From 85c32838ca19e40c8e9aa821a8ea453a9ff8826b Mon Sep 17 00:00:00 2001
From: sedinkinya <yury.sedinkin@nih.gov>
Date: Wed, 2 Mar 2022 15:14:05 -0500
Subject: [PATCH 1/5] Support intersect()

LF-2171
---
 CHANGELOG.md            |  4 ++++
 package-lock.json       |  2 +-
 package.json            |  2 +-
 src/combining.js        | 21 +++++++++++++++++++++
 src/fhirpath.js         |  1 +
 test/cases/fhir-r4.yaml |  1 -
 6 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d7dc8bc..55b00bf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,10 @@
 This log documents significant changes for each release.  This project follows
 [Semantic Versioning](http://semver.org/).
 
+## [2.14.0] - 2022-03-02
+### Added
+- Function to get the intersection of two collections: intersect().
+
 ## [2.13.0] - 2022-02-28
 ### Added
 - Current time function: timeOfDay().
diff --git a/package-lock.json b/package-lock.json
index 4e4eb49..7de1ec2 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "fhirpath",
-  "version": "2.13.0",
+  "version": "2.14.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index 399bee9..6805e84 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "fhirpath",
-  "version": "2.13.0",
+  "version": "2.14.0",
   "description": "A FHIRPath engine",
   "main": "src/fhirpath.js",
   "dependencies": {
diff --git a/src/combining.js b/src/combining.js
index b3958d2..146d62f 100644
--- a/src/combining.js
+++ b/src/combining.js
@@ -11,5 +11,26 @@ combineFns.combineFn = function(coll1, coll2){
   return coll1.concat(coll2);
 };
 
+combineFns.intersect = function(coll1, coll2) {
+  let result = [];
+  if (coll1.length && coll2.length) {
+    let coll2json = {};
+    coll2.forEach(item => {
+      coll2json[JSON.stringify(item)] = true;
+    });
+
+    for (let i=0, len=coll1.length; i<len; ++i) {
+      let item = coll1[i];
+      let json = JSON.stringify(item);
+      if (coll2json[json]) {
+        result.push(item);
+        coll2json[json] = false;
+      }
+    }
+  }
+
+  return result;
+};
+
 
 module.exports = combineFns;
diff --git a/src/fhirpath.js b/src/fhirpath.js
index 522627a..a8bd379 100644
--- a/src/fhirpath.js
+++ b/src/fhirpath.js
@@ -93,6 +93,7 @@ engine.invocationTable = {
   skip:         {fn: filtering.skipFn, arity: {1: ["Integer"]}},
   combine:      {fn: combining.combineFn, arity: {1: ["AnyAtRoot"]}},
   union:        {fn: combining.union,   arity: {1: ["AnyAtRoot"]}},
+  intersect:    {fn: combining.intersect,   arity: {1: ["AnyAtRoot"]}},
   iif:          {fn: misc.iifMacro,    arity: {2: ["Expr", "Expr"], 3: ["Expr", "Expr", "Expr"]}},
   trace:        {fn: misc.traceFn,     arity: {0: [], 1: ["String"]}},
   toInteger:    {fn: misc.toInteger},
diff --git a/test/cases/fhir-r4.yaml b/test/cases/fhir-r4.yaml
index 9945d70..596ab1c 100644
--- a/test/cases/fhir-r4.yaml
+++ b/test/cases/fhir-r4.yaml
@@ -2833,7 +2833,6 @@ tests:
         expression: 1.combine(1).intersect(1).count() = 1
         result:
           - true
-    disable: true
   - 'group: testExclude':
       - desc: '** testExclude1'
         inputfile: patient-example.json

From ebb42cd1095c447806d69dcd585b991d876fc23b Mon Sep 17 00:00:00 2001
From: sedinkinya <yury.sedinkin@nih.gov>
Date: Thu, 3 Mar 2022 18:27:37 -0500
Subject: [PATCH 2/5] union(), distinct() and intersect() should not depend on
 the order of properties in an object

LF-2171
---
 src/combining.js               |  9 +++++----
 src/existence.js               | 36 +++------------------------------
 src/utilities.js               | 37 ++++++++++++++++++++++++++++++++--
 test/cases/5.1_existence.yaml  | 19 +++++++++++++++++
 test/cases/5.3_subsetting.yaml | 18 +++++++++++++++++
 test/cases/5.4_combining.yaml  | 20 ++++++++++++++++++
 6 files changed, 100 insertions(+), 39 deletions(-)

diff --git a/src/combining.js b/src/combining.js
index 146d62f..6d498bb 100644
--- a/src/combining.js
+++ b/src/combining.js
@@ -1,7 +1,8 @@
 // This file holds code to hande the FHIRPath Combining functions.
 
-var combineFns = {};
-var existence = require('./existence');
+const combineFns = {};
+const existence = require('./existence');
+const { orderedJsonStringify } = require("./utilities");
 
 combineFns.union = function(coll1, coll2){
   return existence.distinctFn(coll1.concat(coll2));
@@ -16,12 +17,12 @@ combineFns.intersect = function(coll1, coll2) {
   if (coll1.length && coll2.length) {
     let coll2json = {};
     coll2.forEach(item => {
-      coll2json[JSON.stringify(item)] = true;
+      coll2json[orderedJsonStringify(item)] = true;
     });
 
     for (let i=0, len=coll1.length; i<len; ++i) {
       let item = coll1[i];
-      let json = JSON.stringify(item);
+      let json = orderedJsonStringify(item);
       if (coll2json[json]) {
         result.push(item);
         coll2json[json] = false;
diff --git a/src/existence.js b/src/existence.js
index db3e160..f3d38e0 100644
--- a/src/existence.js
+++ b/src/existence.js
@@ -68,36 +68,6 @@ engine.anyFalseFn  = function(x) {
 };
 
 
-/**
- *  Returns a JSON version of the given object, but with keys of the object in
- *  sorted order (or at least a stable order).
- *  From: https://stackoverflow.com/a/35810961/360782
- */
-function orderedJsonStringify(obj) {
-  return JSON.stringify(sortObjByKey(obj));
-}
-
-/**
- *  If given value is an object, returns a new object with the properties added
- *  in sorted order, and handles nested objects.  Otherwise, returns the given
- *  value.
- *  From: https://stackoverflow.com/a/35810961/360782
- */
-function sortObjByKey(value) {
-  return (typeof value === 'object') ?
-    (Array.isArray(value) ?
-      value.map(sortObjByKey) :
-      Object.keys(value).sort().reduce(
-        (o, key) => {
-          const v = value[key];
-          o[key] = sortObjByKey(v);
-          return o;
-        }, {})
-    ) :
-    value;
-}
-
-
 /**
  *  Returns true if coll1 is a subset of coll2.
  */
@@ -110,13 +80,13 @@ function subsetOf(coll1, coll2) {
     var c2Hash = {};
     for (let p=0, pLen=coll1.length; p<pLen && rtn; ++p) {
       let obj1 = util.valData(coll1[p]);
-      let obj1Str = orderedJsonStringify(obj1);
+      let obj1Str = util.orderedJsonStringify(obj1);
       let found = false;
       if (p===0) { // c2Hash is not yet built
         for (let i=0, len=coll2.length; i<len; ++i) {
           // No early return from this loop, because we're building c2Hash.
           let obj2 = util.valData(coll2[i]);
-          let obj2Str = orderedJsonStringify(obj2);
+          let obj2Str = util.orderedJsonStringify(obj2);
           c2Hash[obj2Str] = obj2;
           found = found || (obj1Str === obj2Str);
         }
@@ -149,7 +119,7 @@ engine.distinctFn = function(x) {
     let uniqueHash = {};
     for (let i=0, len=x.length; i<len; ++i) {
       let xObj = x[i];
-      let xStr = JSON.stringify(xObj);
+      let xStr = util.orderedJsonStringify(xObj);
       let uObj = uniqueHash[xStr];
       if (uObj === undefined) {
         unique.push(xObj);
diff --git a/src/utilities.js b/src/utilities.js
index 4cbc1aa..b476e7e 100644
--- a/src/utilities.js
+++ b/src/utilities.js
@@ -1,7 +1,7 @@
 // This file holds utility functions used in implementing the public functions.
 
-var util =  {};
-var types = require('./types');
+const util =  {};
+const types = require('./types');
 let {ResourceNode} = types;
 
 /**
@@ -101,4 +101,37 @@ util.escapeStringForRegExp = function (str) {
   return str.replace(/[-[\]{}()*+?.,\\/^$|#\s]/g, '\\$&');
 };
 
+/**
+ *  Returns a JSON version of the given object, but with keys of the object in
+ *  sorted order (or at least a stable order).
+ *  From: https://stackoverflow.com/a/35810961/360782
+ */
+util.orderedJsonStringify = function(obj) {
+  return JSON.stringify(sortObjByKey(obj));
+};
+
+/**
+ *  If given value is an object, returns a new object with the properties added
+ *  in sorted order, and handles nested objects.  Otherwise, returns the given
+ *  value.
+ *  From: https://stackoverflow.com/a/35810961/360782
+ */
+function sortObjByKey(value) {
+  // A special case for ResourceNode, which has its own toJSON method
+  if (value instanceof ResourceNode) {
+    return sortObjByKey(value.data);
+  }
+  return (typeof value === 'object') ?
+    (Array.isArray(value) ?
+      value.map(sortObjByKey) :
+      Object.keys(value).sort().reduce(
+        (o, key) => {
+          const v = value[key];
+          o[key] = sortObjByKey(v);
+          return o;
+        }, {})
+    ) :
+    value;
+}
+
 module.exports = util;
diff --git a/test/cases/5.1_existence.yaml b/test/cases/5.1_existence.yaml
index 9825fa0..13d7cff 100644
--- a/test/cases/5.1_existence.yaml
+++ b/test/cases/5.1_existence.yaml
@@ -326,6 +326,16 @@ tests:
     expression: Functions.coll1[0].coll2.attr.distinct()
     result: [1, 2, 3]
 
+  - desc: '** should not depend on the order of properties in an object'
+    expression: Functions.objects.distinct()
+    result:
+      - prop1: 1
+        prop2: 2
+      - prop1: 3
+        prop2: 4
+      - prop1: 5
+        prop2: 6
+
 
   - desc: '5.1.13. count() : integer'
 # Returns a collection with a single value which is
@@ -410,4 +420,13 @@ subject:
       c:
         e: 6
         d: 5
+  objects:
+    - prop1: 1
+      prop2: 2
+    - prop1: 3
+      prop2: 4
+    - prop2: 2
+      prop1: 1
+    - prop1: 5
+      prop2: 6
 
diff --git a/test/cases/5.3_subsetting.yaml b/test/cases/5.3_subsetting.yaml
index 4f54d3c..2c20bb5 100644
--- a/test/cases/5.3_subsetting.yaml
+++ b/test/cases/5.3_subsetting.yaml
@@ -171,6 +171,13 @@ tests:
     expression: Functions.coll1.coll2.attr.take(5)
     result: [1, 2, 3, 4, 5]
 
+  - desc: '5.3.8. intersect(other: collection) : collection'
+  - desc: '** should not depend on the order of properties in an object'
+    expression: Functions.objects.group1.intersect(Functions.objects.group2)
+    result:
+      - prop1: 1
+        prop2: 2
+
 subject:
   resourceType: Functions
   attrempty: []
@@ -216,3 +223,14 @@ subject:
         - attr: '@2015-02-04T14:34:28Z'
         - attr: '@T14:34:28+09:00'
         - attr: 4 days
+  objects:
+    group1:
+      - prop1: 1
+        prop2: 2
+      - prop1: 3
+        prop2: 4
+    group2:
+      - prop2: 2
+        prop1: 1
+      - prop1: 5
+        prop2: 6
diff --git a/test/cases/5.4_combining.yaml b/test/cases/5.4_combining.yaml
index 34598ea..78aa85c 100644
--- a/test/cases/5.4_combining.yaml
+++ b/test/cases/5.4_combining.yaml
@@ -20,6 +20,15 @@ tests:
     expression: Functions.attrdouble | Functions.coll1.coll2.attr
     result: [1, 2, 3, 4, 5]
 
+  - desc: '** should not depend on the order of properties in an object'
+    expression: Functions.objects.group1 | Functions.objects.group2
+    result:
+      - prop1: 1
+        prop2: 2
+      - prop1: 3
+        prop2: 4
+      - prop1: 5
+        prop2: 6
 
   - desc: '5.4.2. combine(other : collection) : collection'
 # Merge the input and other collections into a single collection without eliminating duplicate values. Combining an empty collection with a non-empty collection will return the non-empty collection. There is no expectation of order in the resulting collection.
@@ -85,3 +94,14 @@ subject:
         - attr: '@2015-02-04T14:34:28Z'
         - attr: '@T14:34:28+09:00'
         - attr: 4 days
+  objects:
+    group1:
+      - prop1: 1
+        prop2: 2
+      - prop1: 3
+        prop2: 4
+    group2:
+      - prop2: 2
+        prop1: 1
+      - prop1: 5
+        prop2: 6

From aa00813a1dc38d027deb7ddd35b24bac6762237e Mon Sep 17 00:00:00 2001
From: sedinkinya <yury.sedinkin@nih.gov>
Date: Mon, 14 Mar 2022 15:53:26 -0400
Subject: [PATCH 3/5] Fixed issues found during review

LF-2171
---
 src/combining.js          | 18 ++++--------------
 src/deep-equal.js         |  6 +-----
 src/existence.js          | 38 ++++++++------------------------------
 src/utilities.js          | 33 ---------------------------------
 test/cases/3.2_paths.yaml |  2 +-
 5 files changed, 14 insertions(+), 83 deletions(-)

diff --git a/src/combining.js b/src/combining.js
index 6d498bb..70a4d80 100644
--- a/src/combining.js
+++ b/src/combining.js
@@ -2,7 +2,7 @@
 
 const combineFns = {};
 const existence = require('./existence');
-const { orderedJsonStringify } = require("./utilities");
+const deepEqual = require('./deep-equal');
 
 combineFns.union = function(coll1, coll2){
   return existence.distinctFn(coll1.concat(coll2));
@@ -15,19 +15,9 @@ combineFns.combineFn = function(coll1, coll2){
 combineFns.intersect = function(coll1, coll2) {
   let result = [];
   if (coll1.length && coll2.length) {
-    let coll2json = {};
-    coll2.forEach(item => {
-      coll2json[orderedJsonStringify(item)] = true;
-    });
-
-    for (let i=0, len=coll1.length; i<len; ++i) {
-      let item = coll1[i];
-      let json = orderedJsonStringify(item);
-      if (coll2json[json]) {
-        result.push(item);
-        coll2json[json] = false;
-      }
-    }
+    result = existence.distinctFn(coll1).filter(
+      obj1 => coll2.some(obj2 => deepEqual(obj1, obj2))
+    )
   }
 
   return result;
diff --git a/src/deep-equal.js b/src/deep-equal.js
index be3713b..3f3c30c 100644
--- a/src/deep-equal.js
+++ b/src/deep-equal.js
@@ -54,12 +54,8 @@ var deepEqual = function (actual, expected, opts) {
 
   if (actual instanceof Date && expected instanceof Date) {
     return actual.getTime() === expected.getTime();
-
-    // 7.3. Other pairs that do not both pass typeof value == 'object',
-    // equivalence is determined by ==.
   } else if (!actual || !expected || typeof actual != 'object' && typeof expected != 'object') {
-    return opts.strict ? actual === expected : actual == expected;
-
+    return actual === expected;
   }
   else {
     var actualIsFPT = actual instanceof FP_Type;
diff --git a/src/existence.js b/src/existence.js
index f3d38e0..fea9c56 100644
--- a/src/existence.js
+++ b/src/existence.js
@@ -4,6 +4,7 @@
 const util = require("./utilities");
 const filtering = require("./filtering");
 const misc = require("./misc");
+const deepEqual = require('./deep-equal');
 
 const engine = {};
 engine.emptyFn = util.isEmpty;
@@ -74,26 +75,9 @@ engine.anyFalseFn  = function(x) {
 function subsetOf(coll1, coll2) {
   let rtn = coll1.length <= coll2.length;
   if (rtn) {
-    // This requires a deep-equals comparision of every object in coll1,
-    // against each object in coll2.
-    // Optimize by building a hashmap of JSON versions of the objects.
-    var c2Hash = {};
     for (let p=0, pLen=coll1.length; p<pLen && rtn; ++p) {
       let obj1 = util.valData(coll1[p]);
-      let obj1Str = util.orderedJsonStringify(obj1);
-      let found = false;
-      if (p===0) { // c2Hash is not yet built
-        for (let i=0, len=coll2.length; i<len; ++i) {
-          // No early return from this loop, because we're building c2Hash.
-          let obj2 = util.valData(coll2[i]);
-          let obj2Str = util.orderedJsonStringify(obj2);
-          c2Hash[obj2Str] = obj2;
-          found = found || (obj1Str === obj2Str);
-        }
-      }
-      else
-        found = !!c2Hash[obj1Str];
-      rtn = found;
+      rtn = coll2.some(obj2 => deepEqual(obj1, util.valData(obj2)));
     }
   }
   return rtn;
@@ -113,19 +97,13 @@ engine.isDistinctFn = function(x) {
 
 engine.distinctFn = function(x) {
   let unique = [];
-  // Since this requires a deep equals, use a hash table (on JSON strings) for
-  // efficiency.
   if (x.length > 0) {
-    let uniqueHash = {};
-    for (let i=0, len=x.length; i<len; ++i) {
-      let xObj = x[i];
-      let xStr = util.orderedJsonStringify(xObj);
-      let uObj = uniqueHash[xStr];
-      if (uObj === undefined) {
-        unique.push(xObj);
-        uniqueHash[xStr] = xObj;
-      }
-    }
+    x = x.concat();
+    do {
+      let xObj = x.shift();
+      unique.push(xObj);
+      x = x.filter(o => !deepEqual(xObj, o, {strict: true}));
+    } while (x.length)
   }
   return unique;
 };
diff --git a/src/utilities.js b/src/utilities.js
index b476e7e..27d7ece 100644
--- a/src/utilities.js
+++ b/src/utilities.js
@@ -101,37 +101,4 @@ util.escapeStringForRegExp = function (str) {
   return str.replace(/[-[\]{}()*+?.,\\/^$|#\s]/g, '\\$&');
 };
 
-/**
- *  Returns a JSON version of the given object, but with keys of the object in
- *  sorted order (or at least a stable order).
- *  From: https://stackoverflow.com/a/35810961/360782
- */
-util.orderedJsonStringify = function(obj) {
-  return JSON.stringify(sortObjByKey(obj));
-};
-
-/**
- *  If given value is an object, returns a new object with the properties added
- *  in sorted order, and handles nested objects.  Otherwise, returns the given
- *  value.
- *  From: https://stackoverflow.com/a/35810961/360782
- */
-function sortObjByKey(value) {
-  // A special case for ResourceNode, which has its own toJSON method
-  if (value instanceof ResourceNode) {
-    return sortObjByKey(value.data);
-  }
-  return (typeof value === 'object') ?
-    (Array.isArray(value) ?
-      value.map(sortObjByKey) :
-      Object.keys(value).sort().reduce(
-        (o, key) => {
-          const v = value[key];
-          o[key] = sortObjByKey(v);
-          return o;
-        }, {})
-    ) :
-    value;
-}
-
 module.exports = util;
diff --git a/test/cases/3.2_paths.yaml b/test/cases/3.2_paths.yaml
index 3095d44..205a492 100644
--- a/test/cases/3.2_paths.yaml
+++ b/test/cases/3.2_paths.yaml
@@ -50,7 +50,7 @@ tests:
       result: ['medium', 'low', 'zero']
 
     - desc: "QR with where()"
-      expression: "contained.where(resourceType = 'QuestionnaireResponse').item.where(linkId = 1).answer.value"
+      expression: "contained.where(resourceType = 'QuestionnaireResponse').item.where(linkId = '1').answer.value"
       model: 'r4'
       result: ['Red']
 

From 024fac74a5363eadd824df7444e22d4a6f3cae59 Mon Sep 17 00:00:00 2001
From: sedinkinya <yury.sedinkin@nih.gov>
Date: Wed, 16 Mar 2022 15:47:15 -0400
Subject: [PATCH 4/5] Minor fixes

LF-2171
---
 src/combining.js | 2 +-
 src/existence.js | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/combining.js b/src/combining.js
index 70a4d80..52f80ca 100644
--- a/src/combining.js
+++ b/src/combining.js
@@ -17,7 +17,7 @@ combineFns.intersect = function(coll1, coll2) {
   if (coll1.length && coll2.length) {
     result = existence.distinctFn(coll1).filter(
       obj1 => coll2.some(obj2 => deepEqual(obj1, obj2))
-    )
+    );
   }
 
   return result;
diff --git a/src/existence.js b/src/existence.js
index fea9c56..ee1d95f 100644
--- a/src/existence.js
+++ b/src/existence.js
@@ -102,8 +102,8 @@ engine.distinctFn = function(x) {
     do {
       let xObj = x.shift();
       unique.push(xObj);
-      x = x.filter(o => !deepEqual(xObj, o, {strict: true}));
-    } while (x.length)
+      x = x.filter(o => !deepEqual(xObj, o));
+    } while (x.length);
   }
   return unique;
 };

From 1a24c742108781275e6721696ce5738713ffa60d Mon Sep 17 00:00:00 2001
From: sedinkinya <yury.sedinkin@nih.gov>
Date: Fri, 18 Mar 2022 14:04:29 -0400
Subject: [PATCH 5/5] Updated CHANGELOG.md

LF-2171
---
 CHANGELOG.md | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 55b00bf..6a19d09 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,11 @@ This log documents significant changes for each release.  This project follows
 ## [2.14.0] - 2022-03-02
 ### Added
 - Function to get the intersection of two collections: intersect().
+### Fixed
+- The distinct, union, subsetOf, and intersect functions now use
+  the "6.1.1. = (Equals)" function to compare collection items instead of using
+  a map with JSON keys, which can affect their performance because the
+  complexity of the algorithm has changed from O(n) to O(n**2).
 
 ## [2.13.0] - 2022-02-28
 ### Added