[FEATURE] Added new method betweenLexoRanks which allows to generate multiple between lexoRank based on user input

README.md

@@ -66,6 +66,8 @@ const any1LexoRank = LexoRank.min();
 const any2LexoRank = any1LexoRank.genNext().genNext();
 // calculate between
 const betweenLexoRank = any1LexoRank.between(any2LexoRank);
+// calculate between lexoRanks
+const betweenLexoRanks = any1LexoRank.multipleBetween(any2LexoRank, 5);
 ```
 
 ## Related projects

__tests__/lexoRank.spec.ts

@@ -64,4 +64,111 @@ describe('LexoRank', () => {
     const between = prevRank.between(nextRank);
     expect(between.toString()).toEqual(expected);
   });
+
+  it('find the nearest power', () => {
+    expect(LexoRank.binaryDepthToInsertRanks(1)).toEqual(1);
+    expect(LexoRank.binaryDepthToInsertRanks(2)).toEqual(2);
+    expect(LexoRank.binaryDepthToInsertRanks(3)).toEqual(2);
+    expect(LexoRank.binaryDepthToInsertRanks(4)).toEqual(3);
+    expect(LexoRank.binaryDepthToInsertRanks(5)).toEqual(3);
+    expect(LexoRank.binaryDepthToInsertRanks(6)).toEqual(3);
+    expect(LexoRank.binaryDepthToInsertRanks(7)).toEqual(3);
+    expect(LexoRank.binaryDepthToInsertRanks(8)).toEqual(4);
+    expect(LexoRank.binaryDepthToInsertRanks(15)).toEqual(4);
+    expect(LexoRank.binaryDepthToInsertRanks(31)).toEqual(5);
+    expect(LexoRank.binaryDepthToInsertRanks(63)).toEqual(6);
+    expect(LexoRank.binaryDepthToInsertRanks(124)).toEqual(7);
+    expect(LexoRank.binaryDepthToInsertRanks(127)).toEqual(7);
+  });
+
+  it('find the multipleBetween for 1 lexoRanks to generate', () => {
+    const minRank = LexoRank.min();
+    const maxRank = LexoRank.max();
+    const lexoRanks: LexoRank[] = minRank.multipleBetween(maxRank, 1);
+    expect(lexoRanks.length).toEqual(1);
+    expect(lexoRanks[0].toString()).toEqual('0|hzzzzz:');
+  });
+
+  it('find the multipleBetween for 2 lexoRanks to generate', () => {
+    const minRank = LexoRank.min();
+    const maxRank = LexoRank.max();
+    const lexoRanks: LexoRank[] = minRank.multipleBetween(maxRank, 2);
+    expect(lexoRanks.length).toEqual(2);
+    expect(lexoRanks[0].toString()).toEqual('0|8zzzzz:');
+    expect(lexoRanks[1].toString()).toEqual('0|hzzzzz:');
+    expect(checkSortedInAscendingOrder(lexoRanks)).toEqual(true);
+  });
+
+  it('find the multipleBetween for 2 lexoRanks when one lexoRank is long in length', () => {
+    const maxRank = LexoRank.parse('0|i00006:zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzr');
+    const minRank = LexoRank.parse('0|i00006:zzr');
+    const lexoRanks: LexoRank[] = minRank.multipleBetween(maxRank, 2);
+    expect(lexoRanks.length).toEqual(2);
+    expect(lexoRanks[0].toString()).toEqual('0|i00006:zzt');
+    expect(lexoRanks[1].toString()).toEqual('0|i00006:zzv');
+    expect(checkSortedInAscendingOrder(lexoRanks)).toEqual(true);
+  });
+
+  it('find the multipleBetween for 3 lexoRanks to generate', () => {
+    const minRank = LexoRank.min();
+    const maxRank = LexoRank.max();
+    const lexoRanks: LexoRank[] = minRank.multipleBetween(maxRank, 3);
+    expect(lexoRanks.length).toEqual(3);
+    expect(lexoRanks[0].toString()).toEqual('0|8zzzzz:');
+    expect(lexoRanks[1].toString()).toEqual('0|hzzzzz:');
+    expect(lexoRanks[2].toString()).toEqual('0|qzzzzz:');
+    expect(checkSortedInAscendingOrder(lexoRanks)).toEqual(true);
+  });
+
+  it('find the multipleBetween for 4 lexoRanks to generate', () => {
+    const minRank = LexoRank.min();
+    const maxRank = LexoRank.max();
+    const lexoRanks: LexoRank[] = minRank.multipleBetween(maxRank, 4);
+    expect(lexoRanks.length).toEqual(4);
+    expect(lexoRanks[0].toString()).toEqual('0|4hzzzz:');
+    expect(lexoRanks[1].toString()).toEqual('0|8zzzzz:');
+    expect(lexoRanks[2].toString()).toEqual('0|dhzzzz:');
+    expect(lexoRanks[3].toString()).toEqual('0|hzzzzz:');
+    expect(checkSortedInAscendingOrder(lexoRanks)).toEqual(true);
+  });
+
+  it('find the multipleBetween for 7 lexoRanks to generate', () => {
+    const minRank = LexoRank.min();
+    const maxRank = LexoRank.max();
+    const lexoRanks: LexoRank[] = minRank.multipleBetween(maxRank, 7);
+    expect(lexoRanks.length).toEqual(7);
+    expect(lexoRanks[0].toString()).toEqual('0|4hzzzz:');
+    expect(lexoRanks[1].toString()).toEqual('0|8zzzzz:');
+    expect(lexoRanks[2].toString()).toEqual('0|dhzzzz:');
+    expect(lexoRanks[3].toString()).toEqual('0|hzzzzz:');
+    expect(lexoRanks[4].toString()).toEqual('0|mhzzzz:');
+    expect(lexoRanks[5].toString()).toEqual('0|qzzzzz:');
+    expect(lexoRanks[6].toString()).toEqual('0|vhzzzz:');
+    expect(checkSortedInAscendingOrder(lexoRanks)).toEqual(true);
+  });
+
+  it('find the multipleBetween for 8 lexoRanks when one lexoRank is long in length', () => {
+    const maxRank = LexoRank.parse('0|i00006:zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzr');
+    const minRank = LexoRank.parse('0|i00006:zzr');
+    const lexoRanks: LexoRank[] = minRank.multipleBetween(maxRank, 8);
+    expect(lexoRanks.length).toEqual(8);
+    expect(lexoRanks[0].toString()).toEqual('0|i00006:zzri');
+    expect(lexoRanks[1].toString()).toEqual('0|i00006:zzs');
+    expect(lexoRanks[2].toString()).toEqual('0|i00006:zzsi');
+    expect(lexoRanks[3].toString()).toEqual('0|i00006:zzt');
+    expect(lexoRanks[4].toString()).toEqual('0|i00006:zzti');
+    expect(lexoRanks[5].toString()).toEqual('0|i00006:zzu');
+    expect(lexoRanks[6].toString()).toEqual('0|i00006:zzui');
+    expect(lexoRanks[7].toString()).toEqual('0|i00006:zzv');
+    expect(checkSortedInAscendingOrder(lexoRanks)).toEqual(true);
+  });
+
+  function checkSortedInAscendingOrder(arr) {
+    for (let i = 0; i < arr.length - 1; i++) {
+      if (arr[i] > arr[i + 1]) {
+        return false;
+      }
+    }
+    return true;
+  }
 });

src/lexoRank/lexoRank.ts

@@ -311,6 +311,69 @@ export class LexoRank {
     return new LexoRank(this.bucket, LexoRank.between(this.decimal, other.decimal));
   }
 
+  public multipleBetween(other: LexoRank, ranksToGenerate: number): LexoRank[] {
+
+    if (!this.bucket.equals(other.bucket)) {
+      throw new Error('Between works only within the same bucket');
+    }
+
+    if (ranksToGenerate <= 0) {
+      throw new Error(`'ranksToGenerate' should be greater than 0`);
+    }
+
+    if (ranksToGenerate == 1) {
+      return [this.between(other)];
+    }
+
+    let left: LexoRank = this;
+    let right: LexoRank = other;
+
+    const cmp = this.decimal.compareTo(other.decimal);
+    if (cmp > 0) {
+      left = other;
+      right = this;
+    }
+
+    if (cmp === 0) {
+      throw new Error(
+          'Try to rank between issues with same rank this=' +
+          this +
+          ' other=' +
+          other +
+          ' this.decimal=' +
+          this.decimal +
+          ' other.decimal=' +
+          other.decimal
+      );
+    }
+
+    const binaryDepth: number = LexoRank.binaryDepthToInsertRanks(ranksToGenerate);
+
+    const lexoRanks: LexoRank[] = [];
+
+    LexoRank.prepareLexoRanks(left, right, 1, binaryDepth, lexoRanks);
+
+    return lexoRanks.slice(0, ranksToGenerate);
+  }
+
+  private static prepareLexoRanks(left: LexoRank, right: LexoRank, currentDepth: number, maxDepth: number, lexoRanks: LexoRank[]) {
+    // find the midpoint for this operation
+    const rankAtThisLevel: LexoRank = left.between(right);
+
+    if (currentDepth < maxDepth) {
+      // recursive into the left subtree
+      LexoRank.prepareLexoRanks(left, rankAtThisLevel, currentDepth + 1, maxDepth, lexoRanks);
+    }
+
+    // insert the LexoRank at this level
+    lexoRanks.push(rankAtThisLevel);
+
+    if (currentDepth < maxDepth) {
+      // recursive into the right subtree
+      LexoRank.prepareLexoRanks(rankAtThisLevel, right, currentDepth + 1, maxDepth, lexoRanks);
+    }
+  }
+
   public getBucket(): LexoRankBucket {
     return this.bucket;
   }
@@ -366,4 +429,17 @@ export class LexoRank {
 
     return this.value.localeCompare(other.value);
   }
+
+  // Visible for unit test
+  public static binaryDepthToInsertRanks(noOfRanks: number): number {
+    if (noOfRanks < 1) return 0;
+
+    let power = 1;
+    while (Math.pow(2, power) - 1 < noOfRanks) {
+      power++;
+    }
+
+    return power;
+  }
+
 }