import { SchemaDeclaration, SchemaCheckResult, CheckResult, PlainObject } from './types';
import { MixedType, getFieldType, getFieldValue } from './MixedType';
import { set, get, isEmpty, pathTransform } from './utils';

interface CheckOptions {
  /**
   * Check for nested object
   */
  nestedObject?: boolean;
}

export class Schema<DataType = any, ErrorMsgType = string> {
  readonly $spec: SchemaDeclaration<DataType, ErrorMsgType>;
  
  private data: PlainObject;
  private checkResult: SchemaCheckResult<DataType, ErrorMsgType> = {};

  constructor(schema: SchemaDeclaration<DataType, ErrorMsgType>) {
    this.$spec = schema;
  }

  private getFieldType<T extends keyof DataType>(
    fieldName: T,
    nestedObject?: boolean
  ): SchemaDeclaration<DataType, ErrorMsgType>[T] {
    return getFieldType(this.$spec, fieldName as string, nestedObject);
  }

  private setFieldCheckResult(
    fieldName: string,
    checkResult: CheckResult<ErrorMsgType | string>,
    nestedObject?: boolean
  ) {
    if (nestedObject) {
      const namePath = fieldName.split('.').join('.object.');
      set(this.checkResult, namePath, checkResult);

      return;
    }

    this.checkResult[fieldName] = checkResult;
  }

  private setSchemaOptionsForAllType(data: PlainObject) {
    if (data === this.data) {
      return;
    }

    Object.entries(this.$spec).forEach(([key, type]) => {
      (type as MixedType).setSchemaOptions(this.$spec as any, data?.[key]);
    });

    this.data = data;
  }

  /**
   * Get the check result of the schema
   * @returns CheckResult<ErrorMsgType | string>
   */
  getCheckResult(path?: string, result = this.checkResult): CheckResult<ErrorMsgType | string> {
    if (path) {
      return result?.[path] || get(result, pathTransform(path)) || { hasError: false };
    }

    return result;
  }

  /**
   * Get the error messages of the schema
   */
  getErrorMessages(path?: string, result = this.checkResult): (string | ErrorMsgType)[] {
    let messages: (string | ErrorMsgType)[] = [];

    if (path) {
      const { errorMessage, object, array } =
        result?.[path] || get(result, pathTransform(path)) || {};

      if (errorMessage) {
        messages = [errorMessage];
      } else if (object) {
        messages = Object.keys(object).map(key => object[key]?.errorMessage);
      } else if (array) {
        messages = array.map(item => item?.errorMessage);
      }
    } else {
      messages = Object.keys(result).map(key => result[key]?.errorMessage);
    }

    return messages.filter(Boolean);
  }

  /**
   * Get all the keys of the schema
   */
  getKeys() {
    return Object.keys(this.$spec);
  }

  /**
   * Get the schema specification
   */
  getSchemaSpec() {
    return this.$spec;
  }

  checkForField<T extends keyof DataType>(
    fieldName: T,
    data: DataType,
    options: CheckOptions = {}
  ): CheckResult<ErrorMsgType | string> {
    this.setSchemaOptionsForAllType(data);

    const { nestedObject } = options;
    const fieldChecker = this.getFieldType(fieldName, nestedObject);

    if (!fieldChecker) {
      // fieldValue can be anything if no schema defined
      return { hasError: false };
    }

    const fieldValue = getFieldValue(data, fieldName as string, nestedObject);
    const checkResult = fieldChecker.check(fieldValue, data, fieldName as string);

    this.setFieldCheckResult(fieldName as string, checkResult, nestedObject);

    if (!checkResult.hasError) {
      const { checkIfValueExists } = fieldChecker.proxyOptions;

      // Check other fields if the field depends on them for validation
      fieldChecker.otherFields?.forEach((field: string) => {
        if (checkIfValueExists) {
          if (!isEmpty(getFieldValue(data, field, nestedObject))) {
            this.checkForField(field as T, data, options);
          }
          return;
        }
        this.checkForField(field as T, data, options);
      });
    }

    return checkResult;
  }

  checkForFieldAsync<T extends keyof DataType>(
    fieldName: T,
    data: DataType,
    options: CheckOptions = {}
  ): Promise<CheckResult<ErrorMsgType | string>> {
    this.setSchemaOptionsForAllType(data);

    const { nestedObject } = options;
    const fieldChecker = this.getFieldType(fieldName, nestedObject);

    if (!fieldChecker) {
      // fieldValue can be anything if no schema defined
      return Promise.resolve({ hasError: false });
    }

    const fieldValue = getFieldValue(data, fieldName as string, nestedObject);
    const checkResult = fieldChecker.checkAsync(fieldValue, data, fieldName as string);

    return checkResult.then(async result => {
      this.setFieldCheckResult(fieldName as string, result, nestedObject);

      if (!result.hasError) {
        const { checkIfValueExists } = fieldChecker.proxyOptions;
        const checkAll: Promise<CheckResult<ErrorMsgType | string>>[] = [];

        // Check other fields if the field depends on them for validation
        fieldChecker.otherFields?.forEach((field: string) => {
          if (checkIfValueExists) {
            if (!isEmpty(getFieldValue(data, field, nestedObject))) {
              checkAll.push(this.checkForFieldAsync(field as T, data, options));
            }
            return;
          }

          checkAll.push(this.checkForFieldAsync(field as T, data, options));
        });

        await Promise.all(checkAll);
      }

      return result;
    });
  }

  check<T extends keyof DataType>(data: DataType) {
    const checkResult: SchemaCheckResult<DataType, ErrorMsgType> = {};
    Object.keys(this.$spec).forEach(key => {
      if (typeof data === 'object') {
        checkResult[key] = this.checkForField(key as T, data);
      }
    });

    return checkResult;
  }

  checkAsync<T extends keyof DataType>(data: DataType) {
    const checkResult: SchemaCheckResult<DataType, ErrorMsgType> = {};
    const promises: Promise<CheckResult<ErrorMsgType | string>>[] = [];
    const keys: string[] = [];

    Object.keys(this.$spec).forEach((key: string) => {
      keys.push(key);
      promises.push(this.checkForFieldAsync(key as T, data));
    });

    return Promise.all(promises).then(values => {
      for (let i = 0; i < values.length; i += 1) {
        checkResult[keys[i]] = values[i];
      }

      return checkResult;
    });
  }
}

export function SchemaModel<DataType = PlainObject, ErrorMsgType = string>(
  o: SchemaDeclaration<DataType, ErrorMsgType>
) {
  return new Schema<DataType, ErrorMsgType>(o);
}

SchemaModel.combine = function combine<DataType = any, ErrorMsgType = string>(
  ...specs: Schema<any, ErrorMsgType>[]
) {
  return new Schema<DataType, ErrorMsgType>(
    specs
      .map(model => model.$spec)
      .reduce((accumulator, currentValue) => Object.assign(accumulator, currentValue), {} as any)
  );
};