"""Monitor tools: every uptime check, and one check's failures in depth."""
from __future__ import annotations

import json

from sqlalchemy import select

from steward.core import renames
from steward.mcp._context import mcp_app
from steward.models.hosts import Host
from steward.models.monitors import MONITOR_TYPE_VALUES, Monitor
from steward.models.users import UserRole
from steward.monitors import service as monitor_svc

from ._audit import audit_mcp
from ._shape import (
    age_s, bounded, clamp_limit, db_session, iso, now_utc, pick, redact_url, rnd,
)

_STATES = ("up", "down", "pending", "disabled")


def _state(m: Monitor, latest) -> str:
    if not m.enabled:
        return "disabled"
    if latest is None:
        return "pending"
    return "up" if latest.is_up else "down"


def _interval(m: Monitor) -> dict:
    """How often a monitor runs: its own interval, or the global one it
    follows when it has none (#5433), and which."""
    if m.check_interval_seconds:
        return {"check_interval_s": m.check_interval_seconds, "interval_from": "monitor"}
    return {"check_interval_s": int(mcp_app().config.get("MONITORS_POLL_INTERVAL", 60)),
            "interval_from": "global"}


def _tls_days(latest) -> float | None:
    if latest is None or latest.tls_expires_at is None:
        return None
    return rnd((latest.tls_expires_at - now_utc()).total_seconds() / 86400.0, 1)


def _row(m: Monitor, st: dict, host_names: dict[str, str]) -> dict:
    latest = st["latest"]
    return {
        "monitor_id": m.id,
        "monitor_name": m.name,
        "type": m.type,
        "target": redact_url(m.target),
        "host_id": m.host_id,
        "host_name": host_names.get(m.host_id) if m.host_id else None,
        "state": _state(m, latest),
        "down_since": iso(st["down_since"]),
        "down_for_s": age_s(st["down_since"]),
        "last_checked_at": iso(latest.checked_at) if latest else None,
        "response_ms": rnd(latest.response_ms) if latest else None,
        "error": latest.error_msg if latest is not None and not latest.is_up else None,
        "uptime_pct": st["uptime"] or {"24h": None, "7d": None, "30d": None},
        "tls_expires_in_days": _tls_days(latest),
    }


async def _load(db):
    monitors = list((await db.execute(select(Monitor).order_by(Monitor.name))).scalars())
    host_names = dict((await db.execute(select(Host.id, Host.name))).all())
    return monitors, host_names


async def list_monitors(state: str = "", type: str = "", limit: int = 100) -> dict:
    """Every uptime monitor (ping, TCP, DNS, HTTP) with its current state.

    state: "down", "up", "pending" (never checked yet) or "disabled"; empty for all.
    type: "icmp", "tcp", "dns" or "http"; empty for all.
    limit: default 100, max 500.

    Down monitors come first, each with `down_since` (when its current run of
    failures began) and the latest `error`. `uptime_pct` covers 24h/7d/30d;
    `tls_expires_in_days` is set for HTTPS checks. get_monitor shows one
    monitor's configuration and recent failures.
    """
    if state and state not in _STATES:
        raise ValueError(f"state {state!r} is not one of {', '.join(_STATES)}.")
    if type and type not in MONITOR_TYPE_VALUES:
        raise ValueError(f"type {type!r} is not one of {', '.join(MONITOR_TYPE_VALUES)}.")
    limit = clamp_limit(limit, 100, 500)
    async with db_session() as db:
        monitors, host_names = await _load(db)
        if type:
            monitors = [m for m in monitors if m.type == type]
        states = await monitor_svc.monitor_states(db, monitors)
    rows = [_row(m, states[m.id], host_names) for m in monitors]
    if state:
        rows = [r for r in rows if r["state"] == state]
    order = {"down": 0, "pending": 1, "up": 2, "disabled": 3}
    rows.sort(key=lambda r: (order[r["state"]], r["monitor_name"].lower()))
    counts = {s: 0 for s in _STATES}
    for r in rows:
        counts[r["state"]] += 1
    return {"counts": counts, **bounded(rows, limit, key="monitors",
                                        more="Pass a larger `limit`, or filter by `state` or `type`.")}


def _config(m: Monitor) -> dict:
    try:
        cfg = json.loads(m.config_json or "{}")
    except ValueError:
        return {}
    if isinstance(cfg.get("headers"), dict):
        # Header values are often credentials (Authorization, API keys).
        cfg["headers"] = {k: "<redacted>" for k in cfg["headers"]}
    return cfg


async def get_monitor(monitor: str, failures: int = 10) -> dict:
    """One monitor in depth: configuration, current state, uptime and recent failures.

    monitor: the monitor's name (case-insensitive) or id, as list_monitors shows.
    failures: how many of its latest failed checks to return (default 10, max 50),
      newest first, each with its error message.

    `heartbeat` is its last 30 checks oldest-first as a string, "+" up and "-"
    down, to show a flapping check at a glance. `check_interval_s` is how
    often it runs; `interval_from` says whether that is its own setting
    ("monitor") or the global monitors interval it follows ("global").
    Header values in an HTTP monitor's configuration are redacted.
    """
    failures = clamp_limit(failures, 10, 50)
    async with db_session() as db:
        monitors, host_names = await _load(db)
        m = pick(monitor, monitors, kind="monitor", list_tool="list_monitors")
        st = (await monitor_svc.monitor_states(db, [m]))[m.id]
        failed = await monitor_svc.recent_failures(db, m.id, failures)
    return {
        **_row(m, st, host_names),
        **_interval(m),
        "config": _config(m),
        "heartbeat": "".join("+" if r.is_up else "-" for r in st["recent"]),
        "recent_failures": [
            {
                "checked_at": iso(r.checked_at),
                "age_s": age_s(r.checked_at),
                "error": r.error_msg,
                "status_code": r.status_code,
                "response_ms": rnd(r.response_ms),
            }
            for r in failed
        ],
    }


# ── changes ──────────────────────────────────────────────────────────────────

async def _host_id(db, host: str) -> str | None:
    if not (host or "").strip():
        return None
    hosts = (await db.execute(select(Host))).scalars()
    return pick(host, hosts, kind="host", list_tool="list_hosts").id


def _saved(m: Monitor, host_names: dict[str, str]) -> dict:
    return {
        "monitor_id": m.id,
        "monitor_name": m.name,
        "type": m.type,
        "target": redact_url(m.target),
        "host_name": host_names.get(m.host_id) if m.host_id else None,
        "enabled": m.enabled,
        **_interval(m),
        "config": _config(m),
        "next": f'get_monitor(monitor="{m.id}")',
    }


async def create_monitor(name: str, type: str, target: str, host: str = "",
                         config: dict | None = None, check_interval_s: int = 0,
                         enabled: bool = True) -> dict:
    """Add an uptime check. Recorded in the audit log as "<you> via MCP".

    type: "icmp" (ping), "tcp" (connect to a port), "dns" (resolve a name)
      or "http" (request a URL).
    target: an address or hostname; for http a URL (a bare host gets https://).
    host: a Steward host's name or id to file the check under; empty for a
      free-standing destination.
    config, by type (every key optional, defaults shown):
      tcp:  {"port": 80}
      dns:  {"expected_ip": null, "resolver": null}  (expected_ip: fail when the
             name resolves elsewhere; resolver: a DNS server's IP to ask
             directly, timing its answer; null asks the container's own)
      http: {"method": "GET" | "HEAD" | "POST", "expected_status": 200,
             "content_match": "", "headers": {}, "timeout_seconds": 10 (1-60),
             "follow_redirects": true, "verify_ssl": true}
      icmp takes none.
    check_interval_s: seconds between checks; 0 (default) uses the global
      interval from Settings.

    The check's metrics are reported under source_module = its type and
    resource = its name, which is what an alert rule on it watches.
    """
    fields = monitor_svc.monitor_fields(type, target=target, name=name,
                                        check_interval_seconds=check_interval_s, opts=config or {})
    async with db_session() as db, db.begin():
        await monitor_svc.check_name_free(db, fields["type"], fields["name"])
        m = Monitor(host_id=await _host_id(db, host), enabled=enabled, **fields)
        db.add(m)
        _monitors, host_names = await _load(db)
    await audit_mcp("monitor.created", "monitor", m.name,
                    {"monitor_id": m.id, "type": m.type, "target": redact_url(m.target)})
    return _saved(m, host_names)


async def update_monitor(monitor: str, name: str | None = None, target: str | None = None,
                         host: str | None = None, config: dict | None = None,
                         check_interval_s: int | None = None) -> dict:
    """Change a monitor. Only the arguments you pass change; the rest stay.

    monitor: its name or id (list_monitors).
    host: a host's name or id to file it under, or "" to unlink it.
    config: the keys to change, merged over its current config (see
      create_monitor for the keys of each type). A monitor's type cannot
      change; delete it and create another.

    A rename carries the monitor's alert rules, maintenance windows and
    check history to the new name; `carried` says what moved. A name another
    monitor of the same type has is refused.

    Recorded in the audit log.
    """
    async with db_session() as db, db.begin():
        monitors, host_names = await _load(db)
        m = pick(monitor, monitors, kind="monitor", list_tool="list_monitors")
        current = {k: v for k, v in m.config.items() if k in monitor_svc.CONFIG_KEYS[m.type]}
        fields = monitor_svc.monitor_fields(
            m.type, target=m.target if target is None else target,
            name=m.name if name is None else name,
            check_interval_seconds=(m.check_interval_seconds if check_interval_s is None
                                    else check_interval_s),
            opts={**current, **(config or {})})
        old_name = m.name
        if fields["name"] != old_name:
            await monitor_svc.check_name_free(db, m.type, fields["name"], exclude_id=m.id)
        for k, v in fields.items():
            setattr(m, k, v)
        if host is not None:
            m.host_id = await _host_id(db, host)
        moved = await renames.carry_rename(db, ((m.type, None),), old_name, m.name)
    changed = sorted(k for k, v in {"name": name, "target": target, "host": host, "config": config,
                                    "check_interval_s": check_interval_s}.items() if v is not None)
    detail = {"monitor_id": m.id, "changed": changed}
    if moved:
        detail["renamed_from"] = old_name
        detail["carried"] = moved
    await audit_mcp("monitor.updated", "monitor", m.name, detail)
    out = _saved(m, host_names)
    if moved:
        out["carried"] = {"from": old_name, **moved}
    return out


async def set_monitor_enabled(monitor: str, enabled: bool) -> dict:
    """Pause (enabled=false) or resume a monitor. A paused monitor runs no checks
    and raises no alerts. Recorded in the audit log."""
    async with db_session() as db, db.begin():
        monitors, host_names = await _load(db)
        m = pick(monitor, monitors, kind="monitor", list_tool="list_monitors")
        m.enabled = bool(enabled)
    await audit_mcp("monitor.enabled" if m.enabled else "monitor.disabled", "monitor", m.name,
                    {"monitor_id": m.id})
    return _saved(m, host_names)


async def delete_monitor(monitor: str) -> dict:
    """Delete a monitor and its check history. To stop it but keep its history,
    set_monitor_enabled(enabled=false) instead. Admin only; recorded in the
    audit log."""
    async with db_session() as db, db.begin():
        monitors, _host_names = await _load(db)
        m = pick(monitor, monitors, kind="monitor", list_tool="list_monitors")
        await db.delete(m)
    await audit_mcp("monitor.deleted", "monitor", m.name,
                    {"monitor_id": m.id, "type": m.type, "target": redact_url(m.target)})
    return {"deleted": m.name, "monitor_id": m.id}


def register(register_tool) -> None:
    register_tool(list_monitors, role=UserRole.viewer, read_only=True)
    register_tool(get_monitor, role=UserRole.viewer, read_only=True)
    for fn in (create_monitor, update_monitor, set_monitor_enabled):
        register_tool(fn, role=UserRole.operator, read_only=False)
    register_tool(delete_monitor, role=UserRole.admin, read_only=False)