/*
 * (C) Copyright 2015 Nuxeo SA (http://nuxeo.com/) and others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Contributors:
 *     Thierry Delprat <tdelprat@nuxeo.com>
 *     Antoine Taillefer <ataillefer@nuxeo.com>
 */

package org.nuxeo.ecm.core.redis.contribs;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.function.Function;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.nuxeo.ecm.core.api.Blob;
import org.nuxeo.ecm.core.api.NuxeoException;
import org.nuxeo.ecm.core.redis.RedisAdmin;
import org.nuxeo.ecm.core.redis.RedisCallable;
import org.nuxeo.ecm.core.redis.RedisExecutor;
import org.nuxeo.ecm.core.transientstore.AbstractTransientStore;
import org.nuxeo.ecm.core.transientstore.api.TransientStore;
import org.nuxeo.ecm.core.transientstore.api.TransientStoreConfig;
import org.nuxeo.runtime.api.Framework;

/**
 * Redis implementation (i.e. cluster aware) of the {@link TransientStore}.
 * <p>
 * Since hashes cannot be nested, a storage entry is flattened as follows:
 *
 * <pre>
 *  - Entry summary:
 *
 *    transientStore:transientStoreName:entryKey {
 *      "blobCount":    number of blobs associated with the entry
 *      "size":         storage size of the blobs associated with the entry
 *      "completed":    entry status
 *    }
 *
 * - Entry parameters:
 *
 *   transientStore:transientStoreName:entryKey:params {
 *      "param1": value1
 *      "param2": value2
 *   }
 *
 * - Entry blobs:
 *
 *   transientStore:transientStoreName:entryKey:blobs:0 {
 *      "file"
 *      "filename"
 *      "encoding"
 *      "mimetype"
 *      "digest"
 *   }
 *
 *   transientStore:transientStoreName:entryKey:blobs:1 {
 *      ...
 *   }
 *
 *   ...
 * </pre>
 *
 * @since 7.2
 */
public class RedisTransientStore extends AbstractTransientStore {

    protected static final String SIZE_KEY = "size";

    protected RedisExecutor redisExecutor;

    protected String namespace;

    protected String sizeKey;

    protected KeyMatcher keyMatcher;

    protected RedisAdmin redisAdmin;

    protected int firstLevelTTL;

    protected int secondLevelTTL;

    protected Log log = LogFactory.getLog(RedisTransientStore.class);

    public RedisTransientStore() {
        redisExecutor = Framework.getService(RedisExecutor.class);
        redisAdmin = Framework.getService(RedisAdmin.class);
    }

    @Override
    public void init(TransientStoreConfig config) {
        log.debug("Initializing RedisTransientStore: " + config.getName());
        super.init(config);

        namespace = redisAdmin.namespace("transientStore", config.getName());
        sizeKey = namespace + SIZE_KEY;
        keyMatcher = new KeyMatcher();

        // Use seconds for Redis EXPIRE command
        firstLevelTTL = config.getFirstLevelTTL() * 60;
        secondLevelTTL = config.getSecondLevelTTL() * 60;
    }

    @Override
    public void shutdown() {
        log.debug("Shutting down RedisTransientStore: " + config.getName());
        // Nothing to do here.
    }

    @Override
    public boolean exists(String key) {
        // Jedis#exists(String key) doesn't to work for a key created with hset or hmset
        return getSummary(key) != null || getParameters(key) != null;
    }

    @Override
    public Set<String> keySet() {
        return redisExecutor.execute((RedisCallable<Set<String>>) jedis -> {
            return jedis.keys(namespace + "*")
                        .stream()
                        .map(keyMatcher)
                        .filter(key -> !SIZE_KEY.equals(key))
                        .collect(Collectors.toSet());
        });
    }

    protected class KeyMatcher implements Function<String, String> {

        protected final Pattern KEY_PATTERN = Pattern.compile("(.*?)(:(params|blobs:[0-9]+))?");

        protected final int offset = namespace.length();

        @Override
        public String apply(String t) {
            final Matcher m = KEY_PATTERN.matcher(t.substring(offset));
            m.matches();
            return m.group(1);
        }

    }

    @Override
    public void putParameter(String key, String parameter, Serializable value) {
        redisExecutor.execute((RedisCallable<Void>) jedis -> {
            String paramsKey = namespace + join(key, "params");
            if (log.isDebugEnabled()) {
                log.debug(String.format("Setting field %s to value %s in Redis hash stored at key %s", parameter,
                        value, paramsKey));
            }
            jedis.hset(getBytes(paramsKey), getBytes(parameter), serialize(value));
            return null;
        });
        setTTL(key, firstLevelTTL);
    }

    @Override
    public Serializable getParameter(String key, String parameter) {
        return redisExecutor.execute((RedisCallable<Serializable>) jedis -> {
            String paramsKey = namespace + join(key, "params");
            byte[] paramBytes = jedis.hget(getBytes(paramsKey), getBytes(parameter));
            if (paramBytes == null) {
                return null;
            }
            Serializable res = deserialize(paramBytes);
            if (log.isDebugEnabled()) {
                log.debug(String.format("Fetched field %s from Redis hash stored at key %s -> %s", parameter,
                        paramsKey, res));
            }
            return res;
        });
    }

    @Override
    public void putParameters(String key, Map<String, Serializable> parameters) {
        redisExecutor.execute((RedisCallable<Void>) jedis -> {
            String paramsKey = namespace + join(key, "params");
            if (log.isDebugEnabled()) {
                log.debug(String.format("Setting fields %s in Redis hash stored at key %s", parameters, paramsKey));
            }
            jedis.hmset(getBytes(paramsKey), serialize(parameters));
            return null;
        });
        setTTL(key, firstLevelTTL);
    }

    @Override
    public Map<String, Serializable> getParameters(String key) {
        // TODO NXP-18236: use a transaction?
        String paramsKey = namespace + join(key, "params");
        Map<byte[], byte[]> paramBytes = redisExecutor.execute((RedisCallable<Map<byte[], byte[]>>) jedis -> {
            return jedis.hgetAll(getBytes(paramsKey));
        });
        if (paramBytes.isEmpty()) {
            if (getSummary(key) == null) {
                return null;
            } else {
                return new HashMap<>();
            }
        }
        Map<String, Serializable> res = deserialize(paramBytes);
        if (log.isDebugEnabled()) {
            log.debug(String.format("Fetched fields from Redis hash stored at key %s -> %s", paramsKey, res));
        }
        return res;
    }

    @Override
    public List<Blob> getBlobs(String key) {
        // TODO NXP-18236: use a transaction?

        // Get blob count
        String blobCount = redisExecutor.execute((RedisCallable<String>) jedis -> {
            return jedis.hget(namespace + key, "blobCount");
        });
        if (log.isDebugEnabled()) {
            log.debug(String.format("Fetched field \"blobCount\" from Redis hash stored at key %s -> %s", namespace
                    + key, blobCount));
        }
        if (blobCount == null) {
            // Check for existing parameters
            Map<String, Serializable> parameters = getParameters(key);
            if (parameters == null) {
                return null;
            } else {
                return new ArrayList<Blob>();
            }
        }

        // Get blobs
        int entryBlobCount = Integer.parseInt(blobCount);
        if (entryBlobCount <= 0) {
            return new ArrayList<>();
        }
        List<Map<String, String>> blobInfos = new ArrayList<>();
        for (int i = 0; i < entryBlobCount; i++) {
            String blobInfoIndex = String.valueOf(i);
            Map<String, String> entryBlobInfo = redisExecutor.execute((RedisCallable<Map<String, String>>) jedis -> {
                String blobInfoKey = namespace + join(key, "blobs", blobInfoIndex);
                Map<String, String> blobInfo = jedis.hgetAll(blobInfoKey);
                if (blobInfo.isEmpty()) {
                    throw new NuxeoException(String.format(
                            "Entry with key %s is inconsistent: blobCount = %d but key %s doesn't exist", key,
                            entryBlobCount, blobInfoKey));
                }
                if (log.isDebugEnabled()) {
                    log.debug(String.format("Fetched fields from Redis hash stored at key %s -> %s", blobInfoKey,
                            blobInfo));
                }
                return blobInfo;
            });
            blobInfos.add(entryBlobInfo);
        }

        // Load blobs from the file system
        return loadBlobs(blobInfos);
    }

    @Override
    public long getSize(String key) {
        return redisExecutor.execute((RedisCallable<Long>) jedis -> {
            String size = jedis.hget(namespace + key, SIZE_KEY);
            if (size == null) {
                return -1L;
            }
            if (log.isDebugEnabled()) {
                log.debug(String.format("Fetched field \"%s\" from Redis hash stored at key %s -> %s", SIZE_KEY,
                        namespace + key, size));
            }
            return Long.parseLong(size);
        });
    }

    @Override
    public boolean isCompleted(String key) {
        return redisExecutor.execute((RedisCallable<Boolean>) jedis -> {
            String completed = jedis.hget(namespace + key, "completed");
            if (log.isDebugEnabled()) {
                log.debug(String.format("Fetched field \"completed\" from Redis hash stored at key %s -> %s", namespace
                        + key, completed));
            }
            return Boolean.parseBoolean(completed);
        });
    }

    @Override
    public void setCompleted(String key, boolean completed) {
        redisExecutor.execute((RedisCallable<Void>) jedis -> {
            if (log.isDebugEnabled()) {
                log.debug(String.format("Setting field \"completed\" to value %s in Redis hash stored at key %s",
                        completed, namespace + key));
            }
            jedis.hset(namespace + key, "completed", String.valueOf(completed));
            return null;
        });
        setTTL(key, firstLevelTTL);
    }

    @Override
    public void remove(String key) {
        // TODO NXP-18236: use a transaction?

        Map<String, String> summary = getSummary(key);
        if (summary != null) {
            // Remove blobs
            String blobCount = summary.get("blobCount");
            deleteBlobInfos(key, blobCount);

            // Remove summary
            redisExecutor.execute((RedisCallable<Long>) jedis -> {
                Long deleted = jedis.del(namespace + key);
                if (log.isDebugEnabled()) {
                    log.debug(String.format("Deleted %d Redis hash stored at key %s", deleted, namespace + key));
                }
                return deleted;
            });

            // Decrement storage size
            String size = summary.get(SIZE_KEY);
            if (size != null) {
                long entrySize = Integer.parseInt(size);
                if (entrySize > 0) {
                    decrementStorageSize(entrySize);
                }
            }
        }

        // Remove parameters
        redisExecutor.execute((RedisCallable<Long>) jedis -> {
            String paramsKey = namespace + join(key, "params");
            Long deleted = jedis.del(getBytes(paramsKey));
            if (log.isDebugEnabled()) {
                log.debug(String.format("Deleted %d Redis hash stored at key %s", deleted, paramsKey));
            }
            return deleted;
        });
    }

    @Override
    public void release(String key) {
        if (getStorageSize() <= config.getTargetMaxSizeMB() * (1024 * 1024) || config.getTargetMaxSizeMB() < 0) {
            setTTL(key, secondLevelTTL);
        } else {
            remove(key);
        }
    }

    @Override
    protected void persistBlobs(String key, long sizeOfBlobs, List<Map<String, String>> blobInfos) {
        // TODO NXP-18236: use a transaction?

        Map<String, String> oldSummary = getSummary(key);

        // Update storage size
        long entrySize = -1;
        if (oldSummary != null) {
            String size = oldSummary.get(SIZE_KEY);
            if (size != null) {
                entrySize = Long.parseLong(size);
            }
        }
        if (entrySize > 0) {
            incrementStorageSize(sizeOfBlobs - entrySize);
        } else {
            if (sizeOfBlobs > 0) {
                incrementStorageSize(sizeOfBlobs);
            }
        }

        // Delete old blobs
        if (oldSummary != null) {
            String oldBlobCount = oldSummary.get("blobCount");
            deleteBlobInfos(key, oldBlobCount);
        }

        // Update entry size and blob count
        final Map<String, String> entrySummary = new HashMap<>();
        int blobCount = 0;
        if (blobInfos != null) {
            blobCount = blobInfos.size();
        }
        entrySummary.put("blobCount", String.valueOf(blobCount));
        entrySummary.put(SIZE_KEY, String.valueOf(sizeOfBlobs));
        redisExecutor.execute((RedisCallable<Void>) jedis -> {
            if (log.isDebugEnabled()) {
                log.debug(String.format("Setting fields %s in Redis hash stored at key %s", entrySummary, namespace
                        + key));
            }
            jedis.hmset(namespace + key, entrySummary);
            jedis.expire(namespace + key, firstLevelTTL);
            return null;
        });

        // Set new blobs
        if (blobInfos != null) {
            int blobsTimeout = firstLevelTTL + 60;
            for (int i = 0; i < blobInfos.size(); i++) {
                String blobInfoIndex = String.valueOf(i);
                Map<String, String> blobInfo = blobInfos.get(i);
                redisExecutor.execute((RedisCallable<Void>) jedis -> {
                    String blobInfoKey = namespace + join(key, "blobs", blobInfoIndex);
                    if (log.isDebugEnabled()) {
                        log.debug(String.format("Setting fields %s in Redis hash stored at key %s", blobInfo,
                                blobInfoKey));
                    }
                    jedis.hmset(blobInfoKey, blobInfo);
                    jedis.expire(blobInfoKey, blobsTimeout);
                    return null;
                });
            }
        }

        // Set params TTL
        redisExecutor.execute((RedisCallable<Void>) jedis -> {
            String paramsKey = namespace + join(key, "params");
            jedis.expire(getBytes(paramsKey), firstLevelTTL + 60);
            return null;
        });
    }

    @Override
    public long getStorageSize() {
        return redisExecutor.execute((RedisCallable<Long>) jedis -> {
            String value = jedis.get(sizeKey);
            if (value == null) {
                return 0L;
            }
            if (log.isDebugEnabled()) {
                log.debug(String.format("Fetched value of Redis key %s -> %s", sizeKey, value));
            }
            return Long.parseLong(value);
        });
    }

    @Override
    protected void setStorageSize(final long newSize) {
        redisExecutor.execute((RedisCallable<Void>) jedis -> {
            if (log.isDebugEnabled()) {
                log.debug(String.format("Setting Redis key %s to value %s", sizeKey, newSize));
            }
            jedis.set(sizeKey, "" + newSize);
            return null;
        });
    }

    @Override
    protected long incrementStorageSize(final long size) {
        return redisExecutor.execute((RedisCallable<Long>) jedis -> {
            Long incremented = jedis.incrBy(sizeKey, size);
            if (log.isDebugEnabled()) {
                log.debug(String.format("Incremented Redis key %s to %d", sizeKey, incremented));
            }
            return incremented;
        });
    }

    @Override
    protected long decrementStorageSize(final long size) {
        return redisExecutor.execute((RedisCallable<Long>) jedis -> {
            Long decremented = jedis.decrBy(sizeKey, size);
            if (log.isDebugEnabled()) {
                log.debug(String.format("Decremented Redis key %s to %d", sizeKey, decremented));
            }
            return decremented;
        });
    }

    @Override
    protected void removeAllEntries() {
        // TODO NXP-18236: use a transaction?
        Set<String> keys = redisExecutor.execute((RedisCallable<Set<String>>) jedis -> {
            return jedis.keys(namespace + "*");
        });
        for (String key : keys) {
            redisExecutor.execute((RedisCallable<Void>) jedis -> {
                jedis.del(key);
                return null;
            });
        }
    }

    public long getTTL(String key) {
        long summaryTTL = redisExecutor.execute((RedisCallable<Long>) jedis -> {
            return jedis.ttl(namespace + key);
        });
        if (summaryTTL >= 0) {
            return summaryTTL;
        } else {
            return redisExecutor.execute((RedisCallable<Long>) jedis -> {
                String paramsKey = namespace + join(key, "params");
                return jedis.ttl(getBytes(paramsKey));
            });
        }
    }

    protected Map<String, String> getSummary(String key) {
        return redisExecutor.execute((RedisCallable<Map<String, String>>) jedis -> {
            Map<String, String> summary = jedis.hgetAll(namespace + key);
            if (summary.isEmpty()) {
                return null;
            }
            if (log.isDebugEnabled()) {
                log.debug(String.format("Fetched fields from Redis hash stored at key %s -> %s", namespace + key,
                        summary));
            }
            return summary;
        });
    }

    protected void deleteBlobInfos(String key, String blobCountStr) {
        if (blobCountStr != null) {
            int blobCount = Integer.parseInt(blobCountStr);
            if (blobCount > 0) {
                for (int i = 0; i < blobCount; i++) {
                    String blobInfoIndex = String.valueOf(i);
                    redisExecutor.execute((RedisCallable<Long>) jedis -> {
                        String blobInfoKey = namespace + join(key, "blobs", blobInfoIndex);
                        Long deleted = jedis.del(blobInfoKey);
                        if (log.isDebugEnabled()) {
                            log.debug(String.format("Deleted %d Redis hash stored at key %s", deleted, blobInfoKey));
                        }
                        return deleted;
                    });
                }
            }
        }
    }

    protected String join(String... fragments) {
        return StringUtils.join(fragments, ":");
    }

    protected byte[] getBytes(String key) {
        return key.getBytes(StandardCharsets.UTF_8);
    }

    protected String getString(byte[] bytes) {
        return new String(bytes, StandardCharsets.UTF_8);
    }

    protected byte[] serialize(Serializable value) {
        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream out = new ObjectOutputStream(baos);
            out.writeObject(value);
            out.flush();
            out.close();
            return baos.toByteArray();
        } catch (IOException e) {
            throw new NuxeoException(e);
        }
    }

    protected Serializable deserialize(byte[] bytes) {
        try {
            InputStream bain = new ByteArrayInputStream(bytes);
            ObjectInputStream in = new ObjectInputStream(bain);
            return (Serializable) in.readObject();
        } catch (IOException | ClassNotFoundException e) {
            throw new NuxeoException(e);
        }
    }

    protected Map<byte[], byte[]> serialize(Map<String, Serializable> map) {
        Map<byte[], byte[]> serializedMap = new HashMap<>();
        for (String key : map.keySet()) {
            serializedMap.put(getBytes(key), serialize(map.get(key)));
        }
        return serializedMap;
    }

    protected Map<String, Serializable> deserialize(Map<byte[], byte[]> byteMap) {
        Map<String, Serializable> map = new HashMap<>();
        for (byte[] key : byteMap.keySet()) {
            map.put(getString(key), deserialize(byteMap.get(key)));
        }
        return map;
    }

    protected void setTTL(String key, int seconds) {

        Map<String, String> summary = getSummary(key);
        if (summary != null) {
            // Summary
            redisExecutor.execute((RedisCallable<Void>) jedis -> {
                jedis.expire(namespace + key, seconds);
                return null;
            });
            // Blobs
            String blobCountStr = summary.get("blobCount");
            if (blobCountStr != null) {
                int blobCount = Integer.parseInt(blobCountStr);
                if (blobCount > 0) {
                    final int blobsTimeout = seconds + 60;
                    for (int i = 0; i < blobCount; i++) {
                        String blobInfoIndex = String.valueOf(i);
                        redisExecutor.execute((RedisCallable<Void>) jedis -> {
                            String blobInfoKey = namespace + join(key, "blobs", blobInfoIndex);
                            jedis.expire(blobInfoKey, blobsTimeout);
                            return null;
                        });
                    }
                }
            }
        }
        // Parameters
        final int paramsTimeout;
        if (summary == null) {
            paramsTimeout = seconds;
        } else {
            paramsTimeout = seconds + 60;
        }
        redisExecutor.execute((RedisCallable<Void>) jedis -> {
            String paramsKey = namespace + join(key, "params");
            jedis.expire(getBytes(paramsKey), paramsTimeout);
            return null;
        });
    }

}