From 93a746aaaa092ffc3e7eb37e1df30bfd3a28435f Mon Sep 17 00:00:00 2001 From: sterni Date: Sun, 21 Feb 2021 12:57:40 +0100 Subject: feat(web/bubblegum): nix CGI programming framework So here is what has been keeping me up at night: At some point I realized that nix actually made a somewhat passable language for CGI programming: * That `builtins.getEnv` exists as one of the impurities of Nix is perfect as environment variables are the main way of communication from the web server to the CGI application. * We can actually read from the filesystem via builtins.readDir and builtins.readFile with bearable overhead if we avoid importing the used paths into the nix store. * Templating and routing are convenient to implement via indented strings and attribute sets respectively. Of course there are obvious limitation: * The overhead of derivations is probably much to great for them to be useful via IfD. * Even without derivations, nix evaluation is very slow to the point were a trivial application takes between 100ms and 400ms to produce a response. * We can't really cause effects other than producing a response which makes it not viable for a lot of applications. There are some ways around this: * With a custom interpreter we could have streaming and multiplexed I/O (using lazy lists emulated via attrsets) to cause such effects, but it would probably perform terribly. * We can use builtins.fetchurl to call other HTTP-based microservices, but only in very limited constraints, i. e. only GET, no headers, and only if the tarball ttl is set to 0 in the global nix.conf. * Terrible error handling capabilities because builtins.tryEval actually doesn't catch a lot of errors. To prove that it actually works, there are some demo applications, which I invite you to run and potentially break horribly: nix-build -A web.bubblegum.examples && ./result # navigate to http://localhost:9000 The setup uses thttpd and executes the nix CGI scripts using users.sterni.nint which automatically passed `depot`, so they can import the cgi library. Change-Id: I3a22a749612211627e5f8301c31ec2e7a872812c Reviewed-on: https://cl.tvl.fyi/c/depot/+/2746 Tested-by: BuildkiteCI Reviewed-by: tazjin --- web/bubblegum/examples/blog.nix | 134 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 134 insertions(+) create mode 100644 web/bubblegum/examples/blog.nix (limited to 'web/bubblegum/examples/blog.nix') diff --git a/web/bubblegum/examples/blog.nix b/web/bubblegum/examples/blog.nix new file mode 100644 index 0000000000..f79ab0627e --- /dev/null +++ b/web/bubblegum/examples/blog.nix @@ -0,0 +1,134 @@ +{ depot, ... }: + +let + inherit (depot) + lib + ; + + inherit (depot.users.sterni.nix) + url + fun + string + ; + + inherit (depot.web.bubblegum) + pathInfo + scriptName + respond + absolutePath + ; + + # substituted using substituteAll in default.nix + blogdir = "@blogdir@"; + # blogdir = toString ./posts; # for local testing + + parseDate = post: + let + matched = builtins.match "/?([0-9]+)-([0-9]+)-([0-9]+)-.+" post; + in + if matched == null + then [ 0 0 0 ] + else builtins.map builtins.fromJSON matched; + + parseTitle = post: + let + matched = builtins.match "/?[0-9]+-[0-9]+-[0-9]+-(.+).html" post; + in + if matched == null + then "no title" + else builtins.head matched; + + dateAtLeast = a: b: + builtins.all fun.id + (lib.zipListsWith (partA: partB: partA >= partB) a b); + + byPostDate = a: b: + dateAtLeast (parseDate a) (parseDate b); + + posts = builtins.sort byPostDate + (builtins.attrNames + (lib.filterAttrs (_: v: v == "regular") + (builtins.readDir blogdir))); + + generic = { title, inner, ... }: '' + + + + + ${title} + + + + ${inner} + + + ''; + + index = posts: '' +
+

blog posts

+ +
+ ''; + + formatDate = + let + # Assume we never deal with years < 1000 + formatDigit = d: string.fit { + char = "0"; width = 2; + } (toString d); + in lib.concatMapStringsSep "-" formatDigit; + + post = title: post: '' +
+

${title}

+
+ ${builtins.readFile (blogdir + "/" + post)} +
+
+
+

Posted on ${formatDate (parseDate post)}

+ +
+ ''; + + validatePathInfo = pathInfo: + let + chars = string.toChars pathInfo; + in builtins.length chars > 1 + && !(builtins.elem "/" (builtins.tail chars)); + + response = + if pathInfo == "/" + then { + title = "blog"; + status = "OK"; + inner = index posts; + } + else if !(validatePathInfo pathInfo) + then { + title = "Bad Request"; + status = "Bad Request"; + inner = "No slashes in post names 😡"; + } + # CGI should already url.decode for us + else if builtins.pathExists (blogdir + "/" + pathInfo) + then rec { + title = parseTitle pathInfo; + status = "OK"; + inner = post title pathInfo; + } else { + title = "Not Found"; + status = "Not Found"; + inner = "

404 — not found

"; + }; +in + respond response.status { + "Content-type" = "text/html"; + } (generic response) -- cgit 1.4.1