From 9277fbd0d30ba6aab31eb78cbd262b66075f920b Mon Sep 17 00:00:00 2001
From: Atul Singh <atulsingh2304@gmail.com>
Date: Wed, 13 Jun 2018 10:28:58 +0530
Subject: [PATCH] Create DiskCache

Every time when clearing the cache, app gets crashed when immediately request to get something from cache. Please check the comment with "// Check before proceed." I've added a check and each time it will check journalWriter is null or not.
---
 DiskCache | 140 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 140 insertions(+)
 create mode 100644 DiskCache

diff --git a/DiskCache b/DiskCache
new file mode 100644
index 0000000..6b8477c
--- /dev/null
+++ b/DiskCache
@@ -0,0 +1,140 @@
+import com.jakewharton.disklrucache.DiskLruCache;
+import java.io.BufferedOutputStream;
+import java.io.File;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.UnsupportedEncodingException;
+import java.math.BigInteger;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+public class DiskCache implements Cache {
+    private final String HASH_ALGORITHM = "MD5";
+    private final String STRING_ENCODING = "UTF-8";
+    private final int DEFAULT_CACHE_SIZE = 1024 * 1024 * 10;
+    private final int VALUE_COUNT = 1;
+    private DiskLruCache diskLruCache;
+
+    private File cacheDirectory;
+    private int appVersion;
+    private int cacheSizeKb;
+
+    public DiskCache(File cacheDirectory, int appVersion, int cacheSizeKb) throws IOException {
+        this.cacheDirectory = cacheDirectory;
+        this.appVersion = appVersion;
+        this.cacheSizeKb = cacheSizeKb;
+        open();
+    }
+
+    private void open() throws IOException {
+        diskLruCache = DiskLruCache.open(cacheDirectory, appVersion, VALUE_COUNT,
+                cacheSizeKb <= 0 ? DEFAULT_CACHE_SIZE : cacheSizeKb);
+    }
+
+    @Override
+    public String getValue(String key) throws IOException {
+        String value = null;
+        if (!diskLruCache.isClosed()) {
+            DiskLruCache.Snapshot snapshot = null;
+
+            try {
+                snapshot = diskLruCache.get(getHashOf(key));
+                if (snapshot == null) {
+                    return null;
+                }
+
+                value = snapshot.getString(0);
+            } finally {
+                if (snapshot != null) {
+                    snapshot.close();
+                }
+            }
+        }
+
+        return value;
+    }
+
+    @Override
+    public boolean contains(String key) throws IOException {
+        boolean found = false;
+        if (!diskLruCache.isClosed()) {
+            DiskLruCache.Snapshot snapshot = null;
+
+            try {
+                snapshot = diskLruCache.get(getHashOf(key));
+                if (snapshot != null) {
+                    found = true;
+                }
+            } finally {
+                if (snapshot != null) {
+                    snapshot.close();
+                }
+            }
+        }
+
+        return found;
+    }
+
+    @Override
+    public void setKeyValue(String key, String value) throws IOException {
+        DiskLruCache.Editor editor = null;
+        if (!diskLruCache.isClosed()) {
+            try {
+                editor = diskLruCache.edit(getHashOf(key));
+                if (editor == null) {
+                    return;
+                }
+
+                if (writeValueToCache(value, editor)) {
+                    diskLruCache.flush();
+                    editor.commit();
+                } else {
+                    editor.abort();
+                }
+            } catch (IOException e) {
+                if (editor != null) {
+                    editor.abort();
+                }
+
+                throw e;
+            }
+        }
+    }
+
+    @Override
+    public void clearCache() throws IOException {
+        diskLruCache.delete();
+        //Open the cache again to use the new empty cache
+        open();
+    }
+
+    protected boolean writeValueToCache(String value, DiskLruCache.Editor editor) throws IOException {
+        OutputStream outputStream = null;
+        try {
+            outputStream = new BufferedOutputStream(editor.newOutputStream(0));
+            outputStream.write(value.getBytes(STRING_ENCODING));
+        } finally {
+            if (outputStream != null) {
+                outputStream.close();
+            }
+        }
+
+        return true;
+    }
+
+    protected String getHashOf(String string) throws UnsupportedEncodingException {
+        try {
+            MessageDigest messageDigest = null;
+            messageDigest = MessageDigest.getInstance(HASH_ALGORITHM);
+            messageDigest.update(string.getBytes(STRING_ENCODING));
+            byte[] digest = messageDigest.digest();
+            BigInteger bigInt = new BigInteger(1, digest);
+
+            return bigInt.toString(16);
+        } catch (NoSuchAlgorithmException e) {
+
+            return string;
+        }
+    }
+
+}