//
// Created by rick on 8/18/19.
//

#include <string.h>

#include <myke/drivers/ports.h>
#include <myke/drivers/vgascreen.h>
#include <myke/libk/kprint.h>
#include <myke/util/init.h>

char *_vga_character_memory = (char *) VGA_CHARACTER_MEMORY_LOCATION;

int get_offset(int col, int row);

int get_cursor_offset();

void set_cursor_offset(int offset);

int get_offset_row(int offset);

int get_offset_col(int offset);

int print_char(char character, int col, int row, char attributes);


void vga_clear_screen() {
    int size = VGA_COL_MAX * VGA_ROW_MAX;
    for (int i = 0; i < size; ++i) {
        _vga_character_memory[i * 2] = ' ';
        _vga_character_memory[i * 2 + 1] = VGA_WHITE | (VGA_BLACK << VGA_SHIFT_BG);
    }
    set_cursor_offset(0);
}

void kprint_at(const char *message, int col, int row) {
    int offset;
    if (col > 0 && row > 0) {
        offset = get_offset(col, row);
    } else {
        offset = get_cursor_offset();
        row = get_offset_row(offset);
        col = get_offset_col(offset);
    }

    int i = 0;
    while (message[i] != 0) {
        offset = print_char(message[i++], col, row, VGA_WHITE | (VGA_BLACK << VGA_SHIFT_BG));
        row = get_offset_row(offset);
        col = get_offset_col(offset);
    }
}


void vga_kprint(const char *message) {
    kprint_at(message, -1, -1);
}

int print_char(char character, int col, int row, char attributes) {
    if (!attributes) attributes = VGA_WHITE | (VGA_BLACK < VGA_SHIFT_BG);

    if (col >= VGA_COL_MAX || row > +VGA_ROW_MAX) {
        _vga_character_memory[2 * (VGA_COL_MAX) * (VGA_ROW_MAX) - 2] = 'E';
        _vga_character_memory[2 * (VGA_COL_MAX) * (VGA_ROW_MAX) - 1] = VGA_RED | (VGA_WHITE < VGA_SHIFT_BG);
        return get_offset(col, row);
    }

    int offset;
    if (col >= 0 && row >= 0) {
        offset = get_offset(col, row);
    } else {
        offset = get_cursor_offset();
    }

    switch (character) {
        case '\n':
            row = get_offset_row(offset);
            offset = get_offset(0, row + 1);
            break;
        case '\t':
            col = (col + 4) & (~0b11);
            if (col > VGA_COL_MAX) {
                row = get_offset_row(offset);
                offset = get_offset(0, row + 1);
            } else {
                offset = get_offset(col, row);
            }
            break;
        case '\r':
            row = get_offset_row(offset);
            offset = get_offset(0, row);
            break;
        default:
            _vga_character_memory[offset] = character;
            _vga_character_memory[offset + 1] = attributes;
            offset += 2;
            break;
    }

    if (offset >= (VGA_COL_MAX * 2 * VGA_ROW_MAX)) {
        memcpy(_vga_character_memory,
               _vga_character_memory + (VGA_COL_MAX * 2),
               (2 * VGA_COL_MAX * VGA_ROW_MAX) - (2 * VGA_COL_MAX));
        for (int i = 0; i < VGA_COL_MAX; ++i) {
            _vga_character_memory[get_offset(i, VGA_ROW_MAX - 1)] = ' ';
        }
        offset = get_offset(0, VGA_ROW_MAX - 1);
    }

    set_cursor_offset(offset);
    return offset;
}

int get_cursor_offset() {
    port_byte_out(PORT_REG_SCREEN_CTRL, PORT_REG_SCREEN_CTRL_CURSOR_H);
    int offset = ((int) port_byte_in(PORT_REG_SCREEN_DATA)) << 8;
    port_byte_out(PORT_REG_SCREEN_CTRL, PORT_REG_SCREEN_CTRL_CURSOR_L);
    offset += port_byte_in(PORT_REG_SCREEN_DATA);
    return offset * 2;
}

void set_cursor_offset(int offset) {
    offset /= 2;
    port_byte_out(PORT_REG_SCREEN_CTRL, PORT_REG_SCREEN_CTRL_CURSOR_L);
    port_byte_out(PORT_REG_SCREEN_DATA, (unsigned char) (offset & 0xFF));
    port_byte_out(PORT_REG_SCREEN_CTRL, PORT_REG_SCREEN_CTRL_CURSOR_H);
    port_byte_out(PORT_REG_SCREEN_DATA, (unsigned char) (offset >> 8) & 0xFF);
}

int get_offset(int col, int row) {
    return (row * VGA_COL_MAX + col) * 2;
}

int get_offset_row(int offset) {
    return offset / (VGA_COL_MAX * 2);
}

int get_offset_col(int offset) {
    return (offset - (get_offset_row(offset) * 2 * VGA_COL_MAX)) / 2;
}

void vga_init() {
    vga_clear_screen();
    kprint_register(vga_kprint);
}

INIT_FUNCTION(100) = {
        .name = "vga",
        .stage = INIT_STAGE_EARLY_BOOT_0,
        .init = vga_init,
};