import { Editor } from '../../editor/Editor.js';
import { ContextMenuDirectory, ContextMenuReadOnlyEntry } from '../context-menu/context-menu.js';

class HtmlEditorPanel extends HTMLElement
{
  currentPath: string | null = null;
  _pinned: boolean = false;
  _iframe: HTMLIFrameElement | null = null;
  _undoStack: string[] = [];
  _redoStack: string[] = [];
  _mutationObserver: MutationObserver | null = null;
  _initialized = false;
  _needsRestore = false;

  connectedCallback(): void
  {
    if ( this._initialized ) return;
    this._initialized = true;

    this.className = 'html-editor-panel';
    this.innerHTML = `
      <div class="hep-toolbar">
        <button class="hep-pin" title="Pin — keep this file when selecting others">Pin</button>
        <button class="hep-undo" title="Undo (Ctrl+Z)" disabled>↩</button>
        <button class="hep-redo" title="Redo (Ctrl+Y)" disabled>↪</button>
        <button class="hep-save" title="Save (Ctrl+S)" disabled>Save</button>
        <button class="hep-init" title="Insert Hello World template" disabled>Init</button>
      </div>
      <div class="hep-empty">Open an HTML file from the file tree</div>
      <iframe class="hep-frame" style="display:none"></iframe>
    `;

    this._iframe = this.querySelector( 'iframe' );

    this.querySelector( '.hep-pin' )!.addEventListener( 'click', () => this._togglePin() );
    this.querySelector( '.hep-save' )!.addEventListener( 'click', () => this._save() );
    this.querySelector( '.hep-undo' )!.addEventListener( 'click', () => this._undo() );
    this.querySelector( '.hep-redo' )!.addEventListener( 'click', () => this._redo() );
    this.querySelector( '.hep-init' )!.addEventListener( 'click', () => this._initTemplate() );

    Editor.get().onDocumentOpened.addListener( ( e ) =>
    {
      if ( ! this._pinned ) this._loadDocument( e.path, e.content );
    } );

    document.addEventListener( 'keydown', ( e: KeyboardEvent ) =>
    {
      if ( ! this.currentPath )
      {
        return;
      }

      if ( e.ctrlKey && e.key === 's' ) { e.preventDefault(); this._save(); }
      if ( e.ctrlKey && ! e.shiftKey && e.key === 'z' ) { e.preventDefault(); this._undo(); }
      if ( e.ctrlKey && ( e.key === 'y' || ( e.shiftKey && e.key === 'z' ) ) ) { e.preventDefault(); this._redo(); }
    } );
  }

  disconnectedCallback(): void
  {
    if ( this._undoStack.length > 0 )
    {
      this._needsRestore = true;
    }
  }

  _updateTabLabel( path: string ): void
  {
    const name = path ? path.slice( path.lastIndexOf( '/' ) + 1 ) : '';
    this.dispatchEvent( new CustomEvent( 'panel:label-change', { bubbles: true, detail: { label: '📄 ' + name } } ) );
  }

  _loadDocument( path: string, content: string ): void
  {
    this.currentPath = path;
    this._undoStack = [ content ];
    this._redoStack = [];
    this._updateTabLabel( path );
    this.querySelector( '.hep-empty' )!.setAttribute( 'style', 'display:none' );
    this._iframe!.style.display = '';
    this._renderContent( content );
    this._updateButtons( false );
  }

  _renderContent( html: string ): void
  {
    const iframe = this._iframe!;

    if ( this._mutationObserver )
    {
      this._mutationObserver.disconnect();
      this._mutationObserver = null;
    }

    iframe.srcdoc = html;
    iframe.onload = () =>
    {
      if ( this._needsRestore )
      {
        this._needsRestore = false;
        this._renderContent( this._undoStack[ this._undoStack.length - 1 ] );
        return;
      }

      const doc = iframe.contentDocument!;
      const pc = doc.querySelector( 'page-content' );

      if ( pc )
      {
        ( pc as HTMLElement ).contentEditable = 'true';
        ( pc as HTMLElement ).style.outline = 'none';
        this._mutationObserver = new MutationObserver( () => this._onContentChanged() );
        this._mutationObserver.observe( pc, { subtree: true, childList: true, characterData: true, attributes: true } );
      }
    };
  }

  _onContentChanged(): void
  {
    if ( ! this.currentPath || ! this._iframe?.contentDocument )
    {
      return;
    }

    const html = '<!DOCTYPE html>\n' + this._iframe.contentDocument.documentElement.outerHTML;
    const last = this._undoStack[ this._undoStack.length - 1 ];

    if ( html === last )
    {
      return;
    }

    this._undoStack.push( html );

    if ( this._undoStack.length > 200 )
    {
      this._undoStack.shift();
    }

    this._redoStack = [];
    Editor.get().markDirty( this.currentPath, html );
    this._updateButtons( true );
  }

  _undo(): void
  {
    if ( this._undoStack.length < 2 )
    {
      return;
    }

    const current = this._undoStack.pop()!;
    this._redoStack.push( current );
    const prev = this._undoStack[ this._undoStack.length - 1 ];
    Editor.get().markDirty( this.currentPath!, prev );
    this._renderContent( prev );
    this._updateButtons( true );
  }

  _redo(): void
  {
    if ( ! this._redoStack.length )
    {
      return;
    }

    const next = this._redoStack.pop()!;
    this._undoStack.push( next );
    Editor.get().markDirty( this.currentPath!, next );
    this._renderContent( next );
    this._updateButtons( true );
  }

  _togglePin(): void
  {
    this._pinned = ! this._pinned;
    this.querySelector( '.hep-pin' )!.classList.toggle( 'pinned', this._pinned );
  }

  _initTemplate(): void
  {
    if ( ! this.currentPath ) return;

    const template = [
      '<!DOCTYPE html>',
      '<html lang="en">',
      '<head>',
      '  <meta charset="UTF-8">',
      '  <title>Hello World</title>',
      '</head>',
      '<body>',
      '  <page-content>',
      '    <h1>Hello World</h1>',
      '    <p>Welcome.</p>',
      '  </page-content>',
      '</body>',
      '</html>',
    ].join( '\n' );

    this._undoStack.push( template );
    this._redoStack = [];
    Editor.get().markDirty( this.currentPath, template );
    this._renderContent( template );
    this._updateButtons( true );
  }

  async _save(): Promise<void>
  {
    if ( ! this.currentPath )
    {
      return;
    }

    await Editor.get().save( this.currentPath );
    this._updateButtons( false );
  }

  addContextMenuEntries( dir: ContextMenuDirectory ): void
  {
    if ( this.currentPath )
    {
      dir.add( new ContextMenuReadOnlyEntry( dir, `Editing: ${this.currentPath}` ) );
    }
    else
    {
      dir.add( new ContextMenuReadOnlyEntry( dir, 'No document open' ) );
    }
  }

  _updateButtons( dirty: boolean ): void
  {
    ( this.querySelector( '.hep-save' ) as HTMLButtonElement ).disabled = ! dirty;
    ( this.querySelector( '.hep-undo' ) as HTMLButtonElement ).disabled = this._undoStack.length < 2;
    ( this.querySelector( '.hep-redo' ) as HTMLButtonElement ).disabled = this._redoStack.length === 0;
    ( this.querySelector( '.hep-init' ) as HTMLButtonElement ).disabled = ! this.currentPath;
  }
}

customElements.define( 'html-editor-panel', HtmlEditorPanel );