/* if ever in need of formatting functions like in this file, but signed, they
 * can be found wasted in the version history, commit
 * f975594e55bdc05ee436bc7bdcd6e09aec5357b1. */

#include <math.h>
#include <stdlib.h>
#include <string.h>

#include "intmath.h"
#include "formatting.h"
#include "minitest.h"


size_t int_charcount(int x) {
	size_t n = x < 0;
	x *= -(x < 0) * 2 + 1;
	while (x >= 10) {
		x /= 10;
		n += 1;
	}
	return n + 1;
}

/* Returns `int x` floored to `unsigned int precision` as an `exp_notated`
 * value with given `unsigned int base`.
 *
 * `unsigned int base` affects the precision.
 */
exp_notated ull_floored_exponent_notation_base
(
	unsigned long long x,
	unsigned int precision,
	unsigned int base
) {
	int i = 0;
	while (x >= int_pown(base, precision)) {
		x /= base;
		i++;
	}

	exp_notated res = {
		.mantissa = x,
		.exponent = i,
		.base = base
	};
	return res;
}

exp_notated ull_floored_exponent_notation(
	unsigned long long x,
	unsigned int precision
) {
	return ull_floored_exponent_notation_base(x, precision, 10);
}

exp_notated ull_ceiled_exponent_notation_base(
	unsigned long long x,
	unsigned int precision,
	unsigned int base
) {
	unsigned long long original = x;

	int i = 0;
	while (x >= int_pown(base, precision)) {
		x /= base;
		i++;
	}
	
	if (x * ull_pown(base, i) != original) {
		x += 1;
	}

	exp_notated res = {
		.mantissa = x,
		.exponent = i,
		.base = base
	};
	return res;
}

exp_notated ull_ceiled_exponent_notation(
	unsigned long long x,
	unsigned int precision
) {
	return ull_ceiled_exponent_notation_base(x, precision, 10);
}

unsigned long long exp_notated_to_ull(exp_notated x) {
	return x.mantissa * (unsigned long long) int_pown(x.base, x.exponent);
}

/* Returns the appropriate binary prefix for `exp_notated x`. `x` must have
 * `1024` as its base and its exponent should not be greater than `10` Failing
 * to meet these conditions results in the function returning `NULL`.
 */
const char* binary_prefix(exp_notated x) {
	if (x.base != 1024) return NULL;

	switch (x.exponent) {
		case 0:
			return "";
		case 1:
			return "Ki";
		case 2:
			return "Mi";
		case 3:
			return "Gi";
		case 4:
			return "Ti";
		case 5:
			return "Pi";
		case 6:
			return "Ei";
		case 7:
			return "Zi";
		case 8:
			return "Yi";
		case 9:
			return "Ri";
		case 10:
			return "Qi";
	}

	return NULL;
}

/* Modifies the string pointed to by `char** res` to a string describing the
 * argument `unsigned long long x` floored to the appropriate multiple of 1024
 * followed with a binary prefix (Ki, Mi, Gi...).
 *
 * `size_t* res_bufsize` should point to a value describing the size of the
 * string buffer pointed to by `char** res`. Returns a negative value upon
 * failure in memory allocation or `snprintf`, otherwise returns the length of
 * `char* res`.
 */
int ull_floored_with_binary_prefix(
	char** res,
	size_t* res_bufsize,
	unsigned long long x
) {
	exp_notated x_exp = ull_floored_exponent_notation_base(x, 1, 1024);

	const char* prefix = binary_prefix(x_exp);

	size_t bufsize =
		5 + /* len("-1024") */
		/* length of possible zeroes */
		int_max(0, (x_exp.exponent - 10) * 3) +
		4;  /* len(" Gi\0") */
	if (bufsize > *res_bufsize) {
		free(*res);
		*res = malloc(bufsize);
		*res_bufsize = bufsize;
	}
	if (*res == NULL) return -1;
	return snprintf(*res, *res_bufsize, "%llu %s", x_exp.mantissa, prefix);
}

/* Returns the unit prefix resembling the exponent `int x`. If there is no
 * prefix resembling `x`, NULL is returned, though the special case `x = 0`
 * returns an empty string.
 */
const char* unit_prefix(int exponent) {
	switch (exponent) {
		case -30:
			return "q";
		case -27:
			return "r";
		case -24:
			return "y";
		case -21:
			return "z";
		case -18:
			return "a";
		case -15:
			return "f";
		case -12:
			return "p";
		case -9:
			return "n";
		case -6:
			return "μ";
		case -3:
			return "m";
		case -2:
			return "c";
		case -1:
			return "d";
		case 0:
			return "";
		case 1:
			return "da";
		case 2:
			return "h";
		case 3:
			return "k";
		case 6:
			return "M";
		case 9:
			return "G";
		case 12:
			return "T";
		case 15:
			return "P";
		case 18:
			return "E";
		case 21:
			return "Z";
		case 24:
			return "Y";
		case 27:
			return "R";
		case 30:
			return "Q";
	}

	return NULL;
}

/* Modifies the string pointed to by `char** res` to a string describing the
 * argument `int x` floored to the appropriate precision followed with a unit
 * prefix (k, M, G...).
 *
 * `size_t* res_bufsize` should point to a value describing the size of the
 * string buffer pointed to by `char** res`. Returns a negative value upon
 * failure and the length of `char* res` on success. Failure can be caused by
 * problems in memory allocation or failure in `snprintf`.
 */
int ull_floored_with_prefix(
	char** res,
	size_t* res_bufsize,
	long long unsigned x,
	unsigned int precision
) {
	exp_notated x_exp
		= ull_floored_exponent_notation_base(x, precision, 10);
	double mantissa = (double) x_exp.mantissa * int_pow10(x_exp.exponent % 3);
	unsigned int exponent = x_exp.exponent - x_exp.exponent % 3;

	while (fabs(mantissa) >= 1000) {
		mantissa /= 1000;
		exponent += 3;
	}

	const char* prefix = unit_prefix(exponent);
	size_t prefix_len = strlen(prefix);

	size_t bufsize =
		int_max(precision, 3) /* mantissa */
		+ 4 /* minus, space, decimal dot and NULL byte */
		+ prefix_len;
	if (bufsize > *res_bufsize) {
		free(*res);
		*res_bufsize = bufsize;
		*res = malloc(*res_bufsize);
	}
	if (*res == NULL) return -1;

	return snprintf(
		*res,
		*res_bufsize,
		"%.*f %s",
		int_max(precision - int_charcount((int) fabs(mantissa)), 0),
		mantissa,
		prefix
	);
}

char* test_floored_exponent_notation() {
	const size_t bufsize = 128;
	char* msg = malloc(bufsize);

	exp_notated res = ull_floored_exponent_notation(9489345, 3);
	snprintf(msg, bufsize,
		"ull_floored_exponent_notation(9489345, 3): expected 948*10^4, got %llu*%d^%d",
		res.mantissa, res.base, res.exponent
	);
	mt_assert(
		res.mantissa == 948 &&
		res.base == 10 &&
		res.exponent == 4
	, msg);

	res = ull_floored_exponent_notation_base(3145733, 1, 1024);
	snprintf(msg, bufsize,
		"ull_floored_exponent_notation_base(3145733, 1, 1024): expected 3*1024^2, got %llu*%d^%d",
		res.mantissa, res.base, res.exponent
	);
	mt_assert(
		res.mantissa == 3 &&
		res.base == 1024 &&
		res.exponent == 2
	, msg);

	free(msg);
	return 0;
}

char* test_ceiled_exponent_notation() {
	const size_t bufsize = 128;
	char* msg = malloc(bufsize);

	exp_notated res = ull_ceiled_exponent_notation(9489345, 3);
	snprintf(msg, bufsize,
		"ull_ceiled_exponent_notation(9489345, 3): expected 949*10^4, got %llu*%d^%d",
		res.mantissa, res.base, res.exponent
	);
	mt_assert(
		res.mantissa == 949 &&
		res.base == 10 &&
		res.exponent == 4
	, msg);

	res = ull_ceiled_exponent_notation_base(3145733, 1, 1024);
	snprintf(msg, bufsize,
		"ull_ceiled_exponent_notation_base(3145733, 1, 1024): expected 4*1024^2, got %llu*%d^%d",
		res.mantissa, res.base, res.exponent
	);
	mt_assert(
		res.mantissa == 4 &&
		res.base == 1024 &&
		res.exponent == 2
	, msg);

	free(msg);
	return 0;
}

char* test_exponent_notated_to_ull() {
	exp_notated x = {
		.mantissa = 3,
		.exponent = 2,
		.base = 10
	};
	mt_assert_eq(300, exp_notated_to_ull(x));
	return 0;
}

char* test_floored_with_binary_prefix() {
	const size_t bufsize = 64;
	char* msg = malloc(bufsize);
	size_t res_bufsize = 2;
	char* res = malloc(res_bufsize);

	ull_floored_with_binary_prefix(
		&res,
		&res_bufsize,
		1026
	);
	snprintf(msg, bufsize, "1026 yielded `%s` instead of `1 Ki`", res);
	mt_assert(strcmp(
		res,
		"1 Ki"
	) == 0, msg);

	ull_floored_with_binary_prefix(
		&res,
		&res_bufsize,
		1049088
	);
	snprintf(msg, bufsize, "1049088 yielded `%s` instead of `1 Mi`", res);
	mt_assert(strcmp(
		res,
		"1 Mi"
	) == 0, msg);

	ull_floored_with_binary_prefix(
		&res,
		&res_bufsize,
		5243392
	);
	snprintf(msg, bufsize, "5243392 yielded `%s` instead of `5 Mi`", res);
	mt_assert(strcmp(
		res,
		"5 Mi"
	) == 0, msg);

	free(res);
	free(msg);
	return 0;
}


char* test_floored_with_prefix() {
	const size_t bufsize = 64;
	char* msg = malloc(bufsize);
	size_t res_bufsize = 2;
	char* res = malloc(res_bufsize);

	ull_floored_with_prefix(
		&res,
		&res_bufsize,
		1001,
		3
	);
	snprintf(msg, bufsize, "1001 yielded `%s` instead of `1.00 k`", res);
	mt_assert(strcmp(
		res,
		"1.00 k"
	) == 0, msg);

	ull_floored_with_prefix(
		&res,
		&res_bufsize,
		300,
		1
	);
	snprintf(msg, bufsize, "300 (-p1) yielded `%s` instead of `300 `", res);
	mt_assert(strcmp(
		res,
		"300 "
	) == 0, msg);

	ull_floored_with_prefix(
		&res,
		&res_bufsize,
		1000000,
		2
	);
	snprintf(msg, bufsize, "1 000 000 yielded `%s` instead of `1.0 M`", res);
	mt_assert(strcmp(
		res,
		"1.0 M"
	) == 0, msg);

	ull_floored_with_prefix(
		&res,
		&res_bufsize,
		5243392,
		4
	);
	snprintf(msg, bufsize, "5243692 yielded `%s` instead of `5.243 M`", res);
	mt_assert(strcmp(
		res,
		"5.243 M"
	) == 0, msg);

	free(res);
	free(msg);
	return 0;
}

char* test_int_charcount() {
	mt_assert_eq(int_charcount(5), 1);
	mt_assert_eq(int_charcount(24), 2);
	mt_assert_eq(int_charcount(10), 2);
	mt_assert_eq(int_charcount(0), 1);
	mt_assert_eq(int_charcount(1), 1);
	mt_assert_eq(int_charcount(-1), 2);
	mt_assert_eq(int_charcount(99), 2);
	mt_assert_eq(int_charcount(100), 3);
	return 0;
}


void formatting_tests() {
	mt_run_test(test_int_charcount);
	mt_run_test(test_floored_exponent_notation);
	mt_run_test(test_ceiled_exponent_notation);
	mt_run_test(test_exponent_notated_to_ull);
	mt_run_test(test_floored_with_binary_prefix);
	mt_run_test(test_floored_with_prefix);
}