tp-textarea/tp-textarea.js

/**
@license
Copyright (c) 2024 trading_peter
This program is available under Apache License Version 2.0
*/

import { FormElement } from '@tp/helpers/form-element.js';
import { DomQuery } from '@tp/helpers/dom-query.js';
import { ControlState } from '@tp/helpers/control-state.js';
import { LitElement, html, css } from 'lit';

class TpTextarea extends FormElement(DomQuery(ControlState(LitElement))) {
  static get styles() {
    return [
      css`
        :host {
          display: block;
          position: relative;
          border: solid 1px #9E9E9E;
          overflow: hidden;
        }

        :host([invalid]) {
          border: solid 1px #B71C1C;
        }

        .error-message {
          position: absolute;
          bottom: 0;
          left: 0;
          right: 0;
          font-size: 10px;
          color: var(--tp-textarea-text-color-invalid, #B71C1C);
          transition: opacity 0.3s;
          opacity: 0;
          overflow: hidden;
          text-overflow: ellipsis;
          white-space: nowrap;
          pointer-events: none;
          background: #ffffff;
        }

        :host([invalid]) .error-message {
          opacity: 1;
        }

        .wrap {
          position: absolute;
          top: 0;
          left: 0;
          right: 0;
          bottom: 0;
          padding: var(--tp-textarea-padding, 0);
        }

        .mirror-text {
          visibility: hidden;
          word-wrap: break-word;
          padding: var(--tp-textarea-padding, 0);
        }

        .wrap ::slotted(textarea) {
          position: relative;
          outline: none;
          border: none;
          resize: none;
          background: inherit;
          color: inherit;
          width: 100%;
          height: 100%;
          font-size: inherit;
          font-family: inherit;
          line-height: inherit;
          text-align: inherit;
          box-sizing: border-box;
          overflow: hidden;
          padding: 0;
        }
      `
    ];
  }

  render() {
    const { errorMessage } = this;

    return html`
      <div id="mirror" class="mirror-text" part="mirror" aria-hidden="true">&nbsp;</div>

      <div class="wrap" part="wrap">
        <slot></slot>
      </div>

      <div class="error-message" part="error-message">${errorMessage}</div>
    `;
  }

  static get properties() {
    return {
      readonly: { type: Boolean },
      required: { type: Boolean },
      errorMessage: { type: String },
      invalid: { type: Boolean, reflect: true },
    };
  }

  constructor() {
    super();
    this.value = '';
  }

  connectedCallback() {
    super.connectedCallback();
    this.addEventListener('input', this._onInput);
  }

  disconnectedCallback() {
    super.disconnectedCallback();
    this.removeEventListener('input', this._onInput);
  }

  updated(changes) {
    if (changes.has('value')) {
      this._syncToTextarea();
    }

    if (changes.has('readonly')) {
      this._readOnlyChanged();
    }
  }

  get textarea() {
    return this.querySelector('textarea');
  }

  get selectionStart() {
    return this.textarea.selectionStart;
  }

  get selectionEnd() {
    return this.textarea.selectionEnd;
  }

  validate() {
    // Use the nested input's native validity.
    let valid = this.textarea.validity.valid;

    // Only do extra checking if the browser thought this was valid.
    if (valid) {
      // Empty, required input is invalid
      if (this.required && this.value === '') {
        valid = false;
      }
    }

    this.invalid = !valid;
    return valid;
  }

  reset() {
    this.value = '';
    this.textarea.value = '';
    this.invalid = false;
  }

  _syncToTextarea() {
    if (typeof this.value !== 'string') {
      return this.value = '';
    }

    if (this.textarea) {
      this.textarea.value = this.value || '';
      this.$.mirror.innerHTML = this._valueForMirror();
    }
  }

  _readOnlyChanged(state) {
    this.textarea.readOnly = state;
  }

  _onInput() {
    this.$.mirror.innerHTML = this._valueForMirror();
    this.value = this.textarea.value;
  }

  _constrain(tokens) {
    let _tokens;
    tokens = tokens || [''];
    // Enforce the min and max heights for a multiline input to avoid measurement
    if (this.maxRows > 0 && tokens.length > this.maxRows) {
      _tokens = tokens.slice(0, this.maxRows);
    } else {
      _tokens = tokens.slice(0);
    }
    while (this.rows > 0 && _tokens.length < this.rows) {
      _tokens.push('');
    }
    // Use &#160; instead &nbsp; of to allow this element to be used in XHTML.
    return _tokens.join('<br/>') + '&#160;';
  }

  _valueForMirror() {
    const input = this.textarea;
    if (!input) {
      return;
    }
    this.tokens = (input && input.value) ? input.value.replace(/&/gm, '&amp;').replace(/"/gm, '&quot;').replace(/'/gm, '&#39;').replace(/</gm, '&lt;').replace(/>/gm, '&gt;').split('\n') : [''];
    return this._constrain(this.tokens);
  }

  _updateCached() {
    this.$.mirror.innerHTML = this._constrain(this.tokens);
  }
}

window.customElements.define('tp-textarea', TpTextarea);