Merge pull request #7 from paperhive/transform-ranges

Transform ranges

README.md

@@ -66,3 +66,16 @@ backTransformRange({position: 6, length: 10}, transformations);
     }]
 
 ```
+
+### search(searchStr)
+- returns ranges of `searchStr` in a search index
+```
+const index = new SearchIndex('this  is a  test');
+index.search('is a test');
+=>  [{position: 6, length: 10}]
+
+const index = new SearchIndex('  hello   world ,  HELLO    WORLD   ');
+index.search('hello world');
+=>  [{position: 2, length: 13}, {position: 19, length: 14}]
+
+```

package.json

@@ -1,6 +1,6 @@
 {
   "name": "srch",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "description": "full text search",
   "main": "src/index.js",
   "scripts": {

src/index.js

@@ -108,3 +108,54 @@ exports.backTransformRange = function backTransformRange(range, transformations)
   if (rangePosition !== 0) throw new Error('Out of range');
   return output;
 };
+
+function transformLowercase(str) {
+  return {
+    str: str.toLowerCase(),
+    mapping: [{transformed: str.length, original: str.length}],
+  };
+}
+
+function transform(transformations, str) {
+  let transformedStr = str;
+  const mappings = [];
+  transformations.forEach((transformation) => {
+    const {str: newStr, mapping} = transformation(transformedStr);
+    transformedStr = newStr;
+    mappings.push(mapping);
+  });
+  return {transformedStr, mapping: mappings};
+}
+
+
+exports.SearchIndex = class SearchIndex {
+  constructor(str) {
+    this.transformations = [exports.transformSpaces, transformLowercase];
+
+    const {transformedStr, mapping} = transform(this.transformations, str);
+    this.transformedStr = transformedStr;
+    this.mappings = mapping;
+  }
+
+  search(searchStr) {
+    const {transformedStr} = transform(this.transformations, searchStr);
+    if (transformedStr.length === 0) throw new Error('transformed string is empty');
+
+    // end position points to the last character
+    let startPositions = exports.findPositions(this.transformedStr, transformedStr);
+    let endPositions = startPositions.map(position => position + (transformedStr.length - 1));
+
+    // note: slice() copies the array so reverse() can alter the array
+    this.mappings.slice().reverse().forEach((mapping) => {
+      startPositions = exports.backTransformPositions(startPositions, mapping);
+      endPositions = exports.backTransformPositions(endPositions, mapping);
+    });
+
+    const ranges = [];
+    for (let i = 0; i < startPositions.length; i += 1) {
+      ranges.push({position: startPositions[i], length: (endPositions[i] - startPositions[i]) + 1});
+    }
+
+    return ranges;
+  }
+};

test/index.js

@@ -147,3 +147,38 @@ describe('backTransformRange', () => {
       .should.throw('Empty transformations');
   });
 });
+
+describe('SearchIndex', () => {
+  it('should find ranges', () => {
+    const index = new srch.SearchIndex('this  is a  test');
+    index.search('is a test').should.eql([{position: 6, length: 10}]);
+  });
+
+  it('should find ranges with spaces at the end and beginning', () => {
+    const index = new srch.SearchIndex('   hello  world  ');
+    index.search('hello world').should.eql([{position: 3, length: 12}]);
+  });
+
+  it('should find ranges: transformed string equals original', () => {
+    const index = new srch.SearchIndex('hello world');
+    index.search('hello world').should.eql([{position: 0, length: 11}]);
+  });
+
+  it('should find ranges: 2 occurences of searchStr in text', () => {
+    const index = new srch.SearchIndex('hello world, hello world');
+    index.search('hello world').should.eql([{position: 0, length: 11}, {position: 13, length: 11}]);
+  });
+
+  it('should find ranges: 2 occurences of searchStr in text with spaces', () => {
+    const index = new srch.SearchIndex('  hello   world ,  hello    world   ');
+    index.search('hello world').should.eql([{position: 2, length: 13}, {position: 19, length: 14}]);
+  });
+
+  it('should find ranges: mixed lower and upper case', () => {
+    const index = new srch.SearchIndex('TEST test TEst TeSt  ');
+    index.search('test').should.eql([
+      {position: 0, length: 4}, {position: 5, length: 4},
+      {position: 10, length: 4}, {position: 15, length: 4},
+    ]);
+  });
+});