import { mkdirSync, renameSync, writeFileSync } from "node:fs"
import path from "node:path"
import type { DnsRecord } from "./db"
import { env } from "./env"

const HEADER = "# Generated by dnsmasq-admin — 请勿手动编辑，每次「应用并重启」都会覆盖此文件"

/**
 * dnsmasq's `address=/domain/ip` already answers for the domain *and* every subdomain, so
 * there is no need for a separate wildcard syntax.
 */
export function renderRecord(record: DnsRecord): string {
  return record.type === "A"
    ? `address=/${record.domain}/${record.value}`
    : `cname=${record.domain},${record.value}`
}

export function renderConfig(records: DnsRecord[]): string {
  const lines = records
    .filter((record) => record.enabled)
    .map(renderRecord)

  if (lines.length === 0) {
    return `${HEADER}\n\n# 当前没有启用的记录\n`
  }

  return `${HEADER}\n\n${lines.join("\n")}\n`
}

/**
 * Regenerate the managed config file for the given records.
 *
 * Written to a sibling temp file first and then renamed, so dnsmasq can never read a
 * half-written file.
 */
export async function writeManagedConfig(records: DnsRecord[]): Promise<{
  path: string
  recordCount: number
}> {
  const dir = path.dirname(env.confPath)
  mkdirSync(dir, { recursive: true })

  const content = renderConfig(records)
  const tempPath = `${env.confPath}.${process.pid}.tmp`
  writeFileSync(tempPath, content, "utf8")
  renameSync(tempPath, env.confPath)

  return {
    path: env.confPath,
    recordCount: records.filter((record) => record.enabled).length,
  }
}