import fs from "node:fs";
import path from "node:path";

import { decryptText } from "@/lib/crypto";
import { getEnv } from "@/lib/env";
import type {
  Hy2NodeRow,
  Hy2UserRow,
  ProxyGroupConfig,
} from "@/lib/store";
import { buildNodeAuthUrl, formatBytes } from "@/lib/store";

type ClashSettings = {
  template: string;
  extraProxyGroups: string;
  profileName: string;
  proxyGroups: ProxyGroupConfig[];
};

function readDefaultTemplate() {
  const filePath = path.join(process.cwd(), "app", "config", "config.yaml");
  return fs.readFileSync(filePath, "utf8").trimEnd();
}

function indent(text: string, spaces: number) {
  const prefix = " ".repeat(spaces);
  return text
    .split("\n")
    .map((line) => (line ? `${prefix}${line}` : line))
    .join("\n");
}

function renderProxy(node: Hy2NodeRow, authString: string) {
  const lines = [
    `- name: "${node.client_name || node.name}"`,
    "  type: hysteria2",
    `  server: ${node.server_host}`,
    `  port: ${node.server_port}`,
    `  password: "${authString}"`,
  ];

  if (node.sni) {
    lines.push(`  sni: ${node.sni}`);
  }

  if (node.skip_cert_verify) {
    lines.push("  skip-cert-verify: true");
  }

  lines.push("  bandwidth:");
  lines.push(`    up: ${node.bandwidth_up_mbps} mbps`);
  lines.push(`    down: ${node.bandwidth_down_mbps} mbps`);

  return lines.join("\n");
}

function renderGroupEntry(name: string, proxyNames: string[]) {
  const quoted = proxyNames.map((name) => `"${name}"`).join(", ");
  return [
    `  - name: ${name}`,
    "    type: select",
    `    proxies: [${quoted}]`,
  ].join("\n");
}

export function encodeRFC5987ValueChars(value: string) {
  return encodeURIComponent(value)
    .replace(/['()]/g, (char) => `%${char.charCodeAt(0).toString(16).toUpperCase()}`)
    .replace(/\*/g, "%2A")
    .replace(/%(7C|60|5E)/g, (_, code) =>
      String.fromCharCode(Number.parseInt(code, 16)),
    );
}

function buildAsciiFilenameFallback(value: string) {
  const ascii = value
    .normalize("NFKD")
    .replace(/[^\x20-\x7E]+/g, " ")
    .replace(/["\\]/g, "_")
    .replace(/\s+/g, " ")
    .trim();

  return ascii || "subscription";
}

export function buildSubscriptionHeaders(user: Hy2UserRow, profileName: string) {
  const expire = user.expires_at
    ? Math.round(new Date(user.expires_at).getTime() / 1000)
    : user.is_admin
      ? 4102444800
      : Math.round(Date.now() / 1000) + 3600 * 24 * 365 * 10;

  const total =
    user.is_admin || user.traffic_limit_bytes == null
      ? "9223372036854775807"
      : String(user.traffic_limit_bytes);
  const fallbackFilename = buildAsciiFilenameFallback(profileName);

  return {
    "Content-Disposition": `attachment; filename="${fallbackFilename}"; filename*=UTF-8''${encodeRFC5987ValueChars(profileName)}`,
    "Content-Type": "text/yaml; charset=utf-8",
    "Profile-Update-Interval": "12",
    "subscription-userinfo": `upload=${user.used_tx_bytes}; download=${user.used_rx_bytes}; total=${total}; expire=${expire}`,
  };
}

export function buildSubscriptionUrl(token: string, origin = getEnv().APP_URL) {
  return `${origin}/api/subscription/${token}/clash`;
}

export function buildNodeHy2Config(node: Hy2NodeRow, origin = getEnv().APP_URL) {
  const authUrl = buildNodeAuthUrl(node.slug, node.auth_token, origin);

  return [
    `listen: ${node.hy2_listen || `:${node.server_port}`}`,
    "tls:",
    "  cert: /etc/hysteria/server.crt",
    "  key: /etc/hysteria/server.key",
    "auth:",
    "  type: http",
    "  http:",
    `    url: ${authUrl}`,
    "    insecure: false",
    "trafficStats:",
    `  listen: ${node.traffic_stats_listen}`,
    `  secret: ${node.traffic_stats_secret}`,
  ].join("\n");
}

export function buildSubscriptionConfig(input: {
  user: Hy2UserRow;
  nodes: Hy2NodeRow[];
  settings: ClashSettings;
}) {
  const authPassword = decryptText(input.user.auth_secret_encrypted);
  if (!authPassword) {
    throw new Error("user_secret_unavailable");
  }

  const authString = `${input.user.username}:${authPassword}`;
  const eligibleNodes = input.nodes.filter(
    (node) => node.enabled && node.server_host && node.server_port > 0,
  );
  const nodeNameBySlug = new Map(
    eligibleNodes.map((node) => [node.slug, node.client_name || node.name]),
  );
  const proxyNames = eligibleNodes.map((node) => node.client_name || node.name);
  const proxiesBlock = eligibleNodes.map((node) => renderProxy(node, authString)).join("\n");
  const defaultTemplate = input.settings.template.trimEnd() || readDefaultTemplate();
  const renderedGroups = [
    renderGroupEntry(input.settings.profileName || "FeieProxy", proxyNames),
    ...input.settings.proxyGroups
      .map((group) => {
        const members = group.memberSlugs
          .map((slug) => nodeNameBySlug.get(slug))
          .filter((name): name is string => Boolean(name));
        if (members.length === 0) {
          return null;
        }

        return renderGroupEntry(group.name, members);
      })
      .filter((group): group is string => Boolean(group)),
  ].join("\n");
  const extraGroups = input.settings.extraProxyGroups
    .trim()
    .replace(/^proxy-groups:\s*/i, "");

  return [
    defaultTemplate,
    "",
    "proxies:",
    indent(proxiesBlock, 2),
    "",
    "proxy-groups:",
    renderedGroups,
    extraGroups ? `\n${extraGroups}` : "",
    "",
  ].join("\n");
}

export function getDefaultClashTemplate() {
  return readDefaultTemplate();
}

export function describeRemainingTraffic(user: Hy2UserRow) {
  if (user.is_admin || user.traffic_limit_bytes == null) {
    return "不限流量";
  }

  const remaining = Math.max(
    user.traffic_limit_bytes - user.used_tx_bytes - user.used_rx_bytes,
    0,
  );
  return `${formatBytes(remaining)} 剩余`;
}