Skeleton of basic functionality, all as TODOs

templates/crystal-http/Dockerfile

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+FROM --platform=${TARGETPLATFORM:-linux/amd64} ghcr.io/openfaas/of-watchdog:0.9.10 as watchdog
+FROM --platform=${TARGETPLATFORM:-linux/amd64} alpine as build
+ARG ADDITIONAL_PACKAGE
+
+COPY --from=watchdog /fwatchdog /usr/bin/fwatchdog
+
+RUN apk update && apk upgrade && apk add crystal shards openssl-dev ${ADDITIONAL_PACKAGE} && apk cache clean
+
+WORKDIR /home/app
+
+COPY function/shard.yml shard.yml
+RUN shards install
+COPY . .
+RUN crystal build main.cr -o handler --error-trace -p  && rm -rf /root/.cache
+
+FROM --platform=${TARGETPLATFORM:-linux/amd64} alpine as ship
+ARG ADDITIONAL_PACKAGE
+RUN apk update && apk upgrade && apk add openssl pcre2 libgcc gc libevent ${ADDITIONAL_PACKAGE} && apk cache clean
+# Add non root user
+# Add non root user
+RUN addgroup -S app && adduser app -S -G app
+
+WORKDIR /home/app
+USER app
+
+COPY --from=build /home/app/function/  .
+COPY --from=build /home/app/handler    .
+COPY --from=watchdog /fwatchdog /usr/bin/fwatchdog
+
+ENV fprocess="./handler"
+ENV exec_timeout=30
+EXPOSE 8080
+
+HEALTHCHECK --interval=2s CMD [ -e /tmp/.lock ] || exit 1
+
+ENV upstream_url="http://127.0.0.1:5000"
+ENV mode="http"
+
+CMD ["fwatchdog"]

templates/crystal-http/function/handler.cr

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+require "http/request"
+require "http/headers"
+
+class Handler
+  def run(request : HTTP::Request)
+    {
+      body:        "Hello, Crystal. You said: #{request.body.try(&.gets_to_end)}",
+      status_code: 200,
+      headers:     HTTP::Headers{"Content-Type" => "text/plain"},
+    }
+  end
+end

templates/crystal-http/function/shard.yml

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+name: crystal-http-template
+version: 0.1.0

templates/crystal-http/main.cr

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+require "http/server"
+require "./function/handler"
+
+server = HTTP::Server.new do |context|
+  response_triple : NamedTuple(body: String, headers: HTTP::Headers, status_code: Int32) |
+                    NamedTuple(body: String, headers: HTTP::Headers) |
+                    NamedTuple(body: String, status_code: Int32) |
+                    NamedTuple(body: String) |
+                    NamedTuple(headers: HTTP::Headers, status_code: Int32) |
+                    NamedTuple(headers: HTTP::Headers) |
+                    NamedTuple(status_code: Int32)
+
+  handler = Handler.new
+  response_triple = handler.run(context.request)
+
+  if response_triple.is_a?(NamedTuple(body: String, headers: HTTP::Headers, status_code: Int32) |
+                           NamedTuple(body: String, status_code: Int32) |
+                           NamedTuple(headers: HTTP::Headers, status_code: Int32) |
+                           NamedTuple(status_code: Int32))
+    context.response.status_code = response_triple[:status_code]
+  end
+
+  if response_triple.is_a?(NamedTuple(body: String, headers: HTTP::Headers, status_code: Int32) |
+                           NamedTuple(body: String, headers: HTTP::Headers) |
+                           NamedTuple(headers: HTTP::Headers, status_code: Int32) |
+                           NamedTuple(headers: HTTP::Headers))
+    response_triple[:headers].each do |key, value|
+      context.response.headers[key] = value
+    end
+  end
+
+  if response_triple.is_a?(NamedTuple(body: String, headers: HTTP::Headers, status_code: Int32) |
+                           NamedTuple(body: String, headers: HTTP::Headers) |
+                           NamedTuple(body: String, status_code: Int32) |
+                           NamedTuple(body: String))
+    context.response.print(response_triple[:body])
+  end
+end
+
+server.bind_tcp "0.0.0.0", 5000
+server.listen

templates/crystal-http/template.yml

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+language: crystal
+fprocess: ./handler
+welcome_message: |
+  You have created a new function which uses crystal 1.0.0.
+  To include third-party dependencies, use a vendoring tool like shards:
+  shards documentation: https://github.com/crystal-lang/shards