// Port of cmd/w6a/lex.c.

package w6a;

export fn isidstart(c: i32) bool = {
	if (c == 95) { return true; };
	if (c >= 65) { if (c <= 90)  { return true; }; };	// A-Z
	if (c >= 97) { if (c <= 122) { return true; }; };	// a-z
	return false;
};

export fn isidcont(c: i32) bool = {
	if (isidstart(c)) { return true; };
	if (c >= 48) { if (c <= 57) { return true; }; };	// 0-9
	if (c == 46) { return true; };				// .
	return false;
};

export fn parsenum(p: *u8, n: u64) (i64, u64) = {
	// strtoll(s, end, 0) semantics, matching the C twin cmd/w6a/lex.c:30:
	// skip leading whitespace, optional sign, base-0 prefix detection
	// (0x -> hex, leading 0 -> octal, else decimal). w6c never emits the
	// `$ 5` / `$08` edge shapes; this aligns the hand-written-asm path
	// with cstage so the two assemblers agree byte-for-byte (#62).
	let i: u64 = 0u64;
	for (i < n) {
		if (p[i] != 32u8) { if (p[i] != 9u8) { break; }; };
		i += 1u64;
	};
	let neg: bool = false;
	if (i < n) {
		if (p[i] == 45u8) { neg = true; i += 1u64; }
		else { if (p[i] == 43u8) { i += 1u64; }; };
	};
	let base: i64 = 10i64;
	if (i < n) {
		if (p[i] == 48u8) {	// leading '0' -> octal, unless '0x'/'0X'
			if (i + 1u64 < n) {
				if (p[i + 1u64] == 120u8) { base = 16i64; i += 2u64; }
				else { if (p[i + 1u64] == 88u8) { base = 16i64; i += 2u64; }
				else { base = 8i64; i += 1u64; }; };
			} else { base = 8i64; i += 1u64; };
		};
	};
	let v: i64 = 0i64;
	let scan: bool = true;
	for (scan) {
		if (i >= n) { scan = false; }
		else {
			let c: u8 = p[i];
			let d: i64 = -1i64;
			if (c >= 48u8) { if (c <= 57u8) { d = (c - 48u8): i64; }; };
			if (d < 0i64) {
				if (base == 16i64) {
					if (c >= 97u8) { if (c <= 102u8) { d = (c - 97u8): i64 + 10i64; }; };
					if (c >= 65u8) { if (c <= 70u8)  { d = (c - 65u8): i64 + 10i64; }; };
				};
			};
			if (d < 0i64) { scan = false; }
			else { if (d >= base) { scan = false; }
			else {
				v = v * base + d;
				i += 1u64;
			}; };
		};
	};
	if (neg) { v = -v; };
	return v, i;
};