Switch to base64Url

elm.json

@@ -13,6 +13,7 @@
             "elm/html": "1.0.0",
             "elm/json": "1.1.3",
             "elm/random": "1.0.0",
+            "elm/regex": "1.0.0",
             "elm/svg": "1.0.1",
             "elm/url": "1.0.0",
             "elm-community/array-extra": "2.6.0",

src/UrlBase64.elm

@@ -0,0 +1,70 @@
+module UrlBase64 exposing (fromUrl, toUrl)
+
+import Maybe
+import Regex exposing (Regex)
+
+
+
+-- Simplified version of https://github.com/prozacchiwawa/elm-urlbase64/blob/1.0.6/src/UrlBase64.elm
+
+
+replaceForUrl : Regex
+replaceForUrl =
+    Regex.fromString "[\\+/=]" |> Maybe.withDefault Regex.never
+
+
+{-| Convert from the standard base64 alphabet to urlBase64, and trim trailing '=' characters.
+-}
+toUrl : String -> String
+toUrl t =
+    let
+        replaceChar rematch =
+            case rematch.match of
+                "+" ->
+                    "-"
+
+                "/" ->
+                    "_"
+
+                _ ->
+                    ""
+    in
+    Regex.replace replaceForUrl replaceChar t
+
+
+replaceFromUrl : Regex
+replaceFromUrl =
+    Regex.fromString "[-_]" |> Maybe.withDefault Regex.never
+
+
+{-| Convert from urlBase64 to standard base64
+-}
+fromUrl : String -> String
+fromUrl e =
+    let
+        replaceChar rematch =
+            case rematch.match of
+                "-" ->
+                    "+"
+
+                _ ->
+                    "/"
+
+        strlen =
+            String.length e
+
+        hanging =
+            if strlen == 0 then
+                4
+
+            else
+                modBy 4 strlen
+
+        ilen =
+            if hanging == 0 then
+                0
+
+            else
+                4 - hanging
+    in
+    Regex.replace replaceFromUrl replaceChar (e ++ String.repeat ilen "=")

src/UrlState.elm

@@ -12,6 +12,7 @@ import Point exposing (Point)
 import Url
 import Url.Parser
 import Url.Parser.Query
+import UrlBase64
 
 
 type alias UrlModel =
@@ -33,6 +34,7 @@ compressToBase64 str =
         |> BE.encode
         |> deflate
         |> Base64.fromBytes
+        |> Maybe.map UrlBase64.toUrl
         |> Maybe.withDefault ""
 
 
@@ -43,6 +45,7 @@ decompressFromBase64 str =
             BD.decode (BD.string (Bytes.width buffer)) buffer
     in
     str
+        |> UrlBase64.fromUrl
         |> Base64.toBytes
         |> Result.fromMaybe Base64Error
         |> Result.andThen (inflate >> Result.fromMaybe InflateError)