#include <lib.h>
#include <serial.h>
#include <stdarg.h>
#include <stdint.h>

void kputc(char c) {
	serial_out(c);
}

void kputs(const char *s) {
	serial_out_str(s);
}

enum format_flag {
	FLG_NONE = 0x00,
	FLG_ALTERNATE = 0x01,
	FLG_ZERO = 0x02,
	FLG_LEFT_ALIGN = 0x04,
	FLG_ADD_SIGN = 0x08
};

struct format_width {
	bool defined;
	bool varys;
	int value;
};

struct format_precision {
	bool defined;
	bool varys;
	int value;
};

enum format_modifier {
	MOD_NONE = 0,
	MOD_HALF = 1,
	MOD_HALF_HALF = 3,
	MOD_LONG = 3,
	MOD_LONG_LONG = 4,
	MOD_INVALID = 5,
};

enum format_conversion {
	// decimal numbers
	FMT_CHAR = 0,
	FMT_INT = 4,
	FMT_UINT = 5,
	// otehr numbers
	FMT_OCT,
	FMT_HEX,
	FMT_HEX_UPPER,
	// text
	FMT_STR,
	FMT_PTR,
	// misc
	FMT_INVALID
};

enum format_length {
	LEN_UCHAR,
	LEN_CHAR,
	LEN_USHORT,
	LEN_SHORT,
	LEN_UINT,
	LEN_INT,
	LEN_ULONG,
	LEN_LONG,
	LEN_ULONGLONG,
	LEN_LONGLONG,
	LEN_SIZET,
	LEN_INVALID
};

struct spacing {
	unsigned left;
	unsigned length;
	unsigned right;
	bool zero;
};

enum charcase {
	UPPERCASE,
	LOWERCASE
};

enum printtype {
	NONE,
	OCTAL,
	HEX
};

static enum printtype conversion_to_printtype(enum format_conversion conversion) {
	switch (conversion) {
		case FMT_OCT:
			return OCTAL;
		case FMT_HEX:
		case FMT_HEX_UPPER:
		case FMT_PTR:
			return HEX;
		default:
			return NONE;
	}
}

static enum charcase conversion_to_charcase(enum format_conversion conversion) {
	switch (conversion) {
		case FMT_HEX_UPPER:
			return UPPERCASE;
		default:
			return LOWERCASE;
	}
}

static enum format_flag read_flags(const char *format, const char **end) {

	enum format_flag flags = FLG_NONE;

	for (; *format != '\0'; format++) {
		switch (*format) {
			case '#':
				flags |= FLG_ALTERNATE;
				break;
			case '0':
				flags |= FLG_ZERO;
				break;
			case '-':
				flags |= FLG_LEFT_ALIGN;
				break;
			case '+':
				flags |= FLG_ADD_SIGN;
				break;
			default:
				*end = format;
				return flags;
		}
	}

	*end = format;
	return flags;
}

static struct format_width read_width(const char *format, const char **end) {

	struct format_width width;
	width.defined = false;
	width.varys = false;
	width.value = 0;

	int value = 0;

	for (; *format != '\0'; format++) {
		char c = *format;

		if (c == '*' && width.defined == false) {
			width.defined = true;
			width.varys = true;
			break;
		}

		if (!isdigit(c))
			break;

		int i = c - '0';
		value *= 10;
		value += i;

		width.value = value;
		width.defined = true;
		width.varys = false;
	}

	*end = format;
	return width;

}

static struct format_precision read_precision(const char *format, const char **end) {

	struct format_precision precision;
	precision.varys = false;
	precision.defined = false;
	precision.value = 0;

	if (*format != '.') {
		*end = format;
		return precision;
	}

	format++;

	int value = 0;

	for (; *format != '\0'; format++) {
		char c = *format;

		if (c == '*' && precision.defined == false) {
			precision.defined = true;
			precision.varys = true;
			format++;
			break;
		}

		if (!isdigit(c))
			break;

		int i = c - '0';
		value *= 10;
		value += i;

		precision.value = value;
		precision.defined = true;
		precision.varys = false;
	}

	*end = format;
	return precision;
}

static enum format_modifier read_modifier(const char *format, const char **end) {

	enum format_modifier mod = MOD_NONE;

	for (; *format != '\0'; format++) {
		*end = format;
		switch (*format) {
			case 'l':
				if (mod == MOD_NONE)
					mod = MOD_LONG;
				else if (mod == MOD_LONG)
					return MOD_LONG_LONG;
				else
					return MOD_INVALID;
				break;
			case 'L':
				if (mod == MOD_NONE)
					return MOD_LONG_LONG;
				else
					return MOD_INVALID;
				break;
			case 'h':
				if (mod == MOD_NONE)
					mod = MOD_HALF;
				else if (mod == MOD_HALF)
					return MOD_HALF_HALF;
				else
					return MOD_INVALID;
				break;
			case 'H':
				if (mod == MOD_NONE)
					return MOD_HALF_HALF;
				else
					return MOD_INVALID;
				break;
			default:
				return mod;
		}
	}

	return MOD_INVALID;
}

static enum format_conversion read_conversion(const char *format, const char **end) {
	*end = format + 1;
	switch (*format) {
		case 'd':
		case 'i':
			return FMT_INT;
		case 'o':
			return FMT_OCT;
		case 'u':
			return FMT_UINT;
		case 'x':
			return FMT_HEX;
		case 'X':
			return FMT_HEX_UPPER;
		case 'c':
			return FMT_CHAR;
		case 's':
			return FMT_STR;
		case 'p':
			return FMT_PTR;
		default:
			return FMT_INVALID;
	}
}

static char ctoa_print(
		char c,					 // the single digit to convert to ascii
		enum charcase cc			// if this digit should be uppercase or lowercase
) {
	char ascii_base = cc == UPPERCASE ? 'A' : 'a';
	if (c >= 0 && c <= 9)
		return c + '0';
	c -= 10;
	return c + ascii_base;
}

static char *ulltoa_print(
		unsigned long long num,	 // the number to convert to ascii
		unsigned radix,			 // the divisor for the number (base 10, octal, hex)
		char *buf,				  // the buffer to write to
		enum charcase cc,		   // if any a-z ascii should be uppercase or lowercase
		bool addsign				// add a sign even if its positive
) {
	// we are printing the string backwards, add null byte
	*buf = '\0';
	buf--;

	// if the number is zero, the while loop will never run
	// so we have to add the zero digit ourselves
	if (num == 0) {
		*buf = '0';
		buf--;
	}

	// for each digit, convert to ascii and add to buffer
	while (num != 0) {
		char i = num % radix;
		char c = ctoa_print(i, cc);
		*buf = c;
		buf--;
		num /= radix;
	}

	// since this is the unsigned function, add a plus sign if
	// requested
	if (addsign) {
		*buf = '+';
		buf--;
	}

	buf++; // move forward one to be at the start of the string

	return buf;
}

static char *lltoa_print(
		signed long long num,	   // the number to convert to ascii
		unsigned radix,			 // the divistor for the number (base 10, octal, hex)
		char *buf,				  // the buffer to write to
		enum charcase cc,		   // if any a-z ascii should be uppercase or lowercase
		bool addsign				// add a sign even if its positive
) {
	bool isneg = num < 0;

	if (isneg)
		num = -num;

	buf = ulltoa_print(num, radix, buf, cc, !isneg && addsign);

	if (isneg && num < 0) {
		buf--;
		*buf = '-';
	}

	return buf;
}


static void print_string_buffer(
		const char *buf,			// buffer containing the text we want to print
		struct spacing spacing	  // the spacing on the left right and middle
) {
	for (unsigned i = 0; i < spacing.left; i++) {
		kputc(' ');
	}

	for (unsigned i = 0; i < spacing.length; i++) {
		kputc(*buf++);
	}

	for (unsigned i = 0; i < spacing.right; i++) {
		kputc(' ');
	}
}

static void print_number_buffer(
		const char *buf,			// buffer containing the text we want to print
		struct spacing spacing,	 // the spacing on the left right and middle
		enum printtype type,
		enum charcase cc,
		enum format_flag flags
) {

	// put the 0x at the start of the string
	if (spacing.left && spacing.zero && type == HEX && (flags & FLG_ALTERNATE)) {
		if (cc == UPPERCASE) {
			kputs("0X");
		} else {
			kputs("0x");
		}
	}

	if ((!spacing.left || !spacing.zero) && type == OCTAL && (flags & FLG_ALTERNATE)) {
		kputc('0');
	}

	for (unsigned i = 0; i < spacing.left; i++) {
		spacing.zero ? kputc('0') : kputc(' ');
	}

	if ((!spacing.left || !spacing.zero) && type == HEX && (flags & FLG_ALTERNATE)) {
		if (cc == UPPERCASE) {
			kputs("0X");
		} else {
			kputs("0x");
		}
	}

	for (unsigned i = 0; i < spacing.length; i++) {
		kputc(*buf++);
	}

	for (unsigned i = 0; i < spacing.right; i++) {
		kputc(' ');
	}
}

static unsigned get_string_len(
	const char *str,
	struct format_precision precision
) {
	if (!precision.defined)
		return strlen(str);
	unsigned max = precision.value;
	for (unsigned i = 0; i < max; i++) {
		if (str[i] == '\0') {
			// we broke early
			// precision is greater then strlen
			return i;
		}
	}
	return max;
}

static struct spacing get_spacing(
	struct format_width width,
	struct format_precision precision,
	enum format_flag flags,
	unsigned length
) {
	struct spacing spacing;

	unsigned min = 0,
			 max = 0;

	if (width.defined) {
		min = width.value;
	}

	if (precision.defined) {
		max = precision.value;
		if (length > max) {
			length = max;
		}
		if (min > max) {
			min = max;
		}
	}

	unsigned gap = 0;
	if (min > length) {
		gap = min - length;
	}

	spacing.length = length;

	if (flags & FLG_LEFT_ALIGN) {
		spacing.left = 0;
		spacing.right = gap;
	} else {
		spacing.left = gap;
		spacing.right = 0;
	}

	spacing.zero = (flags & FLG_ZERO);

	return spacing;
}

static struct spacing get_string_spacing(
	const char *str,
	struct format_width width,
	struct format_precision precision,
	enum format_flag flags
) {
	unsigned length = get_string_len(str, precision);
	return get_spacing(width, precision, flags, length);
}

static void print_string(
		const char *str,
		enum format_flag flags,
		struct format_width width,
		struct format_precision precision
) {
	struct spacing spacing =
		get_string_spacing(str, width, precision, flags);
	print_string_buffer(str, spacing);
}

static enum format_length apply_modifier(
		enum format_conversion conversion,
		enum format_modifier modifier
) {
	switch (conversion) {
		case FMT_CHAR:
			if (modifier == MOD_NONE)
				return LEN_CHAR;
			else
				return LEN_INVALID;

		case FMT_PTR:
			if (modifier == MOD_NONE)
				return LEN_SIZET;
			else
				return LEN_INVALID;

		case FMT_INT:
			if (modifier == MOD_LONG)
				return LEN_LONG;
			else if (modifier == MOD_LONG_LONG)
				return LEN_LONGLONG;
			else if (modifier == MOD_HALF)
				return LEN_SHORT;
			else if (modifier == MOD_HALF_HALF)
				return LEN_CHAR;
			else
				return LEN_INT;

		case FMT_UINT:
		case FMT_OCT:
		case FMT_HEX:
		case FMT_HEX_UPPER:
			if (modifier == MOD_LONG)
				return LEN_ULONG;
			else if (modifier == MOD_LONG_LONG)
				return LEN_ULONGLONG;
			else if (modifier == MOD_HALF)
				return LEN_USHORT;
			else if (modifier == MOD_HALF_HALF)
				return LEN_UCHAR;
			else
				return LEN_UINT;

		default:
			return LEN_INVALID;
	}
}

static unsigned printtype_to_radix(
		enum printtype type
) {
	switch (type) {
		case OCTAL:
			return 8;
		case HEX:
			return 16;
		case NONE:
		default:
			return 10;
	}
}

static void print_signed_number(
		signed long long num,
		enum format_flag flags,
		struct format_width width,
		struct format_precision precision,
		enum printtype type,
		enum charcase cc
) {
	unsigned radix = printtype_to_radix(type);
	char buf[256];
	char *ptr = lltoa_print(num, radix, buf + 255, cc, flags & FLG_ADD_SIGN);
	unsigned length = strlen(ptr);
	struct spacing spacing =
		get_spacing(width, precision, flags, length);
	print_number_buffer(ptr, spacing, type, cc, flags);
}

static void print_unsigned_number(
		unsigned long long num,
		enum format_flag flags,
		struct format_width width,
		struct format_precision precision,
		enum printtype type,
		enum charcase cc
) {
	unsigned radix = printtype_to_radix(type);
	char buf[256];
	char *ptr = ulltoa_print(num, radix, buf + 255, cc, flags & FLG_ADD_SIGN);
	unsigned length = strlen(ptr);
	struct spacing spacing =
		get_spacing(width, precision, flags, length);
	print_number_buffer(ptr, spacing, type, cc, flags);
}

static bool is_conversion_number(enum format_conversion conversion) {
	switch (conversion) {
		case FMT_INT:
		case FMT_UINT:
		case FMT_OCT:
		case FMT_HEX:
		case FMT_HEX_UPPER:
		case FMT_PTR:
			return true;
		case FMT_CHAR:
		case FMT_STR:
		case FMT_INVALID:
		default:
			return false;
	}
}

void kvprintf(const char *format, va_list args) {
	for (; *format != '\0'; format++) {
		char c = *format;
		if (c == '%') {
			enum format_flag flags;
			struct format_width width;
			struct format_precision precision;
			enum format_modifier modifier;
			enum format_conversion conversion;

			const char *ptr = format + 1;

			if (*(format + 1) == '%') {
				kputc('%');
				format++;
				continue;
			}

			flags = read_flags(ptr, &ptr);
			width = read_width(ptr, &ptr);
			precision = read_precision(ptr, &ptr);

			modifier = read_modifier(ptr, &ptr);

			if (modifier == MOD_INVALID) {
				goto error;
			}

			conversion = read_conversion(ptr, &ptr);

			if (width.varys) {
				int len = va_arg(args, int);
				width.value = len;
			}

			if (precision.varys) {
				int len = va_arg(args, int);
				precision.value = len;
			}

			if (conversion == FMT_INVALID) {
				goto error;
			}

			if (conversion == FMT_INT) {
				enum format_length length =
					apply_modifier(conversion, modifier);
				enum printtype type = NONE;
				enum charcase cc = LOWERCASE;

				signed long long num = 0;
				switch (length) {
					case LEN_CHAR:
					case LEN_SHORT:
					case LEN_INT:
						num = va_arg(args, signed int);
						break;
					case LEN_LONG:
						num = va_arg(args, signed long);
						break;
					case LEN_LONGLONG:
						num = va_arg(args, signed long long);
						break;
					default:
						goto error;
				}

				print_signed_number(num, flags, width, precision, type, cc);
			} else if (is_conversion_number(conversion)) {
				enum format_length length =
					apply_modifier(conversion, modifier);
				enum printtype type =
					conversion_to_printtype(conversion);
				enum charcase cc =
					conversion_to_charcase(conversion);

				unsigned long long num = 0;
				switch (length) {
					case LEN_UCHAR:
					case LEN_USHORT:
					case LEN_UINT:
						num = va_arg(args, unsigned int);
						break;
					case LEN_ULONG:
						num = va_arg(args, unsigned long);
						break;
					case LEN_ULONGLONG:
						num = va_arg(args, unsigned long long);
						break;
					case LEN_SIZET:
						num = va_arg(args, size_t);
						break;
					default:
						goto error;
				}

				print_unsigned_number(num, flags, width, precision, type, cc);
			} else if (conversion == FMT_STR) {
				char *str = va_arg(args, char *);
				print_string(str, flags, width, precision);
			} else if (conversion == FMT_CHAR) {
				char temp[2];
				temp[0] = va_arg(args, int);
				temp[1] = '\0';
				print_string(temp, flags, width, precision);
			}

			format = ptr - 1;
			continue;

error:
			kputc('%');
			format++;
			continue;
		} else {
			kputc(c);
		}
	}
}

void kprintf(const char *format, ...) {
	va_list args;
	va_start(args, format);
	kvprintf(format, args);
	va_end(args);
}