Move API docs redirects to CloudFront

docs/Makefile

@@ -51,15 +51,13 @@ dist-docs_versions: $(OUTPUT_DIR)/versions-$(CRYSTAL_VERSION).json ## Update `/v
 $(OUTPUT_DIR)/versions-$(CRYSTAL_VERSION).json: $(OUTPUT_DIR)/$(OUTPUT_DOCS_BASE_NAME).tar.gz
 
 .PHONY: dist-redirect_latest
-dist-redirect_latest: $(OUTPUT_DIR)/aws-config.json ## Apply redirect from `api/latest` to `api/$(CRYSTAL_VERSION)` in S3 (needs to be manually applied)
-	$(AWS_CLI) s3api put-bucket-website --bucket "$(AWS_BUCKET)" --website-configuration "file://$<"
+dist-redirect_latest: MATCH_CURRENT_ETAG = --name crystal-api-docs-redirects --if-match "$$($(AWS_CLI) cloudfront describe-function --name crystal-api-docs-redirects --output text --query 'ETag')"
+dist-redirect_latest: $(OUTPUT_DIR)/aws-cloudfront-redirect.js ## Apply redirect from `api/latest` to `api/$(CRYSTAL_VERSION)` in CloudFront (needs to be manually applied)
+	$(AWS_CLI) cloudfront update-function $(MATCH_CURRENT_ETAG) --function-config '{"Runtime":"cloudfront-js-2.0","Comment":"Redirects for Crystal API docs $(CRYSTAL_VERSION)"}' --function-code "$(shell base64 -i $(OUTPUT_DIR)/aws-cloudfront-redirect.js)"
+	$(AWS_CLI) cloudfront publish-function $(MATCH_CURRENT_ETAG)
 
-.PHONY: get-website-configuration
-get-website-configuration: ## Pull website configuration from S3 bucket (run as `make pull-website-configuration -s > aws-config.json`)
-	$(AWS_CLI) s3api get-bucket-website --bucket "$(AWS_BUCKET)"
-
-.PHONY: $(OUTPUT_DIR)/aws-config.json
-$(OUTPUT_DIR)/aws-config.json: aws-config.json $(OUTPUT_DIR)
+.PHONY: $(OUTPUT_DIR)/aws-cloudfront-redirect.js
+$(OUTPUT_DIR)/aws-cloudfront-redirect.js: aws-cloudfront-redirect.js $(OUTPUT_DIR)
 	sed 's/$${CRYSTAL_VERSION}/$(CRYSTAL_VERSION)/g' "$<" > $@
 
 .PHONY: help

docs/aws-cloudfront-redirect.js

@@ -0,0 +1,41 @@
+// Since CloudFront doesn't run functions when the origin returns a statusCode >=400
+// this function has to run upon "viewer request", before hitting the origin
+
+function redirect(path) {
+  return {
+    statusCode: 302,
+    headers: {
+      'location': { value: path }
+    }
+  }
+}
+
+const LATEST_INDEX_REDIRECTION_PATHS = [ '/api', '/api/', '/api/index.html', '/api/latest']
+
+function handler(event) {
+  var requestPath = event.request.uri
+
+  // well-known paths that should be queried as-is
+  if(
+    requestPath == '/api/versions.json' ||
+    requestPath.startsWith('/api/1.') ||
+    requestPath.startsWith('/api/0.') ||
+    requestPath == '/api/master' ||
+    requestPath.startsWith('/api/master/')
+  ) {
+    return event.request
+  }
+
+  // prefixes that go to the current version's index
+  if(LATEST_INDEX_REDIRECTION_PATHS.includes(requestPath)) {
+    return redirect('/api/${CRYSTAL_VERSION}/')
+  }
+
+  // "latest" prefix should be re-written to the current version
+  if(requestPath.startsWith('/api/latest/')) {
+    return redirect(requestPath.replace('/api/latest/', '/api/${CRYSTAL_VERSION}/'))
+  }
+
+  // at this point, we assume the request omited the version - eg, `/api/String.html`
+  return redirect(requestPath.replace('/api/', '/api/${CRYSTAL_VERSION}/'))
+}