import { isIP } from 'node:net'
import { homedir } from 'node:os'
import { basename, resolve } from 'node:path'

export interface ServerConfig {
  host: string
  port: number
  upstream: URL
  allowedHosts: ReadonlySet<string>
  home: string
  mediaRoot: string
  attachmentsRoot: string
  imagesRoot: string
  mediaOwner: string
  tlsCert?: string
  tlsKey?: string
  allowInsecureLan: boolean
  insecureLan: boolean
  production: boolean
  superviseDashboard?: boolean
  yaoyaoPluginSource?: string
}

export const DEFAULT_YAOYAO_PLUGIN_SOURCE = 'https://git.samien.cn/samien/hermes-yaoyao.git#hermes-plugins/yaoyao'

function flag(value: string | undefined): boolean {
  return value === '1' || value?.toLowerCase() === 'true'
}

function parsePort(value: string | undefined): number {
  const port = Number(value ?? '8800')
  if (!Number.isInteger(port) || port < 1 || port > 65_535) {
    throw new Error('HERMES_YAOYAO_PORT must be an integer between 1 and 65535')
  }
  return port
}

function parseUpstream(value: string | undefined): URL {
  const upstream = new URL(value ?? 'http://127.0.0.1:9119')
  if (!['http:', 'https:'].includes(upstream.protocol)) {
    throw new Error('HERMES_YAOYAO_UPSTREAM must use http or https')
  }
  if (upstream.username || upstream.password || upstream.search || upstream.hash) {
    throw new Error('HERMES_YAOYAO_UPSTREAM must not contain credentials, query, or fragment')
  }
  upstream.pathname = upstream.pathname.replace(/\/+$/, '') || '/'
  return upstream
}

function parsePluginSource(value: string | undefined): string {
  const source = value?.trim() || DEFAULT_YAOYAO_PLUGIN_SOURCE
  if (source.length > 2_048 || /[\u0000-\u001f\u007f]/.test(source)) {
    throw new Error('HERMES_YAOYAO_PLUGIN_SOURCE is invalid')
  }
  if (source.startsWith('https://') || source.startsWith('http://')) {
    const url = new URL(source)
    if (url.username || url.password) {
      throw new Error('HERMES_YAOYAO_PLUGIN_SOURCE must not contain credentials')
    }
  } else if (!source.startsWith('git@') && !source.startsWith('ssh://')) {
    throw new Error('HERMES_YAOYAO_PLUGIN_SOURCE must be an HTTPS or SSH Git source')
  }
  return source
}

function normalizeConfiguredHost(raw: string): string {
  const value = raw.trim().toLowerCase()
  if (!value) return ''
  if (value.startsWith('[') && value.endsWith(']')) return value.slice(1, -1)
  return value.replace(/\.$/, '')
}

export function isLoopbackHost(host: string): boolean {
  const normalized = normalizeConfiguredHost(host)
  if (normalized === 'localhost' || normalized === '::1') return true
  if (isIP(normalized) === 4) return normalized.split('.')[0] === '127'
  return false
}

export function isPrivateHost(host: string): boolean {
  const normalized = normalizeConfiguredHost(host)
  if (isLoopbackHost(normalized)) return true
  if (isIP(normalized) === 4) {
    const parts = normalized.split('.').map(Number)
    return parts[0] === 10
      || (parts[0] === 100 && parts[1]! >= 64 && parts[1]! <= 127)
      || (parts[0] === 169 && parts[1] === 254)
      || (parts[0] === 172 && parts[1]! >= 16 && parts[1]! <= 31)
      || (parts[0] === 192 && parts[1] === 168)
  }
  if (isIP(normalized) === 6) {
    return normalized.startsWith('fc')
      || normalized.startsWith('fd')
      || /^fe[89ab]/.test(normalized)
  }
  return false
}

export function isLoopbackUpstream(upstream: URL): boolean {
  return isLoopbackHost(upstream.hostname)
}

export function loadServerConfig(
  env: NodeJS.ProcessEnv = process.env,
): ServerConfig {
  const host = env.HERMES_YAOYAO_HOST?.trim() || '127.0.0.1'
  const port = parsePort(env.HERMES_YAOYAO_PORT)
  const upstream = parseUpstream(env.HERMES_YAOYAO_UPSTREAM)
  const home = resolve(env.HERMES_YAOYAO_HOME?.trim() || `${homedir()}/.hermes-yaoyao`)
  const mediaRoot = resolve(env.HERMES_YAOYAO_MEDIA_ROOT?.trim() || `${homedir()}/Agents`)
  const attachmentsRoot = resolve(`${homedir()}/.hermes/attachments`)
  const imagesRoot = resolve(`${homedir()}/.hermes/images`)
  const tlsCert = env.HERMES_YAOYAO_TLS_CERT?.trim() || undefined
  const tlsKey = env.HERMES_YAOYAO_TLS_KEY?.trim() || undefined
  if (Boolean(tlsCert) !== Boolean(tlsKey)) {
    throw new Error('HERMES_YAOYAO_TLS_CERT and HERMES_YAOYAO_TLS_KEY must be set together')
  }
  const allowInsecureLan = flag(env.HERMES_YAOYAO_ALLOW_INSECURE_LAN)
  const production = env.NODE_ENV === 'production'
  const superviseDashboard = flag(env.HERMES_YAOYAO_SUPERVISE_DASHBOARD)
  const yaoyaoPluginSource = parsePluginSource(env.HERMES_YAOYAO_PLUGIN_SOURCE)
  const insecureLan = !tlsCert && !isLoopbackHost(host)
  if (production && insecureLan && !allowInsecureLan) {
    throw new Error(
      'Plain HTTP on a non-loopback host requires HERMES_YAOYAO_ALLOW_INSECURE_LAN=1',
    )
  }
  const allowedHosts = new Set(
    (env.HERMES_YAOYAO_ALLOWED_HOSTS ?? '')
      .split(',')
      .map(normalizeConfiguredHost)
      .filter(Boolean),
  )
  return {
    host,
    port,
    upstream,
    allowedHosts,
    home,
    mediaRoot,
    attachmentsRoot,
    imagesRoot,
    mediaOwner: basename(homedir()),
    tlsCert,
    tlsKey,
    allowInsecureLan,
    insecureLan,
    production,
    superviseDashboard,
    yaoyaoPluginSource,
  }
}