"""Host queries shared by the Hosts pages, dashboard widgets and MCP tools.

Every function takes an open session and returns plain data; none reads
Quart's request context, so the web routes and the /mcp tools (which run
outside Quart's pipeline) call the same code.
"""
from __future__ import annotations
from datetime import datetime, timedelta, timezone

from sqlalchemy import and_, case, func, select

from steward.core.status import _heartbeat_title, _last_n_results, _uptime_by_monitor
from steward.models.hosts import Host
from steward.models.monitors import Monitor, MonitorResult


# Host-level agent metrics read for the at-a-glance views (plus the root
# mount's disk_used_pct, read from the "<host>:/" sub-resource).
AGENT_GLANCE_METRICS = ("cpu_pct", "mem_used_pct", "disk_used_pct", "disk_used_pct_worst")


async def check_name_free(db, name: str, exclude_id: str | None = None) -> None:
    """ValueError when another host already has this name, or it is blank.

    Agent metrics, container metrics and the alert rules on them go by the
    host's name, so two hosts sharing one would share one history.
    """
    if not name:
        raise ValueError("a host needs a name.")
    q = select(Host.id).where(Host.name == name)
    if exclude_id:
        q = q.where(Host.id != exclude_id)
    if (await db.execute(q.limit(1))).first():
        raise ValueError(f"another host is already named {name!r}; pick a different name.")


def agent_stale_after_seconds(config) -> int:
    """The host_agent plugin's freshness window from app config (default 180s)."""
    return int(((config.get("PLUGINS") or {}).get("host_agent") or {})
               .get("stale_after_seconds", 180))


async def compute_uptime(db) -> dict[str, dict]:
    """Per-host uptime % for 24h/7d/30d, aggregated over the host's monitors.

    Returns {host_id: {"24h": float|None, "7d": float|None, "30d": float|None}}.
    """
    now = datetime.now(timezone.utc)
    cutoff_30d = now - timedelta(days=30)
    cutoff_7d  = now - timedelta(days=7)
    cutoff_24h = now - timedelta(hours=24)

    result = await db.execute(
        select(
            Monitor.host_id,
            func.count(MonitorResult.id).label("total_30d"),
            func.sum(case((MonitorResult.is_up.is_(True), 1), else_=0)).label("up_30d"),
            func.sum(case((MonitorResult.checked_at >= cutoff_7d, 1), else_=0)).label("total_7d"),
            func.sum(case(
                (and_(MonitorResult.checked_at >= cutoff_7d, MonitorResult.is_up.is_(True)), 1),
                else_=0,
            )).label("up_7d"),
            func.sum(case((MonitorResult.checked_at >= cutoff_24h, 1), else_=0)).label("total_24h"),
            func.sum(case(
                (and_(MonitorResult.checked_at >= cutoff_24h, MonitorResult.is_up.is_(True)), 1),
                else_=0,
            )).label("up_24h"),
        )
        .join(Monitor, Monitor.id == MonitorResult.monitor_id)
        .where(Monitor.host_id.isnot(None), MonitorResult.checked_at >= cutoff_30d)
        .group_by(Monitor.host_id)
    )

    def _pct(up, total):
        return round(float(up) / float(total) * 100, 2) if total else None

    stats: dict[str, dict] = {}
    for row in result:
        stats[row.host_id] = {
            "24h": _pct(row.up_24h, row.total_24h),
            "7d":  _pct(row.up_7d,  row.total_7d),
            "30d": _pct(row.up_30d, row.total_30d),
        }
    return stats


async def host_status(db, host_ids: list[str]) -> dict[str, dict]:
    """Per-host status rollup from the latest result of each linked monitor.

    {host_id: {"state": "up"|"down"|"pending", "latency_ms": float|None,
               "count": int}}. State is down if ANY linked monitor's latest
    result is down (worst-case), up if at least one is up, else pending.
    """
    if not host_ids:
        return {}
    rn = func.row_number().over(
        partition_by=MonitorResult.monitor_id, order_by=MonitorResult.checked_at.desc()
    ).label("rn")
    subq = (
        select(MonitorResult.id, rn)
        .join(Monitor, Monitor.id == MonitorResult.monitor_id)
        .where(Monitor.host_id.in_(host_ids), Monitor.enabled.is_(True))
        .subquery()
    )
    rows = (await db.execute(
        select(MonitorResult, Monitor.host_id)
        .join(subq, MonitorResult.id == subq.c.id)
        .join(Monitor, Monitor.id == MonitorResult.monitor_id)
        .where(subq.c.rn == 1)
    )).all()
    out: dict[str, dict] = {}
    for res, host_id in rows:
        d = out.setdefault(host_id, {"state": "pending", "latency_ms": None, "count": 0})
        d["count"] += 1
        if not res.is_up:
            d["state"] = "down"
        elif d["state"] != "down":
            d["state"] = "up"
        if res.is_up and res.response_ms is not None:
            d["latency_ms"] = (res.response_ms if d["latency_ms"] is None
                               else min(d["latency_ms"], res.response_ms))
    return out


async def host_monitors(db, host_id: str) -> list[dict]:
    """Display rows for the monitors linked to one host (host hub section)."""
    monitors = (await db.execute(
        select(Monitor).where(Monitor.host_id == host_id).order_by(Monitor.name)
    )).scalars().all()
    ids = [m.id for m in monitors]
    recent = await _last_n_results(db, ids)
    uptime = await _uptime_by_monitor(db, ids)
    data = []
    for m in monitors:
        mrows = recent.get(m.id, [])
        latest = mrows[-1] if mrows else None
        data.append({
            "monitor": m, "latest": latest,
            "heartbeat": [{"state": "up" if r.is_up else "down",
                           "title": _heartbeat_title(m.type, r)} for r in mrows],
            "uptime_pct": uptime.get(m.id, {}).get("24h"),
        })
    return data


async def agent_metrics_by_host(db, host_names: list[str]) -> dict[str, dict]:
    """Latest agent cpu/mem per host name from the generic PluginMetric table.

    Read directly (PluginMetric is a core model) so the Hosts list can show an
    at-a-glance agent column without importing the host_agent plugin.
    """
    from steward.models.metrics import PluginMetric
    if not host_names:
        return {}
    wanted = ("cpu_pct", "mem_used_pct")
    subq = (
        select(
            PluginMetric.resource_name, PluginMetric.metric_name,
            func.max(PluginMetric.recorded_at).label("m"),
        )
        .where(
            PluginMetric.source_module == "host_agent",
            PluginMetric.metric_name.in_(wanted),
            PluginMetric.resource_name.in_(host_names),
        )
        .group_by(PluginMetric.resource_name, PluginMetric.metric_name)
    ).subquery()
    rows = (await db.execute(
        select(PluginMetric).join(
            subq,
            (PluginMetric.resource_name == subq.c.resource_name)
            & (PluginMetric.metric_name == subq.c.metric_name)
            & (PluginMetric.recorded_at == subq.c.m),
        )
    )).scalars().all()
    out: dict[str, dict] = {}
    for r in rows:
        out.setdefault(r.resource_name, {})[r.metric_name] = r.value
    return out


async def agent_overview_by_host(
    db, host_names: list[str], stale_after_seconds: int = 180,
) -> dict[str, dict]:
    """Per-host agent glance (cpu/mem/disk + freshness) from PluginMetric.

    {host_name: {cpu_pct, mem_used_pct, disk_used_pct_worst, disk_root,
                 last_at, fresh}} for each host with any agent samples.

    Core-safe (no host_agent import). Freshness compares the latest host-level
    sample against the host_agent plugin's stale window (stale_after_seconds;
    callers pass agent_stale_after_seconds(app.config)).
    """
    from steward.models.metrics import PluginMetric
    if not host_names:
        return {}
    now = datetime.now(timezone.utc)
    stale_after = int(stale_after_seconds)
    resources = list(host_names) + [h + ":/" for h in host_names]
    subq = (
        select(
            PluginMetric.resource_name, PluginMetric.metric_name,
            func.max(PluginMetric.recorded_at).label("m"),
        )
        .where(
            PluginMetric.source_module == "host_agent",
            PluginMetric.resource_name.in_(resources),
            PluginMetric.metric_name.in_(AGENT_GLANCE_METRICS),
        )
        .group_by(PluginMetric.resource_name, PluginMetric.metric_name)
    ).subquery()
    rows = (await db.execute(
        select(PluginMetric).join(
            subq,
            (PluginMetric.resource_name == subq.c.resource_name)
            & (PluginMetric.metric_name == subq.c.metric_name)
            & (PluginMetric.recorded_at == subq.c.m),
        ).where(PluginMetric.source_module == "host_agent")
    )).scalars().all()
    out: dict[str, dict] = {}
    for r in rows:
        if r.resource_name.endswith(":/") and r.metric_name == "disk_used_pct":
            out.setdefault(r.resource_name[:-2], {})["disk_root"] = r.value
        elif r.resource_name in host_names:
            d = out.setdefault(r.resource_name, {})
            d[r.metric_name] = r.value
            if d.get("_ts") is None or r.recorded_at > d["_ts"]:
                d["_ts"] = r.recorded_at
    for d in out.values():
        ts = d.pop("_ts", None)
        d["last_at"] = ts
        d["fresh"] = bool(ts and (now - ts).total_seconds() <= stale_after)
    return out


async def agent_cpu_sparks_by_host(db, host_names: list[str], hours: int = 1) -> dict[str, str]:
    """{host_name: inline-SVG cpu sparkline} over the last `hours` (core-safe).

    A tiny at-a-glance trend in each row — the host-view sparkline, on the widget.
    """
    from steward.models.metrics import PluginMetric
    from steward.core.status import sparkline_svg
    if not host_names:
        return {}
    cutoff = datetime.now(timezone.utc) - timedelta(hours=hours)
    rows = (await db.execute(
        select(PluginMetric.resource_name, PluginMetric.value, PluginMetric.recorded_at)
        .where(
            PluginMetric.source_module == "host_agent",
            PluginMetric.metric_name == "cpu_pct",
            PluginMetric.resource_name.in_(host_names),
            PluginMetric.recorded_at >= cutoff,
        )
        .order_by(PluginMetric.recorded_at)
    )).all()
    by_host: dict[str, list[float]] = {}
    for r in rows:
        by_host.setdefault(r.resource_name, []).append(r.value)
    # Amber line to read as "CPU"; only draw when there are a couple of points.
    return {
        name: sparkline_svg(vals[-40:], width=64, height=18, stroke="#c8a840")
        for name, vals in by_host.items() if len(vals) >= 2
    }