"""The `/system` hero-card payload contract, shared by the hermetic and the live tests.

Phase 03 makes `/system` one panel per host with six big colour-coded numbers. The paths
below are the payload fields those cards are allowed to read; they were read out of
`parse_host_snapshot()` and are pinned hermetically in `tests/test_system_contract.py`
(driven from `tests/fixtures/agent_*.json`) and against the real fleet in
`tests/test_live_fleet.py::test_every_host_serves_the_hero_card_contract`.

Keeping the list here rather than in one test file means the live assertions cannot drift
away from the fixture assertions: there is one table, and it is the thing under test.

===========================  ==========================================================
Card                         Path in `/api/system/snapshot` `hosts[]`
===========================  ==========================================================
cpu %                        ``cpu.usage_pct`` (+ ``cpu.severity.usage_pct``)
mem %                        ``memory.used_pct`` (+ ``memory.severity.used_pct``)
cpu temp                     ``cpu.temp_c`` (+ ``cpu.severity.temp_c``)
disk usage %                 ``disks.worst_used_pct`` + ``disks.worst_mount`` (+ verdict)
graphics card                ``gpus[].model/busy_pct/vram_*/mem_used_pct/temp_c`` (no verdict)
network down/up              ``network.rx_bytes_per_s`` / ``tx_bytes_per_s`` (no verdict)
===========================  ==========================================================

CPU temp comes from ``cpu.temp_c`` rather than ``temperatures.cpu_c``: both are the agent's
own ``cpu_temperature_celsius``, and ``cpu.temp_c`` is the field ``/api/summary`` flattens
into its fleet row, so the card and the overview cannot drift apart.

Deliberately *not* card metrics (legibility, not missing data — the series stay in SQLite):
per-core usage (``cpu.usage_pct@coreN``), swap, the process table, the raw sensor list, and
per-interface rows. Network carries no ``severity`` on purpose; throughput has no good/bad,
so ``severity.THRESHOLDS`` has no ``net.*`` row. GPU rows carry no ``severity`` either
(phase 06): these are LLM servers, a 95 %-busy card is the job and not a fault, so
``THRESHOLDS`` has no ``gpu.*`` row and the card prints its numbers uncoloured at every
utilisation — the *absence* of the dict is pinned below, the way ``network``'s is.

``gpus[].temp_c`` is on the card because the number worth reading *while* a card is busy is
how hot it is (phase 06, TODO.md L9). It is the agent's **max over that card's hwmon
labels** — the same max the agent already computes and the same value stored as
``gpu.temp_c@N`` — so the hero prints a measurement rather than a new field, and the value
may honestly be ``None`` on a box whose driver exposes no temperature input.
"""
from __future__ import annotations

from typing import Any

#: Card metric -> dotted payload paths. Present is the contract; a value may be ``None``
#: on a host that genuinely does not have the number (gateway reports no CPU temperature).
CARD_METRICS: dict[str, tuple[str, ...]] = {
    "cpu %": ("cpu.usage_pct", "cpu.severity.usage_pct"),
    "mem %": ("memory.used_pct", "memory.severity.used_pct"),
    "cpu temp": ("cpu.temp_c", "cpu.severity.temp_c", "temperatures.cpu_c"),
    # the mount is what makes the percentage actionable: 88 % used — of which disk?
    "disk %": ("disks.worst_used_pct", "disks.worst_mount", "disks.severity.worst_used_pct"),
    "network down/up": ("network.rx_bytes_per_s", "network.tx_bytes_per_s"),
}

#: Per-GPU paths, checked on every row of `gpus[]` — and on none of them when the list is
#: empty, which is how a host without a GPU stays honest (no card, not a card at 0 % busy).
GPU_METRICS: tuple[str, ...] = (
    "model",
    "busy_pct",
    "vram_used_bytes",
    "vram_total_bytes",
    "vram_used_pct",
    # the honest APU view: vram + GTT, because a Strix Halo keeps the model in GTT
    "mem_used_pct",
    # the hero's footnote: the agent's max over this card's hwmon labels (None is legal —
    # a driver with no temperature input must not be rendered as 0 °C)
    "temp_c",
)

#: `network` must never grow a `severity` dict (see the module docstring).
SEVERITY_FREE_SECTIONS: tuple[str, ...] = ("network",)

#: The host shapes the captures in `tests/fixtures/` cover, and therefore the shapes a card
#: must handle: a discrete GPU, an APU (VRAM *and* GTT), and no GPU at all. A new capture
#: has to be added here — `test_the_contract_covers_every_captured_host` fails otherwise.
HOST_SHAPES: tuple[str, ...] = ("driveripper", "deskwork", "gateway")


def dig(node: Any, path: str) -> Any:
    """Follow a dotted payload path, failing with the path in the message.

    A missing key is a contract break; a ``None`` value is not (that renders `n/a`), which is
    why this returns the value instead of asserting on it.
    """
    walked = ""
    for part in path.split("."):
        assert isinstance(node, dict), f"{path}: hit a non-dict at {walked or 'payload'}"
        assert part in node, (
            f"{path}: no key {part!r} under {walked or 'payload'} — a hero card would print "
            f"n/a for a number the API used to serve"
        )
        node = node[part]
        walked = f"{walked}.{part}" if walked else part
    return node


def assert_card_contract(payload: Any) -> None:
    """Every card path exists on this host payload, GPU rows included."""
    for paths in CARD_METRICS.values():
        for path in paths:
            dig(payload, path)
    gpus = payload.get("gpus")
    assert isinstance(gpus, list), "gpus must be a list — [] when the agent reports no GPU"
    for gpu in gpus:
        for path in GPU_METRICS:
            dig(gpu, path)
        assert "severity" not in gpu, (
            "gpus[].severity would grade utilisation on a fleet built to be busy — "
            "severity.THRESHOLDS has no gpu.* row and a busy GPU is the job, not a fault"
        )
    for section in SEVERITY_FREE_SECTIONS:
        block = payload.get(section)
        assert isinstance(block, dict), f"{section} must be a dict"
        assert "severity" not in block, (
            f"{section}.severity would be a colour nobody measured — throughput has no "
            f"good/bad and severity.THRESHOLDS has no {section}.* row"
        )