1 files changed, 100 insertions, 0 deletions
diff --git a/users/sterni/nix/url/default.nix b/users/sterni/nix/url/default.nix
new file mode 100644
index 0000000000..4a401873a1
--- /dev/null
+++ b/users/sterni/nix/url/default.nix
@@ -0,0 +1,100 @@
+{ depot, lib, ... }:
+
+let
+
+  inherit (depot.users.sterni.nix)
+    char
+    int
+    string
+    flow
+    ;
+
+  reserved = c: builtins.elem c [
+    "!"
+    "#"
+    "$"
+    "&"
+    "'"
+    "("
+    ")"
+    "*"
+    "+"
+    ","
+    "/"
+    ":"
+    ";"
+    "="
+    "?"
+    "@"
+    "["
+    "]"
+  ];
+
+  unreserved = c: char.asciiAlphaNum c
+    || builtins.elem c [ "-" "_" "." "~" ];
+
+  percentEncode = c:
+    if unreserved c
+    then c
+    else "%" + (string.fit
+      {
+        width = 2;
+        char = "0";
+        side = "left";
+      }
+      (int.toHex (char.ord c)));
+
+  encode = { leaveReserved ? false }: s:
+    let
+      chars = lib.stringToCharacters s;
+      tr = c:
+        if leaveReserved && reserved c
+        then c
+        else percentEncode c;
+    in
+    lib.concatStrings (builtins.map tr chars);
+
+  decode = s:
+    let
+      tokens = builtins.split "%" s;
+      decodeStep =
+        { result ? ""
+        , inPercent ? false
+        }: s:
+        flow.cond [
+          [
+            (builtins.isList s)
+            {
+              inherit result;
+              inPercent = true;
+            }
+          ]
+          [
+            inPercent
+            {
+              inPercent = false;
+              # first two characters came after an %
+              # the rest is the string until the next %
+              result = result
+                + char.chr (int.fromHex (string.take 2 s))
+                + (string.drop 2 s);
+            }
+          ]
+          [
+            (!inPercent)
+            {
+              result = result + s;
+            }
+          ]
+        ];
+
+    in
+    (builtins.foldl' decodeStep { } tokens).result;
+
+in
+{
+  inherit
+    encode
+    decode
+    ;
+}