import { Data_Validation_Failed, Data_Coercion_Failed, Superfluous_Data_Field } from '@efforting.tech/errors';


export class Field_Configuration {
	constructor(validation_function=null, coercion_function=null, factory_function=null, expected_description=undefined) {
		Object.assign(this, { validation_function, coercion_function, factory_function, expected_description });
	}

	check_validation(value) {
		const { validation_function } = this;
		return !validation_function || validation_function(value);
	}

	validate(value, target=undefined) {
		const { validation_function, expected_description } = this;
		if (!this.check_validation(value)) {
			throw new Data_Validation_Failed({
				validation_function, value,
				target, expected_description,
			});
		}
	}

	coerce(value, target=undefined) {
		const { coercion_function, expected_description } = this;
		try {
			return coercion_function ? coercion_function(value) : value;
		} catch (e) {
			throw new Data_Coercion_Failed({
				coercion_function, value,
				target, expected_description,
				upstream_error: e,
			})
		}
	}

	load(value=undefined, target=undefined) {

		const { factory_function } = this;

		if ((value === undefined) && factory_function) {
			value = factory_function(target);
		}

		const coerced_value = this.coerce(value, target);
		this.validate(coerced_value, target);
		return coerced_value;
	}


}


export class Schema {

	constructor(field_schema, name=undefined) {
		Object.assign(this, { field_schema, name });
	}

	load(value={}, target=undefined) {
		const { field_schema, name } = this;

		for (const [value_name, value_value] of Object.entries(value)) {
			if (!field_schema[value_name]) {
				throw new Superfluous_Data_Field({
					field_value: value_value, field_name: value_name, target,
				});
			}
		}

		const result = {};
		const this_schema = name ? `schema "${name}"` : 'untitled schema';

		for (const [field_name, field_config] of Object.entries(field_schema)) {
			const sub_target = { schema: this, name: field_name, config: field_config, parent_target: target, info: `Field "${field_name}" of ${this_schema}` };
			result[field_name] = field_config.load(value[field_name], sub_target);
		}

		return result;
	}

}