/**
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* CORS middleware for koa2
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*
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* @param {Object} [options]
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* - {String|Function(ctx)} origin `Access-Control-Allow-Origin`, default is request Origin header
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* - {Array} exposeHeaders `Access-Control-Expose-Headers`
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* - {String|Number} maxAge `Access-Control-Max-Age` in seconds
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* - {Boolean} credentials `Access-Control-Allow-Credentials`
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* - {Array} allowMethods `Access-Control-Allow-Methods`,
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* default is ['GET', 'PUT', 'POST', 'PATCH', 'DELETE', 'HEAD', 'OPTIONS']
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* - {Array} allowHeaders `Access-Control-Allow-Headers`
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* @return {Function}
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* @api public
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*/
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module.exports = function crossOrigin(options = {}) {
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const defaultOptions = {
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allowMethods: ['GET', 'PUT', 'POST', 'PATCH', 'DELETE', 'HEAD', 'OPTIONS'],
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};
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// set defaultOptions to options
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options = Object.assign({}, defaultOptions, options); // eslint-disable-line no-param-reassign
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// eslint-disable-next-line consistent-return
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return async function cors(ctx, next) {
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// always set vary Origin Header
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// https://github.com/rs/cors/issues/10
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ctx.vary('Origin');
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let origin;
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if (typeof options.origin === 'function') {
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origin = options.origin(ctx);
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} else {
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origin = options.origin || ctx.get('Origin') || '*';
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}
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if (!origin) {
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return await next();
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}
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// Access-Control-Allow-Origin
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ctx.set('Access-Control-Allow-Origin', origin);
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if (ctx.method === 'OPTIONS') {
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// Preflight Request
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if (!ctx.get('Access-Control-Request-Method')) {
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return await next();
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}
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// Access-Control-Max-Age
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if (options.maxAge) {
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ctx.set('Access-Control-Max-Age', String(options.maxAge));
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}
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// Access-Control-Allow-Credentials
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if (options.credentials === true) {
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// When used as part of a response to a preflight request,
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// this indicates whether or not the actual request can be made using credentials.
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ctx.set('Access-Control-Allow-Credentials', 'true');
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}
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// Access-Control-Allow-Methods
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if (options.allowMethods) {
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ctx.set('Access-Control-Allow-Methods', options.allowMethods.join(','));
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}
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// Access-Control-Allow-Headers
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if (options.allowHeaders) {
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ctx.set('Access-Control-Allow-Headers', options.allowHeaders.join(','));
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} else {
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ctx.set('Access-Control-Allow-Headers', ctx.get('Access-Control-Request-Headers'));
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}
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ctx.status = 204; // No Content
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} else {
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// Request
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// Access-Control-Allow-Credentials
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if (options.credentials === true) {
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if (origin === '*') {
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// `credentials` can't be true when the `origin` is set to `*`
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ctx.remove('Access-Control-Allow-Credentials');
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} else {
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ctx.set('Access-Control-Allow-Credentials', 'true');
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}
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}
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// Access-Control-Expose-Headers
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if (options.exposeHeaders) {
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ctx.set('Access-Control-Expose-Headers', options.exposeHeaders.join(','));
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}
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try {
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await next();
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} catch (err) {
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throw err;
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}
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}
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};
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};
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