From 7987a459eb941e5b664859e4210565b72b3ff011 Mon Sep 17 00:00:00 2001
From: fkloft <felix.kloft+github@gmail.com>
Date: Mon, 23 Feb 2015 13:13:03 +0100
Subject: [PATCH] [regions] instead of trying all cells, calculate x/y from
 distance according to the Hilbert curve

also, refactoring to reduce duplicate code for level 4/6 cells
---
 plugins/regions.user.js | 96 ++++++++++++++++++++---------------------
 1 file changed, 46 insertions(+), 50 deletions(-)

diff --git a/plugins/regions.user.js b/plugins/regions.user.js
index 4c2ec44b..cd897abb 100644
--- a/plugins/regions.user.js
+++ b/plugins/regions.user.js
@@ -120,6 +120,31 @@ window.plugin.regions.search = function(query) {
   });
 }
 
+// rot and d2xy from Wikipedia
+window.plugin.regions.rot = function(n, x, y, rx, ry) {
+  if(ry == 0) {
+    if(rx == 1) {
+      x = n-1 - x;
+      y = n-1 - y;
+    }
+
+    return [y, x];
+  }
+  return [x, y];
+}
+window.plugin.regions.d2xy = function(n, d) {
+  var rx, ry, s, t = d, xy = [0, 0];
+  for(s=1; s<n; s*=2) {
+    rx = 1 & (t/2);
+    ry = 1 & (t ^ rx);
+    xy = window.plugin.regions.rot(s, xy[0], xy[1], rx, ry);
+    xy[0] += s * rx;
+    xy[1] += s * ry;
+    t /= 4;
+  }
+  return xy;
+}
+
 window.plugin.regions.getSearchResult = function(match) {
   var faceId = window.plugin.regions.FACE_NAMES.indexOf(match[1]);
   var id1 = parseInt(match[2]);
@@ -136,63 +161,34 @@ window.plugin.regions.getSearchResult = function(match) {
   var regionI = id1-1;
   var regionJ = codeWordId;
 
-  // the final 2 bits of I and J are tricky - easiest way is to try all 16 cells given the 4 bits of I/J we have so far...
+  var result = {}, level;
 
-  if(id2 === undefined) { // level 4 cell
-    // as in the name-construction above, for odd numbered faces, the I and J need swapping
-    var cell = (faceId == 1 || faceId == 3 || faceId == 5) ?
-      S2.S2Cell.FromFaceIJ(faceId, [regionJ,regionI], 4) :
-      S2.S2Cell.FromFaceIJ(faceId, [regionI,regionJ], 4) ;
-    var title = window.plugin.regions.FACE_NAMES[faceId] + zeroPad(id1,2) + '-' + window.plugin.regions.CODE_WORDS[codeWordId];
+  if(id2 === undefined) {
+    result.description = 'Regional score cells (cluster of 16 cells)';
+    result.icon = 'data:image/svg+xml;base64,'+btoa('@@INCLUDESTRING:images/icon-cell.svg@@'.replace(/orange/, 'gold'));
+    level = 4;
+  } else {
+    result.description = 'Regional score cell';
+    result.icon = 'data:image/svg+xml;base64,'+btoa('@@INCLUDESTRING:images/icon-cell.svg@@');
+    level = 6;
 
-    var corners = cell.getCornerLatLngs();
-    var layer = L.geodesicPolygon(corners, { fill: false, color: 'red', clickable: false });
-
-    var bounds = L.latLngBounds(corners);
-
-    return {
-      title: title,
-      description: 'Regional score cells (cluster of 16 cells)',
-      icon: 'data:image/svg+xml;base64,'+btoa('@@INCLUDESTRING:images/icon-cell.svg@@'.replace(/orange/, 'gold')),
-      bounds: bounds,
-      layer: layer
-    };
+    var xy = window.plugin.regions.d2xy(4, id2);
+    regionI = (regionI << 2) + xy[0];
+    regionJ = (regionJ << 2) + xy[1];
   }
 
-  for(var i=0; i<4; i++) {
-    for(var j=0; j<4; j++) {
+  // as in the name-construction above, for odd numbered faces, the I and J need swapping
+  var cell = (faceId % 2 == 1)
+    ? S2.S2Cell.FromFaceIJ(faceId, [regionJ,regionI], level)
+    : S2.S2Cell.FromFaceIJ(faceId, [regionI,regionJ], level);
 
-      var cell = S2.S2Cell.FromFaceIJ(faceId, [regionI*4+i,regionJ*4+j], 6);
+  var corners = cell.getCornerLatLngs();
 
-      var facequads = cell.getFaceAndQuads();
-      var number = facequads[1][4]*4+facequads[1][5];
+  result.title = window.plugin.regions.regionName(cell);
+  result.layer = L.geodesicPolygon(corners, { fill: false, color: 'red', clickable: false });
+  result.bounds = L.latLngBounds(corners);
 
-      if (number == id2) {
-        // we have a match!
-
-        // as in the name-construction above, for odd numbered faces, the I and J need swapping
-        if (cell.face == 1 || cell.face == 3 || cell.face == 5) {
-          cell = S2.S2Cell.FromFaceIJ ( cell.face, [cell.ij[1], cell.ij[0]], cell.level );
-        }
-
-        var title = window.plugin.regions.FACE_NAMES[faceId]+zeroPad(id1,2)+'-'+window.plugin.regions.CODE_WORDS[codeWordId]+'-'+zeroPad(id2,2);
-        var corners = cell.getCornerLatLngs();
-        var layer = L.geodesicPolygon(corners, { fill: false, color: 'red', clickable: false });
-
-        var bounds = L.latLngBounds(corners);
-
-        return {
-          title: title,
-          description: 'Regional score cell',
-          icon: 'data:image/svg+xml;base64,'+btoa('@@INCLUDESTRING:images/icon-cell.svg@@'),
-          bounds: bounds,
-          layer: layer
-        };
-      }
-    }
-  }
-
-  console.error('thought we had a region cell search match - but failed to find it!');
+  return result;
 }
 
 window.plugin.regions.update = function() {