Form Validation

/**
 * Reactive form validation with async-validator integration
 * @param value - Form data object to validate
 * @param rules - Validation rules object
 * @param options - Validation configuration options
 * @returns Validation state and control methods
 */
function useAsyncValidator(
  value: MaybeRefOrGetter<Record<string, any>>,
  rules: MaybeRefOrGetter<Rules>,
  options?: UseAsyncValidatorOptions
): UseAsyncValidatorReturn & PromiseLike<UseAsyncValidatorReturn>;

interface UseAsyncValidatorReturn {
  /** Whether all validations pass */
  pass: ShallowRef<boolean>;
  /** Whether validation has completed */
  isFinished: ShallowRef<boolean>;
  /** Array of validation errors */
  errors: ComputedRef<AsyncValidatorError['errors'] | undefined>;
  /** Complete error information object */
  errorInfo: ShallowRef<AsyncValidatorError | null>;
  /** Errors organized by field name */
  errorFields: ComputedRef<AsyncValidatorError['fields'] | undefined>;
  /** Execute validation manually */
  execute: () => Promise<UseAsyncValidatorExecuteReturn>;
}

interface UseAsyncValidatorExecuteReturn {
  /** Whether validation passed */
  pass: boolean;
  /** Array of validation errors */
  errors: AsyncValidatorError['errors'] | undefined;
  /** Complete error information */
  errorInfo: AsyncValidatorError | null;
  /** Errors organized by field */
  errorFields: AsyncValidatorError['fields'] | undefined;
}

interface UseAsyncValidatorOptions {
  /** Options passed to async-validator */
  validateOption?: ValidateOption;
  /** Execute validation immediately */
  immediate?: boolean; // default: true
  /** Manual validation mode (disable auto-validation) */
  manual?: boolean;
}

type AsyncValidatorError = Error & {
  errors: ValidateError[];
  fields: Record<string, ValidateError[]>;
};

// async-validator types
interface Rules {
  [key: string]: RuleItem | RuleItem[];
}

interface RuleItem {
  type?: RuleType;
  required?: boolean;
  pattern?: RegExp | string;
  min?: number;
  max?: number;
  len?: number;
  enum?: Array<string | number | boolean | null | undefined>;
  whitespace?: boolean;
  fields?: Rules;
  defaultField?: RuleItem;
  transform?: (value: any) => any;
  message?: string | ((a?: string) => string);
  asyncValidator?: (rule: InternalRuleItem, value: any, callback: (error?: string | Error) => void, source: Values, options: ValidateOption) => void;
  validator?: (rule: InternalRuleItem, value: any, callback: (error?: string | Error) => void, source: Values, options: ValidateOption) => void;
}

type RuleType = 'string' | 'number' | 'boolean' | 'method' | 'regexp' | 'integer' | 'float' | 'array' | 'object' | 'enum' | 'date' | 'url' | 'hex' | 'email' | 'any';

interface ValidateError {
  message?: string;
  fieldValue?: any;
  field?: string;
}

interface ValidateOption {
  suppressWarning?: boolean;
  first?: boolean;
  firstFields?: boolean | string[];
}

import { useAsyncValidator } from "@vueuse/integrations/useAsyncValidator";
import { ref, reactive } from 'vue';

// Basic form validation
const form = reactive({
  name: '',
  email: '',
  age: 0
});

const rules = {
  name: { type: 'string', required: true, min: 2 },
  email: { type: 'email', required: true },
  age: { type: 'number', required: true, min: 18 }
};

const { pass, errors, errorFields, execute } = useAsyncValidator(form, rules);

// Check validation state
watchEffect(() => {
  if (pass.value) {
    console.log('Form is valid!');
  } else {
    console.log('Validation errors:', errors.value);
  }
});

// Manual validation
const handleSubmit = async () => {
  const result = await execute();
  if (result.pass) {
    // Submit form
    console.log('Submitting:', form);
  } else {
    console.log('Validation failed:', result.errors);
  }
};

// Advanced validation with custom rules
const advancedRules = {
  username: [
    { required: true, message: 'Username is required' },
    { min: 3, max: 20, message: 'Username must be 3-20 characters' },
    { pattern: /^[a-zA-Z0-9_]+$/, message: 'Username can only contain letters, numbers, and underscores' }
  ],
  password: {
    required: true,
    validator: (rule, value, callback) => {
      if (value.length < 8) {
        callback(new Error('Password must be at least 8 characters'));
      } else if (!/(?=.*[a-z])(?=.*[A-Z])(?=.*\d)/.test(value)) {
        callback(new Error('Password must contain uppercase, lowercase, and numbers'));
      } else {
        callback();
      }
    }
  },
  confirmPassword: {
    required: true,
    validator: (rule, value, callback) => {
      if (value !== form.password) {
        callback(new Error('Passwords do not match'));
      } else {
        callback();
      }
    }
  }
};

// Async validation
const asyncRules = {
  email: {
    required: true,
    type: 'email',
    asyncValidator: async (rule, value, callback) => {
      try {
        const response = await fetch(`/api/check-email?email=${value}`);
        const result = await response.json();
        if (!result.available) {
          callback(new Error('Email is already taken'));
        } else {
          callback();
        }
      } catch (error) {
        callback(new Error('Failed to validate email'));
      }
    }
  }
};

// Manual validation mode
const { pass, execute } = useAsyncValidator(form, rules, {
  immediate: false,
  manual: true
});

// Display field-specific errors
const getFieldError = (fieldName: string) => {
  return errorFields.value?.[fieldName]?.[0]?.message;
};

/**
 * Declarative validation component
 */
const UseAsyncValidator = defineComponent({
  name: 'UseAsyncValidator',
  props: {
    /** Form data object to validate */
    form: {
      type: Object as PropType<Record<string, any>>,
      required: true
    },
    /** Validation rules object */
    rules: {
      type: Object as PropType<Rules>,
      required: true
    },
    /** Validation options */
    options: {
      type: Object as PropType<UseAsyncValidatorOptions>,
      default: () => ({})
    }
  },
  slots: {
    default: (props: {
      pass: boolean;
      errors: AsyncValidatorError['errors'] | undefined;
      errorFields: AsyncValidatorError['fields'] | undefined;
      isFinished: boolean;
      execute: () => Promise<UseAsyncValidatorExecuteReturn>;
    }) => any;
  }
});

<template>
  <UseAsyncValidator :form="form" :rules="rules" v-slot="{ pass, errors, errorFields, execute }">
    <form @submit.prevent="execute">
      <div>
        <label>Name:</label>
        <input v-model="form.name" />
        <span v-if="errorFields?.name" class="error">
          {{ errorFields.name[0].message }}
        </span>
      </div>
      
      <div>
        <label>Email:</label>
        <input v-model="form.email" type="email" />
        <span v-if="errorFields?.email" class="error">
          {{ errorFields.email[0].message }}
        </span>
      </div>
      
      <button type="submit" :disabled="!pass">
        Submit
      </button>
      
      <div v-if="errors">
        <h4>Validation Errors:</h4>
        <ul>
          <li v-for="error in errors" :key="error.field">
            {{ error.message }}
          </li>
        </ul>
      </div>
    </form>
  </UseAsyncValidator>
</template>

<script setup>
import { UseAsyncValidator } from "@vueuse/integrations/useAsyncValidator";
import { reactive } from 'vue';

const form = reactive({
  name: '',
  email: ''
});

const rules = {
  name: { required: true, min: 2 },
  email: { required: true, type: 'email' }
};
</script>