convert new puzzle IDs to/from numerical IDs for mobile app BC

app/controllers/Puzzle.scala

@@ -61,16 +61,6 @@ final class Puzzle(
       }
     }
 
-  def load(id: String) =
-    Open { implicit ctx =>
-      NoBot {
-        XhrOnly {
-          ???
-          // OptionFuOk(env.puzzle.api.puzzle find Puz.Id(id))(puzzleJson _).dmap(_ as JSON)
-        }
-      }
-    }
-
   private def nextPuzzleForMe(theme: PuzzleTheme.Key)(implicit ctx: Context): Fu[Puz] =
     ctx.me match {
       case Some(me) => env.puzzle.session.nextPuzzleFor(me, theme)
@@ -173,6 +163,17 @@ final class Puzzle(
       }
     }
 
+  def mobileBcLoad(nid: Long) =
+    Open { implicit ctx =>
+      negotiate(
+        html = notFound,
+        _ =>
+          OptionFuOk(env.puzzle.api.puzzle find Puz.numericalId(nid)) { puz =>
+            env.puzzle.jsonView.bc(puzzle = puz, theme = PuzzleTheme.any, user = ctx.me)
+          }.dmap(_ as JSON)
+      )
+    }
+
   /* Mobile API: select a bunch of puzzles for offline use */
   def batchSelect =
     Auth { implicit ctx => me =>

conf/routes

@@ -81,15 +81,16 @@ GET   /training                        controllers.Puzzle.home
 GET   /training/daily                  controllers.Puzzle.daily
 GET   /training/frame                  controllers.Puzzle.frame
 GET   /training/export/gif/thumbnail/:id.gif controllers.Export.puzzleThumbnail(id: String)
-GET   /training/batch                  controllers.Puzzle.batchSelect
-POST  /training/batch                  controllers.Puzzle.batchSolve
 GET   /training/themes                 controllers.Puzzle.themes
+GET   /training/:id/load               controllers.Puzzle.mobileBcLoad(id: Long)
 GET   /training/:themeOrId             controllers.Puzzle.show(themeOrId: String)
 GET   /training/:theme/$id<\w{5}>      controllers.Puzzle.showWithTheme(theme: String, id: String)
 POST  /training/$id<\w{5}>/vote        controllers.Puzzle.vote(id: String)
 POST  /training/$id<\w{5}>/vote/:theme controllers.Puzzle.voteTheme(id: String, theme: String)
 POST  /training/complete/:theme/$id<\w{5}>  controllers.Puzzle.complete(theme: String, id: String)
 POST  /training/difficulty/:theme      controllers.Puzzle.setDifficulty(theme: String)
+GET   /training/batch                  controllers.Puzzle.batchSelect
+POST  /training/batch                  controllers.Puzzle.batchSolve
 
 # User Analysis
 GET   /analysis/help                   controllers.UserAnalysis.help

modules/puzzle/src/main/JsonView.scala

@@ -101,7 +101,7 @@ final class JsonView(
           .obj(
             "game" -> gameJson,
             "puzzle" -> Json.obj(
-              "id"          -> puzzle.id,
+              "id"          -> Puzzle.numericalId(puzzle.id),
               "rating"      -> puzzle.glicko.intRating,
               "attempts"    -> puzzle.plays,
               "fen"         -> puzzle.fenAfterInitialMove,

modules/puzzle/src/main/Puzzle.scala

@@ -32,8 +32,47 @@ case class Puzzle(
 
 object Puzzle {
 
+  val idSize = 5
+
   case class Id(value: String) extends AnyVal with StringValue
 
+  /* The mobile app requires numerical IDs.
+   * We convert string ids from and to Longs using base 62
+   */
+  object numericalId {
+
+    private val powers: List[Long] =
+      (0 until idSize).toList.map(m => Math.pow(62, m).toLong)
+
+    def apply(id: Id): Long = id.value.toList
+      .zip(powers)
+      .foldLeft(0L) { case (l, (char, pow)) =>
+        l + charToInt(char) * pow
+      }
+
+    def apply(l: Long): Id = Id {
+      powers.reverse
+        .foldLeft(("", l)) { case ((id, rest), pow) =>
+          val frac = rest / pow
+          (s"${intToChar(frac.toInt)}$id", rest - frac * pow)
+        }
+        ._1
+    }
+
+    private def charToInt(c: Char) = {
+      val i = c.toInt
+      if (i > 96) i - 71
+      else if (i > 64) i - 65
+      else i + 4
+    }
+
+    private def intToChar(i: Int): Char = {
+      if (i < 26) i + 65
+      else if (i < 52) i + 71
+      else i - 4
+    }.toChar
+  }
+
   case class UserResult(
       puzzleId: Id,
       userId: lila.user.User.ID,