import { useCallback, useEffect, useRef, useState } from 'react'
import { api, LogEntry, ServiceDetail, ServiceUnit, wsURLPath } from './api'
import { askYes, Btn, CloseBtn, Loading, Spinner, toast } from './ui'
import { LIST_FLOOR, useRefreshMs } from './prefs'
import { useHashSel } from './hashsel'

type Filter = 'all' | 'running' | 'failed' | 'enabled'

function fmtBytes(b: number): string {
  const u = ['B', 'KiB', 'MiB', 'GiB']
  let i = 0
  while (b >= 1024 && i < u.length - 1) { b /= 1024; i++ }
  return `${b < 10 && i > 0 ? b.toFixed(1) : Math.round(b)} ${u[i]}`
}
function fmtCPU(ns: number): string {
  const s = ns / 1e9
  return s >= 3600 ? `${(s / 3600).toFixed(1)} h` : s >= 60 ? `${(s / 60).toFixed(1)} min` : `${s.toFixed(1)} s`
}
// systemd writes "Fri 2026-10-02 23:48:25 PDT", which Chromium parses and Firefox does not; read
// the fields directly, in the browser's own zone (the machine's, on a LAN), and fall back to Date.parse.
function parseSystemdTime(ts: string): number {
  const m = /(\d{4})-(\d{2})-(\d{2}) (\d{2}):(\d{2}):(\d{2})/.exec(ts)
  if (m) return new Date(+m[1], +m[2] - 1, +m[3], +m[4], +m[5], +m[6]).getTime()
  return Date.parse(ts.replace(/^[A-Za-z]{3} /, ''))
}
function since(ts?: string): string {
  if (!ts) return ''
  const t = parseSystemdTime(ts)
  if (isNaN(t)) return ts
  const s = Math.max(0, (Date.now() - t) / 1000)
  const d = Math.floor(s / 86400), h = Math.floor((s % 86400) / 3600), m = Math.floor((s % 3600) / 60)
  return (d > 0 ? `${d}d ${h}h` : h > 0 ? `${h}h ${m}m` : m > 0 ? `${m}m` : `${Math.floor(s)}s`) + ' ago'
}
const fmtTime = (ms: number) => { const d = new Date(ms); return d.toLocaleDateString(undefined, { month: 'short', day: '2-digit' }) + ' ' + d.toLocaleTimeString() }

function stateClass(u: ServiceUnit): string {
  if (u.failed) return 'bad'
  if (u.active === 'active' && u.sub === 'running') return 'ok'
  if (u.active === 'active') return 'exited'
  if (u.active === 'activating' || u.active === 'deactivating') return 'warn'
  return ''
}

// ---- log viewer: seeded from the REST fetch, then followed over a WebSocket ----
export function Logs({ unit }: { unit: string }) {
  const [lines, setLines] = useState<LogEntry[]>([])
  const [live, setLive] = useState(true)
  const [paused, setPaused] = useState(false)
  const [err, setErr] = useState('')
  const [ready, setReady] = useState(false)
  const box = useRef<HTMLDivElement>(null)
  const pausedRef = useRef(false)
  pausedRef.current = paused
  const pending = useRef<LogEntry[]>([])

  useEffect(() => {
    setLines([]); setErr(''); setReady(false); pending.current = []
    let closed = false
    let readyTimer: number | undefined
    let sock: WebSocket | null = null
    let retry: number | undefined
    // fixed when the log opens, for the same reason as a terminal's: a reconnect must not
    // follow the console to another machine
    const url = wsURLPath(`/api/services/${encodeURIComponent(unit)}/logs/tail?n=200`)
    const connect = () => {
      if (closed) return
      const s = new WebSocket(url)
      sock = s
      s.onopen = () => { setLive(true); setErr(''); readyTimer = window.setTimeout(() => setReady(true), 1500) }
      s.onmessage = (ev) => {
        setReady(true)
        const e = JSON.parse(ev.data) as LogEntry
        if (pausedRef.current) { pending.current.push(e); return }
        setLines((prev) => (prev.length > 2000 ? [...prev.slice(-1500), e] : [...prev, e]))
      }
      s.onclose = () => { if (closed) return; setLive(false); retry = window.setTimeout(connect, 3000) }
      s.onerror = () => { setErr('log stream disconnected'); s.close() }
    }
    connect()
    return () => { closed = true; clearTimeout(retry); clearTimeout(readyTimer); sock?.close() }
  }, [unit])

  // Resume: flush what arrived while paused.
  useEffect(() => {
    if (paused || pending.current.length === 0) return
    const p = pending.current; pending.current = []
    setLines((prev) => [...prev, ...p].slice(-2000))
  }, [paused])

  useEffect(() => { if (!paused && box.current) box.current.scrollTop = box.current.scrollHeight }, [lines, paused])

  return (
    <div className="logs">
      <div className="logs-bar">
        <span className={'dot ' + (live ? 'ok' : 'bad')} /> <span className="muted">{live ? 'following' : 'reconnecting…'}{err && ` · ${err}`}</span>
        <span className="spacer" />
        <button className="btn" onClick={() => setPaused(!paused)}>{paused ? `Resume${pending.current.length ? ` (${pending.current.length})` : ''}` : 'Pause'}</button>
        <button className="btn" onClick={() => setLines([])}>Clear</button>
      </div>
      <div className="log-lines" ref={box}>
        {lines.length === 0 && (ready ? <div className="muted">No journal entries.</div> : <div className="muted"><Spinner /> loading journal…</div>)}
        {lines.map((l, i) => (
          <div key={i} className={'log' + (l.p <= 3 ? ' err' : l.p === 4 ? ' warn' : l.p >= 7 ? ' debug' : '')}>
            <span className="lt">{fmtTime(l.t)}</span>
            <span className="li">{l.ident}{l.pid ? `[${l.pid}]` : ''}</span>
            <span className="lm">{l.msg}</span>
          </div>
        ))}
      </div>
    </div>
  )
}

// ---- detail pane ----
function Detail({ name, onChanged, onBack }: { name: string; onChanged: () => void; onBack: () => void }) {
  const [d, setD] = useState<ServiceDetail | null>(null)
  const [tab, setTab] = useState<'logs' | 'file'>('logs')
  const [file, setFile] = useState<string>('')
  const [busy, setBusy] = useState('')
  const [err, setErr] = useState('')

  const load = useCallback(async () => {
    try { setD(await api.service(name)); setErr('') } catch (e) { setErr(e instanceof Error ? e.message : 'failed') }
  }, [name])
  const rate = useRefreshMs(LIST_FLOOR)
  useEffect(() => { setD(null); setFile(''); setTab('logs'); load() }, [load])
  useEffect(() => { const t = setInterval(load, rate); return () => clearInterval(t) }, [load, rate])
  useEffect(() => { if (tab === 'file' && !file) api.serviceFile(name).then((r) => setFile(r.content)).catch((e) => setFile(String(e))) }, [tab, file, name])

  async function act(action: string) {
    const confirmFor: Record<string, string> = { stop: 'Stop', restart: 'Restart', disable: 'Disable' }
    if (confirmFor[action] && !await askYes(`${confirmFor[action]} ${name}?`)) return
    setBusy(action); setErr('')
    try { await api.serviceAction(name, action); await load(); onChanged(); toast(`${name}: ${action} ok`) }
    catch (e) { setErr(e instanceof Error ? e.message : 'failed'); toast(`${name}: ${action} failed`, 'err') }
    finally { setBusy('') }
  }

  if (!d) return <div className="svc-detail"><button className="btn back" onClick={onBack}>‹ Services</button>{err ? <div className="error">{err}</div> : <Loading label="Loading service…" />}</div>
  const p = d.props
  const running = d.active === 'active'
  const enabled = d.enabled === 'enabled'
  const Btn = ({ a, label }: { a: string; label: string }) => <button className="btn" disabled={!!busy} onClick={() => act(a)}>{busy === a && <Spinner />}{label}</button>

  return (
    <div className="svc-detail">
      <CloseBtn onClick={onBack} />
      <button className="btn back" onClick={onBack}>‹ Services</button>
      <div className="svc-head">
        <span className={'sdot ' + stateClass(d)} />
        <h2>{d.name}</h2>
      </div>
      <div className="muted">{d.description}</div>
      <div className="svc-actions">
        {running ? <Btn a="stop" label="Stop" /> : <Btn a="start" label="Start" />}
        <Btn a="restart" label="Restart" />
        {p.ExecReload || d.sub === 'running' ? <Btn a="reload" label="Reload" /> : null}
        {enabled ? <Btn a="disable" label="Disable" /> : d.enabled === 'static' || d.enabled === 'masked' ? null : <Btn a="enable" label="Enable" />}
        {d.failed && <Btn a="reset-failed" label="Reset failed" />}
      </div>
      {err && <div className="error">{err}</div>}

      <div className="props">
        <div><span className="k">State</span><span>{d.active} ({d.sub}){d.failed && p.Result ? ` · ${p.Result}` : ''}</span></div>
        <div><span className="k">Enabled</span><span>{d.enabled || '—'}</span></div>
        <div><span className="k">Since</span><span>{running ? since(p.ActiveEnterTimestamp) : since(p.InactiveEnterTimestamp)}</span></div>
        {p.MainPID && p.MainPID !== '0' && <div><span className="k">PID</span><span>{p.MainPID}</span></div>}
        {p.MemoryCurrent && <div><span className="k">Memory</span><span>{fmtBytes(+p.MemoryCurrent)}{p.MemoryPeak ? ` (peak ${fmtBytes(+p.MemoryPeak)})` : ''}</span></div>}
        {p.CPUUsageNSec && <div><span className="k">CPU time</span><span>{fmtCPU(+p.CPUUsageNSec)}</span></div>}
        {p.TasksCurrent && <div><span className="k">Tasks</span><span>{p.TasksCurrent}</span></div>}
        {p.NRestarts && p.NRestarts !== '0' && <div><span className="k">Restarts</span><span>{p.NRestarts}</span></div>}
        {p.User && <div><span className="k">User</span><span>{p.User}</span></div>}
        {p.FragmentPath && <div><span className="k">Unit file</span><span className="mono">{p.FragmentPath}</span></div>}
      </div>

      <div className="tabs">
        <button className={tab === 'logs' ? 'on' : ''} onClick={() => setTab('logs')}>Logs</button>
        <button className={tab === 'file' ? 'on' : ''} onClick={() => setTab('file')}>Unit file</button>
      </div>
      {tab === 'logs' ? <Logs unit={name} /> : <pre className="unit-file">{file || <span className="muted"><Spinner /> loading…</span>}</pre>}
    </div>
  )
}

// ---- page ----
export default function Services() {
  const [units, setUnits] = useState<ServiceUnit[]>([])
  const [err, setErr] = useState('')
  const [q, setQ] = useState('')
  const [filter, setFilter] = useState<Filter>('all')
  const [hashSel, setHashSel] = useHashSel('services') // the selected unit lives in the URL
  const sel = hashSel || null, setSel = (v: string | null) => setHashSel(v ?? '')
  const [loaded, setLoaded] = useState(false)

  const load = useCallback(async () => {
    try { setUnits(await api.services()); setErr('') } catch (e) { setErr(e instanceof Error ? e.message : 'failed') }
    finally { setLoaded(true) }
  }, [])
  const rate = useRefreshMs(LIST_FLOOR)
  useEffect(() => { load() }, [load])
  useEffect(() => { const t = setInterval(() => { if (document.visibilityState === 'visible') load() }, rate); return () => clearInterval(t) }, [load, rate])

  const needle = q.trim().toLowerCase()
  const shown = units.filter((u) => {
    if (filter === 'running' && !(u.active === 'active' && u.sub === 'running')) return false
    if (filter === 'failed' && !u.failed) return false
    if (filter === 'enabled' && u.enabled !== 'enabled') return false
    return !needle || u.name.toLowerCase().includes(needle) || u.description.toLowerCase().includes(needle)
  })
  const counts = {
    running: units.filter((u) => u.active === 'active' && u.sub === 'running').length,
    failed: units.filter((u) => u.failed).length,
    enabled: units.filter((u) => u.enabled === 'enabled').length,
  }

  return (
    <div className={'svc' + (sel ? ' has-sel' : '')}>
      <div className="svc-list">
        <div className="svc-tools">
          <div className="tools-row"><input placeholder="filter services" value={q} onChange={(e) => setQ(e.target.value)} /><Btn className="btn" title="reload" onClick={load}>↻</Btn></div>
          <div className="chips">
            {([['all', `All ${units.length}`], ['running', `Running ${counts.running}`], ['failed', `Failed ${counts.failed}`], ['enabled', `Enabled ${counts.enabled}`]] as [Filter, string][]).map(([f, label]) => (
              <button key={f} className={'chip' + (filter === f ? ' on' : '') + (f === 'failed' && counts.failed ? ' bad' : '')} onClick={() => setFilter(f)}>{label}</button>
            ))}
          </div>
        </div>
        {err && units.length === 0 && loaded
          ? <div className="notice" style={{ margin: 8 }}>{err}</div> // a host with no systemd, or one that is unreachable: not a filter result
          : err && <div className="error">{err}</div>}
        <div className="svc-rows">
          {!loaded && <Loading label="Listing services…" />}
          {shown.map((u) => (
            <div key={u.name} className={'svc-row' + (u.name === sel ? ' active' : '')} onClick={() => setSel(u.name)}>
              <span className={'sdot ' + stateClass(u)} />
              <span className="svc-name">
                <span className="n">{u.name.replace(/\.service$/, '')}</span>
                <span className="d">{u.description}</span>
              </span>
              <span className="svc-state">{u.failed ? 'failed' : u.sub}{u.enabled === 'enabled' ? '' : u.enabled ? ` · ${u.enabled}` : ''}</span>
            </div>
          ))}
          {loaded && shown.length === 0 && !(err && units.length === 0) && <div className="muted" style={{ padding: 12 }}>Nothing matches.</div>}
        </div>
      </div>
      {sel ? <Detail name={sel} onChanged={load} onBack={() => setSel(null)} /> : <div className="svc-empty muted">Select a service.</div>}
    </div>
  )
}