// File: frontend/app/(auth)/login/page.jsx
"use client";

import { useState, useMemo, Suspense } from "react";
import { useSearchParams, useRouter } from "next/navigation";
import {
  Card, CardHeader, CardTitle, CardDescription, CardContent, CardFooter,
} from "@/components/ui/card";
import { Label } from "@/components/ui/label";
import { Input } from "@/components/ui/input";
import { Button } from "@/components/ui/button";
import { Alert, AlertDescription } from "@/components/ui/alert";

const API_BASE = (process.env.NEXT_PUBLIC_API_BASE || "").replace(/\/$/, "");
const DEBUG =
  String(process.env.NEXT_PUBLIC_DEBUG_AUTH || "").trim() !== "" &&
  process.env.NEXT_PUBLIC_DEBUG_AUTH !== "0" &&
  process.env.NEXT_PUBLIC_DEBUG_AUTH !== "false";

function dlog(...args) {
  if (DEBUG && typeof window !== "undefined") console.debug("[login]", ...args);
}

function LoginForm() {
  const router = useRouter();
  const searchParams = useSearchParams();
  const nextPath = useMemo(() => searchParams.get("next") || "/dashboard", [searchParams]);

  const [username, setUsername] = useState("");
  const [password, setPassword] = useState("");
  const [showPw, setShowPw] = useState(false);
  const [submitting, setSubmitting] = useState(false);
  const [err, setErr] = useState("");

  // Helper function to verify session is ready after login
  async function verifySessionIsReady() {
    const MAX_RETRIES = 5;
    const RETRY_DELAY = 300; // ms

    for (let i = 0; i < MAX_RETRIES; i++) {
      const me = await fetch(`${API_BASE}/api/auth/me`, {
        method: "GET",
        credentials: "include",
        cache: "no-store",
      }).then(r => r.ok ? r.json() : null).catch(() => null);

      if (me?.ok) return true;
      await new Promise(resolve => setTimeout(resolve, RETRY_DELAY));
    }
    return false;
  }

  async function onSubmit(e) {
    e.preventDefault();
    setErr("");

    if (!username.trim() || !password) {
      setErr("กรอกชื่อผู้ใช้และรหัสผ่านให้ครบ");
      return;
    }

    try {
      setSubmitting(true);
      dlog("API_BASE =", API_BASE || "(empty → relative path)"); dlog("nextPath =", nextPath);

      const res = await fetch(`${API_BASE}/api/auth/login`, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        credentials: "include",         // << ใช้คุกกี้
        cache: "no-store",
        body: JSON.stringify({ username, password }),
      });

      dlog("status =", res.status, "ctype =", res.headers.get("content-type"));
      let data = {};
      try { data = await res.json(); } catch {}

      if (!res.ok) {
        const msg =
          data?.error === "INVALID_CREDENTIALS"
            ? "ชื่อผู้ใช้หรือรหัสผ่านไม่ถูกต้อง"
            : data?.error || `เข้าสู่ระบบไม่สำเร็จ (HTTP ${res.status})`;
        setErr(msg);
        return;
      }

      // ✅ ยืนยันว่าเซสชันพร้อมใช้งานก่อน (กัน redirect วน)
      // ✅ รอ session ให้พร้อมจริง (retry สูงสุด ~1.5s)
      const ok = await verifySessionIsReady();
      if (!ok) {
        setErr("ล็อกอินสำเร็จ แต่ยังไม่เห็นเซสชันจากเซิร์ฟเวอร์ (ลองใหม่หรือตรวจคุกกี้)");
        return;
      }

      // ✅ ใช้ hard navigation ให้ SSR เห็นคุกกี้แน่นอน
      if (typeof window !== "undefined") {
        window.location.href = nextPath || "/dashboard";
      } else {
        router.replace(nextPath || "/dashboard");
      }
    } catch (e) {
      dlog("exception =", e);
      setErr("เชื่อมต่อเซิร์ฟเวอร์ไม่ได้ กรุณาลองใหม่");
    } finally {
      setSubmitting(false);
    }
  }

  return (
    <div className="grid min-h-[calc(100vh-4rem)] place-items-center p-4">
      <Card className="w-full max-w-md border-0 shadow-xl ring-1 ring-black/5 bg-white/90 backdrop-blur">
        <CardHeader className="space-y-1">
          <CardTitle className="text-2xl font-bold text-sky-800">เข้าสู่ระบบ</CardTitle>
          <CardDescription className="text-sky-700">Document Management System • LCBP3</CardDescription>
        </CardHeader>

        <CardContent>
          {err ? (
            <Alert className="mb-4"><AlertDescription>{err}</AlertDescription></Alert>
          ) : null}

          <form onSubmit={onSubmit} className="grid gap-4">
            <div className="grid gap-2">
              <Label htmlFor="username">ชื่อผู้ใช้</Label>
              <Input
                id="username" autoFocus autoComplete="username"
                value={username} onChange={(e) => setUsername(e.target.value)}
                placeholder="เช่น superadmin" disabled={submitting}
              />
            </div>

            <div className="grid gap-2">
              <Label htmlFor="password">รหัสผ่าน</Label>
              <div className="relative">
                <Input
                  id="password" type={showPw ? "text" : "password"} autoComplete="current-password"
                  value={password} onChange={(e) => setPassword(e.target.value)}
                  placeholder="••••••••" disabled={submitting} className="pr-10"
                />
                <button
                  type="button" onClick={() => setShowPw((v) => !v)}
                  className="absolute inset-y-0 px-2 my-auto text-xs bg-white border rounded-md right-2 hover:bg-slate-50"
                  aria-label={showPw ? "ซ่อนรหัสผ่าน" : "แสดงรหัสผ่าน"} disabled={submitting}
                >
                  {showPw ? "Hide" : "Show"}
                </button>
              </div>
            </div>

            <Button type="submit" disabled={submitting} className="mt-2 bg-sky-700 hover:bg-sky-800">
              {submitting ? <span className="inline-flex items-center gap-2"><Spinner /> กำลังเข้าสู่ระบบ…</span> : "เข้าสู่ระบบ"}
            </Button>

            {DEBUG ? (
              <p className="mt-2 text-xs text-slate-500">
                DEBUG: NEXT_PUBLIC_API_BASE = <code>{API_BASE || "(empty)"}</code>
              </p>
            ) : null}
          </form>
        </CardContent>

        <CardFooter className="text-xs text-center text-slate-500">
          &copy; {new Date().getFullYear()} np-dms.work
        </CardFooter>
      </Card>
    </div>
  );
}

export default function LoginPage() {
  return (
    <Suspense fallback={<LoginPageSkeleton />}>
      <LoginForm />
    </Suspense>
  );
}

function LoginPageSkeleton() {
  return (
    <div className="grid min-h-[calc(100vh-4rem)] place-items-center p-4">
      <Card className="w-full max-w-md border-0 shadow-xl ring-1 ring-black/5 bg-white/90 backdrop-blur">
        <CardHeader className="space-y-1">
          <CardTitle className="text-2xl font-bold text-sky-800">เข้าสู่ระบบ</CardTitle>
          <CardDescription className="text-sky-700">Document Management System • LCBP3</CardDescription>
        </CardHeader>
        <CardContent>
          {/* ✅ ปรับปรุง Skeleton ให้สมจริงขึ้น */}
          <div className="grid gap-4">
            <div className="grid gap-2">
              <div className="w-20 h-4 rounded bg-slate-200 animate-pulse"></div>
              <div className="h-10 rounded bg-slate-200 animate-pulse"></div>
            </div>
            <div className="grid gap-2">
              <div className="w-16 h-4 rounded bg-slate-200 animate-pulse"></div>
              <div className="h-10 rounded bg-slate-200 animate-pulse"></div>
            </div>
            <div className="h-10 mt-2 rounded bg-slate-200 animate-pulse"></div>
          </div>
        </CardContent>
        {/* ✅ เพิ่ม Skeleton สำหรับ Footer */}
        <CardFooter className="flex justify-center">
          <div className="w-48 h-4 rounded bg-slate-200 animate-pulse"></div>
        </CardFooter>
      </Card>
    </div>
  );
}

function Spinner() {
  return (
    <svg className="animate-spin size-4" viewBox="0 0 24 24" fill="none" aria-hidden="true">
      <circle className="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" strokeWidth="4" />
      <path className="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8v4a4 4 0 00-4 4H4z" />
    </svg>
  );
}