From a4bc8c023063a27b59acc15c81d144ad095393dd Mon Sep 17 00:00:00 2001
From: EatThePooh <eatthepooh@proton.me>
Date: Sat, 2 Aug 2025 08:21:03 +0700
Subject: [PATCH] improve deno cache FOD

---
 flake.nix                     |  5 ++++
 shelf/deno-workspace.nix      | 46 ++++++++++++++++++++++++++++++++---
 shelf/deno/uses-hjq/deno.json |  2 +-
 3 files changed, 48 insertions(+), 5 deletions(-)

diff --git a/flake.nix b/flake.nix
index aa6f0ec..54ab156 100644
--- a/flake.nix
+++ b/flake.nix
@@ -12,6 +12,11 @@
         pkgs = nixpkgs.legacyPackages.${system};
         denoWorkspace = import ./shelf/deno-workspace.nix {
           inherit pkgs system;
+          # collective hash of all deno sources - resulting shared deno cache hash
+          knownDenoHashes = {
+            "UnKGEQo7oF1X5JeWyx7w0oCwqPQ=" =
+              "sha256-7csbrTbGd6J4a0Gkj9ndKhNxv90KeOHjr7DDNal3L4Q=";
+          };
         };
       in
         {
diff --git a/shelf/deno-workspace.nix b/shelf/deno-workspace.nix
index 98109d5..fc03777 100644
--- a/shelf/deno-workspace.nix
+++ b/shelf/deno-workspace.nix
@@ -1,4 +1,4 @@
-{ pkgs, system }:
+{ pkgs, system, knownDenoHashes }:
 
 let
   target =
@@ -18,8 +18,38 @@ let
   scrollsDir = ./deno;
   lib = pkgs.lib;
   packageDirs = builtins.attrNames (builtins.readDir scrollsDir);
-  
-  # Separate FOD for cache only
+
+  # hash only dependency-relevant files (lock files and configs)
+  hashDependencyFiles = dir:
+    let
+      entries = builtins.readDir dir;
+
+      # Only process directories and dependency-relevant files
+      relevantEntry = name: type:
+        if type == "directory"
+        then hashDependencyFiles (dir + "/${name}")
+        else if (lib.hasSuffix ".lock" name ||
+                 lib.hasSuffix ".json" name ||
+                 lib.hasSuffix ".jsonc" name)
+        then builtins.readFile (dir + "/${name}")
+        else null;
+
+      contentMap = lib.filterAttrs (_: v: v != null)
+        (builtins.mapAttrs relevantEntry entries);
+    in builtins.toJSON contentMap;
+
+  sourceContentHash = builtins.convertHash {
+    hash = "sha1:${builtins.hashString "sha1" (hashDependencyFiles scrollsDir)}";
+    toHashFormat = "base64";
+  };
+
+  # we assume that same lock+config files yield same deno caches here
+  # however, jsons need to be sorted and some sqlite files deleted
+
+  # jsr gentlemen specifically require their package metadata
+  # to have multiple timestamps, so they can fuck off
+  outputHash = knownDenoHashes.${sourceContentHash} or lib.fakeSha256;
+
   unifiedCache = pkgs.stdenv.mkDerivation {
     name = "deno-scrolls-cache";
     src = scrollsDir;
@@ -50,13 +80,21 @@ let
           ${pkgs.jq}/bin/jq -S . "$file" > "$file.tmp" && mv "$file.tmp" "$file"
         fi
       done
+
+      echo 'sourceContentHash: ${sourceContentHash}'
+      echo ""
+      echo "add me to knownHashes if you see a fake sha256 error ^"
+      echo "DON'T USE JSR DEPS UNLESS YOU MAKE THEM REPRODUCIBLE SOMEHOW"
+      echo ""
     '';
     
     installPhase = "true";
     
     outputHashMode = "recursive";
     outputHashAlgo = "sha256";
-    outputHash = "sha256-maP/JMY6n95A9FQx72YFwRtnprGXc97v1ZdPgt2GB8s=";
+    # this is basically FOD on steroids cause it
+    # deliberately breaks on relevant source changes
+    inherit outputHash;
   };
   
 in
diff --git a/shelf/deno/uses-hjq/deno.json b/shelf/deno/uses-hjq/deno.json
index b7d93f4..881c23c 100644
--- a/shelf/deno/uses-hjq/deno.json
+++ b/shelf/deno/uses-hjq/deno.json
@@ -2,7 +2,7 @@
   "tasks": {
     "start": "deno run --cached-only main.ts"
   },
-  "patch": [
+  "links": [
     "../hjq"
   ]
 }