refactor(text-field): add validator and use validity mixins

PiperOrigin-RevId: 587086864

labs/behaviors/validators/text-field-validator.ts

@@ -0,0 +1,271 @@
+/**
+ * @license
+ * Copyright 2023 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import {Validator} from './validator.js';
+
+/**
+ * Constraint validation for a text field.
+ */
+export interface TextFieldState {
+  /**
+   * The input or textarea state to validate.
+   */
+  state: InputState | TextAreaState;
+
+  /**
+   * The `<input>` or `<textarea>` that is rendered on the page.
+   *
+   * `minlength` and `maxlength` validation do not apply until a user has
+   * interacted with the control and the element is internally marked as dirty.
+   * This is a spec quirk, the two properties behave differently from other
+   * constraint validation.
+   *
+   * This means we need an actual rendered element instead of a virtual one,
+   * since the virtual element will never be marked as dirty.
+   *
+   * This can be `null` if the element has not yet rendered, and the validator
+   * will fall back to virtual elements for other constraint validation
+   * properties, which do apply even if the control is not dirty.
+   */
+  renderedControl: HTMLInputElement | HTMLTextAreaElement | null;
+}
+
+/**
+ * Constraint validation properties for an `<input>`.
+ */
+export interface InputState extends SharedInputAndTextAreaState {
+  /**
+   * The `<input>` type.
+   *
+   * Not all constraint validation properties apply to every type. See
+   * https://developer.mozilla.org/en-US/docs/Web/HTML/Constraint_validation#validation-related_attributes
+   * for which properties will apply to which types.
+   */
+  readonly type: string;
+
+  /**
+   * The regex pattern a value must match.
+   */
+  readonly pattern: string;
+
+  /**
+   * The minimum value.
+   */
+  readonly min: string;
+
+  /**
+   * The maximum value.
+   */
+  readonly max: string;
+
+  /**
+   * The step interval of the value.
+   */
+  readonly step: string;
+}
+
+/**
+ * Constraint validation properties for a `<textarea>`.
+ */
+export interface TextAreaState extends SharedInputAndTextAreaState {
+  /**
+   * The type, must be "textarea" to inform the validator to use `<textarea>`
+   * instead of `<input>`.
+   */
+  readonly type: 'textarea';
+}
+
+/**
+ * Constraint validation properties shared between an `<input>` and
+ * `<textarea>`.
+ */
+interface SharedInputAndTextAreaState {
+  /**
+   * The current value.
+   */
+  readonly value: string;
+
+  /**
+   * Whether the textarea is required.
+   */
+  readonly required: boolean;
+
+  /**
+   * The minimum length of the value.
+   */
+  readonly minLength: number;
+
+  /**
+   * The maximum length of the value.
+   */
+  readonly maxLength: number;
+}
+
+/**
+ * A validator that provides constraint validation that emulates `<input>` and
+ * `<textarea>` validation.
+ */
+export class TextFieldValidator extends Validator<TextFieldState> {
+  private inputControl?: HTMLInputElement;
+  private textAreaControl?: HTMLTextAreaElement;
+
+  protected override computeValidity({state, renderedControl}: TextFieldState) {
+    let inputOrTextArea = renderedControl;
+    if (isInputState(state) && !inputOrTextArea) {
+      // Get cached <input> or create it.
+      inputOrTextArea = this.inputControl || document.createElement('input');
+      // Cache the <input> to re-use it next time.
+      this.inputControl = inputOrTextArea;
+    } else if (!inputOrTextArea) {
+      // Get cached <textarea> or create it.
+      inputOrTextArea =
+        this.textAreaControl || document.createElement('textarea');
+      // Cache the <textarea> to re-use it next time.
+      this.textAreaControl = inputOrTextArea;
+    }
+
+    // Set this variable so we can check it for input-specific properties.
+    const input = isInputState(state)
+      ? (inputOrTextArea as HTMLInputElement)
+      : null;
+
+    // Set input's "type" first, since this can change the other properties
+    if (input) {
+      input.type = state.type;
+    }
+
+    if (inputOrTextArea.value !== state.value) {
+      // Only programmatically set the value if there's a difference. When using
+      // the rendered control, the value will always be up to date. Setting the
+      // property (even if it's the same string) will reset the internal <input>
+      // dirty flag, making minlength and maxlength validation reset.
+      inputOrTextArea.value = state.value;
+    }
+
+    inputOrTextArea.required = state.required;
+
+    // The following IDLAttribute properties will always hydrate an attribute,
+    // even if set to a the default value ('' or -1). The presence of the
+    // attribute triggers constraint validation, so we must remove the attribute
+    // when empty.
+    if (input) {
+      const inputState = state as InputState;
+      if (inputState.pattern) {
+        input.pattern = inputState.pattern;
+      } else {
+        input.removeAttribute('pattern');
+      }
+
+      if (inputState.min) {
+        input.min = inputState.min;
+      } else {
+        input.removeAttribute('min');
+      }
+
+      if (inputState.max) {
+        input.max = inputState.max;
+      } else {
+        input.removeAttribute('max');
+      }
+
+      if (inputState.step) {
+        input.step = inputState.step;
+      } else {
+        input.removeAttribute('step');
+      }
+    }
+
+    // Use -1 to represent no minlength and maxlength, which is what the
+    // platform input returns. However, it will throw an error if you try to
+    // manually set it to -1.
+    if (state.minLength > -1) {
+      inputOrTextArea.minLength = state.minLength;
+    } else {
+      inputOrTextArea.removeAttribute('minlength');
+    }
+
+    if (state.maxLength > -1) {
+      inputOrTextArea.maxLength = state.maxLength;
+    } else {
+      inputOrTextArea.removeAttribute('maxlength');
+    }
+
+    return {
+      validity: inputOrTextArea.validity,
+      validationMessage: inputOrTextArea.validationMessage,
+    };
+  }
+
+  protected override equals(
+    {state: prev}: TextFieldState,
+    {state: next}: TextFieldState,
+  ) {
+    // Check shared input and textarea properties
+    const inputOrTextAreaEqual =
+      prev.type === next.type &&
+      prev.value === next.value &&
+      prev.required === next.required &&
+      prev.minLength === next.minLength &&
+      prev.maxLength === next.maxLength;
+
+    if (!isInputState(prev) || !isInputState(next)) {
+      // Both are textareas, all relevant properties are equal.
+      return inputOrTextAreaEqual;
+    }
+
+    // Check additional input-specific properties.
+    return (
+      inputOrTextAreaEqual &&
+      prev.pattern === next.pattern &&
+      prev.min === next.min &&
+      prev.max === next.max &&
+      prev.step === next.step
+    );
+  }
+
+  protected override copy({state}: TextFieldState): TextFieldState {
+    // Don't hold a reference to the rendered control when copying since we
+    // don't use it when checking if the state changed.
+    return {
+      state: isInputState(state)
+        ? this.copyInput(state)
+        : this.copyTextArea(state),
+      renderedControl: null,
+    };
+  }
+
+  private copyInput(state: InputState): InputState {
+    const {type, pattern, min, max, step} = state;
+    return {
+      ...this.copySharedState(state),
+      type,
+      pattern,
+      min,
+      max,
+      step,
+    };
+  }
+
+  private copyTextArea(state: TextAreaState): TextAreaState {
+    return {
+      ...this.copySharedState(state),
+      type: state.type,
+    };
+  }
+
+  private copySharedState({
+    value,
+    required,
+    minLength,
+    maxLength,
+  }: SharedInputAndTextAreaState): SharedInputAndTextAreaState {
+    return {value, required, minLength, maxLength};
+  }
+}
+
+function isInputState(state: InputState | TextAreaState): state is InputState {
+  return state.type !== 'textarea';
+}