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 { StudentSelector } from "./components/step2/StudentSelector";
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;
}

interface StudentInfo {
  index: number;
  name: string;
  id: string;
}

export interface StudentReport {
  studentName: string;
  studentIndex: number;
  html: string;
  status: "pending" | "generating" | "done" | "error";
  error?: 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 [students, setStudents] = useState<StudentInfo[]>([]);
  const [selectedIndices, setSelectedIndices] = useState<number[]>([]);
  const [reports, setReports] = useState<StudentReport[]>([]);
  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);
    }
  }, []);

  // 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]);

  // Extract student list from parsed data
  useEffect(() => {
    const sa = parsedData.student_answers as { students?: { name?: string; id?: string }[] } | undefined;
    if (sa?.students) {
      setStudents(
        sa.students.map((s, i) => ({
          index: i,
          name: s.name || `Student ${i + 1}`,
          id: s.id || "",
        }))
      );
    }
  }, [parsedData]);

  const handleLogout = () => {
    setUser(null);
    setSessionId(null);
    setParsedData({});
    setStudents([]);
    setSelectedIndices([]);
    setReports([]);
    setCurrentStep(1);
  };

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

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

  // Sequential per-student report generation
  const handleGenerateReports = useCallback(async (model: string) => {
    if (!sessionId || selectedIndices.length === 0) return;

    const initial: StudentReport[] = selectedIndices.map((idx) => {
      const s = students.find((s) => s.index === idx);
      return {
        studentName: s?.name || `Student ${idx + 1}`,
        studentIndex: idx,
        html: "",
        status: "pending",
      };
    });
    setReports(initial);
    setIsGenerating(true);
    setCurrentStep(3);

    for (let i = 0; i < selectedIndices.length; i++) {
      const idx = selectedIndices[i];

      setReports((prev) =>
        prev.map((r, j) => (j === i ? { ...r, status: "generating" } : r))
      );

      try {
        const res = await apiPost<{
          report_id: number;
          html_content: string;
          student_name: string;
        }>(`/api/sessions/${sessionId}/generate-student-report`, {
          student_index: idx,
          model,
        });

        setReports((prev) =>
          prev.map((r, j) =>
            j === i ? { ...r, html: res.html_content, status: "done" } : r
          )
        );
      } catch (err) {
        const msg = err instanceof Error ? err.message : "Generation failed";
        setReports((prev) =>
          prev.map((r, j) =>
            j === i ? { ...r, status: "error", error: msg } : r
          )
        );
      }
    }

    setIsGenerating(false);
  }, [sessionId, selectedIndices, students]);

  const handleExportAllHtml = useCallback(() => {
    const doneReports = reports.filter((r) => r.status === "done");
    if (doneReports.length === 0) return;

    const combined = `<!DOCTYPE html>
<html lang="zh-TW"><head><meta charset="UTF-8"><title>ClassLens - Student Reports</title>
<style>
  .page-break { page-break-after: always; break-after: page; }
  .report-container { margin-bottom: 2rem; }
</style></head><body>
${doneReports
  .map(
    (r, i) =>
      `<div class="report-container${i < doneReports.length - 1 ? " page-break" : ""}">${r.html}</div>`
  )
  .join("\n")}
</body></html>`;

    const blob = new Blob([combined], { type: "text/html" });
    const url = URL.createObjectURL(blob);
    const a = document.createElement("a");
    a.href = url;
    a.download = "classlens-all-reports.html";
    a.click();
    URL.revokeObjectURL(url);
  }, [reports]);

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

  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>
    );
  }

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

  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)]">
                  選擇學生 & 編輯提示詞
                </h2>
                <p className="text-[var(--color-text-muted)] mt-2">
                  勾選要生成報告的學生，編輯提示詞，預覽資料後生成報告
                </p>
              </div>

              <ParsedDataSummary parsedData={parsedData} />

              {students.length > 0 ? (
                <>
                  <StudentSelector
                    students={students}
                    onSelectionChange={setSelectedIndices}
                  />
                  {sessionId && (
                    <PromptEditor
                      sessionId={sessionId}
                      onGenerate={handleGenerateReports}
                      isGenerating={isGenerating}
                      selectedCount={selectedIndices.length}
                      selectedIndices={selectedIndices}
                    />
                  )}
                </>
              ) : (
                <div className="card p-8 text-center">
                  <p className="text-[var(--color-text-muted)]">
                    尚未上傳學生答案資料，請先回到上一步上傳檔案
                  </p>
                </div>
              )}
            </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)]">
                  學生分析報告
                </h2>
              </div>
              <ReportViewer
                reports={reports}
                isGenerating={isGenerating}
                onBack={() => setCurrentStep(2)}
                onExportAllHtml={handleExportAllHtml}
              />
            </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>
  );
}