USE_IRAM
    if(Device->IF == GDS_IF_SPI)
        Private->Shadowbuffer = heap_caps_malloc(Device->FramebufferSize, MALLOC_CAP_INTERNAL | MALLOC_CAP_DMA);
    else
#endif
        Private->Shadowbuffer = malloc(Device->FramebufferSize);
    NullCheck(Private->Shadowbuffer, return false);
    memset(Private->Shadowbuffer, 0xFF, Device->FramebufferSize);
#endif

    // need to be off and disable display RAM
    Device->DisplayOff(Device);
    Device->WriteCommand(Device, 0xA5);

    // charge pump regulator, do direct init
    Device->WriteCommand(Device, 0x8D);
    Device->WriteCommand(Device, 0x14);

    // COM pins HW config (alternative:EN if 64, DIS if 32, remap:DIS) - some display might need something different
    Device->WriteCommand(Device, 0xDA);
    Device->WriteCommand(Device, ((Device->Height == 64 ? 1 : 0) << 4) | (0 < 5));

    // MUX Ratio
    Device->WriteCommand(Device, 0xA8);
    Device->WriteCommand(Device, Device->Height - 1);
    // Display Offset
    Device->WriteCommand(Device, 0xD3);
    Device->WriteCommand(Device, 0);
    // Display Start Line
    Device->WriteCommand(Device, 0x40 + 0x00);
    Device->SetContrast(Device, 0x7F);
    // set flip modes
    struct GDS_Layout Layout = {};
    Device->SetLayout(Device, &Layout);
    // no Display Inversion
    Device->WriteCommand(Device, 0xA6);
    // set Clocks
    Device->WriteCommand(Device, 0xD5);
    Device->WriteCommand(Device, (0x08 << 4) | 0x00);
    // set Adressing Mode Horizontal
    Device->WriteCommand(Device, 0x20);
    Device->WriteCommand(Device, 0);

    // gone with the wind
    Device->WriteCommand(Device, 0xA4);
    Device->DisplayOn(Device);
    Device->Update(Device);

    return true;
}

static const struct GDS_Device SSD1306 = {
    .DisplayOn = DisplayOn,
    .DisplayOff = DisplayOff,
    .SetContrast = SetContrast,
    .SetLayout = SetLayout,
    .Update = Update,
    .Init = Init,
    .Mode = GDS_MONO,
    .Depth = 1,
#if !defined SHADOW_BUFFER && defined USE_IRAM
    .Alloc = GDS_ALLOC_IRAM_SPI,
#endif
};

struct GDS_Device* SSD1306_Detect(sys_display_config* Driver, struct GDS_Device* Device) {
    if(Driver->common.driver != sys_display_drivers_SSD1306) return NULL;

    if(!Device) Device = calloc(1, sizeof(struct GDS_Device));
    *Device = SSD1306;

    ESP_LOGI(TAG, "SSD1306 driver");

    return Device;
}