#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <string_volatile.h>
#include <stdarg.h>
#include <sys.h>

#include "term.h"

static volatile uint16_t *screen = (uint16_t*)0xb8000;
static size_t term_x = 0;
static size_t term_y = 0;
static uint8_t color = 0x0f;
static uint16_t screen_buf[TERM_W * TERM_H * 2];

static inline uint16_t screen_entry(char c, uint8_t col) {
	return (uint16_t)c | ((uint16_t)col << 8);
}

void putc(char c) {
	switch(c) {
		case '\n':
			term_x = TERM_W;
			break;
		case '\t':
			if(term_x % 8 == 0) term_x += 8;
			term_x += 7 - (term_x % 8);
			break;
		default:
			screen_buf[term_x + term_y * TERM_W] = screen_entry(c, color);
			term_x += 1;
			break;
	}
	if(term_x >= TERM_W) {
		term_x = 0;
		term_y += 1;
	}
	if(term_y >= TERM_H) {
		term_scroll(1);
	}
	if(c == '\n') {
		term_flush();
	}
}

void puts(const char *s) {
	for(; *s != '\0'; s++) {
		putc(*s);
	}
}

static uint8_t hex2i(char hex) {
	if(hex < 'A') {
		return hex - '0';
	} else if(hex < 'a') {
		return hex - 'A' + 10;
	} else {
		return hex - 'a' + 10;
	}
}

static char i2d(int i, bool upper) {
	if(i < 10) {
		return '0' + i;
	} else {
		return 'a' + (i - 10) + (upper ? 'A' - 'a' : 0);
	}
}

static void itoa(int n, char *buf, int base, bool upper) {
	if(n == 0) {
		buf[0] = '0';
		buf[1] = '\0';
		return;
	}
	if(n < 0) {
		n = -n;
		buf[0] = '-';
		buf++;
	}
	char *start = buf;
	while(n != 0) {
		*buf++ = i2d(n % base, upper);
		n /= base;
	}
	*buf-- = '\0';
	while(buf > start) {
		char tmp = *start;
		*start++ = *buf;
		*buf-- = tmp;
	}
}

static void utoa(unsigned int n, char *buf, int base, bool upper) {
	if(n == 0) {
		buf[0] = '0';
		buf[1] = '\0';
		return;
	}
	char *start = buf;
	while(n != 0) {
		*buf++ = i2d(n % base, upper);
		n /= base;
	}
	*buf-- = '\0';
	while(buf > start) {
		char tmp = *start;
		*start++ = *buf;
		*buf-- = tmp;
	}
}

void vprintf(const char *fstr, va_list args) {
	char buf[80];
	for(; *fstr != '\0'; fstr++) {
		if(*fstr == '%') {
			fstr++;
			switch(*fstr) {
			case '%':
				putc('%');
				break;
			case 's':
				puts(va_arg(args, char*));
				break;
			case 'd':
				itoa(va_arg(args, int), buf, 10, false);
				puts(buf);
				break;
			case 'u':
				utoa(va_arg(args, unsigned int), buf, 10, false);
				puts(buf);
				break;
			case 'x':
				utoa(va_arg(args, unsigned int), buf, 16, false);
				puts(buf);
				break;
			case 'X':
				utoa(va_arg(args, unsigned int), buf, 16, true);
				puts(buf);
				break;
			case '@': {
				uint8_t hi = hex2i(*++fstr);
				uint8_t lo = hex2i(*++fstr);
				term_setcol((hi << 4) | lo);
				break;
			}
			default:
				break;
			}
		} else {
			putc(*fstr);
		}
	}
}

void printf(const char *fstr, ...) {
	va_list args;
	va_start(args, fstr);
	vprintf(fstr, args);
	va_end(args);
}


void term_clear(void) {
	memset(screen_buf, 0, TERM_W * TERM_H * 2);
}

void term_setpos(size_t new_x, size_t new_y) {
	term_x = new_x;
	term_y = new_y;
}

void term_setcol(uint8_t new_col) {
	color = new_col;
}

void term_scroll(ptrdiff_t lines) {
	term_y -= lines;
	if(lines == 0) return;
	if(lines >= TERM_H || lines <= -TERM_H) {
		term_clear();
	} else if(lines > 0) {
		memmove(screen_buf, screen_buf + lines * TERM_W, 2 * (TERM_H - lines) * TERM_W);
		memset(screen_buf + (TERM_H - lines) * TERM_W, 0, 2 * lines * TERM_W);
	} else {
		memmove(screen_buf + lines * TERM_W, screen_buf + lines, (TERM_H + lines) * TERM_W);
	}
}

void term_flush(void) {
	int_disable();
	memcpy_volatile(screen, screen_buf, TERM_W * TERM_H * 2);
	int_enable();
}

uint32_t term_save(void) {
	return color | ((term_x + term_y * TERM_W) << 8);
}

void term_load(uint32_t state) {
	color = state & 0xff;
	state >>= 8;
	term_x = state % TERM_W;
	term_y = state / TERM_W;
}