"use client";

import { useCallback, useEffect, useMemo, useState } from "react";
import Link from "next/link";
import {
  BookOpenCheck,
  Clapperboard,
  FileText,
  Layers3,
  LoaderCircle,
  RotateCw,
  UploadCloud,
} from "lucide-react";
import { listDocuments } from "@/lib/api/documents";
import type { ApiDocument } from "@/lib/api/types";
import { buildDemoSeedDocuments } from "@/lib/demo-seed-documents";
import { getPublicDemoMode } from "@/lib/env";
import { buildStudyIntentUrl, type StudyIntent } from "@/lib/study-intents";
import { cn } from "@/lib/utils";

function sourceStatusLabel(status: string | null | undefined) {
  if (status === "ready" || status === "complete") return "Ready";
  if (status === "processing" || status === "uploaded" || status === "running") return "Reading";
  if (status === "failed") return "Needs clearer file";
  return "Saved";
}

function studyIntentHref(doc: ApiDocument, intent: StudyIntent, prompt: string) {
  return buildStudyIntentUrl({
    intent,
    sourceId: doc.id,
    prompt,
    run: true,
  });
}

export function FirstHourShell() {
  const [documents, setDocuments] = useState<ApiDocument[]>([]);
  const [selectedId, setSelectedId] = useState<string | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);

  const loadSources = useCallback(async () => {
    setIsLoading(true);
    setError(null);
    try {
      let docs = await listDocuments();
      if (getPublicDemoMode() !== "live" && docs.length === 0) {
        docs = buildDemoSeedDocuments();
      }
      setDocuments(docs);
      setSelectedId((current) => current ?? docs.find((doc) => doc.status === "ready")?.id ?? docs[0]?.id ?? null);
    } catch {
      if (getPublicDemoMode() !== "live") {
        const docs = buildDemoSeedDocuments();
        setDocuments(docs);
        setSelectedId(docs[0]?.id ?? null);
      } else {
        setError("DocDoe could not load your sources. Upload still works, and you can retry this panel after the connection recovers.");
      }
    } finally {
      setIsLoading(false);
    }
  }, []);

  useEffect(() => {
    const timeoutId = window.setTimeout(() => {
      void loadSources();
    }, 0);
    return () => window.clearTimeout(timeoutId);
  }, [loadSources]);

  const readyDocuments = useMemo(
    () => documents.filter((doc) => doc.status === "ready"),
    [documents],
  );
  const selectedDocument = documents.find((doc) => doc.id === selectedId) ?? readyDocuments[0] ?? documents[0] ?? null;
  const selectedIsReady = selectedDocument?.status === "ready";

  const kitActions = selectedDocument
    ? [
        {
          label: "Teach source",
          icon: BookOpenCheck,
          href: studyIntentHref(selectedDocument, "explain_source", `Explain ${selectedDocument.title} in simple exam language`),
          disabled: !selectedIsReady,
        },
        {
          label: "Scoring notes",
          icon: FileText,
          href: studyIntentHref(selectedDocument, "generate_notes", `Make exam-ready notes from ${selectedDocument.title}`),
          disabled: !selectedIsReady,
        },
        {
          label: "Quiz",
          icon: Layers3,
          href: studyIntentHref(selectedDocument, "generate_quiz", `Make a quiz from ${selectedDocument.title}`),
          disabled: !selectedIsReady,
        },
        {
          label: "Flashcards",
          icon: Layers3,
          href: studyIntentHref(selectedDocument, "generate_flashcards", `Make flashcards from ${selectedDocument.title}`),
          disabled: !selectedIsReady,
        },
        {
          label: "Study video plan",
          icon: Clapperboard,
          href: `/video-generator?source_id=${encodeURIComponent(selectedDocument.id)}`,
          disabled: !selectedIsReady,
        },
      ]
    : [];

  return (
    <main className="min-h-screen bg-[#030303] px-4 py-8 text-white sm:px-6 sm:py-12 lg:px-8">
      <div className="mx-auto w-full max-w-6xl">
        <div className="flex flex-col gap-6 lg:flex-row lg:items-end lg:justify-between">
          <div className="max-w-3xl">
            <p className="text-[11px] font-semibold uppercase tracking-[0.22em] text-white/42">Study Generator</p>
            <h1 className="mt-3 text-4xl font-semibold leading-tight tracking-normal text-white sm:text-5xl">
              Upload your material. Generate a complete study kit.
            </h1>
            <p className="mt-4 max-w-2xl text-base leading-7 text-white/58">
              Video, quiz, flashcards, notes, and questions from one upload. Pick a ready source below or add fresh material first.
            </p>
          </div>

          <div className="flex flex-col gap-2 sm:flex-row">
            <Link
              href="/upload"
              className="inline-flex min-h-11 items-center justify-center gap-2 rounded-lg bg-white px-4 text-sm font-semibold text-black transition hover:bg-white/90"
            >
              <UploadCloud className="size-4" />
              Upload material
            </Link>
            <Link
              href="/sources"
              className="inline-flex min-h-11 items-center justify-center rounded-lg border border-white/[0.12] px-4 text-sm font-semibold text-white/70 transition hover:border-white/24 hover:text-white"
            >
              Open sources
            </Link>
          </div>
        </div>

        {error ? (
          <div className="mt-8 flex flex-col gap-3 rounded-lg border border-white/[0.12] bg-white/[0.04] p-4 text-sm text-white/70 sm:flex-row sm:items-center sm:justify-between">
            <p>{error}</p>
            <button
              type="button"
              onClick={() => void loadSources()}
              className="inline-flex min-h-10 items-center justify-center gap-2 rounded-lg border border-white/[0.12] px-4 text-sm font-semibold text-white transition hover:border-white/25"
            >
              <RotateCw className="size-4" />
              Retry
            </button>
          </div>
        ) : null}

        <div className="mt-10 grid gap-6 lg:grid-cols-[minmax(0,0.95fr)_minmax(0,1.05fr)]">
          <section className="rounded-lg border border-white/[0.1] bg-white/[0.03] p-5">
            <div className="flex items-center justify-between gap-3">
              <div>
                <h2 className="text-lg font-semibold text-white">Choose source</h2>
                <p className="mt-1 text-sm text-white/48">The selected source is passed into every study-kit action.</p>
              </div>
              {isLoading ? <LoaderCircle className="size-5 animate-spin text-white/45" /> : null}
            </div>

            {isLoading ? (
              <div className="mt-5 space-y-3">
                {Array.from({ length: 3 }).map((_, index) => (
                  <div key={index} className="h-20 animate-pulse rounded-lg border border-white/[0.08] bg-white/[0.03]" />
                ))}
              </div>
            ) : documents.length > 0 ? (
              <div className="mt-5 space-y-3">
                {documents.slice(0, 8).map((doc) => {
                  const selected = doc.id === selectedDocument?.id;
                  return (
                    <button
                      key={doc.id}
                      type="button"
                      onClick={() => setSelectedId(doc.id)}
                      className={cn(
                        "w-full rounded-lg border p-4 text-left transition",
                        selected
                          ? "border-white/28 bg-white/[0.075] text-white"
                          : "border-white/[0.08] bg-black/20 text-white/68 hover:border-white/18 hover:text-white",
                      )}
                    >
                      <div className="flex items-start justify-between gap-3">
                        <div className="min-w-0">
                          <p className="line-clamp-2 text-sm font-semibold">{doc.title || "Untitled source"}</p>
                          <p className="mt-1 text-xs text-white/42">
                            {[doc.subject, doc.chapter, doc.material_type].filter(Boolean).join(" · ") || "Study material"}
                          </p>
                        </div>
                        <span className="shrink-0 rounded-full border border-white/[0.1] px-2 py-0.5 text-[10px] font-semibold text-white/48">
                          {sourceStatusLabel(doc.status)}
                        </span>
                      </div>
                    </button>
                  );
                })}
              </div>
            ) : (
              <div className="mt-5 rounded-lg border border-dashed border-white/[0.14] p-6 text-center">
                <p className="text-base font-semibold text-white">No source uploaded yet</p>
                <p className="mx-auto mt-2 max-w-sm text-sm leading-6 text-white/50">
                  Upload a selectable-text PDF or TXT export of your notes, chapter, syllabus, or question paper to unlock the study kit.
                </p>
                <Link href="/upload" className="mt-5 inline-flex rounded-lg bg-white px-4 py-2 text-sm font-semibold text-black">
                  Upload first material
                </Link>
              </div>
            )}
          </section>

          <section className="rounded-lg border border-white/[0.1] bg-white/[0.03] p-5">
            <h2 className="text-lg font-semibold text-white">Generate study kit</h2>
            <p className="mt-1 text-sm text-white/48">
              {selectedDocument
                ? `Using: ${selectedDocument.title || "selected source"}`
                : "Upload or choose a source first."}
            </p>

            {selectedDocument && !selectedIsReady ? (
              <div className="mt-5 rounded-lg border border-white/[0.1] bg-white/[0.035] p-4 text-sm leading-6 text-white/62">
                This source is still being read or needs a clearer upload. The original source stays visible; retry these actions once it is ready.
              </div>
            ) : null}

            <div className="mt-5 grid gap-3 sm:grid-cols-2">
              {kitActions.map((action) => {
                const Icon = action.icon;
                const className = cn(
                  "inline-flex min-h-14 items-center justify-center gap-2 rounded-lg border px-4 text-sm font-semibold transition",
                  action.disabled
                    ? "pointer-events-none border-white/[0.07] bg-white/[0.02] text-white/30"
                    : "border-white/[0.12] bg-white/[0.045] text-white/78 hover:border-white/25 hover:bg-white/[0.075] hover:text-white",
                );
                return action.disabled ? (
                  <span key={action.label} className={className} aria-disabled="true">
                    <Icon className="size-4" />
                    {action.label}
                  </span>
                ) : (
                  <Link key={action.label} href={action.href} className={className}>
                    <Icon className="size-4" />
                    {action.label}
                  </Link>
                );
              })}
            </div>

            {!selectedDocument ? (
              <div className="mt-5 rounded-lg border border-white/[0.1] bg-white/[0.035] p-4 text-sm leading-6 text-white/58">
                Study Generator is ready as soon as you add material. No fake generated kit is shown before a real source exists.
              </div>
            ) : null}
          </section>
        </div>
      </div>
    </main>
  );
}