readme - tighten

README.md

@@ -1,47 +1,32 @@
 # Electric Starter App
 
-A minimal Electric Clojure app.
-Plus instructions on how to integrate it into an existing app.
+A minimal Electric Clojure app, and instructions on how to integrate it into an existing app. For more demos and examples, see [Electric Fiddle](https://github.com/hyperfiddle/electric-fiddle).
 
-For real-world examples, check out [Electric Fiddle](https://github.com/hyperfiddle/electric-fiddle).
+## Instructions
 
-## Run it
+Dev build:
 
-```shell
-clj -A:dev
-```
-
-At the REPL:
-```clojure
-(dev/-main)
-```
-
-Navigate to [http://localhost:8080](http://localhost:8080)
-
-## Customize it
+* Shell: `clj -A:dev -X dev/-main`, or repl: `(dev/-main)`
+* http://localhost:8080
+* Electric root function: [src/electric_starter_app/main.cljc](src/electric_starter_app/main.cljc)
+* Hot code reloading works: edit -> save -> see app reload in browser
 
-With the app running:
-1. Go to [src/electric_starter_app/main.cljc](src/electric_starter_app/main.cljc)
-2. Edit and save
-3. App will automatically update in your browser
-
-## Release it for prod
+Prod build:
 
 ```shell
-clj -X:build:prod build-client # build it
-clj -M:prod -m prod            # run it
+clj -X:build:prod build-client
+clj -M:prod -m prod
 ```
 
-### Uberjar
-
-```shell
+Uberjar (optional):
+```
 clj -X:build:prod uberjar :build/jar-name "target/app.jar"
 java -cp target/app.jar clojure.main -m prod
 ```
 
-There is also:
-- an example [Dockerfile](Dockerfile)
-- `fly.io` deployment example (look at [.github/workflows/deploy.yml](.github/workflows/deploy.yml) and [fly.toml](fly.toml))
+Deployment example:
+- [Dockerfile](Dockerfile)
+- fly.io deployment through github actions: [.github/workflows/deploy.yml](.github/workflows/deploy.yml) & [fly.toml](fly.toml)
 
 ## Integrate it in an existing clojure app
 
@@ -53,53 +38,16 @@ There is also:
    - an example Jetty integration
    - required ring middlewares
 
-You'll also need to account for the following requirements:
-
-### For a client to connect to the server, the two program’s version must match.
-
-Electric Clojure compiles a single program into two artifacts:
-- a javascript program - runs in the browser,
-- a JVM program - runs on the server,
-- these two programs work in pairs,
-- they communicate via websocket.
-
-If an mismatching client tries to connect to the server, the server will:
-- reject the connection,
-- inform the client it needs to refresh (so to get the newer client js file)
-
-How it works:
-- `clj -X:build:prod build-client` will:
-  - generate js files with the version baked in,
-  - write the version in `resources/electric-manifest.edn`
-- On server start, the server will:
-  - read `resources/electric-manifest.edn`
-  - configure a ring middleware rejecting mismatching (supposedly outdated) clients’ connection.
-- On client -> server connection, the client will:
-  - send it's baked-in version,
-  - try to refresh the page if the server rejects the version.
-
-Here are examples you might want to adapt to your existing app:
-- [src/electric_starter_app/server_jetty.clj](src/electric_starter_app/server_jetty.clj) esp. `reject-stale-client`
-- [src-build/build.clj](src-build/build.clj)
-
-
-Notice that [src-prod/prod.clj](src-prod/prod.clj) reads `electric-manifest.edn`.
-
-### Ensuring cache invalidation
-
-Only if your production system doesn't already handles it.
-
-Complied js files are fingerprinted with their respective hash, to ensure a new release
-properly invalidates asset caches. [index.html](resources/public/electric_starter_app/index.html) is templated with the generated
-js file name. The generated name comes from the `manifest.edn` file
-(in `resources/public/electric_starter_app/js/manifest.edn`), produced by `clj -X:build:prod build-client`.
-
-Notice that [src/electric_starter_app/server_jetty.clj](src/electric_starter_app/server_jetty.clj) -> `wrap-index-page` reads `:manifest-path` from config.
-The config comes from [src-prod/prod.clj](src-prod/prod.clj).
-
+## Build documentation
 
+Electric Clojure programs compile down to separate client and server target programs, which are compiled from the same Electric application source code.
 
----
-Notes
+* For an Electric client/server pair to successfully connect, they must be built from matching source code. The server will reject mismatched clients (based on a version number handshake coordinated by the Electric build) and instruct the client to refresh (to get the latest javascript artifact).
+* [src-build/build.cljc](src-build/build.clj bakes the Electric app version into both client and server artifacts.
+  * server Electric app version is baked into `electric-manifest.edn` which is read in [src-prod/prod.clj](src-prod/prod.clj).
+  * client Electric app version is baked into the .js artifact as `hyperfiddle.electric-client/ELECTRIC_USER_VERSION`
 
-- This starter app logs with Logback for simplicity. Feel free to replace it by your favorite equivalent.
+Consequently, you need **robust cache invalidation** in prod!
+  * In this example, complied js files are fingerprinted with their respective hash, to ensure a new release properly invalidates asset caches. [index.html](resources/public/electric_starter_app/index.html) is templated with the generated js file name.
+  * The generated name comes from shadow-cljs's `manifest.edn` file (in `resources/public/electric_starter_app/js/manifest.edn`), produced by `clj -X:build:prod build-client`. Watch out: this shadow-cljs compilation manifest is not the same manifest as `electric-manifest.edn`!
+  * Notice that [src/electric_starter_app/server_jetty.clj](src/electric_starter_app/server_jetty.clj) -> `wrap-index-page` reads `:manifest-path` from config. The config comes from [src-prod/prod.cljc](src-prod/prod.cljc).