import type { DatabaseClient } from "./database";
import { getRuntimeEnv } from "./runtime-env";
import { hashText } from "./mvp-db";

export const WECOM_IDENTITY_TTL_MS = 30 * 60 * 1_000;
const WECOM_IDENTITY_GRACE_MS = 60 * 1_000;

type WecomIdentityPayload = {
  v: 1;
  ext: string;
  uid?: string;
  name: string;
  iat: number;
  exp: number;
  jti: string;
};

export type WecomIdentity = {
  externalUserId: string;
  displayName: string;
  userId?: string;
};

export function getWecomOAuthSecret(): string {
  const secret = String(getRuntimeEnv().ADMIN_INTERNAL_TOKEN ?? "").trim();
  if (!secret) {
    throw new Error("ADMIN_INTERNAL_TOKEN 未配置，无法签发企微身份票据");
  }
  return secret;
}

function toBase64Url(bytes: Uint8Array): string {
  let binary = "";
  for (const byte of bytes) binary += String.fromCharCode(byte);
  return btoa(binary).replace(/\+/g, "-").replace(/\//g, "_").replace(/=+$/, "");
}

function fromBase64Url(value: string): Uint8Array {
  const padded = value
    .replace(/-/g, "+")
    .replace(/_/g, "/")
    .padEnd(Math.ceil(value.length / 4) * 4, "=");
  const binary = atob(padded);
  const bytes = new Uint8Array(binary.length);
  for (let index = 0; index < binary.length; index += 1) {
    bytes[index] = binary.charCodeAt(index);
  }
  return bytes;
}

async function hmacSha256(secret: string, data: string): Promise<Uint8Array> {
  const key = await crypto.subtle.importKey(
    "raw",
    new TextEncoder().encode(secret),
    { name: "HMAC", hash: "SHA-256" },
    false,
    ["sign"],
  );
  const signature = await crypto.subtle.sign(
    "HMAC",
    key,
    new TextEncoder().encode(data),
  );
  return new Uint8Array(signature);
}

function constantTimeEquals(a: Uint8Array, b: Uint8Array): boolean {
  if (a.length !== b.length) return false;
  let diff = 0;
  for (let index = 0; index < a.length; index += 1) {
    diff |= a[index] ^ b[index];
  }
  return diff === 0;
}

export async function signWecomIdentityTicket(
  externalUserId: string,
  displayName: string,
  options: {
    secret?: string;
    nowMs?: number;
    ttlMs?: number;
    userId?: string;
  } = {},
): Promise<{ ticket: string; expiresIn: number }> {
  const secret = options.secret ?? getWecomOAuthSecret();
  const issuedAt = options.nowMs ?? Date.now();
  const ttl = options.ttlMs ?? WECOM_IDENTITY_TTL_MS;
  const ext = String(externalUserId ?? "").trim();
  const uid = String(options.userId ?? "").trim().slice(0, 64);
  if (!ext && !uid) throw new Error("缺少企微身份 ID（外部联系人或内部成员）");
  const payload: WecomIdentityPayload = {
    v: 1,
    ext,
    name: String(displayName ?? "").trim().slice(0, 120),
    iat: issuedAt,
    exp: issuedAt + ttl,
    jti: toBase64Url(crypto.getRandomValues(new Uint8Array(12))),
  };
  if (uid) payload.uid = uid;
  const payloadSegment = toBase64Url(
    new TextEncoder().encode(JSON.stringify(payload)),
  );
  const signature = await hmacSha256(secret, payloadSegment);
  return {
    ticket: `${payloadSegment}.${toBase64Url(signature)}`,
    expiresIn: Math.floor(ttl / 1_000),
  };
}

export async function verifyWecomIdentityTicket(
  ticket: string,
  options: { secret?: string; nowMs?: number } = {},
): Promise<WecomIdentity | null> {
  const raw = String(ticket ?? "").trim();
  const dotIndex = raw.indexOf(".");
  if (dotIndex <= 0 || dotIndex === raw.length - 1) return null;
  const payloadSegment = raw.slice(0, dotIndex);
  const signatureSegment = raw.slice(dotIndex + 1);
  if (/[^A-Za-z0-9_-]/.test(payloadSegment) || /[^A-Za-z0-9_-]/.test(signatureSegment)) {
    return null;
  }
  let payload: WecomIdentityPayload;
  try {
    payload = JSON.parse(
      new TextDecoder().decode(fromBase64Url(payloadSegment)),
    ) as WecomIdentityPayload;
  } catch {
    return null;
  }
  if (
    payload?.v !== 1 ||
    typeof payload.ext !== "string" ||
    typeof payload.exp !== "number"
  ) {
    return null;
  }
  const extId = payload.ext.trim();
  const uid =
    typeof payload.uid === "string" ? payload.uid.trim().slice(0, 64) : "";
  if (!extId && !uid) return null;
  const secret = options.secret ?? getWecomOAuthSecret();
  const expected = await hmacSha256(secret, payloadSegment);
  const provided = fromBase64Url(signatureSegment);
  if (!constantTimeEquals(expected, provided)) return null;
  const now = options.nowMs ?? Date.now();
  if (now > payload.exp + WECOM_IDENTITY_GRACE_MS) return null;
  return {
    externalUserId: extId,
    displayName: payload.name || "企微客户",
    ...(uid ? { userId: uid } : {}),
  };
}

export function wecomClaimantPartnerId(externalUserId: string): string {
  return `partner-ext-${hashText(`claimant:wecom:${externalUserId}`)}`;
}

export const WECOM_BIND_STATE_TTL_MS = 10 * 60 * 1_000;

type WecomBindStatePayload = {
  v: 2;
  uid: string;
  iat: number;
  exp: number;
  jti: string;
};

export async function signWecomBindState(
  userId: string,
  options: { secret?: string; nowMs?: number; ttlMs?: number } = {},
): Promise<string> {
  const secret = options.secret ?? getWecomOAuthSecret();
  const issuedAt = options.nowMs ?? Date.now();
  const ttl = options.ttlMs ?? WECOM_BIND_STATE_TTL_MS;
  const uid = String(userId ?? "").trim().slice(0, 64);
  if (!uid) throw new Error("缺少后台账号 ID，无法发起企微绑定");
  const payload: WecomBindStatePayload = {
    v: 2,
    uid,
    iat: issuedAt,
    exp: issuedAt + ttl,
    jti: toBase64Url(crypto.getRandomValues(new Uint8Array(12))),
  };
  const payloadSegment = toBase64Url(
    new TextEncoder().encode(JSON.stringify(payload)),
  );
  const signature = await hmacSha256(secret, payloadSegment);
  return `${payloadSegment}.${toBase64Url(signature)}`;
}

export async function verifyWecomBindState(
  state: string,
  options: { secret?: string; nowMs?: number } = {},
): Promise<{ userId: string } | null> {
  const raw = String(state ?? "").trim();
  const dotIndex = raw.indexOf(".");
  if (dotIndex <= 0 || dotIndex === raw.length - 1) return null;
  const payloadSegment = raw.slice(0, dotIndex);
  const signatureSegment = raw.slice(dotIndex + 1);
  if (/[^A-Za-z0-9_-]/.test(payloadSegment) || /[^A-Za-z0-9_-]/.test(signatureSegment)) {
    return null;
  }
  let payload: WecomBindStatePayload;
  try {
    payload = JSON.parse(
      new TextDecoder().decode(fromBase64Url(payloadSegment)),
    ) as WecomBindStatePayload;
  } catch {
    return null;
  }
  if (payload?.v !== 2 || typeof payload.uid !== "string") return null;
  const uid = payload.uid.trim().slice(0, 64);
  if (!uid) return null;
  const secret = options.secret ?? getWecomOAuthSecret();
  const expected = await hmacSha256(secret, payloadSegment);
  const provided = fromBase64Url(signatureSegment);
  if (!constantTimeEquals(expected, provided)) return null;
  const now = options.nowMs ?? Date.now();
  if (now > payload.exp + WECOM_IDENTITY_GRACE_MS) return null;
  return { userId: uid };
}

export async function resolveWecomClaimant(
  db: DatabaseClient,
  externalUserId: string,
): Promise<{ partnerId: string; matchedExisting: boolean }> {
  const ext = String(externalUserId ?? "").trim();
  if (!ext) throw new Error("缺少企微外部联系人 ID");
  const existing = await db
    .prepare("SELECT id FROM partners WHERE wecom_external_user_id = ?")
    .bind(ext)
    .first<{ id: string }>();
  if (existing?.id) {
    return { partnerId: existing.id, matchedExisting: true };
  }
  return { partnerId: wecomClaimantPartnerId(ext), matchedExisting: false };
}