Zoom range formalizing.

lib/mess/tree/filter.js

@@ -1,10 +1,24 @@
 (function(tree) {
 
 tree.Filter = function(key, op, val, index) {
+    var max_zoom = 22; // maximum number of zoom levels
     this.key = key;
     this.op = op;
     this.val = val;
     this.index = index;
+
+    if (this.key === 'zoom') {
+        var val = parseInt(this.val, 10);
+        if (this.op.value === '>' || this.op.value === '>=') {
+            if (this.op.value === '>') val++;
+            this.zoom_range = [val, max_zoom]
+        // TODO: non-correct ops will fail here
+        } else {
+            if (this.op.value === '<') val--;
+            this.zoom_range = [0, val]
+        }
+    }
+
     this.zooms = {
       '1': [200000000, 500000000],
       '2': [100000000, 200000000],
@@ -31,6 +45,15 @@ tree.Filter = function(key, op, val, index) {
    };
 };
 
+tree.Filter.prototype.union = function(filter) {
+    if (filter.zoom_range) {
+        return [
+            Math.max(this.zoom_range[0], filter.zoom_range[0]),
+            Math.min(this.zoom_range[1], filter.zoom_range[1])
+        ];
+    }
+}
+
 tree.Filter.prototype.toCSS = function(env) {
     if (this.key === 'zoom') {
         if (parseInt(this.val) > 22 || parseInt(this.val) < 0) {
@@ -55,8 +78,7 @@ tree.Filter.prototype.toCSS = function(env) {
             return '<MinScaleDenominator>' + this.zooms[this.val][0] +
                 '</MinScaleDenominator>';
         }
-    }
+    } else {
-    else {
         if (this.val.is) {
             this.val = this.val.toCSS((this.val.is == 'string'));
         }