"""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.monitors import Monitor, MonitorResult


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/root-disk + freshness) from PluginMetric.

    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_(("cpu_pct", "mem_used_pct", "disk_used_pct")),
        )
        .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["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
    }