2022-09-13 23:17:20 +00:00
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import type { MiddlewareHandler } from '../../hono.ts'
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2022-07-02 06:09:45 +00:00
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type CORSOptions = {
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2022-09-16 11:59:27 +00:00
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origin: string | string[] | ((origin: string) => string | undefined | null)
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2022-07-02 06:09:45 +00:00
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allowMethods?: string[]
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allowHeaders?: string[]
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maxAge?: number
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credentials?: boolean
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exposeHeaders?: string[]
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}
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2022-09-13 23:17:20 +00:00
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export const cors = (options?: CORSOptions): MiddlewareHandler => {
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2022-07-02 06:09:45 +00:00
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const defaults: CORSOptions = {
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origin: '*',
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allowMethods: ['GET', 'HEAD', 'PUT', 'POST', 'DELETE', 'PATCH'],
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allowHeaders: [],
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exposeHeaders: [],
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}
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const opts = {
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...defaults,
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...options,
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}
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2022-09-16 11:59:27 +00:00
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const findAllowOrigin = ((optsOrigin) => {
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if (typeof optsOrigin === 'string') {
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return () => optsOrigin
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} else if (typeof optsOrigin === 'function') {
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return optsOrigin
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} else {
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return (origin: string) => (optsOrigin.includes(origin) ? origin : optsOrigin[0])
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}
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})(opts.origin)
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2022-09-13 23:17:20 +00:00
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return async (c, next) => {
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2022-07-02 06:09:45 +00:00
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await next()
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function set(key: string, value: string) {
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c.res.headers.append(key, value)
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}
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2022-09-16 11:59:27 +00:00
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const allowOrigin = findAllowOrigin(c.req.headers.get('origin') || '')
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if (allowOrigin) {
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set('Access-Control-Allow-Origin', allowOrigin)
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2022-09-15 15:19:02 +00:00
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}
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2022-07-02 06:09:45 +00:00
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// Suppose the server sends a response with an Access-Control-Allow-Origin value with an explicit origin (rather than the "*" wildcard).
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// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Origin
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if (opts.origin !== '*') {
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set('Vary', 'Origin')
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}
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if (opts.credentials) {
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set('Access-Control-Allow-Credentials', 'true')
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}
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if (opts.exposeHeaders?.length) {
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set('Access-Control-Expose-Headers', opts.exposeHeaders.join(','))
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}
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if (c.req.method === 'OPTIONS') {
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// Preflight
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if (opts.maxAge != null) {
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set('Access-Control-Max-Age', opts.maxAge.toString())
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}
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if (opts.allowMethods?.length) {
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set('Access-Control-Allow-Methods', opts.allowMethods.join(','))
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}
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let headers = opts.allowHeaders
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if (!headers?.length) {
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const requestHeaders = c.req.headers.get('Access-Control-Request-Headers')
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if (requestHeaders) {
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headers = requestHeaders.split(/\s*,\s*/)
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}
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}
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if (headers?.length) {
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set('Access-Control-Allow-Headers', headers.join(','))
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set('Vary', 'Access-Control-Request-Headers')
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}
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c.res.headers.delete('Content-Length')
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c.res.headers.delete('Content-Type')
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c.res = new Response(null, {
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headers: c.res.headers,
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status: 204,
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statusText: c.res.statusText,
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})
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}
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}
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}
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