import React, { useCallback, useEffect, useMemo, useRef, useState, useSyncExternalStore } from 'react';
import { useEditor } from '@craftjs/core';
import { Modal } from '../../ui/Modal';
import { useSiteDesign } from '../../state/SiteDesignContext';
import { useProjectExtras } from '../../state/ProjectExtrasContext';
import { useNotices } from '../../state/NoticeContext';
import { useRegisterCommands } from '../../editor/commands';
import {
  CUSTOM_SECTIONS_KEY, CustomSection, SECTION_FAMILIES, SectionDef, SectionFamily,
  insertSection, isTopLevelSection, nodeTreeToSerializedTree, searchSections, useSections,
} from '../../sections/catalog';
import { buildSectionPreviewDoc } from '../../sections/thumbnails';
import { exportToHtml } from '../../utils/html-export';
import { masterZoneState, type GlobalMaster } from '../../utils/global-sections';
import { useGlobalSections } from '../../state/GlobalSectionsContext';
import { usePages } from '../../state/PageContext';

// ---- open state: module-level so the command, the empty-state button and the
// Blocks panel button can open the modal without a provider ----
interface LibraryState { open: boolean; saving: boolean }
let state: LibraryState = { open: false, saving: false };
const listeners = new Set<() => void>();
const setState = (s: LibraryState) => { state = s; listeners.forEach((l) => l()); };
const subscribe = (cb: () => void) => { listeners.add(cb); return () => { listeners.delete(cb); }; };

export function openSectionLibrary(opts: { saving?: boolean } = {}): void {
  setState({ open: true, saving: !!opts.saving });
}
export function closeSectionLibrary(): void { setState({ open: false, saving: false }); }
export function useSectionLibraryState(): LibraryState {
  return useSyncExternalStore(subscribe, () => state, () => state);
}

/** Renders its iframe only once scrolled into view (60 live iframes at once is heavy). */
const LazyPreview: React.FC<{ def?: SectionDef; master?: GlobalMaster; title: string }> = ({ def, master, title }) => {
  const { design } = useSiteDesign();
  const ref = useRef<HTMLDivElement>(null);
  const [seen, setSeen] = useState(typeof IntersectionObserver === 'undefined');
  useEffect(() => {
    if (seen || !ref.current) return;
    const io = new IntersectionObserver((entries) => {
      if (entries.some((e) => e.isIntersecting)) { setSeen(true); io.disconnect(); }
    });
    io.observe(ref.current);
    return () => io.disconnect();
  }, [seen]);
  const doc = useMemo(() => {
    if (!seen) return '';
    try {
      if (master) return exportToHtml(masterZoneState(master), { design, includeFonts: true }).html;
      return def ? buildSectionPreviewDoc(def, design) : '';
    } catch { return ''; }
  }, [seen, def, master, design]);
  return (
    <div className="section-lib-thumb" ref={ref}>
      {doc && (
        <iframe
          className="section-lib-frame"
          title={title}
          sandbox=""
          srcDoc={doc}
          tabIndex={-1}
          loading="lazy"
        />
      )}
    </div>
  );
};

export const SectionLibraryModal: React.FC = () => {
  const { open, saving } = useSectionLibraryState();
  const { query, actions, selectedId } = useEditor((s) => ({ selectedId: Array.from(s.events.selected || [])[0] as string | undefined }));
  const extras = useProjectExtras();
  const { notify } = useNotices();
  const [version, setVersion] = useState(0);
  const sections = useSections(version, open);
  const [family, setFamily] = useState<SectionFamily | null>(null);
  // #57: the Global tab lists the site's global sections (instances, not copies).
  const [globalTab, setGlobalTab] = useState(false);
  const globals = useGlobalSections();
  const { isEditingGlobal } = usePages();
  const [q, setQ] = useState('');
  const [saveName, setSaveName] = useState('');

  const canSave = open && isTopLevelSection(query, selectedId);

  useRegisterCommands([
    {
      id: 'insert.section-library',
      title: 'Browse sections…',
      group: 'insert',
      keywords: ['section', 'library', 'hero', 'faq', 'template', 'add section'],
      run: () => openSectionLibrary(),
    },
    {
      id: 'site.save-as-section',
      title: 'Save selection as section…',
      group: 'site',
      keywords: ['section', 'library', 'save', 'reusable'],
      when: (ctx) => ctx.selectedIds.length === 1 && isTopLevelSection(ctx.query, ctx.selectedIds[0]),
      run: () => openSectionLibrary({ saving: true }),
    },
  ], []);

  useEffect(() => { if (open) { setQ(''); setFamily(null); setGlobalTab(false); setSaveName(''); } }, [open]);
  const usage = useMemo(() => (open && globalTab ? globals.usage() : {}), [open, globalTab, globals]);
  const globalEntries = useMemo(() => {
    const words = q.toLowerCase().split(/\s+/).filter(Boolean);
    return Object.entries(globals.library)
      .filter(([, m]) => words.every((w) => m.name.toLowerCase().includes(w)))
      .sort((a, b) => a[1].name.localeCompare(b[1].name));
  }, [globals.library, q]);

  const onPickGlobal = (libraryId: string, name: string) => {
    const id = globals.insertInstance(libraryId, selectedId ?? null);
    if (!id) {
      notify({ kind: 'error', message: isEditingGlobal ? 'A global section cannot be placed inside another one.' : 'Could not add that section.' });
      return;
    }
    closeSectionLibrary();
    notify({ kind: 'success', message: `Added global section "${name}"` });
  };
  const onDeleteGlobal = (libraryId: string, name: string) => {
    if (!globals.remove(libraryId)) {
      notify({ kind: 'info', message: `"${name}" is still used on the site. Delete or detach its copies first.` });
    }
  };

  const results = useMemo(() => searchSections(q, family, sections), [q, family, sections]);

  const onPick = useCallback((def: SectionDef) => {
    try {
      const id = insertSection(query, actions, def, { afterSelection: true, select: true });
      closeSectionLibrary();
      notify({ kind: 'success', message: `Added "${def.name}"` });
      requestAnimationFrame(() => requestAnimationFrame(() => {
        try { query.node(id).get()?.dom?.scrollIntoView({ behavior: 'smooth', block: 'center' }); } catch { /* best effort */ }
      }));
    } catch (e) {
      console.error('Failed to insert section:', e);
      notify({ kind: 'error', message: 'Could not add that section.' });
    }
  }, [query, actions, notify]);

  const onSave = () => {
    const name = saveName.trim();
    if (!name || !selectedId) return;
    try {
      const entry: CustomSection = {
        id: `custom-${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 6)}`,
        name,
        family: 'custom',
        tree: nodeTreeToSerializedTree(query, selectedId),
        createdAt: Date.now(),
      };
      extras.update<CustomSection[]>(CUSTOM_SECTIONS_KEY, (prev) => [...prev, entry], []);
      setVersion((v) => v + 1);
      setSaveName('');
      setFamily('custom');
      openSectionLibrary({ saving: false });
      notify({ kind: 'success', message: `Saved "${name}" to My sections` });
    } catch (e) {
      console.error('Failed to save section:', e);
      notify({ kind: 'error', message: 'Could not save that section.' });
    }
  };

  const onDelete = (id: string) => {
    extras.update<CustomSection[]>(CUSTOM_SECTIONS_KEY, (prev) => prev.filter((c) => c.id !== id), []);
    setVersion((v) => v + 1);
  };

  return (
    <Modal
      open={open}
      onClose={closeSectionLibrary}
      width="min(960px, 94vw)"
      backdropProps={{ role: 'dialog', 'aria-modal': true, 'aria-label': 'Section library' }}
    >
      <div className="section-lib">
        <div className="section-lib-head">
          <h2>Add a section</h2>
          <button type="button" className="section-lib-close" aria-label="Close" onClick={closeSectionLibrary}>
            <i className="fa fa-times" aria-hidden />
          </button>
        </div>
        <div className="section-lib-controls">
          <input
            type="search"
            className="section-lib-search"
            placeholder="Search sections…"
            aria-label="Search sections"
            value={q}
            onChange={(e) => setQ(e.target.value)}
          />
          {canSave && !saving && (
            <button type="button" className="section-lib-save-btn" onClick={() => openSectionLibrary({ saving: true })}>
              <i className="fa fa-bookmark" aria-hidden /> Save current section
            </button>
          )}
        </div>
        {saving && canSave && (
          <form className="section-lib-save" onSubmit={(e) => { e.preventDefault(); onSave(); }}>
            <input
              className="section-lib-search"
              placeholder="Name this section"
              aria-label="Section name"
              value={saveName}
              autoFocus
              onChange={(e) => setSaveName(e.target.value)}
            />
            <button type="submit" className="section-lib-save-btn" disabled={!saveName.trim()}>Save</button>
            <button type="button" className="section-lib-save-btn" onClick={() => openSectionLibrary({ saving: false })}>Cancel</button>
          </form>
        )}
        <div className="section-lib-chips" role="tablist" aria-label="Section families">
          <button type="button" role="tab" aria-selected={!globalTab && family === null} className={`section-lib-chip${!globalTab && family === null ? ' active' : ''}`} onClick={() => { setGlobalTab(false); setFamily(null); }}>All</button>
          {SECTION_FAMILIES.map((f) => (
            <button
              key={f.id}
              type="button"
              role="tab"
              aria-selected={!globalTab && family === f.id}
              className={`section-lib-chip${!globalTab && family === f.id ? ' active' : ''}`}
              onClick={() => { setGlobalTab(false); setFamily(f.id); }}
            >{f.label}</button>
          ))}
          <button
            type="button"
            role="tab"
            aria-selected={globalTab}
            className={`section-lib-chip section-lib-chip-global${globalTab ? ' active' : ''}`}
            onClick={() => setGlobalTab(true)}
          ><i className="fa fa-globe" aria-hidden /> Global</button>
        </div>
        {globalTab ? (
        <div className="section-lib-grid">
          {globalEntries.map(([id, m]) => (
            <div key={id} className="section-lib-card" data-global-id={id}>
              <button type="button" className="section-lib-pick" onClick={() => onPickGlobal(id, m.name)} aria-label={`Add ${m.name}`}>
                <LazyPreview master={m} title={`${m.name} preview`} />
                <span className="section-lib-name">{m.name}</span>
                <span className="section-lib-usage" data-testid="global-usage">
                  Used {usage[id] ?? 0} {(usage[id] ?? 0) === 1 ? 'time' : 'times'}
                </span>
              </button>
              <button type="button" className="section-lib-delete" aria-label={`Delete ${m.name}`} onClick={() => onDeleteGlobal(id, m.name)}>
                <i className="fa fa-trash" aria-hidden />
              </button>
            </div>
          ))}
          {globalEntries.length === 0 && (
            <div className="section-lib-empty">
              No global sections yet. Right-click a section on the canvas and choose "Make global section".
            </div>
          )}
        </div>
        ) : (
        <div className="section-lib-grid">
          {results.map((def) => (
            <div key={def.id} className="section-lib-card" data-section-id={def.id}>
              <button type="button" className="section-lib-pick" onClick={() => onPick(def)} aria-label={`Add ${def.name}`}>
                <LazyPreview def={def} title={`${def.name} preview`} />
                <span className="section-lib-name">{def.name}</span>
              </button>
              {def.family === 'custom' && (
                <button type="button" className="section-lib-delete" aria-label={`Delete ${def.name}`} onClick={() => onDelete(def.id)}>
                  <i className="fa fa-trash" aria-hidden />
                </button>
              )}
            </div>
          ))}
          {results.length === 0 && (
            <div className="section-lib-empty">
              {family === 'custom' ? 'Nothing saved yet. Select a section on the canvas and choose "Save current section".' : `No sections match "${q.trim()}"`}
            </div>
          )}
        </div>
        )}
      </div>
    </Modal>
  );
};