import { useEffect, useMemo, useState } from "react";
import { useNavigate, useSearchParams } from "react-router-dom";
import { useMutation, useQuery } from "@tanstack/react-query";
import { z } from "zod";
import { zodResolver } from "@hookform/resolvers/zod";
import { useForm } from "react-hook-form";
import { Button } from "@/components/ui/button";
import { Card, CardContent, CardDescription, CardHeader, CardTitle } from "@/components/ui/card";
import { Form, FormControl, FormField, FormItem, FormLabel, FormMessage } from "@/components/ui/form";
import { Input } from "@/components/ui/input";
import { authService } from "@/services/auth.service";
import { brandingService } from "@/services/branding.service";
import { cn } from "@/lib/utils";
import { toast } from "sonner";

const schema = z
  .object({
    password: z.string().min(8, "At least 8 characters"),
    confirm: z.string(),
  })
  .refine((d) => d.password === d.confirm, { message: "Passwords must match", path: ["confirm"] });

type FormValues = z.infer<typeof schema>;

function strengthLabel(p: string): "weak" | "medium" | "strong" {
  let s = 0;
  if (p.length >= 8) s++;
  if (p.length >= 12) s++;
  if (/[A-Z]/.test(p) && /[a-z]/.test(p)) s++;
  if (/\d/.test(p)) s++;
  if (/[^A-Za-z0-9]/.test(p)) s++;
  if (s <= 2) return "weak";
  if (s <= 4) return "medium";
  return "strong";
}

export default function ResetPassword() {
  const [searchParams] = useSearchParams();
  const token = searchParams.get("token") ?? "";
  const navigate = useNavigate();
  const { data: branding } = useQuery({
    queryKey: ["branding", "current"],
    queryFn: () => brandingService.getCurrentBranding(),
  });

  const entityName = branding?.entity_name ?? "your organization";

  const form = useForm<FormValues>({
    resolver: zodResolver(schema),
    defaultValues: { password: "", confirm: "" },
  });

  const pwd = form.watch("password");
  const strength = useMemo(() => strengthLabel(pwd), [pwd]);

  useEffect(() => {
    const root = document.documentElement;
    if (branding?.primary_color) root.style.setProperty("--encoach-brand-primary", branding.primary_color);
    if (branding?.secondary_color) root.style.setProperty("--encoach-brand-secondary", branding.secondary_color);
    if (branding?.background_color) root.style.setProperty("--encoach-brand-bg", branding.background_color);
    return () => {
      root.style.removeProperty("--encoach-brand-primary");
      root.style.removeProperty("--encoach-brand-secondary");
      root.style.removeProperty("--encoach-brand-bg");
    };
  }, [branding]);

  const submitMut = useMutation({
    mutationFn: (values: FormValues) => authService.setInvitePassword({ token, password: values.password }),
    onSuccess: () => {
      toast.success("Password saved.");
      navigate("/student/placement", { replace: true });
    },
    onError: (e) => toast.error(e instanceof Error ? e.message : "Could not set password"),
  });

  const onSubmit = (values: FormValues) => {
    if (!token) {
      toast.error("Missing invite token.");
      return;
    }
    submitMut.mutate(values);
  };

  return (
    <div
      className="min-h-screen flex items-center justify-center p-6"
      style={{
        backgroundColor: "var(--encoach-brand-bg, hsl(var(--background)))",
      }}
    >
      <Card className="w-full max-w-md border shadow-lg">
        <CardHeader className="text-center space-y-1">
          <CardTitle style={{ color: "var(--encoach-brand-primary, hsl(var(--primary)))" }}>
            Welcome to {entityName}&apos;s Learning Platform
          </CardTitle>
          <CardDescription>Set a new password</CardDescription>
        </CardHeader>
        <CardContent>
          <Form {...form}>
            <form onSubmit={form.handleSubmit(onSubmit)} className="space-y-4">
              <FormField
                control={form.control}
                name="password"
                render={({ field }) => (
                  <FormItem>
                    <FormLabel>New password</FormLabel>
                    <FormControl>
                      <Input type="password" autoComplete="new-password" {...field} />
                    </FormControl>
                    <div
                      className={cn(
                        "text-xs font-medium",
                        strength === "weak" && "text-red-600",
                        strength === "medium" && "text-amber-600",
                        strength === "strong" && "text-green-600",
                      )}
                    >
                      {pwd ? `${strength.charAt(0).toUpperCase() + strength.slice(1)} password` : " "}
                    </div>
                    <FormMessage />
                  </FormItem>
                )}
              />
              <FormField
                control={form.control}
                name="confirm"
                render={({ field }) => (
                  <FormItem>
                    <FormLabel>Confirm password</FormLabel>
                    <FormControl>
                      <Input type="password" autoComplete="new-password" {...field} />
                    </FormControl>
                    <FormMessage />
                  </FormItem>
                )}
              />
              <Button type="submit" className="w-full" disabled={submitMut.isPending}>
                Set Password & Continue
              </Button>
            </form>
          </Form>
        </CardContent>
      </Card>
    </div>
  );
}