1 files changed, 123 insertions, 0 deletions
diff --git a/lib/default.nix b/lib/default.nix
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index 0000000..8086059
--- /dev/null
+++ b/lib/default.nix
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+let
+  inherit
+    (builtins)
+    attrNames
+    hashFile
+    fetchurl
+    fromJSON
+    listToAttrs
+    mapAttrs
+    readDir
+    readFile
+    replaceStrings
+    toFile
+    toJSON
+    ;
+
+  # loads data from a toml json given
+  # the directory (dir) and filename (name)
+  # string -> string -> attrset
+  fromMod = dir: name: fromTOML (readFile "${dir}/${name}");
+
+  # replaces `.pw.toml` extensions with `.jar`
+  # to correct the store paths of jarfiles
+  # string -> string
+  fixupName = replaceStrings [".pw.toml"] [".jar"];
+
+  # *pkgs*.fetchurl wrapper that downloads a
+  # jarfile mod. pkgs.fetchurl is used over builtins
+  # here since we have a checksum and can take advantage
+  # of fixed output derivations
+  # attrset -> string -> attrset -> store path
+  mkMod = pkgs: name: mod:
+    pkgs.fetchurl {
+      name = fixupName name;
+      inherit (mod) url sha256;
+    };
+
+  # maps each mod in our checksums.json format
+  # to the store path of a fixed output derivation
+  # attrset -> attrset
+  genMods = pkgs:
+    mapAttrs (mkMod pkgs);
+
+  # this is probably what you're looking for if
+  # you're a developer trying to use this in your modpack.
+  # this is where you create a checksums file for end users
+  # to put into mkPackwizPackages, so make sure you keep it up to
+  # date!
+  #
+  # `dir` is a path to the folder containing your .pw.toml files
+  # files for mods. make sure they are the only files in the folder
+  #
+  # path -> file
+  mkChecksums = dir: let
+    mods = readDir dir;
+
+    getChecksum = name: url:
+      hashFile "sha256" (fetchurl {
+        name = fixupName name;
+        inherit url;
+      });
+
+    toWrite =
+      toJSON
+      (mapAttrs (mod: _: let
+          data = fromMod dir mod;
+        in {
+          inherit (data.download) url;
+          sha256 = getChecksum mod data.download.url;
+        })
+        mods);
+  in
+    toFile "checksums-json" toWrite;
+in {
+  inherit mkChecksums;
+
+  # this is probably what you're looking for if
+  # you're an end user trying to implement a modpack in
+  # your module.
+  #
+  # `pkgs` is an instance of nixpkgs for your system,
+  # must at least contain `fetchurl`.
+  #
+  # `checksums` is a json file from an upstream modpack
+  # containing the names, urls, and sha256sums of mods
+  #
+  # attrset -> path -> attrset
+  mkPackwizPackages = pkgs: checksums: genMods pkgs (fromJSON (readFile checksums));
+
+  # this creates an `apps` attribute for a flake
+  # which runs a bash script to generate a checksums
+  # file
+  #
+  # `pkgs` is an instance of nixpkgs for your system,
+  # must at least contain `writeShellScriptBin`
+  #
+  # `dir` is a path to the folder containing your .pw.toml files
+  # files for mods. make sure they are the only files in the folder
+  #
+  # attrset -> path -> attrset
+  mkChecksumsApp = pkgs: dir: let
+    inherit (pkgs) writeShellScriptBin;
+    checksums = mkChecksums dir;
+    name = "generate-checksums";
+    script = writeShellScriptBin name ''
+      cat ${checksums} > checksums.json
+    '';
+  in {
+    type = "app";
+    program = script.outPath + "/bin/${name}";
+  };
+
+  # this creates an attrset value for
+  # minecraft-servers.servers.<server>.symlinks
+  # attrset -> attrset
+  mkModLinks = mods: let
+    fixup = map (name: {
+      name = "mods/" + fixupName name;
+      value = mods.${name};
+    }) (attrNames mods);
+  in
+    listToAttrs fixup;
+}