import { readdir, stat } from "node:fs/promises";
import { checkRoot, DEFAULT_ROOT_SENTINEL, type DiskUsage, diskUsage } from "@umt/adapters";
import type {
  HealthLevel,
  SystemDisk,
  SystemHealth,
  SystemHealthHistory,
  SystemMount,
  SystemProcess,
} from "@umt/contracts";
import { type DB, type Kysely, type Selectable, sql } from "@umt/db";
import { CURRENT_HOST_WINDOW_MS, HEARTBEAT_ROW_RETENTION_MS, HEARTBEAT_STALE_MS } from "./heartbeat.ts";

// GET /system/health 各段的取数(W9-I)。每段独立 try/catch:一段失败只把该段标 unknown,不让整页 500。
// 慢 IO(statfs / 哨兵检查)都带超时:挂载卡死时只标 timeout,不拖住请求。

export interface HealthDeps {
  db: Kysely<DB>;
  engineSchema: string;
  dataDir: string;
  /** 本进程(处理请求的 api)信息 */
  self: { version: string; startedAt: Date; sseConnections: number; instanceId?: string };
  /** 磁盘阈值(百分比):warn / critical */
  thresholds: { warnPercent: number; criticalPercent: number };
  /** 测试注入 */
  now?: () => Date;
  diskUsage?: (path: string) => Promise<DiskUsage>;
  checkRoot?: typeof checkRoot;
  /** 单个路径 IO 检查超时(ms),缺省 3000 */
  ioTimeoutMs?: number;
  /** 存储段(CACHE-2);不给时该段为 unknown */
  storage?: () => Promise<{ level: HealthLevel; alerts: string[] }>;
}

const LEVEL_ORDER: HealthLevel[] = ["ok", "warn", "critical"];
export function worst(levels: HealthLevel[]): HealthLevel {
  let w: HealthLevel = "ok";
  for (const l of levels) if (l !== "unknown" && LEVEL_ORDER.indexOf(l) > LEVEL_ORDER.indexOf(w)) w = l;
  return w;
}

class Timeout extends Error {}
function withTimeout<T>(p: Promise<T>, ms: number): Promise<T> {
  let t: ReturnType<typeof setTimeout> | undefined;
  return Promise.race([
    p,
    new Promise<T>((_, reject) => {
      t = setTimeout(() => reject(new Timeout("timeout")), ms);
    }),
  ]).finally(() => clearTimeout(t));
}

const toDate = (v: Date | string) => (v instanceof Date ? v : new Date(v));
const num = (v: unknown) => (v == null ? null : Number(v));

// ── 进程 ──

type HeartbeatRow = Selectable<DB["process_heartbeat"]>;

function toProcess(r: HeartbeatRow, now: Date): SystemProcess {
  const beat = toDate(r.last_beat_at);
  const age = Math.max(0, now.getTime() - beat.getTime());
  const extra = (r.extra ?? {}) as Record<string, unknown>;
  const conc = (r.concurrency ?? {}) as { io?: number; agent?: number };
  const sse = extra.sseConnections;
  return {
    instanceId: r.instance_id,
    processKind: r.process_kind,
    pid: r.pid,
    host: r.host,
    version: r.version,
    startedAt: toDate(r.started_at).toISOString(),
    lastBeatAt: beat.toISOString(),
    beatAgeSec: Math.round(age / 100) / 10,
    stale: age > HEARTBEAT_STALE_MS,
    stoppedAt: r.stopped_at ? toDate(r.stopped_at).toISOString() : null,
    eventLoopLagMs: r.event_loop_lag_ms,
    eventLoopLagMaxMs: r.event_loop_lag_max_ms,
    concurrency: {
      ...(typeof conc.io === "number" ? { io: conc.io } : {}),
      ...(typeof conc.agent === "number" ? { agent: conc.agent } : {}),
    },
    runningRuns: r.running_runs,
    sseConnections: typeof sse === "number" ? sse : null,
    extra,
  };
}

/**
 * 把心跳行分成当前实例与已下线实例:
 * - 当前 host = 最近 10 分钟内有心跳且没标 stopped_at 的行所在 host(容器重建后 host 会变);
 * - 当前实例 = 当前 host 上、没标 stopped_at、且是同 host 同 kind 里最新启动的那一行;
 * - 其余(已正常退出、host 已不在、被同 host 新进程替换)都算已下线实例,不参与 stale 判定与告警。
 */
export function splitProcesses(
  ps: SystemProcess[],
  now: Date,
): { processes: SystemProcess[]; retiredProcesses: SystemProcess[] } {
  const alive = ps.filter((p) => !p.stoppedAt);
  const hosts = new Set(
    alive.filter((p) => now.getTime() - Date.parse(p.lastBeatAt) <= CURRENT_HOST_WINDOW_MS).map((p) => p.host),
  );
  const newest = new Map<string, SystemProcess>();
  for (const p of alive) {
    if (!hosts.has(p.host)) continue;
    const k = `${p.host}\u0000${p.processKind}`;
    const cur = newest.get(k);
    if (!cur || Date.parse(p.startedAt) > Date.parse(cur.startedAt)) newest.set(k, p);
  }
  const current = new Set([...newest.values()].map((p) => p.instanceId));
  const processes = ps.filter((p) => current.has(p.instanceId));
  const retiredProcesses = ps
    .filter((p) => !current.has(p.instanceId))
    .sort((a, b) => Date.parse(b.lastBeatAt) - Date.parse(a.lastBeatAt));
  return { processes, retiredProcesses };
}

export async function loadProcesses(
  db: Kysely<DB>,
  now: Date,
): Promise<{ processes: SystemProcess[]; retiredProcesses: SystemProcess[] }> {
  const rows = await db
    .selectFrom("process_heartbeat")
    .selectAll()
    .where("last_beat_at", ">", new Date(now.getTime() - HEARTBEAT_ROW_RETENTION_MS))
    .orderBy("process_kind")
    .orderBy("instance_id")
    .execute();
  return splitProcesses(
    rows.map((r) => toProcess(r, now)),
    now,
  );
}

/** 进程段的档位(只看当前实例):有 stale 或延迟 ≥ 1s 为 warn;延迟 ≥ 5s 为 critical;没有任何 worker 心跳为 warn */
export function processLevel(ps: SystemProcess[]): HealthLevel {
  const live = ps.filter((p) => !p.stale);
  const levels: HealthLevel[] = [];
  if (ps.some((p) => p.stale)) levels.push("warn");
  if (!live.some((p) => p.processKind !== "api")) levels.push("warn");
  for (const p of live) {
    if (p.eventLoopLagMaxMs >= 5000) levels.push("critical");
    else if (p.eventLoopLagMaxMs >= 1000) levels.push("warn");
  }
  return worst(levels);
}

// ── DB ──

export async function loadDb(db: Kysely<DB>): Promise<SystemHealth["db"]> {
  try {
    const t0 = performance.now();
    await sql`select 1`.execute(db);
    const latencyMs = Math.round((performance.now() - t0) * 10) / 10;
    const size = await sql<{ size: string }>`select pg_database_size(current_database())::text as size`.execute(db);
    const conns = await sql<{ total: number; active: number; idle: number; iit: number; max: number }>`
      select count(*)::int as total,
             count(*) filter (where state = 'active')::int as active,
             count(*) filter (where state = 'idle')::int as idle,
             count(*) filter (where state like 'idle in transaction%')::int as iit,
             current_setting('max_connections')::int as max
        from pg_stat_activity where datname = current_database()`.execute(db);
    const c = conns.rows[0]!;
    const usage = c.max > 0 ? c.total / c.max : 0;
    const level: HealthLevel =
      latencyMs >= 500 || usage >= 0.9 ? "critical" : latencyMs >= 100 || usage >= 0.75 || c.iit > 5 ? "warn" : "ok";
    return {
      level,
      latencyMs,
      sizeBytes: Number(size.rows[0]?.size ?? 0),
      connections: { total: c.total, active: c.active, idle: c.idle, idleInTransaction: c.iit, max: c.max },
      error: null,
    };
  } catch (err) {
    return { level: "critical", latencyMs: null, sizeBytes: null, connections: null, error: (err as Error).message };
  }
}

// ── 磁盘与挂载根 ──

interface PathTarget {
  scope: SystemDisk["scope"];
  id: string | null;
  name: string;
  path: string;
}

export async function loadPathTargets(db: Kysely<DB>) {
  const roots = await db
    .selectFrom("library_root")
    .select(["id", "name", "local_path", "sentinel_file"])
    .where("enabled", "=", true)
    .orderBy("name")
    .execute();
  const maps = await db
    .selectFrom("path_mapping")
    .leftJoin("downloader_instance", "downloader_instance.id", "path_mapping.downloader_instance_id")
    .select([
      "path_mapping.id as id",
      "path_mapping.remote_prefix as remote",
      "path_mapping.local_prefix as local",
      "downloader_instance.name as downloader",
    ])
    .where("path_mapping.enabled", "=", true)
    .where("path_mapping.view_kind", "=", "downloader")
    .orderBy("path_mapping.local_prefix")
    .execute();
  return { roots, maps };
}

export function diskLevel(ratio: number, t: HealthDeps["thresholds"]): HealthLevel {
  const pct = ratio * 100;
  return pct >= t.criticalPercent ? "critical" : pct >= t.warnPercent ? "warn" : "ok";
}

export async function loadDisksAndMounts(d: HealthDeps): Promise<{ disks: SystemDisk[]; mounts: SystemMount[] }> {
  const usage = d.diskUsage ?? diskUsage;
  const check = d.checkRoot ?? checkRoot;
  const ms = d.ioTimeoutMs ?? 3000;
  const { roots, maps } = await loadPathTargets(d.db);

  const targets: PathTarget[] = [
    { scope: "data_dir", id: null, name: "DATA_DIR", path: d.dataDir },
    ...roots.map((r) => ({ scope: "library_root" as const, id: r.id, name: r.name, path: r.local_path })),
    ...maps.map((m) => ({
      scope: "download_dir" as const,
      id: m.id,
      name: m.downloader ? `${m.downloader} ${m.remote}` : m.remote,
      path: m.local,
    })),
  ];
  const disks = await Promise.all(
    targets.map(async (t): Promise<SystemDisk> => {
      const base = { scope: t.scope, id: t.id, name: t.name, path: t.path };
      try {
        const u = await withTimeout(usage(t.path), ms);
        if (u.status !== "ok")
          return {
            ...base,
            level: "unknown",
            totalBytes: null,
            usedBytes: null,
            availableBytes: null,
            usedRatio: null,
            error: u.code,
          };
        return {
          ...base,
          level: diskLevel(u.usedRatio, d.thresholds),
          totalBytes: u.totalBytes,
          usedBytes: u.usedBytes,
          availableBytes: u.availableBytes,
          usedRatio: Math.min(1, Math.max(0, u.usedRatio)),
          error: null,
        };
      } catch (err) {
        return {
          ...base,
          level: err instanceof Timeout ? "critical" : "unknown",
          totalBytes: null,
          usedBytes: null,
          availableBytes: null,
          usedRatio: null,
          error: err instanceof Timeout ? "timeout" : (err as Error).message,
        };
      }
    }),
  );

  const mounts = await Promise.all([
    ...roots.map(async (r): Promise<SystemMount> => {
      const base = { kind: "library_root" as const, id: r.id, name: r.name, path: r.local_path, sentinelChecked: true };
      try {
        const h = await withTimeout(check(r.local_path, r.sentinel_file ?? DEFAULT_ROOT_SENTINEL), ms);
        return h.kind === "online"
          ? { ...base, status: "online", reason: null }
          : { ...base, status: "offline", reason: h.reason };
      } catch (err) {
        return err instanceof Timeout
          ? { ...base, status: "timeout", reason: "timeout" }
          : { ...base, status: "offline", reason: "error" };
      }
    }),
    ...maps.map(async (m): Promise<SystemMount> => {
      const base = {
        kind: "path_mapping" as const,
        id: m.id,
        name: m.downloader ? `${m.downloader} ${m.remote}` : m.remote,
        path: m.local,
        sentinelChecked: false,
      };
      try {
        await withTimeout(
          (async () => {
            const st = await stat(m.local);
            if (!st.isDirectory()) throw Object.assign(new Error("不是目录"), { code: "ENOTDIR" });
            await readdir(m.local);
          })(),
          ms,
        );
        return { ...base, status: "online", reason: null };
      } catch (err) {
        if (err instanceof Timeout) return { ...base, status: "timeout", reason: "timeout" };
        const code = (err as { code?: string }).code;
        const reason =
          code === "ENOENT" ? "root_missing" : code === "EACCES" || code === "EPERM" ? "permission_denied" : "error";
        return { ...base, status: "offline", reason };
      }
    }),
  ]);
  return { disks, mounts };
}

// ── 引擎 ──

const schemaTable = (schema: string, table: string) => {
  if (!/^[a-z_][a-z0-9_]*$/.test(schema)) throw new Error(`非法 schema 名 ${schema}`);
  return sql.raw(`"${schema}".${table}`);
};

export async function loadEngine(db: Kysely<DB>, schema: string, now: Date): Promise<SystemHealth["engine"]> {
  const t = schemaTable(schema, "workflow_runs");
  const since = new Date(now.getTime() - 24 * 3600_000);
  const r = await sql<{
    pending: number;
    running: number;
    oldest: Date | null;
    finished: number;
    failed: number;
  }>`select
      count(*) filter (where status = 'pending')::int as pending,
      count(*) filter (where status = 'running' and worker_id is not null)::int as running,
      min(coalesce(available_at, created_at)) filter (where status = 'pending' and coalesce(available_at, created_at) <= ${now}) as oldest,
      count(*) filter (where status in ('completed', 'succeeded', 'failed') and finished_at >= ${since})::int as finished,
      count(*) filter (where status = 'failed' and finished_at >= ${since})::int as failed
    from ${t} where namespace_id = 'default'`.execute(db);
  const row = r.rows[0]!;
  const oldestAge = row.oldest ? Math.max(0, (now.getTime() - toDate(row.oldest).getTime()) / 1000) : null;
  const rate = row.finished > 0 ? row.failed / row.finished : null;
  const level: HealthLevel = worst([
    oldestAge != null && oldestAge >= 1800 ? "critical" : oldestAge != null && oldestAge >= 300 ? "warn" : "ok",
    rate != null && row.finished >= 10 && rate >= 0.3 ? "critical" : rate != null && rate >= 0.1 ? "warn" : "ok",
  ]);
  return {
    level,
    pending: row.pending,
    running: row.running,
    oldestPendingAgeSec: oldestAge == null ? null : Math.round(oldestAge),
    finished24h: row.finished,
    failed24h: row.failed,
    failureRate24h: rate,
  };
}

// ── 定时任务 ──

export async function loadSchedules(db: Kysely<DB>, now: Date): Promise<SystemHealth["schedules"]> {
  const jobs = await db
    .selectFrom("scheduled_job")
    .select(["id", "name", "enabled", "available", "last_status", "last_run_at", "last_error", "running_since"])
    .orderBy("id")
    .execute();
  const failedRuns = await sql<{ n: number }>`
    select count(*)::int as n from scheduled_job_run
     where status = 'failed' and started_at >= ${new Date(now.getTime() - 24 * 3600_000)}`.execute(db);
  const enabled = jobs.filter((j) => j.enabled && j.available);
  const failing = enabled
    .filter((j) => j.last_status === "failed")
    .map((j) => ({
      id: j.id,
      name: j.name,
      lastRunAt: j.last_run_at ? toDate(j.last_run_at).toISOString() : null,
      lastError: j.last_error,
    }));
  return {
    level: failing.length ? "warn" : "ok",
    total: jobs.length,
    enabled: enabled.length,
    running: jobs.filter((j) => j.running_since).length,
    failing,
    failedRuns24h: failedRuns.rows[0]?.n ?? 0,
  };
}

// ── 汇总 ──

export async function buildHealth(d: HealthDeps): Promise<SystemHealth> {
  const now = d.now?.() ?? new Date();
  const [{ processes, retiredProcesses }, db, paths, engine, schedules, storage] = await Promise.all([
    loadProcesses(d.db, now).catch(() => ({
      processes: [] as SystemProcess[],
      retiredProcesses: [] as SystemProcess[],
    })),
    loadDb(d.db),
    loadDisksAndMounts(d).catch(() => ({ disks: [] as SystemDisk[], mounts: [] as SystemMount[] })),
    loadEngine(d.db, d.engineSchema, now).catch((): SystemHealth["engine"] => ({
      level: "unknown",
      pending: 0,
      running: 0,
      oldestPendingAgeSec: null,
      finished24h: 0,
      failed24h: 0,
      failureRate24h: null,
    })),
    loadSchedules(d.db, now).catch((): SystemHealth["schedules"] => ({
      level: "unknown",
      total: 0,
      enabled: 0,
      running: 0,
      failing: [],
      failedRuns24h: 0,
    })),
    (d.storage?.() ?? Promise.resolve({ level: "unknown" as HealthLevel, alerts: [] })).catch(() => ({
      level: "unknown" as HealthLevel,
      alerts: [] as string[],
    })),
  ]);
  // SSE:存活的 api/all 进程上报的连接数合计;本进程若还没写过心跳,用实时值
  const selfCounted = processes.some((p) => !p.stale && p.instanceId === d.self.instanceId && p.sseConnections != null);
  const sse =
    processes.filter((p) => !p.stale).reduce((s, p) => s + (p.sseConnections ?? 0), 0) +
    (selfCounted ? 0 : d.self.sseConnections);
  const mountLevel: HealthLevel = paths.mounts.some((m) => m.status !== "online") ? "critical" : "ok";
  return {
    level: worst([
      processLevel(processes),
      db.level,
      ...paths.disks.map((x) => x.level),
      mountLevel,
      engine.level,
      schedules.level,
      storage.level,
    ]),
    checkedAt: now.toISOString(),
    api: {
      version: d.self.version,
      startedAt: d.self.startedAt.toISOString(),
      uptimeSec: Math.max(0, Math.round((now.getTime() - d.self.startedAt.getTime()) / 1000)),
    },
    processes,
    retiredProcesses,
    sse: { connections: sse },
    db,
    disks: paths.disks,
    diskThresholds: d.thresholds,
    mounts: paths.mounts,
    engine,
    schedules,
    storage,
  };
}

// ── 历史 ──

export async function loadHistory(db: Kysely<DB>, hours: number, now = new Date()): Promise<SystemHealthHistory> {
  const from = new Date(now.getTime() - hours * 3600_000);
  // 约 360 个点;最细 15s(一个心跳周期)
  const bucketSec = Math.max(15, Math.ceil((hours * 3600) / 360 / 15) * 15);
  const r = await sql<{
    instance_id: string;
    process_kind: string;
    bucket: Date;
    lag: number;
    lag_max: number;
    running: number | null;
    sse: number | null;
  }>`select instance_id, max(process_kind) as process_kind,
        date_bin(make_interval(secs => ${bucketSec}), at, timestamptz 'epoch') as bucket,
        avg(event_loop_lag_ms)::float8 as lag, max(event_loop_lag_max_ms)::float8 as lag_max,
        max(running_runs)::float8 as running, max(sse_connections)::float8 as sse
      from process_heartbeat_sample where at >= ${from} and at <= ${now}
      group by instance_id, bucket order by instance_id, bucket`.execute(db);
  const series = new Map<string, SystemHealthHistory["series"][number]>();
  for (const row of r.rows) {
    let s = series.get(row.instance_id);
    if (!s) {
      s = { instanceId: row.instance_id, processKind: row.process_kind, points: [] };
      series.set(row.instance_id, s);
    }
    s.points.push({
      at: toDate(row.bucket).toISOString(),
      lagMs: Math.round(Number(row.lag) * 10) / 10,
      lagMaxMs: Number(row.lag_max),
      runningRuns: num(row.running),
      sseConnections: num(row.sse),
    });
  }
  return { from: from.toISOString(), to: now.toISOString(), bucketSec, series: [...series.values()] };
}