Added support for parametric rewrite prefix (#294)

Author: VazeeKevin

README.md

@@ -55,6 +55,14 @@ server.register(proxy, {
   http2: false // optional
 })
 
+// /rest-api/123/endpoint will be proxied to http://my-rest-api.example.com/123/endpoint
+server.register(proxy, {
+  upstream: 'http://my-rest-api.example.com',
+  prefix: '/rest-api/:id/endpoint', // optional
+  rewritePrefix: '/:id/endpoint', // optional
+  http2: false // optional
+})
+
 // /auth/user will be proxied to http://single-signon.example.com/signon/user
 server.register(proxy, {
   upstream: 'http://single-signon.example.com',
@@ -118,6 +126,8 @@ An URL (including protocol) that represents the target server to use for proxyin
 
 The prefix to mount this plugin on. All the requests to the current server starting with the given prefix will be proxied to the provided upstream.
 
+Parametric path is supported. To register a parametric path, use the colon before the parameter name.
+
 The prefix will be removed from the URL when forwarding the HTTP
 request.
 

index.js

@@ -302,7 +302,13 @@ async function fastifyHttpProxy (fastify, opts) {
     if (this.prefix.includes(':')) {
       const requestedPathElements = request.url.split('/')
       const prefixPathWithVariables = this.prefix.split('/').map((_, index) => requestedPathElements[index]).join('/')
-      dest = dest.replace(prefixPathWithVariables, rewritePrefix)
+
+      let rewritePrefixWithVariables = rewritePrefix
+      for (const [name, value] of Object.entries(request.params)) {
+        rewritePrefixWithVariables = rewritePrefixWithVariables.replace(`:${name}`, value)
+      }
+
+      dest = dest.replace(prefixPathWithVariables, rewritePrefixWithVariables)
     } else {
       dest = dest.replace(this.prefix, rewritePrefix)
     }

test/test.js

@@ -33,6 +33,10 @@ async function run () {
     return 'this is /api2/a'
   })
 
+  origin.get('/variable-api/:id/endpoint', async (request, reply) => {
+    return `this is "variable-api" endpoint with id ${request.params.id}`
+  })
+
   origin.get('/timeout', async (request, reply) => {
     await new Promise((resolve) => setTimeout(resolve, 600))
     return 'this is never received'
@@ -453,7 +457,7 @@ async function run () {
     t.equal(firstProxyPrefix.body, 'this is /api2/a')
   })
 
-  test('rewritePrefix with variables', async t => {
+  test('prefix with variables', async t => {
     const proxyServer = Fastify()
 
     proxyServer.register(proxy, {
@@ -474,6 +478,69 @@ async function run () {
     t.equal(firstProxyPrefix.body, 'this is /api2/a')
   })
 
+  test('prefix and rewritePrefix with variables', async t => {
+    const proxyServer = Fastify()
+
+    proxyServer.register(proxy, {
+      upstream: `http://localhost:${origin.server.address().port}`,
+      prefix: '/api/:id',
+      rewritePrefix: '/variable-api/:id'
+    })
+
+    await proxyServer.listen({ port: 0 })
+
+    t.teardown(() => {
+      proxyServer.close()
+    })
+
+    const firstProxyPrefix = await got(
+      `http://localhost:${proxyServer.server.address().port}/api/123/endpoint`
+    )
+    t.equal(firstProxyPrefix.body, 'this is "variable-api" endpoint with id 123')
+  })
+
+  test('prefix (complete path) and rewritePrefix with variables and similar path', async t => {
+    const proxyServer = Fastify()
+
+    proxyServer.register(proxy, {
+      upstream: `http://localhost:${origin.server.address().port}`,
+      prefix: '/api/:id/static',
+      rewritePrefix: '/variable-api/:id/endpoint'
+    })
+
+    await proxyServer.listen({ port: 0 })
+
+    t.teardown(() => {
+      proxyServer.close()
+    })
+
+    const firstProxyPrefix = await got(
+      `http://localhost:${proxyServer.server.address().port}/api/123/static`
+    )
+    t.equal(firstProxyPrefix.body, 'this is "variable-api" endpoint with id 123')
+  })
+
+  test('prefix and rewritePrefix with variables with different paths', async t => {
+    const proxyServer = Fastify()
+
+    proxyServer.register(proxy, {
+      upstream: `http://localhost:${origin.server.address().port}`,
+      prefix: '/:id',
+      rewritePrefix: '/variable-api/:id/endpoint'
+    })
+
+    await proxyServer.listen({ port: 0 })
+
+    t.teardown(() => {
+      proxyServer.close()
+    })
+
+    const firstProxyPrefix = await got(
+      `http://localhost:${proxyServer.server.address().port}/123`
+    )
+    t.equal(firstProxyPrefix.body, 'this is "variable-api" endpoint with id 123')
+  })
+
   test('rewrite location headers', async t => {
     const proxyServer = Fastify()