#ifndef KERNEL_VGA_H
#define KERNEL_VGA_H

// Base memory address for MM VGA
#define VGA_ADDRESS 0xb8000

// Max character cell dimensions
#define VGA_MAX_ROWS 25
#define VGA_MAX_COLS 80

// Default color scheme
#define VGA_WHITE_ON_BLACK 0x0f

// Screen device I/O ports
#define REG_VGA_CTL 0x3d4
#define REG_VGA_DATA 0x3d5

class VGA {
protected:
    /**
     * Given a column and row of a VGA character cell, compute the memory
     * offset from the beginning of the VGA video memory of its char and
     * attr bytes.
     * @param col
     * @param row
     * @return the computed offset
     */
    int getOffset(int col, int row);

    int getOffsetRow(int offset);

    int getOffsetCol(int offset);

    /**
     * Get the memory offset of the character cell where the cursor is.
     *
     * 1. Ask for the high-byte of the offset (data 14)
     * 2. Ask for the low-byte (data 15)
     *
     * @return
     */
    int getCursorOffset();

    /**
     * Given a VGA memory offset, set the cursor to that offset's character cell.
     * @param offset
     */
    void setCursorOffset(int offset);

    /**
     * Print a character to the specified position.
     *
     * If col/row are negative, print to the current cursor position.
     * If attribute_byte is 0, default white on black.
     *
     * @param character
     * @param col
     * @param row
     * @param attribute_byte
     */
    int printChar(char character, int col, int row, char attrs);

    int adjustScrolling(int offset);

    /**
     * Scrolls all the character cells up one row, replacing the top
     * row and creating a new empty row on the bottom.
     */
    void advanceScrolling();

public:
    /**
     * Resets all video memory characters to empty space and all formatting
     * to the default white on black. Then, reset the cursor to the first cell.
     */
    void clearScreen();

    void printAt(char* string, int col, int row);

    void print(char* string);
};

#endif //KERNEL_VGA_H