// Pure, dependency-free logic for the Door epic. No Supabase/React/Next.
// Unit-tested directly. The card UID is a credential, so the canonical
// masking lives here and is reused everywhere a non-manager could see it.

export function last4(uid: string): string {
  return uid.length <= 4 ? uid : uid.slice(-4)
}

// "••••AB12" — never reveals more than the last 4 characters. For a UID of 4
// or fewer characters nothing is revealed.
export function maskCardUid(uid: string): string {
  if (uid.length <= 4) return '•'.repeat(uid.length || 4)
  return '•'.repeat(uid.length - 4) + uid.slice(-4)
}

// ─── Known door controllers (shown in the UI, with source links) ────────────
// The app is cloud-hosted, so a connection's target may be a publicly
// reachable controller/proxy OR a VPN-reachable LAN device. The adapter is
// not assumed to be on a private network; the SSRF guard pins the exact host
// (public or private) and always blocks metadata/link-local + redirects.

export type KnownController = {
  id: string
  label: string
  adapter: 'native_heatsync' | 'generic_http'
  repos: { label: string; url: string }[]
  note: string
}

export const KNOWN_DOOR_CONTROLLERS: KnownController[] = [
  {
    id: 'heatsync',
    label: 'HeatSync / 23b Open Source Access Control (native)',
    adapter: 'native_heatsync',
    repos: [
      { label: 'heatsynclabs/Open-Source-Access-Control-Web-Interface', url: 'https://github.com/heatsynclabs/Open-Source-Access-Control-Web-Interface' },
      { label: 'zyphlar/Open_Access_Control_Ethernet (23b lineage)', url: 'https://github.com/zyphlar/Open_Access_Control_Ethernet' },
    ],
    note: 'Arduino HTTP query-string controller. Built-in verb encoding (fixed-width, password as a query param). Point base_url at the controller or a proxy that reaches it.',
  },
  {
    id: 'generic',
    label: 'Other / generic HTTP controller',
    adapter: 'generic_http',
    repos: [],
    note: 'Any controller you can drive over HTTP. Configure a per-verb URL/query template with {slot}, {tag}, {perm}, {door}, {pw} placeholders.',
  },
]

export function controllerForAdapter(adapter: string): KnownController | undefined {
  return KNOWN_DOOR_CONTROLLERS.find(c => c.adapter === adapter)
}

// ─── SSRF guard (the dangerous part) ─────────────────────────────────────────
// A door connection deliberately targets a LAN device, so private ranges are
// allowed — but ONLY the exact host the admin pinned, and never the cloud
// metadata / link-local range. The executor additionally forbids redirects
// and caps response size/time; this pure function decides if a target URL is
// allowed to be called at all.

// Always-blocked, regardless of pin: IMDS / link-local and unspecified.
// Block policy applied to a RESOLVED numeric IP (defeats DNS-rebind: the
// executor resolves once, checks every address here, then connects to the
// validated IP literal so fetch performs no second resolution). RFC1918/LAN
// (10/8, 172.16/12, 192.168/16) and ULA/GUA IPv6 are intentionally ALLOWED
// (door controllers live there); only loopback, unspecified, link-local and
// cloud-metadata are blocked. Unrecognizable input fails closed.
export function isBlockedDoorIp(ip: string): boolean {
  let h = ip.trim().toLowerCase().replace(/^\[|\]$/g, '')
  const mapped = h.match(/^::ffff:(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})$/)
  if (mapped) h = mapped[1]
  if (h.includes(':')) {
    if (h === '::1' || h === '::' || h === '0:0:0:0:0:0:0:0') return true
    if (h === 'fd00:ec2::254') return true            // AWS IPv6 IMDS
    if (h.startsWith('fe80:') || h.startsWith('fe80::')) return true // link-local
    return false                                       // other IPv6 (ULA/GUA/LAN) allowed
  }
  const m = h.match(/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/)
  if (!m) return true                                  // not a clean IPv4 -> fail closed
  const o = m.slice(1).map(Number)
  if (o.some(n => n > 255)) return true
  if (o[0] === 127) return true                        // loopback 127.0.0.0/8
  if (o[0] === 0) return true                          // 0.0.0.0/8 (incl. unspecified)
  if (o[0] === 169 && o[1] === 254) return true        // link-local + 169.254.169.254 metadata
  return false                                         // RFC1918 / LAN / public allowed
}

export function isAlwaysBlockedHost(host: string): boolean {
  const h = host.toLowerCase().replace(/^\[|\]$/g, '')
  if (h === '169.254.169.254' || h === 'metadata' || h === 'metadata.google.internal') return true
  if (h.startsWith('169.254.')) return true // IPv4 link-local (includes IMDS)
  if (h === '0.0.0.0' || h === '::' || h === '0:0:0:0:0:0:0:0') return true
  if (h === 'fd00:ec2::254') return true // AWS IPv6 IMDS
  if (h.startsWith('fe80:')) return true // IPv6 link-local
  return false
}

// Normalize a host for pin comparison. Accepts either a bare hostname/IP or
// what an admin pasted (scheme, userinfo, port, path, brackets) and reduces
// it to just the host identity, so the pinned host and the request host
// compare apples-to-apples. IPv6 is handled: `[::1]`, `[::1]:8080` and
// `http://[2001:db8::1]/` all normalize to the inner address; a bare IPv6
// (`fe80::1`) is kept whole (no port concept). Plain `host:port` drops the
// port. This only strips transport decoration; it never rewrites the host
// identity, so it cannot widen what the SSRF guard allows (mismatches still
// fail closed, and `isAlwaysBlockedHost` runs independently).
export function normalizeHost(input: string): string {
  let h = input.trim().toLowerCase()
  h = h.replace(/^[a-z][a-z0-9+.-]*:\/\//, '') // scheme://
  h = h.replace(/^[^/@]*@/, '')                // userinfo@
  h = h.split(/[/?#]/)[0]                       // path/query/fragment
  if (h.startsWith('[')) {
    const end = h.indexOf(']')
    return end === -1 ? h.slice(1) : h.slice(1, end) // [ipv6](:port)? -> ipv6
  }
  const colons = (h.match(/:/g) ?? []).length
  if (colons >= 2) return h          // bare IPv6, no port concept
  if (colons === 1) return h.split(':')[0] // host:port -> host
  return h
}

export type DoorTarget =
  | { ok: true; url: string; host: string }
  | { ok: false; reason: string }

// Validate a fully-formed request URL against the connection's pinned host.
// pinnedHost is exactly what the admin entered (hostname or IP, optional
// :port is compared on the host only). The request host must equal the pin
// (case-insensitive) and must not be an always-blocked address.
export function validateDoorTarget(rawUrl: string, pinnedHost: string): DoorTarget {
  let u: URL
  try {
    u = new URL(rawUrl)
  } catch {
    return { ok: false, reason: 'The request URL is not a valid URL.' }
  }
  if (u.protocol !== 'http:' && u.protocol !== 'https:') {
    return { ok: false, reason: 'Only http and https are allowed.' }
  }
  const rawHost = u.hostname.toLowerCase()
  const host = normalizeHost(rawHost)
  const pin = normalizeHost(pinnedHost)
  if (!pin) return { ok: false, reason: 'This connection has no pinned host.' }
  if (isAlwaysBlockedHost(rawHost) || isAlwaysBlockedHost(host)) {
    return { ok: false, reason: 'That host is blocked (link-local / metadata).' }
  }
  if (host !== pin) {
    return { ok: false, reason: `Request host "${host}" does not match the pinned host "${pin}".` }
  }
  return { ok: true, url: u.toString(), host }
}

// ─── HeatSync native adapter encoders ────────────────────────────────────────
// Firmware (zyphlar/Open_Access_Control_Ethernet.ino, re-verified 2026-05-17)
// parses FIXED-WIDTH ZERO-PADDED query params by byte offset: user slot = 3
// digits, perm mask = 3 digits, tag = 8 hex chars, password = the shared
// secret. Auth is satisfied when "?e=" or "&e=" is present, so every
// privileged verb appends "&e=<pw>". Getting the widths wrong addresses the
// WRONG slot — so these are pure and unit-tested.

function pad(n: number, width: number): string {
  return String(n).padStart(width, '0')
}

export type EncodeResult = { ok: true; query: string } | { ok: false; reason: string }

function checkSlot(slot: number): string | null {
  if (!Number.isInteger(slot) || slot < 0 || slot > 200) return 'Card slot must be an integer 0-200.'
  return null
}

export function encodeHeatSyncGrant(input: {
  slot: number
  permissionMask: number
  tagHex: string
  password: string
}): EncodeResult {
  const slotErr = checkSlot(input.slot)
  if (slotErr) return { ok: false, reason: slotErr }
  if (!Number.isInteger(input.permissionMask) || input.permissionMask < 0 || input.permissionMask > 255) {
    return { ok: false, reason: 'Permission mask must be an integer 0-255.' }
  }
  if (!/^[0-9a-fA-F]{1,8}$/.test(input.tagHex)) {
    return { ok: false, reason: 'Tag must be 1-8 hexadecimal characters.' }
  }
  if (input.password.length < 1 || input.password.length > 16) {
    return { ok: false, reason: 'Door password is missing or implausible.' }
  }
  const tag = input.tagHex.toLowerCase().padStart(8, '0')
  return {
    ok: true,
    query: `?m${pad(input.slot, 3)}&p${pad(input.permissionMask, 3)}&t${tag}&e=${input.password}`,
  }
}

export function encodeHeatSyncRevoke(slot: number, password: string): EncodeResult {
  const slotErr = checkSlot(slot)
  if (slotErr) return { ok: false, reason: slotErr }
  if (!password) return { ok: false, reason: 'Door password is missing.' }
  return { ok: true, query: `?r${pad(slot, 3)}&e=${password}` }
}

// verb: 'open1' | 'open2' | 'unlock' | 'lock' | 'arm' | 'disarm' | 'status' | 'log'
export function encodeHeatSyncControl(verb: string, password: string): EncodeResult {
  if (!password) return { ok: false, reason: 'Door password is missing.' }
  const map: Record<string, string> = {
    open1: '?o1',
    open2: '?o2',
    unlock: '?u',
    lock: '?l',
    disarm: '?1',
    arm: '?2',
    status: '?9',
    log: '?z',
  }
  const base = map[verb]
  if (!base) return { ok: false, reason: `Unknown door verb "${verb}".` }
  return { ok: true, query: `${base}&e=${password}` }
}

// ─── Generic adapter template substitution ───────────────────────────────────
// A generic connection stores a path/query template per verb with {slot},
// {tag}, {perm}, {door}, {pw} placeholders. Substitution is literal and the
// values are URL-encoded; unknown placeholders are left untouched so a
// misconfig fails loudly rather than silently calling something unintended.

export function applyTemplate(
  template: string,
  vars: Record<string, string | number>,
): string {
  return template.replace(/\{(\w+)\}/g, (m, key) =>
    key in vars ? encodeURIComponent(String(vars[key])) : m,
  )
}

// Before anything (URL, response snippet) is written to the audit log, scrub
// the shared door password: any literal occurrence, and any e=/&e= query
// value (the firmware auth param), become "<redacted>". The password is a
// credential and must never land in door_access_log.
export function redactDoorSecrets(
  text: string,
  password?: string | null,
  authParam?: string | null,
): string {
  let out = text
  if (password && password.length > 0) {
    out = out.split(password).join('<redacted>')
  }
  // The connection's actual auth query param (generic adapters may name it
  // anything, not just e=/pw=). Scrub its value regardless of the name so a
  // verbose upstream error echoing the URL cannot leak the secret even when
  // `password` is empty/unknown.
  if (authParam && /^\w+$/.test(authParam)) {
    out = out.replace(
      new RegExp(`([?&]${authParam}=)[^&\\s"']*`, 'gi'),
      '$1<redacted>',
    )
  }
  out = out.replace(/([?&](?:e|pw|password|api[_-]?key|token)=)[^&\s"']*/gi, '$1<redacted>')
  return out
}