ww/lib/path/path.ww

// path — filesystem path manipulation. UTF-8 paths, '/' separator.
// Mirrors Hare's path:: surface (ref/hare/path/). This is the
// path::buffer stack-buffer port (c2-stack subset: error/posix defs +
// buffer + isroot + appendlit + appendnorm + push + string + set).
// init/abs/dirname/basename and the rest land in later folds.

package path;

import bytes;
import strings;
import os;

// ref/hare/path/error.ha:6-12. The 3 !void singletons are
// structurally identical; cstage discriminates them correctly
// (#142 is a wwstage-only flatvariantidxt ambiguity, rides #125).
export type cant_extend = !void;
export type too_long    = !void;
export type not_prefix  = !void;
export type error = !(cant_extend | too_long | not_prefix);

// ref/hare/path/error.ha:15-24.
export fn strerror(e: error) str = {
	match (e) {
	case cant_extend => return "Can't add extension (filename is root or all dots)";
	case too_long    => return "Path buffer overflow";
	case not_prefix  => return "Prefix not present";
	};
};

// ref/hare/path/+linux.ha:7.
export def SEP: u8 = '/';
// ref/hare/path/+linux.ha:9. No c2 use; c3 abs/isroot-str consume it.
const sepstr: str = "/";
// ref/hare/path/+linux.ha:18 (sys::PATH_MAX-1). Div: route through
// os.PATH_MAX (lib/os/os.ww:84, i32=4096) → MAX=4095; const-folds as
// the buffer array dim (c1 #141). No hardcoded literal (rule-13).
export def MAX: i32 = os.PATH_MAX - 1;

// ref/hare/path/buffer.ha:6-9. Div: end size→i32 (lib/CLAUDE.md
// str.len:i32; bytes.index→(i32|void)).
export type buffer = struct {
	buf: [MAX]u8,
	end: i32,
};

// ref/hare/path/stack.ha:30-31. Faithful module-global []u8 (D2 #148
// fixes the by-value-arg garbage header) — no [N]u8, no copy-loop.
const dot: []u8 = ['.'];
const dotdot: []u8 = ['.', '.'];

// ref/hare/path/buffer.ha:44-51. c3 WIDENS to isroot(path:(*buffer|str))
// alongside abs; c2 needs only the *buffer arm (appendnorm/appendlit
// callers).
export fn isroot(buf: *buffer) bool = {
	return buf.end == 1 && buf.buf[0] == SEP;
};

// ref/hare/path/stack.ha:63-74.
fn appendlit(buf: *buffer, bs: []u8) (i32 | error) = {
	let newend: i32 = buf.end;
	if (buf.end == 0 || isroot(buf)) {
		if (MAX < buf.end + bs.len) {
			// cstage rejects bare `return too_long` into the nested
			// (i32|error); two-step widen (io precedent stream.ww:56-58).
			let e: error = too_long; return e;
		};
	} else {
		if (MAX < buf.end + bs.len + 1) {
			let e: error = too_long; return e;
		};
		buf.buf[buf.end] = SEP;
		newend += 1;
	};
	// Div: Hare `buf.buf[newend..newend+len(bs)] = bs` in colon
	// spelling — the #145 slice-copy-assign LHS arm (stack.ha:72).
	buf.buf[newend:newend+bs.len] = bs;
	return newend + bs.len;
};

// ref/hare/path/stack.ha:43-59. Div: `..` reslice→colon; Hare if-expr
// → if-statement; `0z` yield → `0i32` (match arms must agree, bare 0
// is untyped_int).
fn appendnorm(buf: *buffer, seg: []u8) (i32 | error) = {
	if (seg.len == 0 || bytes.equal(dot, seg)) { return buf.end; };
	if (bytes.equal(dotdot, seg)) {
		if (isroot(buf)) { return buf.end; };
		let isep: i32 = match (bytes.rindex(buf.buf[0:buf.end], SEP)) {
		case void => yield 0i32;
		case let i: i32 => yield i + 1;
		};
		if (buf.end == 0 || bytes.equal(buf.buf[isep:buf.end], dotdot)) {
			return appendlit(buf, dotdot)?;
		} else {
			if (isep <= 1) { return isep; };
			return isep - 1;
		};
	} else {
		return appendlit(buf, seg)?;
	};
};

// ref/hare/path/buffer.ha:28-31. Div: fromutf8_unsafe→strings.frombytes
// (rule-9 carve-out); `..` reslice→colon.
export fn string(buf: *buffer) str = {
	if (buf.end == 0) { return "."; };
	return strings.frombytes(buf.buf[0:buf.end]);
};

// ref/hare/path/stack.ha:9-28. Div: `..` reslice→colon; len(x)→x.len.
export fn push(buf: *buffer, items: str...) (str | error) = {
	for (let item .. items) {
		let elem: []u8 = strings.toutf8(item);
		// Hare's `for(true) match{...}` (stack.ha:13-25) breaks out of
		// the void arm and re-loops the j-arm; ww spells the loop step
		// as explicit `continue` (j-arm) + `break` (after match).
		for (true) {
			match (bytes.index(elem, SEP)) {
			case void => { buf.end = appendnorm(buf, elem)?; };
			case let j: i32 => {
				if (j == 0 && buf.end == 0) {
					buf.buf[0] = SEP; buf.end = 1;
				} else {
					buf.end = appendnorm(buf, elem[0:j])?;
				};
				elem = elem[j+1:];
				continue;
			};
			};
			break;
		};
	};
	return string(buf);
};

// ref/hare/path/buffer.ha:20-23. (str|error) ≤32B return → in c2-stack.
export fn set(buf: *buffer, items: str...) (str | error) = {
	buf.end = 0;
	return push(buf, items...);
};