#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <sys.h>
#include <print.h>

#include "term.h"
#include "color.h"
#include "cursor.h"

uint16_t buffer[TERM_W * TERM_H * sizeof(uint16_t)];
uint16_t *front;
uint8_t x, y;
uint8_t color;

const uint16_t blank = (uint16_t) 0 | VGA_BLACK << 12 | VGA_WHITE << 8;

static void term_clear_line(int y) {
    if (y < 0 || y >= TERM_H)
        return;
    for (uint8_t x = 0; x < TERM_W; x++) {
	    const size_t index = y * TERM_W + x;
	    buffer[index] = blank;
    }
}

void term_init (void) {
    x = 0;
    y = 0;
    front = (uint16_t*) 0xb8000;
    term_setfg(VGA_WHITE);
    term_setbg(VGA_BLACK);
    term_clear();
}

void term_setpos(uint8_t xp, uint8_t yp) {
    x = xp;
    y = yp;
    cursor_setpos(x, y);
}

void term_scroll (int lines) {
    int_disable(); 
    y -= lines;
    if (!lines) return;
    if(lines >= TERM_H || lines <= -TERM_H) {
		term_clear();
	} else if(lines > 0) {
		memmove(buffer, buffer + lines * TERM_W, 2 * (TERM_H - lines) * TERM_W);
        term_clear_line(TERM_H - lines);
	} else {
		memmove(buffer + lines * TERM_W, buffer + lines, (TERM_H + lines) * TERM_W);
	}
    int_enable();
}

void term_setfg(enum VGAColor c) {
    color = (color & 0xF0) | c;
}

void term_setbg(enum VGAColor c) {
    color = (color & 0x0F) | c << 4;
}

void term_clear (void) {
    for (uint8_t y = 0; y < TERM_H; y++)
        term_clear_line(y);
}

uint32_t term_save(void) {
    uint32_t state = 0;
    state |= (uint32_t) x << 16;
    state |= (uint32_t) y << 8;
    state |= (uint32_t) color << 0;
    return state;
}

void term_load(uint32_t state) {
    x = (uint8_t) (state >> 16);
    y = (uint8_t) (state >> 8);
    color = (uint8_t) (state >> 0);
    cursor_setpos(x, y);
}

uint16_t term_save_col(void) {
    return color;
}

void term_load_col(uint16_t c) {
    color = c;
}

void putchar(int c) {
    switch (c) {
        case '\n':
            x = 0;
            y++;
            break;
        case '\t':
            x += 4;
            break;
        case '\v':
        case '\f':
            y++;
            break;
        case '\r':
            x = 0;
            break;
        default: {
	        const size_t index = y * TERM_W + x;
	        buffer[index] = c | (uint16_t) color << 8;
            x++;
        }
    }

	if (x >= TERM_W) {
		x = 0;
        y++;
	}

	if (y >= TERM_H) {
		term_scroll(y - (TERM_H - 1));
        y = TERM_H - 1;
    }

    cursor_setpos(x, y);
}

bool term_newline(void) {
    return x == 0;
}

void term_flush(void) {
    int_disable();
    memcpy(front, buffer, TERM_W * TERM_H * sizeof(uint16_t));
    int_enable();
}