#!/usr/bin/env python3
"""Mutation harness for deporder: does the test suite actually have teeth?

Each mutation is a literal source edit to deporder.py, applied in an isolated
temp directory holding a copy of deporder.py + test_deporder.py.  A mutation is
"caught" when the suite exits non-zero on the mutant.

Exit code is 0 only when every mutation labelled expect="caught" is caught and
every mutation labelled expect="equivalent" survives (a documented redundant
guard, not a hole in the tests).

    python3 mutate_teeth.py
"""

from __future__ import annotations

import os
import shutil
import subprocess
import sys
import tempfile

HERE = os.path.dirname(os.path.abspath(__file__))
SRC = os.path.join(HERE, "deporder.py")
TESTS = os.path.join(HERE, "test_deporder.py")

# (label, old, new, expectation, why)
MUTATIONS = [
    ("waves: drop the +1 level bump",
     "level[n] = 1 + max(level[d] for d in deps[n])",
     "level[n] = max(level[d] for d in deps[n])",
     "caught", "every task collapses into wave 0"),
    ("order: pop the heap tail instead of the min",
     "n = heapq.heappop(ready)",
     "n = ready.pop()",
     "caught", "lexicographic tie-break lost in Kahn"),
    ("cycles: disable the residual-node check",
     "if len(order) != len(deps):",
     "if False:",
     "caught", "cycle silently yields a partial order"),
    ("cycle path: report a single node",
     "return path[path.index(nxt):]",
     "return [nxt]",
     "caught", "reported 'cycle' is not a cycle"),
    ("unknown deps: stop validating",
     "if unknown:",
     "if False:",
     "caught", "ghost dependency accepted"),
    ("spec: allow est == 0",
     "if not (est > 0.0) or est == INF:",
     "if not (est >= 0.0) or est == INF:",
     "caught", "zero-duration task accepted"),
    ("critical path: break the predecessor tie-break",
     "if best_d is None or dist[d] > best or (dist[d] == best and d < best_d):",
     "if best_d is None or dist[d] >= best:",
     "caught", "path no longer lexicographically canonical"),
    ("schedule: release completions strictly before now",
     "while running and running[0][0] <= now:",
     "while running and running[0][0] < now:",
     "caught", "worker never freed / clock stalls"),
    ("schedule: double every task duration",
     "end = now + est[name]",
     "end = now + est[name] * 2",
     "caught", "makespan and critical-path bound violated"),
    ("schedule: pin the clock to itself (kill the stall guard)",
     "nxt = running[0][0] if running else None",
     "nxt = now",
     "caught", "guard fires: stalled scheduler must not spin"),
    ("graph: drop the redundant set() in build_graph",
     'deps = {n: tuple(sorted(set(tasks[n]["deps"]))) for n in names}',
     'deps = {n: tuple(sorted(tasks[n]["deps"])) for n in names}',
     "equivalent", "parse_spec already deduplicates; guard is redundant"),
]


def run_mutant(label, old, new, timeout=300):
    tmp = tempfile.mkdtemp(prefix="deporder_mut_")
    try:
        src = open(SRC, "r", encoding="utf-8").read()
        hits = src.count(old)
        if hits == 0:
            return None, "ANCHOR MISSING"
        mutated = src.replace(old, new)
        with open(os.path.join(tmp, "deporder.py"), "w", encoding="utf-8") as fh:
            fh.write(mutated)
        shutil.copy(TESTS, os.path.join(tmp, "test_deporder.py"))
        try:
            proc = subprocess.run([sys.executable, "test_deporder.py"], cwd=tmp,
                                  capture_output=True, text=True, timeout=timeout)
        except subprocess.TimeoutExpired:
            return True, "timeout/hang -> caught"
        if proc.returncode == 0:
            return False, "suite PASSED on mutant (not caught)"
        tail = [ln for ln in proc.stderr.strip().splitlines() if ln.strip()]
        detail = tail[-1] if tail else "nonzero exit"
        return True, "exit %d | %s" % (proc.returncode, detail[:90])
    finally:
        shutil.rmtree(tmp, ignore_errors=True)


def main():
    print("deporder mutation harness: %d mutations" % len(MUTATIONS))
    print("-" * 100)
    bad = 0
    caught = 0
    for label, old, new, expect, why in MUTATIONS:
        got, detail = run_mutant(label, old, new)
        if got is None:
            bad += 1
            status = "BROKEN  (%s)" % detail
        else:
            ok = (got and expect == "caught") or (not got and expect == "equivalent")
            bad += 0 if ok else 1
            caught += 1 if got else 0
            status = ("CAUGHT   " if got else "SURVIVED ") + detail
            if not ok:
                status += "   <-- UNEXPECTED (expect=%s)" % expect
        print("%-46s %s" % (label, status))
        print("%-46s   why: %s" % ("", why))
    print("-" * 100)
    print("caught %d/%d mutants that must die; %d problem(s)" % (caught, len(MUTATIONS), bad))
    return 1 if bad else 0


if __name__ == "__main__":
    sys.exit(main())