1 files changed, 54 insertions, 0 deletions
diff --git a/lib/shard-regex.nix b/lib/shard-regex.nix
new file mode 100644
index 0000000..06fba4d
--- /dev/null
+++ b/lib/shard-regex.nix
@@ -0,0 +1,54 @@
+{bionix, n}:
+
+with bionix;
+with lib.types;
+
+input:
+let
+  re = let f = matchFiletype' "shard-regex" {
+      fa = _: "^>";
+      fq = _: "^@";
+      gz = f;
+      bz2 = f;
+    };
+  in f input.filetype;
+  decompress = matchFiletype "shard-regex-decompression" {
+      fa = _: "cat";
+      fq = _: "cat";
+      gz = _: "gunzip";
+      bz2 = _: "bunzip2";
+    } input;
+  compress = matchFiletype "shard-regex-compression" {
+      fa = _: "cat";
+      fq = _: "cat";
+      gz = _: "gzip";
+      bz2 = _: "bzip2";
+    } input;
+  compressPkgs = with bionix.pkgs; matchFiletype "shard-regex-compression" {
+      fa = _: [];
+      fq = _: [];
+      gz = _: [ gzip ];
+      bz2 = _: [ bzip2 ];
+    } input;
+in stage {
+  name = "shard";
+  outputs = [ "out" ] ++ builtins.genList (i: "out" + toString (i + 2)) (n - 1);
+  buildInputs = [ pkgs.gawk ] ++ compressPkgs;
+  buildCommand = let
+    awkScript = pkgs.writeText "shard.awk" ''
+      BEGIN{cout=0}
+      FNR==NR{out[nout++] = $0;next}
+      /${re}/{cout = (cout + 1) % nout}
+      {print > out[cout]}
+    '';
+  in ''
+    for o in $outputs ; do
+      echo $(basename ''${!o}) >> outputs
+    done
+    awk -f ${awkScript} outputs <(${decompress} < ${input})
+    for o in $outputs ; do
+      ${compress} < $(basename ''${!o}) > ''${!o}
+    done
+  '';
+  passthru.filetype = input.filetype;
+}