Add Dockerfile

Dockerfile

@@ -0,0 +1,16 @@
+FROM alpine:latest
+
+RUN apk add python3 py3-pip
+RUN pip3 install Flask cachelib
+
+# By default run on port 5000, because README.md currently mentions it
+ARG PORT=5000
+EXPOSE $PORT
+
+COPY . BuildYourOwnLisp
+WORKDIR BuildYourOwnLisp
+# Make the containerized Flask server visible from the host machine
+RUN sed --in-place s'/\(app.run(.*\))/\1, host="0.0.0.0")/' lispy.py
+# Set PORT environment variable to ARG 'PORT' for lispy.py
+ENV PORT=$PORT
+CMD python3 lispy.py

Makefile

@@ -0,0 +1,31 @@
+.PHONY:
+# Make target-specific variables; so as to not pollute the Makefile
+byol-docker: PORT := 5000
+# prev-byol is deliberately a recursively expanded variable as
+# automatic variable $@ is not available outside of the recipes.
+# If a docker image with the name 'byol-docker' already exists
+# when this Make target is called, it expands to the id of that
+# image; else, it expands to an empty string.
+byol-docker: prev-byol = $(shell \
+                            docker inspect --format '{{ .ID }}' $@ \
+                              | sed s'/\(.*:\)\(.*\)/\2/' || echo "")
+byol-docker:
+# We need to delete (docker rmi) the existing 'byol-docker' image
+# before we create a new one or else untagged <none> images start
+# piling up. However, we can't `docker rmi` that image before the
+# build or else we'd lose the cache and will have  to  start over
+# from the base image. Neither can we use `docker rmi --no-prune`
+# as it, too, will pile up <none> images since  not  all untagged
+# parents of last  image  can be used as cache for the new build.
+# (A quick look at the Dockerfile  will  show that  any practical
+# rebuild of the image will at least branch off from the Dockerfile
+# instruction 'COPY . BuildYourOwnLisp')  Therefore, we use $(eval)
+# to create a Make variable, 'last-byol-image', and set it to the
+# id of the previous byol docker image, so as to `rmi` it once the
+# build is complete.
+	$(eval last-byol-image := $(prev-byol))
+	docker build --build-arg PORT=$(PORT) --tag $@ .
+# Now that the build is complete, delete the previous byol-docker image
+# Also, ignore if this recipe's failure (when last-byol-image is "")
+	-docker rmi $(last-byol-image) > /dev/null 2>&1
+	docker run --rm --publish $(PORT):$(PORT) $@

README.md

@@ -34,3 +34,10 @@ env PORT=5000 python lispy.py
 ```
 
 This will serve the site locally at `http://127.0.0.1:5000/`. You can browse it from there.
+
+Or, if you have docker installed, and don't want to install the dependencies locally, run:
+```
+docker build --tag buildyourownlisp --build-arg PORT=5000 .
+docker run --rm --publish 5000:5000 buildyourownlisp
+```
+Or, perhaps, just let `make` take care of it all with `make [PORT=5000] byol-docker`