HTMLElement.prototype.isChildOf = function(parent) {
	var node = this.parentNode;
	while (node != null) {
		if (node == parent) {
			return true;
		}
		node = node.parentNode;
	}
	return false;
};

class SerializerField {
	/**
	 * constructor
	 *
	 * @param {HTMLElement} f Input field (input|select|textarea)
	 * @returns {SerializerField}
	 */
	constructor(f) {
		this.name;
		this.parent;
		this.field = f;
		this.required = f.required;
		this.type = this.field.getAttribute("type");
		this.flatten = this.field.hasAttribute("flatten");
	}

	/**
	 * serialize
	 *
	 * @returns {(String|Number|Boolean|Date)}
	 */
	serialize() {
		if (this.field.tagName == "SELECT" && this.field.multiple) {
			return Array.apply(null, this.field.options).filter(o => o.selected).map(o => o.value)
		}

		if (this.type == "number" || this.type == "range") {
			return Number(this.field.value);
		} 

		if (
			this.type == "date" ||
			this.type == "datetime-local" ||
			this.type == "month" ||
			this.type == "week"
		) {
			return new Date(this.field.value);
		} 

		if (this.type == "radio") {
			if (!this.field.checked) {
				return null
			}
		}

		if (this.type == "checkbox") {
			let checked = this.field.checked;
			if (this.field.hasAttribute("string")) {
				if (!checked) {
					return null;
				}
				return this.field.value;
			}
			return checked;
		}

		return this.field.value;
	}
}

class Serializer {
	/**
	 * constructor
	 *
	 * @param {HTMLElement} element
	 * @returns {Serializer}
	 */
	constructor(element) {
		let fields = element.querySelectorAll(
			`:scope input:not([type="submit"]), :scope select, :scope textarea, :scope group`
		);
		let groups = [].slice.call(element.querySelectorAll(`:scope group`));

		this.name = ":root";
		this.parent;
		this._fields = new Map();
		this.min = Number(element.getAttribute("min") || -1);
		this.flatten = element.hasAttribute("flatten")

		this.required = element.getAttribute("required") !== null || this.min != -1;

		for (let f of fields) {
			if (f.isChildOf(element) && groups.every(g => !f.isChildOf(g))) {
				this.addField(f);
			}
		}
	}

	/**
	 * addField
	 *
	 * @param {HTMLElement} f
	 */
	addField(f) {
		let fieldName = f.getAttribute("name");
		if(!fieldName) {
			return
		}

		let isArray = fieldName.match(/^\[(\d*)\]/);
		let isRadio = f.type == "radio";

		fieldName = fieldName.replace(/^\[\d*\]/, "");

		let field;
		if (f.tagName == "GROUP") {
			field = new Serializer(f);
		} else {
			field = new SerializerField(f);
		}

		if (field.type == "file") {
			return;
		}

		field.name = fieldName;
		field.parent = this;

		f.serializer = field;

		if (isArray) {
			if (!this._fields.has(fieldName)) {
				this._fields.set(fieldName, []);
			}
			if (isArray[1] != "") {
				this._fields.get(fieldName)[isArray[1]] = field;
			} else {
				this._fields.get(fieldName).push(field);
			}
		} else if (isRadio) {
			if (!this._fields.has(fieldName)) {
				this._fields.set(fieldName, []);
			}

			this._fields.get(fieldName).push(field);
		} else {
			this._fields.set(fieldName, field);
		}
	}

	/**
	 * removeField
	 *
	 * @param {(HTMLElement|Serializer|SerializerField)} f Serializer child
	 */
	removeField(f) {
		if (this._fields.has(f.name)) {
			let fields = this._fields.get(f.name);
			if (Array.isArray(fields)) {
				let index = fields.indexOf(f);
				this._fields.set(f.name, fields.splice(index, 1));
			} else {
				this._fields.delete();
			}
		}
	}

	/**
	 * serialize
	 *
	 * @returns {Object}
	 */
	serialize() {
		let json = {};
		for (let [k, f] of this._fields) {
			if (Array.isArray(f)) {
				if (k != "") {
					json[k] = [];
				} else {
					json = [];
				}
				for (let key in f) {
					if (f[key].type == "radio") {
						json = {}

						let d = f[key].serialize();
						if (d !== null) {
							if (k == "") {
								json = d;
								break;
							}
							json[k] = d;
							break;
						}

						continue
					}
					if (f[key]) {
						let d = f[key].serialize();
						if (d == null) {
							continue
						}

						if(k == "") {
							if(f[key].flatten || this.flatten){
								json[key].push(d);
							} else {
								json[key] = d;
							}

							continue
						}

						if(f[key].flatten || this.flatten){
							json[k].push(d);
							continue;
						}

						json[k][key] = d;
					}
				}
			} else {
				let d = f.serialize();
				if (d !== null) {
					if (k == "") {
						json = d;
						continue;
					}
					json[k] = d;
				}
			}
		}
		return Object.keys(json).length > 0 ? json : null;}
}

class Validator {
	/**
	 * validateRequired
	 *
	 * @static
	 * @param {(erializer|SerializerField)} field
	 * @returns {Object}
	 */
	static validateRequired(field) {
		let e = {
			valid: true,
			errors: {}
		};
		let v;
		if (field instanceof Serializer) {
			v = Validator.validateRequiredSerializer(field);
		} else {
			v = Validator.validateRequiredSerialzerField(field);
		}
		if (!v.valid) {
			e.valid = false;
			e.errors = v.errors;
		}
		return e;
	}

	/**
	 * validateRequiredSerializer
	 *
	 * @static
	 * @param {Serializer} field
	 * @returns {Object}
	 */
	static validateRequiredSerializer(field) {
		let e = {
			valid: true,
			errors: {}
		};

		let min = field.min;
		let validFieldsCount = 0;
		for (let [k, f] of field._fields) {
			if (Array.isArray(f)) {
				e.errors = {
					message: null
				};
				let validCount = 0;
				for (let sf of f) {
					if (!(sf.name in e.errors)) {
						e.errors[sf.name] = [];
					}

					let v = Validator.validateRequired(sf);
					if (!v.valid) {
						console.error(e.errors);
						e.errors[sf.name].push(v.errors);
						continue;
					}
					validCount++;
				}

				e.valid = min <= validCount;
				if (e.valid) {
					e.errors = {};
				} else {
					e.errors.message = `Should contain atleast ${min} value(s)`;
				}
			} else {
				let v = Validator.validateRequired(f);
				if (!v.valid) {
					e.valid = false;
					e.errors[f.name] = v.errors;
				}
			}
		}

		return e;
	}

	/**
	 * validateRequiredSerialzerField
	 *
	 * @static
	 * @param {SerializerField} field
	 * @returns {Object}
	 */
	static validateRequiredSerialzerField(field) {
		let e = {
			valid: true,
			errors: {}
		};

		if (field.required || (field.parent && field.parent.required)) {
			if (field.type != "checkbox") {
				e.valid = field.field.validity.valueMissing !== true;
				e.errors = "Is required";
			} else {
				e.valid = field.field.checked;
				e.errors = "Not checked";
			}
		}
		return e;
	}
}