import { useState, useEffect, useCallback } from "react";
import { Header } from "./components/Header";
import { InviteGate } from "./components/InviteGate";
import { LoginForm } from "./components/LoginForm";
import { StepIndicator } from "./components/StepIndicator";
import { FileUploadPanel } from "./components/step1/FileUploadPanel";
import { ParsedDataSummary } from "./components/step2/ParsedDataSummary";
import { PromptEditor } from "./components/step2/PromptEditor";
import { ReportViewer } from "./components/step3/ReportViewer";
import { apiGet, apiPost, getToken, clearToken } from "./lib/api";

const INVITE_CODE = "taboola-npo-cz";

interface User {
  id: number;
  email: string;
  display_name: string;
}

export default function App() {
  const [invited, setInvited] = useState(() => localStorage.getItem("invite_code") === INVITE_CODE);
  const [user, setUser] = useState<User | null>(null);
  const [loading, setLoading] = useState(true);
  const [currentStep, setCurrentStep] = useState<1 | 2 | 3>(1);
  const [sessionId, setSessionId] = useState<number | null>(null);
  const [parsedData, setParsedData] = useState<Record<string, unknown>>({});
  const [promptContent, setPromptContent] = useState("");
  const [reportHtml, setReportHtml] = useState("");
  const [isGenerating, setIsGenerating] = useState(false);

  // Check for saved JWT on mount
  useEffect(() => {
    const token = getToken();
    if (token) {
      apiGet<User>("/api/auth/me")
        .then(setUser)
        .catch(() => clearToken())
        .finally(() => setLoading(false));
    } else {
      setLoading(false);
    }
  }, []);

  // Load default prompt
  useEffect(() => {
    if (user && !promptContent) {
      apiGet<{ content: string }>("/api/prompts/default")
        .then((res) => setPromptContent(res.content))
        .catch(() => {});
    }
  }, [user]);

  // Create session when user is authenticated and no session exists
  useEffect(() => {
    if (user && !sessionId) {
      apiPost<{ id: number }>("/api/sessions", { title: "New Session" })
        .then((session) => setSessionId(session.id))
        .catch(() => {});
    }
  }, [user]);

  const handleLogout = () => {
    setUser(null);
    setSessionId(null);
    setParsedData({});
    setPromptContent("");
    setReportHtml("");
    setCurrentStep(1);
  };

  const handleParsedDataUpdate = useCallback((dataType: string, data: unknown) => {
    setParsedData((prev) => ({ ...prev, [dataType]: data }));
  }, []);

  const handleGoToStep2 = useCallback(() => {
    setCurrentStep(2);
  }, []);

  const handleRunSummary = useCallback(async (model: string) => {
    if (!sessionId || !promptContent.trim()) return;
    setIsGenerating(true);
    try {
      const res = await apiPost<{ report_id: number; html_content: string }>(
        `/api/sessions/${sessionId}/generate-report`,
        { prompt_content: promptContent, model }
      );
      setReportHtml(res.html_content);
      setCurrentStep(3);
    } catch (err) {
      alert(err instanceof Error ? err.message : "Report generation failed");
    } finally {
      setIsGenerating(false);
    }
  }, [sessionId, promptContent]);

  const handleExportPdf = useCallback(async () => {
    // Dynamic import to avoid loading html2pdf.js unless needed
    const html2pdf = (await import("html2pdf.js")).default;
    const container = document.createElement("div");
    container.innerHTML = reportHtml;
    document.body.appendChild(container);
    await html2pdf()
      .set({ margin: 10, filename: "classlens-report.pdf", html2canvas: { scale: 2 } })
      .from(container)
      .save();
    document.body.removeChild(container);
  }, [reportHtml]);

  const handleExportPng = useCallback(async () => {
    const html2canvas = (await import("html2canvas")).default;
    const container = document.createElement("div");
    container.innerHTML = reportHtml;
    container.style.width = "1200px";
    container.style.position = "absolute";
    container.style.left = "-9999px";
    document.body.appendChild(container);
    const canvas = await html2canvas(container, { scale: 2 });
    document.body.removeChild(container);
    const link = document.createElement("a");
    link.download = "classlens-report.png";
    link.href = canvas.toDataURL("image/png");
    link.click();
  }, [reportHtml]);

  const handleStepClick = (step: 1 | 2 | 3) => {
    if (step <= currentStep) setCurrentStep(step);
  };

  // Loading state
  if (loading) {
    return (
      <div className="min-h-screen flex items-center justify-center bg-[var(--color-background)]">
        <div className="w-8 h-8 border-2 border-[var(--color-primary)] border-t-transparent rounded-full animate-spin" />
      </div>
    );
  }

  // Invite code gate
  if (!invited) {
    return (
      <InviteGate
        onSuccess={() => {
          localStorage.setItem("invite_code", INVITE_CODE);
          setInvited(true);
        }}
        correctCode={INVITE_CODE}
      />
    );
  }

  // Login gate
  if (!user) {
    return <LoginForm onLogin={setUser} />;
  }

  return (
    <div className="min-h-screen">
      <Header userEmail={user.email} onLogout={handleLogout} />

      <div className="pt-20">
        <StepIndicator currentStep={currentStep} onStepClick={handleStepClick} />

        <main className="max-w-6xl mx-auto px-4 pb-12">
          {currentStep === 1 && (
            <div className="space-y-6 animate-fade-in-up">
              <div className="text-center mb-8">
                <h2 className="font-display text-2xl font-bold text-[var(--color-text)]">
                  上傳考試資料
                </h2>
                <p className="text-[var(--color-text-muted)] mt-2">
                  上傳考試題目、學生答案和標準答案，分別解析後確認資料再前往下一步
                </p>
              </div>
              {sessionId && (
                <FileUploadPanel
                  sessionId={sessionId}
                  parsedData={parsedData}
                  onParsedDataUpdate={handleParsedDataUpdate}
                  onGoToStep2={handleGoToStep2}
                />
              )}
            </div>
          )}

          {currentStep === 2 && (
            <div className="space-y-6 animate-fade-in-up">
              <div className="text-center mb-4">
                <h2 className="font-display text-2xl font-bold text-[var(--color-text)]">
                  編輯分析提示詞
                </h2>
                <p className="text-[var(--color-text-muted)] mt-2">
                  編輯提示詞來自訂分析報告的內容與格式
                </p>
              </div>
              <ParsedDataSummary parsedData={parsedData} />
              {sessionId && (
                <PromptEditor
                  promptContent={promptContent}
                  onPromptChange={setPromptContent}
                  sessionId={sessionId}
                  onRunSummary={handleRunSummary}
                  isGenerating={isGenerating}
                />
              )}
            </div>
          )}

          {currentStep === 3 && (
            <div className="animate-fade-in-up">
              <div className="text-center mb-4">
                <h2 className="font-display text-2xl font-bold text-[var(--color-text)]">
                  分析報告
                </h2>
              </div>
              <ReportViewer
                reportHtml={reportHtml}
                onBack={() => setCurrentStep(2)}
                onExportPdf={handleExportPdf}
                onExportPng={handleExportPng}
              />
            </div>
          )}
        </main>

        <footer className="py-8 text-center text-sm text-[var(--color-text-muted)]">
          <p>&copy; 2026 ClassLens &bull; AI-Powered Teaching Assistant</p>
        </footer>
      </div>
    </div>
  );
}