Add cachix push stage (#11)

Optionally configure auth token in CLI. Then, all builds will have their
full outputs (from omnix) pushed to cachix.

nix/modules/flake-parts/devshell.nix

@@ -15,6 +15,7 @@
         ghciwatch
         # vira extraBuildDepends from haskell.nix
         git
+        cachix
         inputs'.omnix.packages.default
       ];
     };

nix/modules/flake-parts/haskell.nix

@@ -49,6 +49,7 @@
         vira = {
           extraBuildDepends = [
             pkgs.git
+            pkgs.cachix
             inputs'.omnix.packages.default
           ];
           stan = true;
@@ -76,7 +77,12 @@
     process-compose."vira-dev" = {
       settings = {
         processes = {
-          haskell.command = "ghcid -c 'cabal repl exe:vira --flags=ghcid' -T :main";
+          # The cachix token here is for a dummy cache, managed by Srid.
+          haskell.command = ''
+            set -x
+            ghcid -c 'cabal repl exe:vira --flags=ghcid' -T Main.main \
+                --setup ':set args --repo-cachix-name scratch-vira-dev --repo-cachix-auth-token eyJhbGciOiJIUzI1NiJ9.eyJqdGkiOiI5NDI4ZjhkZi1mZWM5LTQ1ZjctYjMzYi01MTFiZTljNTNkNjciLCJzY29wZXMiOiJjYWNoZSJ9.WgPWUSYIie2rUdfuPqHS5mxrkT0lc7KIN7QPBPH4H-U'
+          '';
           tailwind = {
             # Suppress tailwind output so only ghcid log comes through
             command = "echo Running tailwind silently.; ${lib.getExe pkgs.haskellPackages.tailwind} -w -o ./static/tailwind.css './src/**/*.hs' > tailwind.log 2>&1";

src/Vira/App/CLI.hs

@@ -27,6 +27,16 @@ data RepoSettings = RepoSettings
   -- ^ Repositories (git clone URL) to watch and build
   , branchWhitelist :: Set Text
   -- ^ Limit to building these branches to build
+  , cachix :: Maybe CachixSettings
+  -- ^ Cachix settings
+  }
+  deriving stock (Show)
+
+data CachixSettings = CachixSettings
+  { cachixName :: Text
+  -- ^ Name of the cachix cache
+  , authToken :: Text
+  -- ^ Auth token for the cachix cache
   }
   deriving stock (Show)
 
@@ -77,8 +87,27 @@ instance HasParser RepoSettings where
         , name "branch-whitelist"
         , value defaultBranchesToBuild
         ]
+    cachix <- optional $ subSettings "cachix"
     pure RepoSettings {..}
 
+instance HasParser CachixSettings where
+  settingsParser = withoutConfig $ do
+    cachixName <-
+      setting
+        [ reader str
+        , metavar "CACHIX_NAME"
+        , help "Name of the cachix cache"
+        , name "name"
+        ]
+    authToken <-
+      setting
+        [ reader str
+        , metavar "CACHIX_AUTH_TOKEN"
+        , help "Auth token for the cachix cache"
+        , name "auth-token"
+        ]
+    pure CachixSettings {..}
+
 defaultRepos :: [Text]
 defaultRepos =
   [ "https://github.com/srid/emanote.git"

src/Vira/Page/JobPage.hs

@@ -4,7 +4,7 @@ module Vira.Page.JobPage where
 
 import Effectful (Eff)
 import Effectful.Error.Static (throwError)
-import Effectful.Process (CreateProcess (cwd), proc)
+import Effectful.Process (CreateProcess (cwd), env, proc)
 import Effectful.Reader.Dynamic (ask, asks)
 import GHC.IO.Exception (ExitCode (..))
 import Htmx.Servant.Response
@@ -90,13 +90,15 @@ triggerNewBuild repoName branchName = do
   repo <- App.query (St.GetRepoByNameA repoName) >>= maybe (throwError $ err404 {errBody = "No such repo"}) pure
   branch <- App.query (St.GetBranchByNameA repoName branchName) >>= maybe (throwError $ err404 {errBody = "No such branch"}) pure
   log Info $ "Building commit " <> show (repoName, branch.headCommit)
+  mCachix <- asks $ App.cachix . App.repo . App.settings
   asks App.supervisor >>= \supervisor -> do
     job <- App.update $ St.AddNewJobA repoName branchName branch.headCommit supervisor.baseWorkDir
     log Info $ "Added job " <> show job
     let stages =
           stageCreateProjectDir
             :| stagesClone repo branch
             <> [stageBuild]
+            <> maybe mempty (one . stageCachix) mCachix
     Supervisor.startTask supervisor job.jobId job.jobWorkingDir stages $ \exitCode -> do
       let status = case exitCode of
             ExitSuccess -> St.JobFinished St.JobSuccess
@@ -114,3 +116,8 @@ triggerNewBuild repoName branchName = do
       Omnix.omnixCiProcess
         { cwd = Just "project"
         }
+    stageCachix cachix =
+      (proc "cachix" ["push", toString cachix.cachixName, "result"])
+        { env = Just [("CACHIX_AUTH_TOKEN", toString cachix.authToken)]
+        , cwd = Just "project"
+        }