/**
 * Copyright (c) 2011, The University of Southampton and the individual contributors.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 *   *  Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 *
 *   *  Redistributions in binary form must reproduce the above copyright notice,
 *      this list of conditions and the following disclaimer in the documentation
 *      and/or other materials provided with the distribution.
 *
 *   *  Neither the name of the University of Southampton nor the names of its
 *      contributors may be used to endorse or promote products derived from this
 *      software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.openimaj.io;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Scanner;


import cern.colt.Arrays;


/**
 * In its simplest form this function constructs an object using the construct found for the objects
 * specified. This works with all java classes. If the class also happens to be cachable, the property
 * org.openimaj.cache.dir is use (or $HOME/.OIcache) to save the class. The object instance is saved in
 * $CACHE_DIR/classpackage/classname/unique-name where unique-name is taken from cachable. 
 * 
 * If cachable objects already exist they are read in using {@link IOUtils#read(java.io.File)}.
 * 
 * Once created, cachable objects are saved using either {@link IOUtils#writeASCII(java.io.File, WriteableASCII)} or
 * {@link IOUtils#writeBinary(java.io.File, WriteableBinary)}
 * 
 * 
 * @author Sina Samangooei (ss@ecs.soton.ac.uk)
 *
 */
public class Cache {
        
        private final static String cacheProp = "org.openimaj.cache.dir";
        private static final String CACHE_DIR_NAME = ".OIcache";
        
        /**
         * load an instance using {@link #load(Object, Class, boolean)} with class as instance#getClass. The cache lookup is not
         * skipped. 
         * @param <T>
         * @param instance
         * @return a loaded instance
         */
        public static <T> T load(T instance){
                @SuppressWarnings("unchecked")
                T ret = (T) load(instance,instance.getClass(),false);
                return ret; 
        }
        
        /**
         * Create an instance of the clazz for the objects (for the constructor).
         * If the class creates {@link Cachable} instances, an attempt is made to load
         * the instance from the Cache. 
         * 
         * @param <T> The type of the object returned
         * @param clazz the class which to get a cached instance of
         * @param objects the parameters used to instantiate and index the cached object
         * @return an instance of the clazz 
         */
        public static <T> T load(Class<? extends T> clazz, Object ... objects ) {
                return load(clazz,false,objects);
        }
        
        /**
         * Create an instance of the clazz for the objects (for the constructor).
         * If the class creates {@link Cachable} instances, an attempt is made to load
         * the instance from the Cache. 
         * 
         * @param <T> The type of the object returned
         * @param clazz the class which to get a cached instance of
         * @param objects the parameters used to instantiate and index the cached object
         * @return an instance of the clazz 
         */
        public static <T> T loadSkipCache(Class<? extends T> clazz, Object ... objects ) {
                return load(clazz,true,objects);
        }
        
        /**
         * Clear the cache entry for a given clazz and a set of constructors
         * @param <T>
         * @param clazz
         * @param objects
         */
        public static <T extends Cachable> void clear(Class<T> clazz, Object ... objects) {
                T instance = createInstance(clazz,objects);
                File location = constructCachedLocation(instance, clazz);
                FileUtils.deleteRecursive(location);
        }
        
        /**
         * Clear the cache entry for a given cachable object
         * @param instance
         */
        public static void clear(Cachable instance) {
                File location = constructCachedLocation(instance, instance.getClass());
                FileUtils.deleteRecursive(location);
        }
        
        /**
         * @param <T> The type of the object returned
         * @param clazz the class which to get a cached instance of
         * @param skipcache force the cache to be skipped, for a new instance to be returned 
         * @param objects the parameters used to instantiate and index the cached object
         * @return an instance of the clazz
         */
        private static <T> T load(Class<? extends T> clazz, boolean skipcache, Object ... objects ) {
                T instance = createInstance(clazz,objects);
                return load(instance,clazz,skipcache);
        }
        
        /**
         * @param <T> The type of the object returned
         * @param instance the instance to attempt to load from the cache if the instance is {@link Cachable}
         * @param clazz the class which to get a cached instance of
         * @param skipcache force the cache to be skipped, for a new instance to be returned
         * @return an instance of the clazz
         */
        @SuppressWarnings("unchecked")
        public static <T> T load(T instance, Class<? extends T> clazz, boolean skipcache) {
                if(instance instanceof Cachable && !skipcache){
                        Cachable cinstance = (Cachable)instance;
                        File cachedLocation = constructCachedLocation(cinstance,clazz);
                        try{
                                // if it exists load it!
                                if(cachedLocation.exists()){
                                        if(cinstance instanceof ReadWriteableASCII){
                                                ReadWriteableASCII rwinstance = cacheFromASCII((ReadWriteableASCII)cinstance,cachedLocation);
                                                instance = (T) rwinstance;
                                        }
                                        else if(cinstance instanceof ReadWriteableBinary){
                                                ReadWriteableBinary rwinstance = cacheFromBinary((ReadWriteableBinary)cinstance,cachedLocation);
                                                instance = (T) rwinstance;
                                        }
                                }
                                // if not, create the parent directory and save it!
                                else{
                                        if(!cachedLocation.getParentFile().exists() && !cachedLocation.getParentFile().mkdirs()){
                                                throw new IOException("Couldn't create cache directory!");
                                        }
                                        if(cinstance instanceof ReadWriteableASCII){
                                                IOUtils.writeASCII(cachedLocation, (ReadWriteableASCII) instance);
                                        }
                                        else if(cinstance instanceof ReadWriteableBinary){
                                                IOUtils.writeBinary(cachedLocation, (ReadWriteableBinary) instance);
                                        }
                                }
                                
                        }
                        catch(Exception e){
                                e.printStackTrace();
                                System.err.println("Error reading or writing object from cache");
                        }
                }
                return instance;
        }
        
        private static File constructCachedLocation(Cachable cinstance, Class<?> clazz) {
                String cdir = System.getProperty(cacheProp);
                if(cdir == null || cdir.equals(""))
                        cdir = System.getProperty("user.home") + "/" + CACHE_DIR_NAME;
                
                String pname = clazz.getPackage().getName();
                String cname = clazz.getName();
                String uname = cinstance.identifier();
                File cachedLocation = new File(cdir,String.format("%s/%s/%s",pname,cname,uname));
                return cachedLocation;
        }

        private static <T> T createInstance(Class<T> clazz, Object ... objects) {
                Class<?>[] classes = new Class<?>[objects.length];
                int i = 0;
                for (Object object : objects) {
                        classes[i++] = object.getClass();
                }
                T instance = null;
                try {
                        instance = clazz.getConstructor(classes).newInstance(objects);
                } catch (Exception e) {
                        System.err.format("Error finding constructor for class %s with classes %s\n",clazz.toString(),Arrays.toString(classes));
                }
                return instance;
        }

        @SuppressWarnings("unchecked")
        private static <T extends ReadWriteableASCII> T cacheFromASCII(T rwascii,File f) throws IOException {
                return IOUtils.read(f, (Class<T>)rwascii.getClass());
        }
        
        @SuppressWarnings("unchecked")
        private static <T extends ReadWriteableBinary > T cacheFromBinary(T rwbin,File f) throws IOException {
                return IOUtils.read(f, (Class<T>)rwbin.getClass());
        }
        
        static class CachableStringInteger implements CachableASCII{
                int integer;
                String string;
                
                public CachableStringInteger(){
                        
                }
                
                public CachableStringInteger(Integer integer, String string) {
                        this.integer = integer;
                        this.string = string;
                }
                
                @Override
                public void readASCII(Scanner in) throws IOException {
                        this.integer = Integer.parseInt(in.nextLine());
                        this.string = in.nextLine();
                }

                @Override
                public String asciiHeader() {
                        return "STRING_INT\n";
                }

                @Override
                public void writeASCII(PrintWriter out) throws IOException {
                        out.println(integer);
                        out.println(string);
                }

                @Override
                public String identifier() {
                        return String.format("%d-%s",integer,string);
                }
                
                @Override
                public String toString() {
                        return identifier();
                }
        }
        
        /**
         * @param args
         */
        public static void main(String[] args) {
                String a = load(String.class,"wang");
                System.out.println("This is the created string: " + a);
                CachableStringInteger csi = load(CachableStringInteger.class,1,"wang");
                System.out.println("Got this from the cache.create():" + csi);
        }
        
}