import React, { useState, useRef, useEffect } from 'react';
import Draggable from 'react-draggable';
import { getWidget, DEFAULT_WIDGETS } from './widgets';
import { TrashIcon } from '../Icons';
import setPosition from './setPosition';
import i18n from '../i18n';

/** We need to compare bounds by value, not by object ref **/
const bounds = elem => {
  const { top, left, width, height } = elem.getBoundingClientRect();
  return `${top}, ${left}, ${width}, ${height}`;
}

/**
 * The popup editor component.
 * 
 * TODO instead of just updating the current annotation state,
 * we could create a stack of revisions, and allow going back
 * with CTRL+Z.
 */
const Editor = props => {

  // The current state of the edited annotation vs. original
  const [ currentAnnotation, setCurrentAnnotation ] = useState();

  const [ dragged, setDragged ] = useState(false);

  // Reference to the DOM element, so we can set position
  const element = useRef();

  // Set derived annotation state
  useEffect(() => {
    setCurrentAnnotation(props.annotation);
  }, [ props.annotation ]);

  // Change editor position if element has moved
  useEffect(() => {
    if (element.current) {
      // Note that ResizeObserver fires once when observation starts
      return initResizeObserver();
    }
  }, [ bounds(props.selectedElement) ]);

  useEffect(() => {
    if (currentAnnotation)
      setCurrentAnnotation(currentAnnotation.clone({ target: props.modifiedTarget }));
  }, [ props.modifiedTarget ])

  const initResizeObserver = () => {
    if (window?.ResizeObserver) {
      const resizeObserver = new ResizeObserver(() => {
        if (!dragged)
          setPosition(props.wrapperEl, element.current, props.selectedElement);
      });

      resizeObserver.observe(props.wrapperEl);
      return () => resizeObserver.disconnect();
    } else {
      // Fire setPosition *only* for devices that don't support ResizeObserver
      if (!dragged)
        setPosition(props.wrapperEl, element.current, props.selectedElement);
    }  
  }

  // Creator and created/modified timestamp metadata
  const creationMeta = body => {
    const meta = {};

    const { user } = props.env;

    // Metadata is only added when a user is set, otherwise
    // the Editor operates in 'anonymous mode'.
    if (user) {
      meta.creator = {};
      if (user.id) meta.creator.id = user.id;
      if (user.displayName) meta.creator.name = user.displayName;

      meta[body.created ? 'modified' : 'created'] = props.env.getCurrentTimeAdjusted();
    }

    return meta;
  }

  const onAppendBody = body => setCurrentAnnotation(
    currentAnnotation.clone({ 
      body: [ ...currentAnnotation.bodies, { ...body, ...creationMeta(body) } ] 
    })
  );

  const onUpdateBody = (previous, updated) => setCurrentAnnotation(
    currentAnnotation.clone({
      body: currentAnnotation.bodies.map(body => 
        body === previous ? { ...updated, ...creationMeta(updated) } : body)
    })
  );

  const onRemoveBody = body => setCurrentAnnotation(
    currentAnnotation.clone({
      body: currentAnnotation.bodies.filter(b => b !== body)
    })
  );

  /** A convenience shorthand **/
  const onUpsertBody = (arg1, arg2) => {
    if (arg1 == null && arg2 != null) {
      // Append arg 2 as a new body
      onAppendBody(arg2);
    } else if (arg1 != null && arg2 != null) {
      // Replace body arg1 with body arg2
      onUpdateBody(arg1, arg2);
    } else if (arg1 != null && arg2 == null) {
      // Find the first body with the same purpose as arg1,
      // and upsert
      const existing = currentAnnotation.bodies.find(b => b.purpose === arg1.purpose);
      if (existing)
        onUpdateBody(existing, arg1);
      else
        onAppendBody(arg1);
    }
  }

  const onSetProperty = (property, value) => {
    // A list of properties the user is NOT allowed to set
    const isForbidden = [ '@context', 'id', 'type', 'body', 'target' ].includes(property); 

    if (isForbidden)
      throw new Exception(`Cannot set ${property} - not allowed`);

    if (value) {
      setCurrentAnnotation(currentAnnotation.clone({ [property]: value }));
    } else {
      const updated = currentAnnotation.clone();
      delete updated[property];
      setCurrentAnnotation(updated);
    }
  };

  const onCancel = () => 
    props.onCancel(props.annotation);

  const onOk = _ => {
    // Removes the state payload from all bodies
    const undraft = annotation => 
      annotation.clone({
        body : annotation.bodies.map(({ draft, ...rest }) => rest)
      });

    // Current annotation is either a selection (if it was created from 
    // scratch just now) or an annotation (if it existed already and was
    // opened for editing)
    if (currentAnnotation.bodies.length === 0 && !props.allowEmpty) {
      if (currentAnnotation.isSelection)
        onCancel();
      else 
        props.onAnnotationDeleted(props.annotation);
    } else {
      if (currentAnnotation.isSelection)
        props.onAnnotationCreated(undraft(currentAnnotation).toAnnotation());
      else
        props.onAnnotationUpdated(undraft(currentAnnotation), props.annotation);
    }
  };

  const onDelete = () => 
    props.onAnnotationDeleted(props.annotation);

  // Use default comment + tag widget unless host app overrides
  const widgets = props.widgets ? 
    props.widgets.map(getWidget) : DEFAULT_WIDGETS;

  const isReadOnlyWidget = w => w.type.disableDelete ?
    w.type.disableDelete(currentAnnotation, {
      ...w.props,
      readOnly:props.readOnly,
      env: props.env
    }) : false;

  const hasDelete = currentAnnotation && 
    // annotation has bodies or allowEmpty,
    (currentAnnotation.bodies.length > 0 || props.allowEmpty) && // AND
    !props.readOnly && // we are not in read-only mode AND
    !currentAnnotation.isSelection && // this is not a selection AND
    !widgets.some(isReadOnlyWidget);  // every widget is deletable

  return (
    <Draggable 
      disabled={!props.detachable}
      cancel=".r6o-btn, .r6o-nodrag" 
      onDrag={() => setDragged(true)}>

      <div ref={element} className={dragged ? 'r6o-editor dragged' : 'r6o-editor'}>
        <div className="r6o-arrow" />
        <div className="r6o-editor-inner">
          {widgets.map(widget => 
            React.cloneElement(widget, { 
              annotation : currentAnnotation,
              readOnly : props.readOnly,
              env: props.env,
              onAppendBody,
              onUpdateBody,
              onRemoveBody,
              onUpsertBody,
              onSetProperty,
              onSaveAndClose: onOk              
            })
          )}
          
          { props.readOnly ? (
            <div className="r6o-footer">
              <button
                className="r6o-btn" 
                onClick={onCancel}>{i18n.t('Close')}</button>
            </div>
          ) : (
            <div className="r6o-footer">
              { hasDelete && (
                <button 
                  className="r6o-btn left delete-annotation" 
                  title={i18n.t('Delete')}
                  onClick={onDelete}>
                  <TrashIcon width={12} />
                </button>
              )}

              <button 
                className="r6o-btn outline"
                onClick={onCancel}>{i18n.t('Cancel')}</button>

              <button 
                className="r6o-btn "
                onClick={onOk}>{i18n.t('Ok')}</button>
            </div>
          )}
        </div>
      </div>

    </Draggable>
  )

}

export default Editor;