/**
 * headers.js
 *
 * Headers class offers convenient helpers
 */

module.exports = Headers;

/**
 * Headers class
 *
 * @param   Object  headers  Response headers
 * @return  Void
 */
function Headers(headers) {

	var self = this;
	this._headers = {};

	// Headers
	if (headers instanceof Headers) {
		headers = headers.raw();
	}

	// plain object
	for (var prop in headers) {
		if (!headers.hasOwnProperty(prop)) {
			continue;
		}

		if (typeof headers[prop] === 'string') {
			this.set(prop, headers[prop]);

		} else if (typeof headers[prop] === 'number' && !isNaN(headers[prop])) {
			this.set(prop, headers[prop].toString());

		} else if (Array.isArray(headers[prop])) {
			headers[prop].forEach(function(item) {
				self.append(prop, item.toString());
			});
		}
	}

}

/**
 * Return first header value given name
 *
 * @param   String  name  Header name
 * @return  Mixed
 */
Headers.prototype.get = function(name) {
	var list = this._headers[name.toLowerCase()];
	return list ? list[0] : null;
};

/**
 * Return all header values given name
 *
 * @param   String  name  Header name
 * @return  Array
 */
Headers.prototype.getAll = function(name) {
	if (!this.has(name)) {
		return [];
	}

	return this._headers[name.toLowerCase()];
};

/**
 * Iterate over all headers
 *
 * @param   Function  callback  Executed for each item with parameters (value, name, thisArg)
 * @param   Boolean   thisArg   `this` context for callback function
 * @return  Void
 */
Headers.prototype.forEach = function(callback, thisArg) {
	Object.getOwnPropertyNames(this._headers).forEach(function(name) {
		this._headers[name].forEach(function(value) {
			callback.call(thisArg, value, name, this)
		}, this)
	}, this)
}

/**
 * Overwrite header values given name
 *
 * @param   String  name   Header name
 * @param   String  value  Header value
 * @return  Void
 */
Headers.prototype.set = function(name, value) {
	this._headers[name.toLowerCase()] = [value];
};

/**
 * Append a value onto existing header
 *
 * @param   String  name   Header name
 * @param   String  value  Header value
 * @return  Void
 */
Headers.prototype.append = function(name, value) {
	if (!this.has(name)) {
		this.set(name, value);
		return;
	}

	this._headers[name.toLowerCase()].push(value);
};

/**
 * Check for header name existence
 *
 * @param   String   name  Header name
 * @return  Boolean
 */
Headers.prototype.has = function(name) {
	return this._headers.hasOwnProperty(name.toLowerCase());
};

/**
 * Delete all header values given name
 *
 * @param   String  name  Header name
 * @return  Void
 */
Headers.prototype['delete'] = function(name) {
	delete this._headers[name.toLowerCase()];
};

/**
 * Return raw headers (non-spec api)
 *
 * @return  Object
 */
Headers.prototype.raw = function() {
	return this._headers;
};