Pull request router

README.md

@@ -36,17 +36,18 @@ The [`master`](https://github.com/codequest-eu/terraform-single-page-app/tree/ma
 
 ## Inputs
 
-| Name                            | Description                                                                                                                                 |  Type  |      Default       | Required |
-| ------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------- | :----: | :----------------: | :------: |
-| bucket                          | Kebab-cased bucket name override                                                                                                            | string |        `""`        |    no    |
-| certificate\_arn                | ACM certificate ARN to use instead of the default cloudfront certificate                                                                    | string |        `""`        |    no    |
-| cloudfront\_price\_class        | CloudFront price class, which specifies where the distribution should be replicated, one of: PriceClass_100, PriceClass_200, PriceClass_All | string | `"PriceClass_100"` |    no    |
-| domains                         | List of domains which will serve the application. If empty, will use the default cloudfront domain                                          |  list  |      `<list>`      |    no    |
-| environment                     | Kebab-cased name of the environment, eg. production, staging, development, preview. Will be included in resource names                      | string |        n/a         |   yes    |
-| project                         | Kebab-cased name of the project. Will be included in resource names                                                                         | string |        n/a         |   yes    |
-| static\_cors\_max\_age\_seconds | How long can CORS OPTIONS request responses be cached                                                                                       | string |      `"3600"`      |    no    |
-| static\_path                    | Base path for static assets                                                                                                                 | string |    `"/static"`     |    no    |
-| tags                            | Additional tags to add to each resource that supports them                                                                                  |  map   |      `<map>`       |    no    |
+| Name                            | Description                                                                                                                                 |  Type  |       Default        | Required |
+| ------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------- | :----: | :------------------: | :------: |
+| bucket                          | Kebab-cased bucket name override                                                                                                            | string |         `""`         |    no    |
+| certificate\_arn                | ACM certificate ARN to use instead of the default cloudfront certificate                                                                    | string |         `""`         |    no    |
+| cloudfront\_price\_class        | CloudFront price class, which specifies where the distribution should be replicated, one of: PriceClass_100, PriceClass_200, PriceClass_All | string |  `"PriceClass_100"`  |    no    |
+| domains                         | List of domains which will serve the application. If empty, will use the default cloudfront domain                                          |  list  |       `<list>`       |    no    |
+| environment                     | Kebab-cased name of the environment, eg. production, staging, development, preview. Will be included in resource names                      | string |         n/a          |   yes    |
+| project                         | Kebab-cased name of the project. Will be included in resource names                                                                         | string |         n/a          |   yes    |
+| pull\_request\_path\_re         | Regular expression which extracts the base directory of a PR as it's first match group                                                      | string | `"^/(PR-\\d+)($|/)"` |    no    |
+| static\_cors\_max\_age\_seconds | How long can CORS OPTIONS request responses be cached                                                                                       | string |       `"3600"`       |    no    |
+| static\_path                    | Base path for static assets                                                                                                                 | string |     `"/static"`      |    no    |
+| tags                            | Additional tags to add to each resource that supports them                                                                                  |  map   |       `<map>`        |    no    |
 
 ## Outputs
 

example/main.tf

@@ -26,7 +26,7 @@ module "basic" {
 
 resource "aws_s3_bucket_object" "basic_index" {
   bucket        = "${module.basic.bucket_name}"
-  key           = "index.html"
+  key           = "PR-1/index.html"
   content       = "<h1>Hello world</h1>"
   content_type  = "text/html"
   cache_control = "no-cache no-store"

main.tf

@@ -1,3 +1,7 @@
+provider "aws" {
+  alias = "middleware"
+}
+
 resource "aws_s3_bucket" "assets" {
   bucket = "${var.bucket != "" ? var.bucket : "${local.name_prefix}-assets"}"
   acl    = "private"
@@ -94,13 +98,12 @@ resource "aws_cloudfront_distribution" "assets" {
         forward = "none"
       }
     }
-  }
 
-  custom_error_response {
-    error_code            = 404
-    error_caching_min_ttl = 0
-    response_code         = 200
-    response_page_path    = "/index.html"
+    lambda_function_association {
+      event_type   = "origin-request"
+      lambda_arn   = "${module.pull_request_router.arn}"
+      include_body = false
+    }
   }
 
   restrictions {
@@ -118,3 +121,34 @@ resource "aws_cloudfront_distribution" "assets" {
 
   tags = "${local.tags}"
 }
+
+module "middleware_common" {
+  source = "./middleware_common"
+
+  name_prefix = "${local.name_prefix}"
+
+  providers = {
+    aws = "aws.middleware"
+  }
+}
+
+data "template_file" "pull_request_router" {
+  template = "${file("${path.module}/templates/pull-request-router.js")}"
+
+  vars {
+    path_re = "${var.pull_request_path_re}"
+  }
+}
+
+module "pull_request_router" {
+  source = "./middleware"
+
+  name     = "${local.name_prefix}-pull-request-router"
+  code     = "${data.template_file.pull_request_router.rendered}"
+  role_arn = "${module.middleware_common.role_arn}"
+  tags     = "${local.tags}"
+
+  providers = {
+    aws = "aws.middleware"
+  }
+}

templates/pull-request-router.js

@@ -0,0 +1,19 @@
+const path = require("path")
+
+const r = String.raw
+const pathRe = new RegExp(r`${path_re}`)
+
+exports.handler = (evt, ctx, cb) => {
+  const { request } = evt.Records[0].cf
+  console.log("<-", request.uri)
+
+  const match = pathRe.exec(request.uri)
+  const extension = path.extname(request.uri)
+
+  if (match && !extension) {
+    request.uri = `/$${match[1]}/index.html`
+  }
+
+  console.log("->", request.uri)
+  cb(null, request)
+}

variables.tf

@@ -46,3 +46,8 @@ variable "bucket" {
   description = "Kebab-cased bucket name override"
   default     = ""
 }
+
+variable "pull_request_path_re" {
+  description = "Regular expression which extracts the base directory of a PR as it's first match group"
+  default     = "^/(PR-\\d+)($|/)"
+}