From 9ba624b0cf22109be3a7c76aa13ca7cedabdc319 Mon Sep 17 00:00:00 2001
From: Vladimir Agafonkin <agafonkin@gmail.com>
Date: Fri, 29 Jan 2016 15:51:10 +0200
Subject: [PATCH] fast eval-less filter implementation

Closes #6, closes #8, closes #10.
---
 index.js | 135 ++++++++++++++++++++++++++++---------------------------
 1 file changed, 70 insertions(+), 65 deletions(-)

diff --git a/index.js b/index.js
index b54dc4b..8fa3467 100644
--- a/index.js
+++ b/index.js
@@ -1,66 +1,9 @@
 'use strict';
 
-var VectorTileFeatureTypes = ['Unknown', 'Point', 'LineString', 'Polygon'];
+module.exports = createFilter;
 
-function infix(operator) {
-    return function(_, key, value) {
-        if (key === '$type') {
-            return 't' + operator + VectorTileFeatureTypes.indexOf(value);
-        } else {
-            return 'p[' + JSON.stringify(key) + ']' + operator + JSON.stringify(value);
-        }
-    };
-}
-
-function strictInfix(operator) {
-    var nonstrictInfix = infix(operator);
-    return function(_, key, value) {
-        if (key === '$type') {
-            return nonstrictInfix(_, key, value);
-        } else {
-            return 'typeof(p[' + JSON.stringify(key) + ']) === typeof(' + JSON.stringify(value) + ') && ' +
-                nonstrictInfix(_, key, value);
-        }
-    };
-}
-
-var operators = {
-    '==': infix('==='),
-    '!=': infix('!=='),
-    '>': strictInfix('>'),
-    '<': strictInfix('<'),
-    '<=': strictInfix('<='),
-    '>=': strictInfix('>='),
-    'in': function(_, key) {
-        return '(function(){' + Array.prototype.slice.call(arguments, 2).map(function(value) {
-            return 'if (' + operators['=='](_, key, value) + ') return true;';
-        }).join('') + 'return false;})()';
-    },
-    '!in': function() {
-        return '!(' + operators.in.apply(this, arguments) + ')';
-    },
-    'any': function() {
-        return Array.prototype.slice.call(arguments, 1).map(function(filter) {
-            return '(' + compile(filter) + ')';
-        }).join('||') || 'false';
-    },
-    'all': function() {
-        return Array.prototype.slice.call(arguments, 1).map(function(filter) {
-            return '(' + compile(filter) + ')';
-        }).join('&&') || 'true';
-    },
-    'none': function() {
-        return '!(' + operators.any.apply(this, arguments) + ')';
-    }
-};
-
-function compile(filter) {
-    return operators[filter[0]].apply(filter, filter);
-}
-
-function truth() {
-    return true;
-}
+var types = ['Unknown', 'Point', 'LineString', 'Polygon'];
+var typeLookup = {'Point': 1, 'LineString': 2, 'Polygon': 3}
 
 /**
  * Given a filter expressed as nested arrays, return a new function
@@ -70,9 +13,71 @@ function truth() {
  * @param {Array} filter mapbox gl filter
  * @returns {Function} filter-evaluating function
  */
-module.exports = function (filter) {
+function createFilter(filter) {
     if (!filter) return truth;
-    var filterStr = 'var p = f.properties || f.tags || {}, t = f.type; return ' + compile(filter) + ';';
-    // jshint evil: true
-    return new Function('f', filterStr);
-};
+
+    var op = filter[0];
+    var key = filter[1];
+
+    var val =
+        op === '==' ||
+        op === '!=' ||
+        op === '>' ||
+        op === '<' ||
+        op === '<=' ||
+        op === '>=' ? filter[2] :
+        op === 'in' ||
+        op === '!in' ? filter.slice(2) : filter.slice(1);
+
+    var opFn =
+        op === 'in' ? (key === '$type' ? inType : _in) :
+        op === '!in' ? (key === '$type' ? notInType : notIn) :
+        op === '==' ? (key === '$type' ? equalsType : equals) :
+        op === '!=' ? (key === '$type' ? notEqualsType : notEquals) :
+        op === '<' ? lesser :
+        op === '>' ? greater :
+        op === '<=' ? lesserEqual :
+        op === '>=' ? greaterEqual :
+        val.map(createFilter);
+
+    if (op === 'any') {
+        return function (f) {
+            for (var i = 0; i < opFn.length; i++) {
+                if (opFn[i](f)) return true;
+            }
+            return false;
+        }
+    } else if (op === 'all') {
+        return function (f) {
+            for (var i = 0; i < opFn.length; i++) {
+                if (!opFn[i](f)) return false;
+            }
+            return true;
+        }
+    } else if (op === 'none') {
+        return function (f) {
+            for (var i = 0; i < opFn.length; i++) {
+                if (opFn[i](f)) return false;
+            }
+            return true;
+        }
+    }
+
+    return function (f) {
+        return opFn(f.properties || f.tags || {}, f.type);
+    };
+
+    function _in(p, t) { return val.indexOf(p[key]) !== -1; }
+    function inType(p, t) { return val.indexOf(types[t]) !== -1; }
+    function notIn(p, t) { return val.indexOf(p[key]) === -1; }
+    function notInType(p, t) { return val.indexOf(types[t]) === -1; }
+    function equals(p, t) { return p[key] === val; }
+    function equalsType(p, t) { return t === typeLookup[val]; }
+    function notEquals(p, t) { return p[key] !== val; }
+    function notEqualsType(p, t) { return t !== typeLookup[val]; }
+    function lesser(p, t) { return typeof p[key] === typeof val && p[key] < val; }
+    function greater(p, t) { return typeof p[key] === typeof val && p[key] > val; }
+    function lesserEqual(p, t) { return typeof p[key] === typeof val && p[key] <= val; }
+    function greaterEqual(p, t) { return typeof p[key] === typeof val && p[key] >= val; }
+    function truth() { return true; }
+}