"""Deterministic stand-in for the LLM (no GPU, no network).

`mock_generate` returns exactly the JSON the real model is supposed to return:
it picks the top rule-derived candidate and attaches sensible checks/safety.
Used by the test suite and by any local dry-run that does not hit Modal.
"""
from __future__ import annotations

import json
import random

CHECKS_DB = {
    "bearing": ["Inspect the bearing housing for play or heat.",
                "Spin the shaft by hand - roughness confirms wear.",
                "Apply bearing grease; if noise persists, replace."],
    "belt": ["Inspect the belt for cracks, glazing, or fraying.",
             "Check belt tension - should deflect ~10mm under thumb.",
             "Replace belt if glazing or cracking is visible."],
    "imbalance": ["Redistribute the load evenly inside the drum.",
                  "Check that the appliance is level.",
                  "Inspect shock absorbers or springs for damage."],
    "blade": ["Disconnect power and inspect each blade for cracks.",
              "Check for debris caught in the blade assembly.",
              "Replace blade if any damage is found."],
    "compressor": ["Listen for grinding or knocking from the compressor.",
                   "Check refrigerant lines for frost or oil stains.",
                   "Contact a certified HVAC technician."],
    "pump": ["Check the pump inlet filter for blockages.",
             "Listen for cavitation (gurgling sounds).",
             "Inspect the impeller for damage."],
    "magnetron": ["DO NOT open the casing - high voltage danger.",
                  "If arcing sounds are heard, stop using immediately.",
                  "Have a qualified technician inspect."],
    "chain": ["Check chain tension - 20-30mm vertical play.",
              "Look for stiff links or rust.",
              "Lubricate with bicycle chain oil."],
    "derailleur": ["Check derailleur hanger alignment.",
                   "Inspect cable tension and adjust.",
                   "Clean and lubricate pivot points."],
    "brush": ["Inspect motor brushes (less than 5mm = replace).",
              "Check the commutator for scoring.",
              "Clean commutator with contact cleaner."],
    "gear": ["Check gear lubrication - apply fresh grease.",
             "Listen for grinding under load.",
             "Replace gear set if teeth are worn."],
    "spray": ["Remove and inspect the spray arm for blockages.",
              "Check that it rotates freely by hand.",
              "Clean nozzles with a thin wire."],
    "turntable": ["Check if the motor coupling is intact.",
                  "Ensure the roller ring is clean.",
                  "If the motor hums but does not turn, it may be seized."],
    "roller": ["Inspect the drum rollers for flat spots.",
               "Check roller shaft for wear.",
               "Replace worn rollers in pairs."],
    "foreign": ["Check pockets for coins or buttons before loading.",
                "Open the drum and inspect between drum and tub.",
                "Remove any trapped foreign objects."],
    "evaporator": ["Check the evaporator fan for ice buildup.",
                   "Inspect the fan blade for damage.",
                   "Listen for grinding or squealing."],
    "condenser": ["Clean the condenser coils with a brush.",
                  "Check the condenser fan motor bearings.",
                  "Ensure adequate airflow around the unit."],
    "refrigerant": ["Check for oil stains on refrigerant lines.",
                    "Listen for hissing near the evaporator.",
                    "Call a certified HVAC technician for a leak test."],
    "cavitat": ["Check the drain pump filter for blockages.",
                "Listen for gurgling during the drain cycle.",
                "Inspect the impeller for debris."],
    "rod": ["STOP DRIVING IMMEDIATELY - rod knock is critical.",
            "Have the engine towed to a mechanic.",
            "Do not rev the engine."],
    "squeal": ["Check belt tension and condition.",
               "Inspect the belt tensioner for wear.",
               "Replace glazed or worn belts."],
    "whine": ["Check lubrication on the bearing.",
              "Listen for pitch changes under load.",
              "Replace the bearing if lubrication does not help."],
    "default": ["Inspect the most likely component.",
                "Listen again after each check.",
                "Consult a technician if it persists."],
}

SAFETY_DB = {
    "CRITICAL": "STOP USE IMMEDIATELY. Disconnect power.",
    "HIGH": "Disconnect power before inspecting.",
    "MEDIUM": "Use with caution. Schedule inspection soon.",
    "LOW": "Normal operation likely. Monitor and maintain.",
}


def mock_generate(prompt: str, candidates: list, features=None) -> str:
    """Return JSON for the top candidate — what the real model should produce."""
    rng = random.Random(hash(prompt) % 2**31)

    if candidates:
        top = candidates[0]
        name, urgency, weight = top.name, top.urgency, top.weight
    else:
        name, urgency, weight = "Inconclusive", "LOW", 0.0

    fault_lower = name.lower()
    checks = []
    for keyword, pool in CHECKS_DB.items():
        if keyword in fault_lower:
            checks = rng.sample(pool, min(3, len(pool)))
            break
    if not checks:
        checks = list(CHECKS_DB["default"])

    confidence = max(10, min(95, int(weight * 100) + rng.randint(-3, 3)))
    return json.dumps({
        "fault": name,
        "urgency": urgency,
        "checks": checks,
        "safety": SAFETY_DB.get(urgency, "None"),
        "confidence": confidence,
    })