# steward/core/status.py
"""Unified monitor-status aggregation.

A single readable "is everything up?" surface (the Status page + dashboard
widget) is assembled from heterogeneous monitors. The core unified Monitor
entity (ping/dns/http) contributes via `monitor_status_source`; plugins may
register their own sources from setup(). Each source is an async callable(db)
returning normalised StatusEntry objects so the Status page never imports
plugin tables directly.
"""
from __future__ import annotations

import logging
from dataclasses import dataclass, field
from datetime import datetime, timedelta, timezone
from typing import Awaitable, Callable

from sqlalchemy import and_, case, func, select

logger = logging.getLogger(__name__)

HEARTBEAT_COUNT = 30  # number of recent checks shown in the heartbeat bar


@dataclass
class StatusEntry:
    """One monitored thing, normalised across monitor types for display."""
    kind: str                       # "icmp" | "tcp" | "dns" | "http" | ...
    key: str                        # unique within kind (monitor id)
    name: str
    target: str = ""                # address / URL shown as subtitle
    status: str = "pending"         # "up" | "down" | "pending"
    last_checked: datetime | None = None
    uptime: dict[str, float | None] = field(default_factory=dict)  # 24h/7d/30d
    heartbeat: list[dict] = field(default_factory=list)  # oldest-first {state,title}
    latency_ms: float | None = None
    spark: list[float] = field(default_factory=list)     # response series
    tls_days: float | None = None   # days until TLS expiry (http only)
    detail_url: str | None = None
    # When the current up/down state began, as far as the recent checks show;
    # since_at_least means every check we have agrees, so it began earlier.
    since: datetime | None = None
    since_at_least: bool = False


StatusSource = Callable[[object], Awaitable[list[StatusEntry]]]
_SOURCES: list[StatusSource] = []


def register_status_source(fn: StatusSource) -> None:
    """Register a status source. Idempotent on the same callable."""
    if fn not in _SOURCES:
        _SOURCES.append(fn)


def clear_status_sources() -> None:
    """Reset the registry (used by tests)."""
    _SOURCES.clear()


async def collect_status(db) -> list[StatusEntry]:
    """Gather entries from every registered source, down-first then by name.

    A failing source is logged and skipped so one broken plugin can't blank
    the whole Status page.
    """
    entries: list[StatusEntry] = []
    for src in list(_SOURCES):
        try:
            entries.extend(await src(db))
        except Exception:
            logger.exception("status source %r failed", getattr(src, "__name__", src))
    # Down first (most urgent), then pending, then up; alphabetical within.
    order = {"down": 0, "pending": 1, "up": 2}
    entries.sort(key=lambda e: (order.get(e.status, 3), e.kind, e.name.lower()))
    return entries


def sparkline_svg(values: list[float], width: int = 80, height: int = 20,
                  stroke: str = "#6060c0", fill_width: bool = False,
                  floor: float | None = None) -> str:
    """Tiny inline SVG polyline for a response-time series. With fill_width
    the line stretches across its container (CSS sets the width) and keeps a
    1.5px stroke.

    With `floor` the line is drawn from zero up to its own peak, but never
    against less than `floor`, so a value idling near zero draws flat rather
    than its noise filling the height (UI & Design ruling 8)."""
    vals = [v for v in values if v is not None]
    size = (f'width="100%" height="{height}" preserveAspectRatio="none"' if fill_width
            else f'width="{width}" height="{height}"')
    if len(vals) < 2:
        return f'<svg {size}></svg>'
    if floor is not None:
        mn, mx = 0.0, max(max(vals), floor)
    else:
        mn, mx = min(vals), max(vals)
    if mx == mn:
        mx = mn + 1.0
    step = width / (len(vals) - 1)
    pts = []
    for i, v in enumerate(vals):
        x = i * step
        y = height - (v - mn) / (mx - mn) * (height - 2) - 1
        pts.append(f"{x:.1f},{y:.1f}")
    poly = " ".join(pts)
    style = "display:block;" if fill_width else "vertical-align:middle;"
    keep = ' vector-effect="non-scaling-stroke"' if fill_width else ""
    return (
        f'<svg {size} viewBox="0 0 {width} {height}" style="{style}">'
        f'<polyline points="{poly}" fill="none" stroke="{stroke}" stroke-width="1.5"{keep}/>'
        f'</svg>'
    )


# ── Unified monitor status source ─────────────────────────────────────────────

async def _last_n_results(db, monitor_ids: list[str],
                          n: int = HEARTBEAT_COUNT) -> dict[str, list]:
    """Return {monitor_id: [MonitorResult]} of the last n results, oldest-first.

    One LATERAL probe per monitor walks ix_monitor_results_monitor_checked
    backwards and stops after n rows. A row_number() over each monitor's
    results read its whole history first, which held Status and the monitor
    widgets at ~16 s (#5208).
    """
    from sqlalchemy import true
    from sqlalchemy.orm import aliased
    from steward.models.monitors import Monitor, MonitorResult
    if not monitor_ids:
        return {}
    ids = select(Monitor.id.label("mid")).where(Monitor.id.in_(monitor_ids)).subquery("wanted")
    recent = (
        select(MonitorResult)
        .where(MonitorResult.monitor_id == ids.c.mid)
        .order_by(MonitorResult.checked_at.desc())
        .limit(n)
        .lateral("recent")
    )
    row = aliased(MonitorResult, recent)
    res = await db.execute(select(row).select_from(ids).join(recent, true()))
    out: dict[str, list] = {mid: [] for mid in monitor_ids}
    for r in res.scalars():
        out[r.monitor_id].append(r)
    for rows in out.values():
        rows.sort(key=lambda r: r.checked_at)
    return out


async def _uptime_by_monitor(db, monitor_ids: list[str]) -> dict[str, dict]:
    """Per-monitor uptime % over 24h/7d/30d in one grouped query."""
    from steward.models.monitors import MonitorResult
    if not monitor_ids:
        return {}
    now = datetime.now(timezone.utc)
    c30, c7, c24 = now - timedelta(days=30), now - timedelta(days=7), now - timedelta(hours=24)
    res = await db.execute(
        select(
            MonitorResult.monitor_id,
            func.count().label("total_30d"),
            func.sum(case((MonitorResult.is_up.is_(True), 1), else_=0)).label("up_30d"),
            func.sum(case((MonitorResult.checked_at >= c7, 1), else_=0)).label("total_7d"),
            func.sum(case((and_(MonitorResult.checked_at >= c7, MonitorResult.is_up.is_(True)), 1), else_=0)).label("up_7d"),
            func.sum(case((MonitorResult.checked_at >= c24, 1), else_=0)).label("total_24h"),
            func.sum(case((and_(MonitorResult.checked_at >= c24, MonitorResult.is_up.is_(True)), 1), else_=0)).label("up_24h"),
        )
        .where(MonitorResult.monitor_id.in_(monitor_ids))
        .where(MonitorResult.checked_at >= c30)
        .group_by(MonitorResult.monitor_id)
    )

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

    out: dict[str, dict] = {}
    for r in res:
        out[r.monitor_id] = {
            "24h": _pct(r.up_24h, r.total_24h),
            "7d": _pct(r.up_7d, r.total_7d),
            "30d": _pct(r.up_30d, r.total_30d),
        }
    return out


def streak_start(results) -> tuple[datetime | None, bool]:
    """(checked_at of the first check in the latest run of the same result,
    whether that run fills every check given). Results are oldest-first."""
    if not results:
        return None, False
    i = len(results) - 1
    while i > 0 and results[i - 1].is_up == results[-1].is_up:
        i -= 1
    return results[i].checked_at, i == 0


def _heartbeat_title(mtype: str, r) -> str:
    """Type-aware tooltip for one heartbeat cell."""
    ts = f"{r.checked_at:%H:%M:%S} UTC"
    if not r.is_up:
        return f"{(r.error_msg or 'Down')} — {ts}"
    if mtype == "http":
        code = r.status_code or "—"
        ms = f"{r.response_ms:.0f} ms" if r.response_ms is not None else ""
        return f"{code} · {ms} — {ts}".replace(" · — ", " — ")
    if mtype == "dns":
        return f"{r.resolved_ip or 'resolved'} — {ts}"
    if r.response_ms is not None:
        return f"{r.response_ms:.0f} ms — {ts}"
    return f"Up — {ts}"


async def monitor_status_source(db) -> list[StatusEntry]:
    """Contribute every enabled Monitor (all types) to the Status page."""
    from steward.models.monitors import Monitor

    monitors = list((await db.execute(
        select(Monitor).where(Monitor.enabled.is_(True)).order_by(Monitor.name)
    )).scalars())
    ids = [m.id for m in monitors]
    recent = await _last_n_results(db, ids)
    uptime = await _uptime_by_monitor(db, ids)
    now = datetime.now(timezone.utc)

    entries: list[StatusEntry] = []
    for m in monitors:
        rows = recent.get(m.id, [])
        latest = rows[-1] if rows else None
        status = "pending" if latest is None else ("up" if latest.is_up else "down")
        since, since_at_least = streak_start(rows)
        tls_days = None
        if latest and latest.tls_expires_at:
            tls_days = (latest.tls_expires_at - now).total_seconds() / 86400.0
        entries.append(StatusEntry(
            kind=m.type, key=m.id, name=m.name, target=m.target, status=status,
            last_checked=latest.checked_at if latest else None,
            uptime=uptime.get(m.id, {}),
            heartbeat=[{"state": "up" if r.is_up else "down",
                        "title": _heartbeat_title(m.type, r)} for r in rows],
            latency_ms=latest.response_ms if latest else None,
            spark=[r.response_ms for r in rows if r.response_ms is not None],
            tls_days=tls_days, detail_url=f"/monitors/{m.id}",
            since=since, since_at_least=since_at_least,
        ))
    return entries