From c4dcdff9844e2404e3bc035f4cea9fce2f7770ab Mon Sep 17 00:00:00 2001
From: Shin'ya Ueoka <ueokande@i-beam.org>
Date: Sun, 19 May 2019 15:40:23 +0900
Subject: Add HintKeyProducer

---
 src/content/usecases/FollowMasterUseCase.ts   |  2 +-
 src/content/usecases/HintKeyProducer.ts       | 38 +++++++++++++++++++++++++++
 test/content/hint-key-producer.test.ts        | 24 -----------------
 test/content/usecases/HintKeyProducer.test.ts | 25 ++++++++++++++++++
 4 files changed, 64 insertions(+), 25 deletions(-)
 create mode 100644 src/content/usecases/HintKeyProducer.ts
 delete mode 100644 test/content/hint-key-producer.test.ts
 create mode 100644 test/content/usecases/HintKeyProducer.test.ts

diff --git a/src/content/usecases/FollowMasterUseCase.ts b/src/content/usecases/FollowMasterUseCase.ts
index c2c6835..9cbb790 100644
--- a/src/content/usecases/FollowMasterUseCase.ts
+++ b/src/content/usecases/FollowMasterUseCase.ts
@@ -4,7 +4,7 @@ import FollowMasterRepository, { FollowMasterRepositoryImpl }
   from '../repositories/FollowMasterRepository';
 import FollowSlaveClient, { FollowSlaveClientImpl }
   from '../client/FollowSlaveClient';
-import HintKeyProducer from '../hint-key-producer';
+import HintKeyProducer from './HintKeyProducer';
 import SettingRepository, { SettingRepositoryImpl }
   from '../repositories/SettingRepository';
 
diff --git a/src/content/usecases/HintKeyProducer.ts b/src/content/usecases/HintKeyProducer.ts
new file mode 100644
index 0000000..241cd56
--- /dev/null
+++ b/src/content/usecases/HintKeyProducer.ts
@@ -0,0 +1,38 @@
+export default class HintKeyProducer {
+  private charset: string;
+
+  private counter: number[];
+
+  constructor(charset: string) {
+    if (charset.length === 0) {
+      throw new TypeError('charset is empty');
+    }
+
+    this.charset = charset;
+    this.counter = [];
+  }
+
+  produce(): string {
+    this.increment();
+
+    return this.counter.map(x => this.charset[x]).join('');
+  }
+
+  private increment(): void {
+    let max = this.charset.length - 1;
+    if (this.counter.every(x => x === max)) {
+      this.counter = new Array(this.counter.length + 1).fill(0);
+      return;
+    }
+
+    this.counter.reverse();
+    let len = this.charset.length;
+    let num = this.counter.reduce((x, y, index) => x + y * len ** index) + 1;
+    for (let i = 0; i < this.counter.length; ++i) {
+      this.counter[i] = num % len;
+      num = ~~(num / len);
+    }
+    this.counter.reverse();
+  }
+}
+
diff --git a/test/content/hint-key-producer.test.ts b/test/content/hint-key-producer.test.ts
deleted file mode 100644
index dcf477d..0000000
--- a/test/content/hint-key-producer.test.ts
+++ /dev/null
@@ -1,24 +0,0 @@
-import HintKeyProducer from 'content/hint-key-producer';
-
-describe('HintKeyProducer class', () => {
-  describe('#constructor', () => {
-    it('throws an exception on empty charset', () => {
-      expect(() => new HintKeyProducer([])).to.throw(TypeError);
-    });
-  });
-
-  describe('#produce', () => {
-    it('produce incremented keys', () => {
-      let charset = 'abc';
-      let sequences = [
-        'a', 'b', 'c',
-        'aa', 'ab', 'ac', 'ba', 'bb', 'bc', 'ca', 'cb', 'cc',
-        'aaa', 'aab', 'aac', 'aba']
-
-      let producer = new HintKeyProducer(charset);
-      for (let i = 0; i < sequences.length; ++i) {
-        expect(producer.produce()).to.equal(sequences[i]);
-      }
-    });
-  });
-});
diff --git a/test/content/usecases/HintKeyProducer.test.ts b/test/content/usecases/HintKeyProducer.test.ts
new file mode 100644
index 0000000..feafffb
--- /dev/null
+++ b/test/content/usecases/HintKeyProducer.test.ts
@@ -0,0 +1,25 @@
+import HintKeyProducer from '../../../src/content/usecases/HintKeyProducer';
+import { expect } from 'chai';
+
+describe('HintKeyProducer class', () => {
+  describe('#constructor', () => {
+    it('throws an exception on empty charset', () => {
+      expect(() => new HintKeyProducer('')).to.throw(TypeError);
+    });
+  });
+
+  describe('#produce', () => {
+    it('produce incremented keys', () => {
+      let charset = 'abc';
+      let sequences = [
+        'a', 'b', 'c',
+        'aa', 'ab', 'ac', 'ba', 'bb', 'bc', 'ca', 'cb', 'cc',
+        'aaa', 'aab', 'aac', 'aba']
+
+      let producer = new HintKeyProducer(charset);
+      for (let i = 0; i < sequences.length; ++i) {
+        expect(producer.produce()).to.equal(sequences[i]);
+      }
+    });
+  });
+});
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