// VPN: this machine's WireGuard tunnels, and the devices on them.
//
// Per machine, like every other tab, which here is the whole point: the tunnel people dial
// into and a tunnel this machine dials out through are different machines, and showing them
// together would invite the question "which box is this actually on".
import { FormEvent, useCallback, useEffect, useState } from 'react'
import qrcode from 'qrcode-generator'
import { api, CreatedVPNPeer, VPNReport, VPNPeer, VPNTunnel } from './api'
import { fmtBytes } from './fmt'
import { Btn, Loading, askText, toast, useEscape } from './ui'
import { useRefreshMs } from './prefs'

// WireGuard says nothing when it has nothing to say, so "online" is a handshake in the last
// few minutes rather than a connection — there is no connection to have.
const ago = (iso?: string) => {
  if (!iso) return 'never'
  const s = Math.max(0, (Date.now() - new Date(iso).getTime()) / 1000)
  if (s < 60) return `${Math.floor(s)}s ago`
  if (s < 3600) return `${Math.floor(s / 60)} min ago`
  if (s < 86400) return `${Math.floor(s / 3600)} h ago`
  return `${Math.floor(s / 86400)} d ago`
}

// A public key is long and nobody reads the middle of it; the ends are what you compare.
const shortKey = (k: string) => (k.length > 16 ? `${k.slice(0, 8)}…${k.slice(-6)}` : k)

function Peer({ p, server, iface, editable, onChanged }: { p: VPNPeer; server: boolean; iface: string; editable: boolean; onChanged: () => void }) {
  const rename = async () => {
    const name = await askText(`Rename ${p.name || 'this device'}`, p.name ?? '')
    if (!name || name.trim() === p.name) return
    try { await api.editVPNPeer(iface, p.section!, { name: name.trim() }); toast('renamed'); onChanged() }
    catch (e) { toast(e instanceof Error ? e.message : 'failed', 'err') }
  }
  const remove = async () => {
    const typed = await askText(`Remove ${p.name}? Its profile stops working at once and cannot be brought back — the device would need a new one.\n\nType its name to confirm.`, '', 'Remove')
    if (typed === null) return
    try { await api.removeVPNPeer(iface, p.section!, typed.trim()); toast(`${p.name} removed`); onChanged() }
    catch (e) { toast(e instanceof Error ? e.message : 'failed', 'err') }
  }
  return (
    <div className="card iface vpn-peer">
      <div className="sub-head">
        <span className={'sdot ' + (p.online ? 'ok' : p.handshake ? '' : 'bad')} />
        <span className="dname">{p.name || <span className="muted">unnamed</span>}</span>
        {p.online && <span className="badge ok">online</span>}
        {!p.handshake && <span className="badge">never connected</span>}
        <span className="spacer" />
        <span className="muted small mono">{(p.allowed_ips ?? []).join(', ')}</span>
        {editable && p.section && <>
          <Btn className="btn" onClick={rename}>Rename</Btn>
          <Btn className="btn danger" onClick={remove}>Remove</Btn>
        </>}
      </div>
      <div className="props">
        <div><span className="k">Last handshake</span><span>{ago(p.handshake)}</span></div>
        {p.endpoint && <div><span className="k">{server ? 'Comes from' : 'Endpoint'}</span><span className="mono">{p.endpoint}</span></div>}
        <div><span className="k">Moved</span><span className="mono">↓ {fmtBytes(p.rx)} · ↑ {fmtBytes(p.tx)}</span></div>
        {!!p.keepalive && <div><span className="k">Keepalive</span><span>every {p.keepalive}s</span></div>}
        <div><span className="k">Public key</span><span className="mono" title={p.public_key}>{shortKey(p.public_key)}</span></div>
        {p.psk && <div><span className="k">Pre-shared key</span><span>in use</span></div>}
      </div>
    </div>
  )
}

function Tunnel({ t, onChanged }: { t: VPNTunnel; onChanged: () => void }) {
  const server = t.kind === 'server'
  const [adding, setAdding] = useState(false)
  const [made, setMade] = useState<CreatedVPNPeer | null>(null)
  const peers = t.peers ?? []
  const online = peers.filter((p) => p.online).length
  return (
    <>
      <div className="dash-bar">
        <h2 className="section">{t.name}</h2>
        <span className="badge">{server ? 'devices dial in' : t.kind === 'client' ? 'this machine dials out' : 'tunnel'}</span>
        <span className="spacer" />
        <span className="muted small">{server ? `${online} of ${peers.length} online` : t.exit ? `via ${t.exit}` : ''}</span>
        {t.managed && server && <Btn className="btn on" onClick={() => { setMade(null); setAdding(true) }}>+ Add device</Btn>}
      </div>
      <section className="card">
        <div className="props">
          {!!t.addrs?.length && <div><span className="k">Address</span><span className="mono">{t.addrs.join(', ')}</span></div>}
          {!!t.listen_port && <div><span className="k">Listening on</span><span className="mono">{t.listen_port}/udp</span></div>}
          {!!t.mtu && <div><span className="k">MTU</span><span>{t.mtu}</span></div>}
          <div><span className="k">Public key</span><span className="mono" title={t.public_key}>{shortKey(t.public_key)}</span></div>
          {t.fwmark && <div><span className="k">Firewall mark</span><span className="mono">{t.fwmark}</span></div>}
        </div>
      </section>
      {adding && <AddDevice t={t} onClose={() => setAdding(false)} onMade={(c) => { setAdding(false); setMade(c); onChanged() }} />}
      {made && <Profile made={made} onClose={() => setMade(null)} />}
      {peers.map((p) => <Peer key={p.public_key} p={p} server={server} iface={t.name} editable={!!t.managed} onChanged={onChanged} />)}
      {peers.length === 0 && <section className="card"><div className="empty">No peers are configured on this tunnel.</div></section>}
    </>
  )
}

// The form for a new device. The endpoint is what the device will dial from outside, so it is
// the one thing Ham Lab cannot work out for itself — remembered per machine once given.
function AddDevice({ t, onClose, onMade }: { t: VPNTunnel; onClose: () => void; onMade: (c: CreatedVPNPeer) => void }) {
  const key = `hamlab.wg.endpoint.${t.name}`
  const [name, setName] = useState('')
  const [endpoint, setEndpoint] = useState(localStorage.getItem(key) ?? '')
  const [address, setAddress] = useState('')
  const [dns, setDns] = useState('1.1.1.1, 1.0.0.1')
  const [split, setSplit] = useState(false)
  const [busy, setBusy] = useState(false)
  const [err, setErr] = useState('')
  useEscape(onClose)
  const submit = async (e: FormEvent) => {
    e.preventDefault()
    setBusy(true); setErr('')
    try {
      const made = await api.addVPNPeer(t.name, { name: name.trim(), endpoint: endpoint.trim(), address: address.trim(), dns: dns.trim(), split })
      localStorage.setItem(key, endpoint.trim())
      onMade(made)
    } catch (e) { setErr(e instanceof Error ? e.message : 'failed') }
    finally { setBusy(false) }
  }
  return (
    <form className="card addform" onSubmit={submit} style={{ marginTop: 8 }}>
      <label>Device name <input autoFocus value={name} onChange={(e) => setName(e.target.value)} placeholder="phone" spellCheck={false} required /></label>
      <label>What it dials <input value={endpoint} onChange={(e) => setEndpoint(e.target.value)} placeholder="home.example.com:51820" spellCheck={false} autoCapitalize="off" required /></label>
      <label>Address in the tunnel <input value={address} onChange={(e) => setAddress(e.target.value)} placeholder="the next free one" spellCheck={false} /></label>
      <label>DNS while connected <input value={dns} onChange={(e) => setDns(e.target.value)} placeholder="none" spellCheck={false} /></label>
      <label className="row-check"><input type="checkbox" checked={split} onChange={(e) => setSplit(e.target.checked)} /> Only route the home networks, not everything</label>
      {err && <div className="error">{err}</div>}
      <div className="svc-actions">
        <button className="btn on" disabled={busy || !name.trim() || !endpoint.trim()}>Create device</button>
        <span className="spacer" />
        <button type="button" className="btn" onClick={onClose}>Cancel</button>
      </div>
    </form>
  )
}

// The profile, once. Everything a device needs is in it, including a private key that exists
// nowhere else — so it is shown until dismissed, with the QR the WireGuard apps expect.
function Profile({ made, onClose }: { made: CreatedVPNPeer; onClose: () => void }) {
  const qr = qrcode(0, 'M')
  qr.addData(made.config)
  qr.make()
  const copy = async () => {
    try { await navigator.clipboard.writeText(made.config); toast('profile copied') }
    catch { toast('select and copy it by hand', 'err') }
  }
  const download = () => {
    const url = URL.createObjectURL(new Blob([made.config], { type: 'text/plain' }))
    const a = document.createElement('a')
    a.href = url
    a.download = `${made.name.replace(/[^a-zA-Z0-9._-]+/g, '-')}.conf`
    a.click()
    URL.revokeObjectURL(url)
  }
  return (
    <section className="card fresh vpn-profile" style={{ marginTop: 8 }}>
      <div className="sub-head"><span className="dname">{made.name}</span><span className="badge ok">created</span><span className="spacer" /><span className="muted small mono">{made.address}</span></div>
      <div className="vpn-qr">
        <img src={qr.createDataURL(5, 8)} alt={`WireGuard profile for ${made.name}`} width={220} height={220} />
        <div>
          <div className="muted small">Scan it in the WireGuard app, or copy the profile into one.</div>
          <pre className="mono vpn-conf">{made.config}</pre>
        </div>
      </div>
      <div className="svc-actions" style={{ marginTop: 8 }}>
        <Btn className="btn on" onClick={copy}>Copy profile</Btn>
        <Btn className="btn" onClick={download}>Download .conf</Btn>
        <span className="muted small">Shown once. The private key in it is not stored here — if it is lost, make the device again.</span>
        <span className="spacer" />
        <button className="btn" onClick={onClose}>Done</button>
      </div>
    </section>
  )
}

export default function VPN() {
  const [d, setD] = useState<VPNReport | null>(null)
  const [err, setErr] = useState('')
  const rate = useRefreshMs()
  const load = useCallback(async () => {
    try { setD(await api.vpn()); setErr('') } catch (e) { setErr(e instanceof Error ? e.message : 'failed') }
  }, [])
  useEffect(() => { load() }, [load])
  // Handshakes and counters move; nothing here is expensive to read.
  useEffect(() => {
    const t = setInterval(() => { if (document.visibilityState === 'visible') load() }, Math.max(5000, rate))
    return () => clearInterval(t)
  }, [load, rate])

  if (!d) return <div className="dash">{err ? <div className="notice">{err === 'not found' ? "This machine's Ham Lab is older than the VPN tab. Update it from Machines." : err}</div> : <Loading label="Reading the tunnels…" />}</div>

  // A machine running an older build answers with null rather than an empty list, and taking
  // the length of that is what a blank page is made of.
  const tunnels = d.tunnels ?? []

  return (
    <div className="dash net">
      {tunnels.length === 0 && (
        <>
          <div className="dash-bar"><h2 className="section">VPN</h2></div>
          <section className="card"><div className="empty">{d.note || 'Nothing here.'}</div>
            <div className="muted small" style={{ marginTop: 6 }}>
              Tunnels are the machine's own, so look on the one that carries them — the switcher at the top of the rail.
            </div>
          </section>
        </>
      )}
      {tunnels.map((t) => <Tunnel key={t.name} t={t} onChanged={load} />)}
      {tunnels.length > 0 && (
        <div className="muted small method" style={{ marginTop: 12 }}>
          Read from the kernel with <span className="mono">wg show</span>; names come from the configuration beside it.
          Online means a handshake in the last three minutes — WireGuard is silent when idle, so there is no connection to be in.
          Private and pre-shared keys are never read.
        </div>
      )}
    </div>
  )
}