// strconv — number↔string conversions. Decimal i64 to/from a fixed
// buffer. Error shapes mirror Hare's strconv types: (T | invalid |
// overflow) where each error is a named alias over a payload type
// (Hare uses !size / !void; ww uses i32 / void without the `!` mark).

// invalid — input wasn't a valid number in the requested format.
// Payload is the byte index of the first offending position (Hare
// strconv::invalid is `!size` carrying the same).
export type invalid = i32;

// overflow — input was valid but doesn't fit the target type. No
// payload (a single yes/no signal). Mirrors Hare's `!void` shape.
export type overflow = void;

// u64tos — write `v` in decimal into `buf` and return the byte count.
// Hare name; the buffer-in shape is the sanctioned Plan 9 subset of
// Hare's `u64tos(u, base) const str`. Unsigned-only so callers don't
// have to think about wraparound when printing a u64 with the high
// bit set.
export fn u64tos(buf: []u8, v: u64) i32 = {
	let tmp: [32]u8;
	let i: i32 = 0;
	let n: u64 = v;
	for (n > 0u64) {
		tmp[i] = ((n % 10u64) + 48u64): u8;
		n = n / 10u64;
		i += 1;
	};
	if (i == 0) {
		tmp[0] = 48u8;
		i = 1;
	};
	let out: i32 = 0;
	for (i > 0) {
		i -= 1;
		buf[out] = tmp[i];
		out += 1;
	};
	return out;
};

export fn i64tos(buf: []u8, v: i64) i32 = {
	let neg: bool = false;
	let n: i64 = v;
	if (n < 0) {
		neg = true;
		n = -n;
	};
	let tmp: [32]u8;
	let i: i32 = 0;
	for (n > 0) {
		tmp[i] = ((n % 10) + 48): u8;
		n = n / 10;
		i += 1;
	};
	if (i == 0) {
		tmp[0] = 48u8;
		i = 1;
	};
	let out: i32 = 0;
	if (neg) {
		buf[out] = 45u8;	// '-'
		out += 1;
	};
	for (i > 0) {
		i -= 1;
		buf[out] = tmp[i];
		out += 1;
	};
	return out;
};

// stoi64 — Hare-style fallible signed decimal parser. No locale, no
// whitespace, no underscores: a leading '-' is the only non-digit
// accepted, and only at position 0.
export fn stoi64(s: str) (i64 | invalid | overflow) = {
	if (s.len == 0) { return 0: invalid; };
	let i: i32 = 0;
	let neg: bool = false;
	if (s[0] == 45u8) { neg = true; i = 1; };
	if (i >= s.len) { return i: invalid; };
	let v: i64 = 0;
	for (i < s.len) {
		let c: u8 = s[i];
		if (c < 48u8) { return i: invalid; };
		if (c > 57u8) { return i: invalid; };
		v = v * 10 + ((c: i64) - 48);
		i += 1;
	};
	if (neg) { v = -v; };
	return v;
};

// stou64 — fallible unsigned decimal parser. No leading sign.
export fn stou64(s: str) (u64 | invalid | overflow) = {
	if (s.len == 0) { return 0: invalid; };
	let v: u64 = 0u64;
	let i: i32 = 0;
	for (i < s.len) {
		let c: u8 = s[i];
		if (c < 48u8) { return i: invalid; };
		if (c > 57u8) { return i: invalid; };
		v = v * 10u64 + ((c: u64) - 48u64);
		i += 1;
	};
	return v;
};