import React, { useRef, useState, useEffect, useMemo } from "react";
import { Button } from "./ui/button";
import { Input } from "./ui/input";
import { Label } from "./ui/label";
import { Dialog, DialogContent, DialogTitle } from "./ui/dialog";
import type { User as UserType } from "../App";
import { toast } from "sonner";
import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "./ui/select";
import { ChevronLeft, ChevronRight } from "lucide-react";
import { Textarea } from "./ui/textarea";

// ✅ Add Bio step. Total steps: 5
const TOTAL_STEPS = 5;

type InitQ = {
  id: string;
  title: string;
  placeholder?: string;
};

const INIT_QUESTIONS: InitQ[] = [
  {
    id: "course_goal",
    title: "What’s the single most important outcome you want from this course?",
    placeholder: "e.g., understand LLM basics, build a project, prep for an exam, apply to work…",
  },
  {
    id: "background",
    title: "What’s your current background (major, job, or anything relevant)?",
    placeholder: "One sentence is totally fine.",
  },
  {
    id: "ai_experience",
    title: "Have you worked with AI/LLMs before? If yes, at what level?",
    placeholder: "e.g., none / used ChatGPT / built small projects / research…",
  },
  {
    id: "python_level",
    title: "How comfortable are you with Python? (Beginner / Intermediate / Advanced)",
    placeholder: "Type one: Beginner / Intermediate / Advanced",
  },
  {
    id: "preferred_format",
    title: "What helps you learn best? (You can list multiple, separated by commas)",
    placeholder: "Step-by-step, examples, visuals, concise answers, Socratic questions…",
  },
  {
    id: "pace",
    title: "What pace do you prefer from me? (Fast / Steady / Very detailed)",
    placeholder: "Type one: Fast / Steady / Very detailed",
  },
  {
    id: "biggest_pain",
    title: "Where do you typically get stuck when learning technical topics?",
    placeholder: "Concepts, tools, task breakdown, math, confidence, time management…",
  },
  {
    id: "support_pref",
    title: "When you’re unsure, how should I support you?",
    placeholder: "Hints first / guided questions / direct answer / ask then answer…",
  },
];

interface OnboardingProps {
  user: UserType;
  onComplete: (user: UserType) => void;
  onSkip: () => void;
}

export function Onboarding({ user, onComplete, onSkip }: OnboardingProps) {
  const [currentStep, setCurrentStep] = useState(1);

  // Step 1: Basic
  const [name, setName] = useState(user.name ?? "");
  const [email, setEmail] = useState(user.email ?? "");

  // Step 2: Academic
  const [studentId, setStudentId] = useState(user.studentId ?? "");
  const [department, setDepartment] = useState(user.department ?? "");
  const [yearLevel, setYearLevel] = useState(user.yearLevel ?? "");
  const [major, setMajor] = useState(user.major ?? "");

  // Step 3: Preferences
  const [learningStyle, setLearningStyle] = useState(user.learningStyle ?? "visual");
  const [learningPace, setLearningPace] = useState(user.learningPace ?? "moderate");

  // Step 4: Bio (8 questions -> generate bio)
  const [bioQIndex, setBioQIndex] = useState(0);
  const [bioInput, setBioInput] = useState("");
  const [bioAnswers, setBioAnswers] = useState<Record<string, string>>({});
  const [bioSubmitting, setBioSubmitting] = useState(false);
  const [generatedBio, setGeneratedBio] = useState<string>(user.bio ?? "");
  const [bioReady, setBioReady] = useState<boolean>(!!(user.bio && user.bio.trim().length > 0));

  const currentBioQ = useMemo(() => INIT_QUESTIONS[bioQIndex], [bioQIndex]);

  // Optional: if user already has bio, mark ready.
  useEffect(() => {
    if (user.bio && user.bio.trim().length > 0) {
      setGeneratedBio(user.bio);
      setBioReady(true);
    }
  }, [user.bio]);

  // Step 5: Photo
  const [photoPreview, setPhotoPreview] = useState<string | null>(user.avatarUrl ?? null);
  const fileInputRef = useRef<HTMLInputElement>(null);

  const handlePhotoSelect = (e: React.ChangeEvent<HTMLInputElement>) => {
    const file = e.target.files?.[0];
    if (!file) return;

    if (!file.type.startsWith("image/")) {
      toast.error("Please select an image file");
      return;
    }
    if (file.size > 2 * 1024 * 1024) {
      toast.error("File size must be less than 2MB");
      return;
    }

    const reader = new FileReader();
    reader.onload = (ev) => setPhotoPreview(ev.target?.result as string);
    reader.readAsDataURL(file);
  };

  const handleChangePhotoClick = () => fileInputRef.current?.click();

  const handlePrevious = () => {
    if (currentStep > 1) setCurrentStep((s) => s - 1);
  };

  const handleSkip = () => onSkip();

  // --------------------------
  // Step 4: Bio generation flow
  // --------------------------
  const handleBioNext = async () => {
    const v = bioInput.trim();
    if (!v) return;

    const q = INIT_QUESTIONS[bioQIndex];
    const nextAnswers = { ...bioAnswers, [q.id]: v };

    setBioAnswers(nextAnswers);
    setBioInput("");

    const nextIndex = bioQIndex + 1;

    // Continue questions
    if (nextIndex < INIT_QUESTIONS.length) {
      setBioQIndex(nextIndex);
      return;
    }

    // Last question -> submit to backend and generate bio
    // NOTE: use same backend logic as before; we do NOT touch parsing/storage logic.
    setBioSubmitting(true);
    try {
      const r = await fetch("/api/profile/init_submit", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          user_id: email.trim() || user.email, // prefer current email input
          answers: nextAnswers,
          language_preference: "English",
        }),
      });

      if (!r.ok) throw new Error("init_submit failed");
      const j = await r.json();

      const bio = (j?.bio || "").toString();
      if (!bio.trim()) {
        throw new Error("empty bio");
      }

      setGeneratedBio(bio);
      setBioReady(true);

      toast.success("Bio generated!");
    } catch (e) {
      toast.error("Failed to generate bio. Please try again.");
      // allow retry: keep last answer stored; user can edit generated flow by resetting if needed
    } finally {
      setBioSubmitting(false);
    }
  };

  const handleBioReset = () => {
    setBioQIndex(0);
    setBioInput("");
    setBioAnswers({});
    setBioSubmitting(false);
    setGeneratedBio("");
    setBioReady(false);
  };

  // Main Next handler (respects Step 4 gating)
  const handleNext = async () => {
    // Step 1 validation (kept)
    if (currentStep === 1) {
      if (!name.trim() || !email.trim()) {
        toast.error("Please fill in all required fields");
        return;
      }
    }

    // Step 4 gating: must finish + have bioReady before moving on
    if (currentStep === 4) {
      if (!bioReady) {
        // If still answering questions, Next acts as “Next question”
        if (bioQIndex < INIT_QUESTIONS.length) {
          await handleBioNext();
          return;
        }
        // Safety: should not happen, but block
        toast.error("Please finish the Bio questions first.");
        return;
      }
    }

    if (currentStep < TOTAL_STEPS) setCurrentStep((s) => s + 1);
    else handleComplete();
  };

  const handleComplete = () => {
    if (!name.trim() || !email.trim()) {
      toast.error("Please fill in all required fields");
      return;
    }

    // ✅ Bio now comes from Onboarding Step 4
    const finalBio = (generatedBio || user.bio || "").trim() || undefined;

    const next: UserType = {
      ...user,
      name: name.trim(),
      email: email.trim(),

      studentId: studentId.trim() || undefined,
      department: department.trim() || undefined,
      yearLevel: yearLevel || undefined,
      major: major.trim() || undefined,

      learningStyle: learningStyle || undefined,
      learningPace: learningPace || undefined,

      avatarUrl: photoPreview || undefined,

      bio: finalBio, // ✅ sync to profile via your existing onComplete->save logic
      onboardingCompleted: true,
    };

    onComplete(next);
    toast.success("Profile setup completed!");
  };

  const renderStepContent = () => {
    switch (currentStep) {
      case 1:
        return (
          <div className="space-y-4">
            <h3 className="text-lg font-medium">Basic Information</h3>
            <p className="text-sm text-muted-foreground">Let's start with your basic information</p>

            <div className="space-y-4">
              <div className="space-y-2">
                <Label htmlFor="onboarding-name">Full Name *</Label>
                <Input
                  id="onboarding-name"
                  value={name}
                  onChange={(e) => setName(e.target.value)}
                  placeholder="Enter your full name"
                />
              </div>

              <div className="space-y-2">
                <Label htmlFor="onboarding-email">Email *</Label>
                <Input
                  id="onboarding-email"
                  type="email"
                  value={email}
                  onChange={(e) => setEmail(e.target.value)}
                  placeholder="Enter your email"
                />
              </div>
            </div>
          </div>
        );

      case 2:
        return (
          <div className="space-y-4">
            <h3 className="text-lg font-medium">Academic Background</h3>
            <p className="text-sm text-muted-foreground">Tell us about your academic information</p>

            <div className="space-y-4">
              <div className="space-y-2">
                <Label htmlFor="onboarding-student-id">Student ID</Label>
                <Input
                  id="onboarding-student-id"
                  value={studentId}
                  onChange={(e) => setStudentId(e.target.value)}
                  placeholder="Enter your student ID"
                />
              </div>

              <div className="space-y-2">
                <Label htmlFor="onboarding-department">Department</Label>
                <Input
                  id="onboarding-department"
                  value={department}
                  onChange={(e) => setDepartment(e.target.value)}
                  placeholder="Enter your department"
                />
              </div>

              <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
                <div className="space-y-2">
                  <Label htmlFor="onboarding-year">Year Level</Label>
                  <Select value={yearLevel} onValueChange={setYearLevel}>
                    <SelectTrigger id="onboarding-year">
                      <SelectValue placeholder="Select year level" />
                    </SelectTrigger>
                    <SelectContent>
                      <SelectItem value="1st Year">1st Year</SelectItem>
                      <SelectItem value="2nd Year">2nd Year</SelectItem>
                      <SelectItem value="3rd Year">3rd Year</SelectItem>
                      <SelectItem value="4th Year">4th Year</SelectItem>
                      <SelectItem value="Graduate">Graduate</SelectItem>
                    </SelectContent>
                  </Select>
                </div>

                <div className="space-y-2">
                  <Label htmlFor="onboarding-major">Major</Label>
                  <Input
                    id="onboarding-major"
                    value={major}
                    onChange={(e) => setMajor(e.target.value)}
                    placeholder="Enter your major"
                  />
                </div>
              </div>
            </div>
          </div>
        );

      case 3:
        return (
          <div className="space-y-4">
            <h3 className="text-lg font-medium">Learning Preferences</h3>
            <p className="text-sm text-muted-foreground">Help us personalize your learning experience</p>

            <div className="space-y-4">
              <div className="space-y-2">
                <Label htmlFor="onboarding-learning-style">Preferred Learning Style</Label>
                <Select value={learningStyle} onValueChange={setLearningStyle}>
                  <SelectTrigger id="onboarding-learning-style">
                    <SelectValue />
                  </SelectTrigger>
                  <SelectContent>
                    <SelectItem value="visual">Visual</SelectItem>
                    <SelectItem value="auditory">Auditory</SelectItem>
                    <SelectItem value="reading">Reading/Writing</SelectItem>
                    <SelectItem value="kinesthetic">Kinesthetic</SelectItem>
                  </SelectContent>
                </Select>
              </div>

              <div className="space-y-2">
                <Label htmlFor="onboarding-pace">Learning Pace</Label>
                <Select value={learningPace} onValueChange={setLearningPace}>
                  <SelectTrigger id="onboarding-pace">
                    <SelectValue />
                  </SelectTrigger>
                  <SelectContent>
                    <SelectItem value="slow">Slow & Steady</SelectItem>
                    <SelectItem value="moderate">Moderate</SelectItem>
                    <SelectItem value="fast">Fast-paced</SelectItem>
                  </SelectContent>
                </Select>
              </div>
            </div>
          </div>
        );

      case 4:
        return (
          <div className="space-y-4">
            <h3 className="text-lg font-medium">Profile Bio</h3>
            <p className="text-sm text-muted-foreground">
              Answer a few quick questions and we’ll generate a Bio that syncs to your profile.
            </p>

            {!bioReady ? (
              <div className="space-y-3">
                <div className="rounded-lg border border-border bg-muted/30 p-4 space-y-2">
                  <div className="text-sm font-medium">{currentBioQ.title}</div>
                  {currentBioQ.placeholder && (
                    <div className="text-xs text-muted-foreground">{currentBioQ.placeholder}</div>
                  )}
                  <div className="text-xs text-muted-foreground">
                    Question {bioQIndex + 1} of {INIT_QUESTIONS.length}
                  </div>

                  <Textarea
                    value={bioInput}
                    onChange={(e) => setBioInput(e.target.value)}
                    placeholder="Type your answer here..."
                    className="min-h-[96px] mt-2"
                    disabled={bioSubmitting}
                    onKeyDown={(e) => {
                      if (e.key === "Enter" && !e.shiftKey) {
                        e.preventDefault();
                        handleBioNext();
                      }
                    }}
                  />

                  <div className="flex items-center justify-between pt-2">
                    <Button variant="outline" onClick={handleBioReset} disabled={bioSubmitting}>
                      Reset
                    </Button>

                    <Button onClick={handleBioNext} disabled={bioSubmitting || !bioInput.trim()}>
                      {bioQIndex === INIT_QUESTIONS.length - 1
                        ? bioSubmitting
                          ? "Generating…"
                          : "Generate Bio"
                        : "Next Question"}
                    </Button>
                  </div>
                </div>

                <div className="text-xs text-muted-foreground">
                  Tip: Press Enter to go next (Shift+Enter for a new line).
                </div>
              </div>
            ) : (
              <div className="space-y-3">
                <div className="rounded-lg border border-border bg-background p-4 space-y-2">
                  <div className="text-sm font-medium">Generated Bio</div>
                  <div className="text-xs text-muted-foreground">
                    You can edit it before continuing. This will be saved to your profile.
                  </div>

                  <Textarea
                    value={generatedBio}
                    onChange={(e) => setGeneratedBio(e.target.value)}
                    className="min-h-[140px] mt-2"
                  />

                  <div className="flex items-center justify-between pt-2">
                    <Button variant="outline" onClick={handleBioReset}>
                      Regenerate
                    </Button>
                    <div className="text-xs text-muted-foreground">
                      Click “Next Step” to continue.
                    </div>
                  </div>
                </div>
              </div>
            )}
          </div>
        );

      case 5:
        return (
          <div className="space-y-4">
            <h3 className="text-lg font-medium">Profile Picture</h3>
            <p className="text-sm text-muted-foreground">Upload a photo to personalize your profile (optional)</p>

            <div className="flex items-center gap-4">
              <div className="w-24 h-24 rounded-full bg-gradient-to-br from-red-500 to-orange-500 flex items-center justify-center text-white text-3xl overflow-hidden">
                {photoPreview ? (
                  <img src={photoPreview} alt="Profile" className="w-full h-full object-cover" />
                ) : (
                  (name?.charAt(0) || "U").toUpperCase()
                )}
              </div>

              <div>
                <input
                  ref={fileInputRef}
                  type="file"
                  accept="image/jpeg,image/png,image/gif,image/webp"
                  onChange={handlePhotoSelect}
                  className="hidden"
                />
                <Button variant="outline" size="sm" onClick={handleChangePhotoClick}>
                  Change Photo
                </Button>
                <p className="text-xs text-muted-foreground mt-1">JPG, PNG or GIF. Max size 2MB</p>
              </div>
            </div>
          </div>
        );

      default:
        return null;
    }
  };

  return (
    <Dialog
      open
      onOpenChange={(open) => {
        if (!open) onSkip();
      }}
    >
      <DialogContent
        className="sm:max-w-lg p-0 gap-0 max-h-[90vh] overflow-hidden"
        style={{ zIndex: 1001 }}
        overlayClassName="!inset-0 !z-[99]"
        overlayStyle={{ top: 0, left: 0, right: 0, bottom: 0, zIndex: 99, position: "fixed" }}
      >
        <div className="flex flex-col max-h-[90vh]">
          {/* Header */}
          <div className="border-b border-border p-4 flex items-center justify-between flex-shrink-0">
            <div className="flex-1">
              <DialogTitle className="text-xl font-medium">Welcome! Let's set up your profile</DialogTitle>
              <p className="text-sm text-muted-foreground mt-1">
                Step {currentStep} of {TOTAL_STEPS}
              </p>
            </div>

            {/* Progress indicator */}
            <div className="flex gap-1">
              {Array.from({ length: TOTAL_STEPS }).map((_, index) => (
                <div
                  key={index}
                  className={`h-2 w-2 rounded-full transition-colors ${
                    index + 1 <= currentStep ? "bg-primary" : "bg-muted"
                  }`}
                />
              ))}
            </div>
          </div>

          {/* Content */}
          <div className="p-6 overflow-y-auto flex-1">{renderStepContent()}</div>

          {/* Footer */}
          <div className="border-t border-border p-4 flex justify-between gap-2 flex-shrink-0">
            <div className="flex gap-2">
              {currentStep > 1 && (
                <Button variant="outline" onClick={handlePrevious} disabled={bioSubmitting}>
                  <ChevronLeft className="h-4 w-4 mr-1" />
                  Previous
                </Button>
              )}
            </div>

            <div className="flex gap-2">
              <Button variant="outline" onClick={handleSkip} disabled={bioSubmitting}>
                Skip all
              </Button>

              <Button onClick={handleNext} disabled={bioSubmitting}>
                {currentStep === TOTAL_STEPS ? "Complete" : "Next Step"}
                {currentStep < TOTAL_STEPS && <ChevronRight className="h-4 w-4 ml-1" />}
              </Button>
            </div>
          </div>
        </div>
      </DialogContent>
    </Dialog>
  );
}