# plugins/snmp/routes.py
"""The SNMP pages. Every GET reads Steward's own records: the device rows the
editor writes and the poller annotates, and the readings it stores. Only Test,
an admin's explicit action, asks a device anything (System 178's ruling)."""
from __future__ import annotations

import json
from datetime import datetime, timedelta, timezone

from quart import Blueprint, abort, current_app, redirect, render_template, request, session
from sqlalchemy import delete, select, update

from steward.auth.middleware import require_role
from steward.core.audit import log_audit
from steward.core.metric_series import latest_by_resource
from steward.models.metrics import PluginMetric, PluginMetricLatest
from steward.models.users import UserRole

from .models import SnmpDevice
from .readings import INTERFACES_LABEL, PRESETS, PRESET_ORDER, UNITS, chart_axis, reading_text, stored_unit
from .service import (FormError, device_state, form_credentials, form_values, parse_form,
                      readings_for)

snmp_bp = Blueprint("snmp", __name__, template_folder="templates")


def _poll_seconds() -> int:
    return int(current_app.config["PLUGINS"]["snmp"].get("poll_interval_seconds", 60))


async def _all_devices(db) -> list[SnmpDevice]:
    return list((await db.execute(select(SnmpDevice).order_by(SnmpDevice.name))).scalars().all())


async def _latest(db, names: list[str]) -> dict[str, dict]:
    """{device name: {key: value}} from plugin_metric_latest."""
    latest = await latest_by_resource(db, "snmp", names)
    return {name: {m: r.value for m, r in metrics.items()} for name, metrics in latest.items()}


def shown_readings(device: SnmpDevice, values: dict) -> list[dict]:
    """The device's readings in its own order, each named and in its unit (a
    state in the device's own word); "—" for one with no value yet."""
    return [{"key": r.key, "name": r.name, "counter": r.counter,
             "text": reading_text(r, values.get(r.key), device.texts)}
            for r in readings_for(device)]


def view(device: SnmpDevice, values: dict, now: datetime) -> dict:
    state = device_state(device, _poll_seconds(), now)
    names = {r.key: r.name for r in readings_for(device)}
    return {"id": device.id, "name": device.name, "address": device.address, "port": device.port,
            "host_id": device.host_id,
            "version": device.version, "reach": state.reach, "says": state.says,
            "polled_at": device.last_polled_at, "ok_at": device.last_ok_at,
            "readings": shown_readings(device, values),
            "missing": [names.get(k, k) for k in device.missing or []]}


_REACH_ORDER = {"down": 0, "stale": 1, "pending": 2, "up": 3}


@snmp_bp.get("/")
@require_role(UserRole.viewer)
async def index():
    async with current_app.db_sessionmaker() as db:
        devices = await _all_devices(db)
        latest = await _latest(db, [d.name for d in devices])
    now = datetime.now(timezone.utc)
    shown = [view(d, latest.get(d.name, {}), now) for d in devices]
    shown.sort(key=lambda v: (_REACH_ORDER[v["reach"]], v["name"].lower()))
    return await render_template("snmp/index.html", devices=shown)


# ── The editor ────────────────────────────────────────────────────────────────

async def _hosts(db) -> list:
    from steward.models.hosts import Host
    return list((await db.execute(select(Host.id, Host.name).order_by(Host.name))).all())


async def _render_form(device: SnmpDevice | None, values: dict, error: str | None = None, status: int = 200):
    async with current_app.db_sessionmaker() as db:
        hosts = await _hosts(db)
    presets = [(pid, *(INTERFACES_LABEL if pid == "interfaces" else PRESETS[pid][:2])) for pid in PRESET_ORDER]
    return await render_template("snmp/form.html", device=device, v=values, error=error, hosts=hosts,
                                 presets=presets, units=UNITS), status


def _actor() -> tuple[str | None, str]:
    return session.get("user_id"), session.get("username", "")


@snmp_bp.get("/devices/new")
@require_role(UserRole.admin)
async def new_device():
    return await _render_form(None, form_values(None))


@snmp_bp.post("/devices/new")
@require_role(UserRole.admin)
async def create_device():
    form = await request.form
    try:
        values = parse_form(form)
    except FormError as exc:
        return await _render_form(None, _typed(form), str(exc), 422)
    async with current_app.db_sessionmaker() as db:
        async with db.begin():
            if await _name_taken(db, values["name"]):
                return await _render_form(None, _typed(form), f"A device is already named “{values['name']}”.", 422)
            device = SnmpDevice(**values)
            db.add(device)
            await db.flush()
            device_id = device.id
    await log_audit(current_app, *_actor(), "snmp.device_created", entity_type="snmp_device",
                    entity_id=device_id, detail={"name": values["name"], "address": values["address"]})
    return redirect(f"/plugins/snmp/devices/{device_id}")


async def _name_taken(db, name: str, other_than: str | None = None) -> bool:
    q = select(SnmpDevice.id).where(SnmpDevice.name == name)
    if other_than:
        q = q.where(SnmpDevice.id != other_than)
    return (await db.execute(q)).first() is not None


def _typed(form) -> dict:
    """What was typed, to show the form again with an error. Secrets are not
    echoed back."""
    return {"name": form.get("name", ""), "address": form.get("address", ""), "port": form.get("port", ""),
            "version": form.get("version", "2c"), "v3_user": form.get("v3_user", ""),
            "v3_auth": form.get("v3_auth", "none"), "v3_priv": form.get("v3_priv", "none"),
            "presets": form.getlist("presets"), "interfaces": form.get("interfaces", ""),
            "custom": form.get("custom", ""), "host_id": form.get("host_id", "")}


async def _device_or_404(db, device_id: str) -> SnmpDevice:
    device = await db.get(SnmpDevice, device_id)
    if device is None:
        abort(404)
    return device


@snmp_bp.get("/devices/<device_id>/edit")
@require_role(UserRole.admin)
async def edit_device(device_id: str):
    async with current_app.db_sessionmaker() as db:
        device = await _device_or_404(db, device_id)
    return await _render_form(device, form_values(device))


@snmp_bp.post("/devices/<device_id>/edit")
@require_role(UserRole.admin)
async def save_device(device_id: str):
    form = await request.form
    async with current_app.db_sessionmaker() as db:
        async with db.begin():
            device = await _device_or_404(db, device_id)
            try:
                values = parse_form(form, device)
            except FormError as exc:
                return await _render_form(device, {**_typed(form), **_kept_secrets(device)}, str(exc), 422)
            if await _name_taken(db, values["name"], other_than=device.id):
                return await _render_form(device, {**_typed(form), **_kept_secrets(device)},
                                          f"A device is already named “{values['name']}”.", 422)
            old_name = device.name
            for column, value in values.items():
                setattr(device, column, value)
            # What it is asked, or how, may have changed: the last outcome no
            # longer describes it, so the page says "not polled yet" until the
            # next poll, which also walks its vendor tables again.
            device.last_polled_at = device.last_ok_at = device.last_error = device.tables_at = None
            device.missing, device.texts = [], {}
            if old_name != device.name:
                # Its history is stored under its name; move it with the rename.
                for model in (PluginMetric, PluginMetricLatest):
                    await db.execute(update(model).where(
                        model.source_module == "snmp", model.resource_name == old_name
                    ).values(resource_name=device.name))
    from . import scheduler
    if scheduler.RATES is not None:
        scheduler.RATES.forget(device_id)
    detail = {"name": values["name"]}
    if old_name != values["name"]:
        detail["old_name"] = old_name
    await log_audit(current_app, *_actor(), "snmp.device_updated", entity_type="snmp_device",
                    entity_id=device_id, detail=detail)
    return redirect(f"/plugins/snmp/devices/{device_id}")


def _kept_secrets(device: SnmpDevice) -> dict:
    return {"has_community": bool(device.community), "has_auth_key": bool(device.v3_auth_key),
            "has_priv_key": bool(device.v3_priv_key)}


@snmp_bp.post("/devices/<device_id>/delete")
@require_role(UserRole.admin)
async def delete_device(device_id: str):
    async with current_app.db_sessionmaker() as db:
        async with db.begin():
            device = await _device_or_404(db, device_id)
            name = device.name
            await db.delete(device)
            # Its newest readings go with it, so nothing reads it as a device
            # that stopped answering. Its history ages out with retention.
            await db.execute(delete(PluginMetricLatest).where(
                PluginMetricLatest.source_module == "snmp", PluginMetricLatest.resource_name == name))
    await log_audit(current_app, *_actor(), "snmp.device_deleted", entity_type="snmp_device",
                    entity_id=device_id, detail={"name": name})
    return redirect("/plugins/snmp/")


@snmp_bp.post("/devices/test")
@require_role(UserRole.admin)
async def test_device():
    """Ask the device on the (unsaved) form who it is and what interfaces it
    has. An admin's explicit action, so it may contact the device."""
    from .poller import describe_device
    form = await request.form
    existing = None
    if form.get("device_id"):
        async with current_app.db_sessionmaker() as db:
            existing = await db.get(SnmpDevice, form["device_id"])
    address, port, creds = form_credentials(form, existing)
    if not address:
        found = {"error": "Enter the device's address first."}
    else:
        found = await describe_device(address, port, creds)
    return await render_template("snmp/_test.html", found=found, address=address, port=port)


# ── The device page, the dashboard widget, the host page's panel ─────────────

async def _history(db, device_name: str, since: datetime) -> dict[str, list]:
    """{key: [(iso time, value), ...]} for one device since `since`."""
    rows = (await db.execute(
        select(PluginMetric.metric_name, PluginMetric.recorded_at, PluginMetric.value)
        .where(PluginMetric.source_module == "snmp", PluginMetric.resource_name == device_name,
               PluginMetric.recorded_at >= since)
        .order_by(PluginMetric.recorded_at))).all()
    out: dict[str, list] = {}
    for key, at, value in rows:
        out.setdefault(key, []).append((at.isoformat(), value))
    return out


RANGES = (1, 6, 24, 168)


@snmp_bp.get("/devices/<device_id>")
@require_role(UserRole.viewer)
async def device_detail(device_id: str):
    hours = request.args.get("hours", type=int, default=24)
    if hours not in RANGES:
        hours = 24
    now = datetime.now(timezone.utc)
    async with current_app.db_sessionmaker() as db:
        device = await _device_or_404(db, device_id)
        latest = await _latest(db, [device.name])
        hist = await _history(db, device.name, now - timedelta(hours=hours))
    charts = []
    for r in readings_for(device):
        unit = stored_unit(r)
        axis, factor = chart_axis(unit)
        charts.append({"key": r.key, "name": r.name, "axis": axis,
                       "now": reading_text(r, latest.get(device.name, {}).get(r.key), device.texts),
                       "points": [(t, v * factor) for t, v in hist.get(r.key, [])]})
    return await render_template("snmp/device.html", device=view(device, latest.get(device.name, {}), now),
                                 charts=charts, charts_json=json.dumps(charts), hours=hours, ranges=RANGES)


DEVICES_SHOWN = 10


@snmp_bp.get("/widget")
@require_role(UserRole.viewer)
async def widget():
    """The dashboard SNMP widget (#5255), in widget shape: a verdict, devices
    not answering first with why, then the rest with two readings each."""
    async with current_app.db_sessionmaker() as db:
        devices = await _all_devices(db)
        latest = await _latest(db, [d.name for d in devices])
    now = datetime.now(timezone.utc)
    shown = [view(d, latest.get(d.name, {}), now) for d in devices]
    shown.sort(key=lambda v: (_REACH_ORDER[v["reach"]], v["name"].lower()))
    for v in shown:
        v["key"] = [r for r in v["readings"] if r["text"] != "—"][:2]
    counts = {r: sum(1 for d in shown if d["reach"] == r) for r in _REACH_ORDER}
    return await render_template("snmp/widget.html", devices=shown[:DEVICES_SHOWN],
                                 more=max(0, len(shown) - DEVICES_SHOWN), counts=counts, total=len(shown))


def devices_for_host(devices: list[SnmpDevice], host_id: str, address: str | None,
                     name: str | None) -> list[SnmpDevice]:
    """The devices shown on a host's page: those bound to it, and those bound
    to no host whose address is the host's address or name. A binding is
    exclusive, so a device bound elsewhere never matches by address."""
    keys = {(address or "").strip().lower(), (name or "").strip().lower()} - {""}
    return [d for d in devices
            if (d.host_id == host_id if d.host_id else d.address.strip().lower() in keys)]


@snmp_bp.get("/host/<host_id>")
@require_role(UserRole.viewer)
async def host_panel(host_id: str):
    """The SNMP panel on a host's page; nothing when no device maps to it."""
    from steward.models.hosts import Host
    async with current_app.db_sessionmaker() as db:
        host = await db.get(Host, host_id)
        if host is None:
            return ""
        matched = devices_for_host(await _all_devices(db), host.id, host.address, host.name)
        if not matched:
            return ""
        latest = await _latest(db, [d.name for d in matched])
    now = datetime.now(timezone.utc)
    return await render_template("snmp/host_panel.html",
                                 devices=[{**view(d, latest.get(d.name, {}), now), "bound": bool(d.host_id)}
                                          for d in matched])