"""Keep the metrics database writable so the public dashboards can render."""

from pathlib import Path

import yaml


REPO_ROOT = Path(__file__).resolve().parents[2]

# VictoriaMetrics stops accepting samples once free space under -storageDataPath
# falls below its 10MB floor. On 2026-08-18T15:25Z the volume filled, the
# database flipped read-only, and every panel on the public dashboards rendered
# "No data" while Grafana and all 119 scrape targets stayed healthy.
MINIMUM_STORAGE_GIB = 400


def _documents(path: Path) -> list[dict]:
    """Load every non-empty YAML document from a repository manifest."""
    return [document for document in yaml.safe_load_all(path.read_text()) if document]


def _victoria_metrics_server() -> dict:
    """Return the VictoriaMetrics server values from its HelmRelease."""
    manifests = _documents(REPO_ROOT / "services/monitoring/helmrelease.yaml")
    release = next(
        manifest
        for manifest in manifests
        if manifest.get("kind") == "HelmRelease"
        and manifest.get("metadata", {}).get("name") == "victoria-metrics-single"
    )
    return release["spec"]["values"]["server"]


def _alert_rules() -> dict[str, dict]:
    """Return every provisioned Grafana alert rule keyed by uid."""
    manifest = _documents(
        REPO_ROOT / "services/monitoring/grafana-alerting-config.yaml"
    )[0]
    groups = yaml.safe_load(manifest["data"]["rules.yaml"])["groups"]
    return {rule["uid"]: rule for group in groups for rule in group["rules"]}


def test_metrics_storage_holds_a_full_retention_period() -> None:
    """Size the volume for the retention actually configured, plus headroom."""
    server = _victoria_metrics_server()
    size = server["persistentVolume"]["size"]

    assert size.endswith("Gi")
    assert int(size.removesuffix("Gi")) >= MINIMUM_STORAGE_GIB
    assert server["extraArgs"]["retentionPeriod"] == "1y"


def test_full_metrics_storage_pages_before_it_blocks_ingestion() -> None:
    """Warn on shrinking headroom and page once the database refuses writes."""
    rules = _alert_rules()
    low = rules["victoria-metrics-storage-low"]
    read_only = rules["victoria-metrics-storage-readonly"]

    assert "vm_free_disk_space_bytes" in low["data"][0]["model"]["expr"]
    assert low["labels"]["severity"] == "warning"
    assert "vm_storage_is_read_only" in read_only["data"][0]["model"]["expr"]
    assert read_only["labels"]["severity"] == "critical"


def test_a_silent_metrics_database_still_pages() -> None:
    """A stalled database returns no samples, so absent data must alert."""
    rules = _alert_rules()
    stalled = rules["victoria-metrics-ingestion-stalled"]

    assert "vm_rows_added_to_storage_total" in stalled["data"][0]["model"]["expr"]
    assert stalled["noDataState"] == "Alerting"
    assert stalled["execErrState"] == "Alerting"
    assert stalled["labels"]["severity"] == "critical"
    assert rules["victoria-metrics-storage-readonly"]["noDataState"] == "Alerting"