package matchdispatch_test;

// Direct-w6c asm-window gate over match tag dispatch under
// cross-module fn-name shadowing. Port of the retired native carrier
// test/wcc/728_match_4arm_cross_module.c (#31); every assertion
// preserved. The mod-disambiguated match-scrutinee claim has no other
// owner: pre-fix wwstage's name-only fnretlookup collapsed arms 2/3
// of a `match (a.next())` inside a shadowing `b.next` to CMPQ $0,
// leaving their case bodies silently unreachable.
//
// Per row: every `CMPQ $K, AX` inside [TEXT b.next .. next TEXT) is
// collected; at least `arms` must exist and the first `arms` values
// must be pairwise distinct and inside [0, arms). Checked on both
// stages.
//
// Strengthened: a per-row byte-id leg (testenv.same over both .s).
// The C header claimed a cmp -s that its code never ran; the leg
// verifies green on all three rows.
//
// Dropped C machinery, not assertions: the w6c_ww-absent skip gate,
// getpid()-keyed /tmp names, slurp caps.

import os;
import os.exec;
import strings;
import testenv;
import time;

fn fail(label: str, why: str) void = {
	let m: str = strings.concat("matchdispatch FAIL: ", label, " -- ",
		why, "\n");
	os.write(2, m.ptr, m.len: u64);
	assert(false);
};

fn tmo() time.duration = {
	return (180i64 * (time.second: i64)): time.duration;
};

fn emitstage(td: str, label: str, stage: str, drv: str,
	outname: str) void = {
	let av: []str = [];
	append(av, drv);
	append(av, "-o");
	append(av, outname);
	append(av, "src.ww");
	let co: testenv.commandout;
	testenv.runcommand(td, td, stage, av, tmo(), &co);
	let ok: bool = co.termination == exec.termination.EXIT && co.code == 0;
	if (!ok) { fail(label, strings.concat(stage, " compile failed")); };
};

fn posafter(s: str, start: i32, needle: str) i32 = {
	let p: i32 = testenv.pos(strings.sub(s, start, s.len), needle);
	if (p < 0) { return -1; };
	return start + p;
};

// Collect every `CMPQ $K, AX` tag inside [TEXT b.next .. next TEXT)
// (the C capped collection at 16 entries and K < 16), then assert
// count, range and pairwise distinctness over the first `arms`.
fn cmpqcheck(label: str, stage: str, s: str, arms: i32) void = {
	let fnhdr: str = "TEXT b.next";
	let fp: i32 = testenv.pos(s, fnhdr);
	if (fp < 0) {
		fail(label, strings.concat(stage, ": no ", fnhdr, " in .s"));
	};
	let ep: i32 = posafter(s, fp + fnhdr.len, "\nTEXT ");
	if (ep < 0) { ep = s.len; };
	let w: str = strings.sub(s, fp, ep);
	let seen: []i32 = alloc([], 16u64)!;
	let p: i32 = 0;
	for (p < w.len) {
		let m: i32 = posafter(w, p, "CMPQ\t$");
		if (m < 0) { break; };
		let d: i32 = m + 6;
		let k: i32 = 0;
		let nd: i32 = 0;
		for (d < w.len) {
			let c: u8 = w[d];
			if (c < '0' || c > '9') { break; };
			k = k * 10 + ((c - '0'): i32);
			nd += 1;
			d += 1;
		};
		if (nd > 0 && d + 4 <= w.len
			&& testenv.same(strings.sub(w, d, d + 4), ", AX")) {
			if (seen.len < 16 && k < 16) { append(seen, k); };
		};
		p = m + 1;
	};
	if (seen.len < arms) {
		fail(label, strings.concat(stage,
			": too few `CMPQ $K, AX` in b.next body"));
	};
	let i: i32 = 0;
	for (i < arms) {
		if (seen[i] < 0 || seen[i] >= arms) {
			fail(label, strings.concat(stage,
				": arm tag out of [0, arms)"));
		};
		let j: i32 = 0;
		for (j < i) {
			if (seen[j] == seen[i]) {
				fail(label, strings.concat(stage,
					": repeated arm tag (collapse)"));
			};
			j += 1;
		};
		i += 1;
	};
};

fn cmpqrow(label: str, src: str, arms: i32) void = {
	let td: str = testenv.fresh();
	testenv.writefile(strings.concat(td, "/src.ww"), src);
	emitstage(td, label, "cstage", testenv.driver("w6c"), "cs.s");
	emitstage(td, label, "wwstage", testenv.driver("w6c_ww"), "ws.s");
	let cs: str = testenv.readfile(strings.concat(td, "/cs.s"));
	let ws: str = testenv.readfile(strings.concat(td, "/ws.s"));
	cmpqcheck(label, "cstage", cs, arms);
	cmpqcheck(label, "wwstage", ws, arms);
	if (!testenv.same(cs, ws)) {
		fail(label, "cstage vs wwstage asm differs");
	};
	testenv.clean(td);
};

// Callee `a.next` returns the wide tagged; caller `b.next` shadows
// the leaf with a 2-arm subset return so a name-only lookup sees the
// wrong scrutinee type. The reverse row pins that dispatch follows
// variantindex, not source order; the 3-arm row pins the boundary
// (collapse begins at arms >= the caller's variant count).
@test fn match4armcrossmodule() void = {
	cmpqrow("4arm_shadowed_callee", strings.concat(
		"package a;\n",
		"export type more = void;\n",
		"export type invalid = !void;\n",
		"export type done = void;\n",
		"export fn next() (rune | done | more | invalid) = {\n",
		"    let r: rune;\n",
		"    return r;\n",
		"};\n",
		"package b;\n",
		"import a;\n",
		"type done = void;\n",
		"fn next() (rune | done) = {\n",
		"    match (a.next()) {\n",
		"    case let r: rune       => return r;\n",
		"    case let dn: a.done    => { let v: done; return v; };\n",
		"    case let m:  a.more    => { abort(\"i\"); };\n",
		"    case let e:  a.invalid => { abort(\"i\"); };\n",
		"    };\n",
		"};\n",
		"export fn main() i32 = { return 0; };\n"), 4);
	cmpqrow("4arm_shadowed_reverse", strings.concat(
		"package a;\n",
		"export type more = void;\n",
		"export type invalid = !void;\n",
		"export type done = void;\n",
		"export fn next() (rune | done | more | invalid) = {\n",
		"    let r: rune;\n",
		"    return r;\n",
		"};\n",
		"package b;\n",
		"import a;\n",
		"type done = void;\n",
		"fn next() (rune | done) = {\n",
		"    match (a.next()) {\n",
		"    case let e:  a.invalid => { abort(\"i\"); };\n",
		"    case let m:  a.more    => { abort(\"i\"); };\n",
		"    case let dn: a.done    => { let v: done; return v; };\n",
		"    case let r: rune       => return r;\n",
		"    };\n",
		"};\n",
		"export fn main() i32 = { return 0; };\n"), 4);
	cmpqrow("3arm_shadowed_callee", strings.concat(
		"package a;\n",
		"export type more = void;\n",
		"export type done = void;\n",
		"export fn next() (rune | done | more) = {\n",
		"    let r: rune;\n",
		"    return r;\n",
		"};\n",
		"package b;\n",
		"import a;\n",
		"type done = void;\n",
		"fn next() (rune | done) = {\n",
		"    match (a.next()) {\n",
		"    case let r: rune    => return r;\n",
		"    case let dn: a.done => { let v: done; return v; };\n",
		"    case let m:  a.more => { abort(\"i\"); };\n",
		"    };\n",
		"};\n",
		"export fn main() i32 = { return 0; };\n"), 3);
};