/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.
 */

package org.apache.nifi.minifi.c2.service;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.base.Supplier;
import com.google.common.base.Suppliers;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.util.concurrent.UncheckedExecutionException;
import com.wordnik.swagger.annotations.Api;
import org.apache.nifi.minifi.c2.api.Configuration;
import org.apache.nifi.minifi.c2.api.ConfigurationProvider;
import org.apache.nifi.minifi.c2.api.ConfigurationProviderException;
import org.apache.nifi.minifi.c2.api.InvalidParameterException;
import org.apache.nifi.minifi.c2.api.security.authorization.AuthorizationException;
import org.apache.nifi.minifi.c2.api.security.authorization.Authorizer;
import org.apache.nifi.minifi.c2.api.util.Pair;
import org.apache.nifi.minifi.c2.util.HttpRequestUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.security.core.context.SecurityContextHolder;

import javax.servlet.http.HttpServletRequest;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.UriInfo;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;

@Path("/config")
@Api(
        value = "/config",
        description = "Provides configuration for MiNiFi instances"
)
public class ConfigService {
    private static final Logger logger = LoggerFactory.getLogger(ConfigService.class);
    private final Authorizer authorizer;
    private final ObjectMapper objectMapper;
    private final Supplier<ConfigurationProviderInfo> configurationProviderInfo;
    private final LoadingCache<ConfigurationProviderKey, ConfigurationProviderValue> configurationCache;

    public ConfigService(List<ConfigurationProvider> configurationProviders, Authorizer authorizer) {
        this(configurationProviders, authorizer, 1000, 300_000);
    }
    public ConfigService(List<ConfigurationProvider> configurationProviders, Authorizer authorizer, long maximumCacheSize, long cacheTtlMillis) {
        this.authorizer = authorizer;
        this.objectMapper = new ObjectMapper();
        if (configurationProviders == null || configurationProviders.size() == 0) {
            throw new IllegalArgumentException("Expected at least one configuration provider");
        }
        this.configurationProviderInfo = Suppliers.memoizeWithExpiration(() -> initContentTypeInfo(configurationProviders), cacheTtlMillis, TimeUnit.MILLISECONDS);
        CacheBuilder<Object, Object> cacheBuilder = CacheBuilder.newBuilder();
        if (maximumCacheSize >= 0) {
            cacheBuilder = cacheBuilder.maximumSize(maximumCacheSize);
        }
        if (cacheTtlMillis >= 0) {
            cacheBuilder = cacheBuilder.refreshAfterWrite(cacheTtlMillis, TimeUnit.MILLISECONDS);
        }
        this.configurationCache = cacheBuilder
                .build(new CacheLoader<ConfigurationProviderKey, ConfigurationProviderValue>() {
                    @Override
                    public ConfigurationProviderValue load(ConfigurationProviderKey key) throws Exception {
                        return initConfigurationProviderValue(key);
                    }
                });
    }

    public ConfigurationProviderValue initConfigurationProviderValue(ConfigurationProviderKey key) {
        if (logger.isDebugEnabled()) {
            logger.debug("Attempting to load and cache configuration with key " + key);
        }
        try {
            List<MediaType> acceptValues = key.getAcceptValues();
            Pair<MediaType, ConfigurationProvider> providerPair = getProvider(acceptValues);

            Map<String, List<String>> parameters = key.getParameters();

            Integer version = null;
            List<String> versionList = parameters.get("version");
            if (versionList != null && versionList.size() > 0) {
                try {
                    version = Integer.parseInt(versionList.get(0));
                } catch (NumberFormatException e) {
                    throw new InvalidParameterException("Unable to parse " + version + " as integer.", e);
                }
            }
            return new ConfigurationProviderValue(providerPair.getSecond().getConfiguration(providerPair.getFirst().toString(), version, parameters), providerPair.getFirst(), null);
        } catch (ConfigurationProviderException e) {
            return new ConfigurationProviderValue(null, null, e);
        }
    }

    protected ConfigurationProviderInfo initContentTypeInfo(List<ConfigurationProvider> configurationProviders) {
        List<Pair<MediaType, ConfigurationProvider>> mediaTypeList = new ArrayList<>();
        List<String> contentTypes = new ArrayList<>();
        Set<MediaType> seenMediaTypes = new LinkedHashSet<>();

        for (ConfigurationProvider configurationProvider : configurationProviders) {
            try {
                for (String contentTypeString : configurationProvider.getContentTypes()) {
                    MediaType mediaType = MediaType.valueOf(contentTypeString);
                    if (seenMediaTypes.add(mediaType)) {
                        contentTypes.add(contentTypeString);
                        mediaTypeList.add(new Pair<>(mediaType, configurationProvider));
                    }
                }
            } catch (ConfigurationProviderException e) {
                return new ConfigurationProviderInfo(null, null, e);
            }
        }
        return new ConfigurationProviderInfo(mediaTypeList, contentTypes, null);
    }

    @GET
    @Path("/contentTypes")
    @Produces(MediaType.APPLICATION_JSON)
    public Response getContentTypes(@Context HttpServletRequest request, @Context UriInfo uriInfo) {
        try {
            authorizer.authorize(SecurityContextHolder.getContext().getAuthentication(), uriInfo);
        } catch (AuthorizationException e) {
            logger.warn(HttpRequestUtil.getClientString(request) + " not authorized to access " + uriInfo, e);
            return Response.status(403).build();
        }
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        List<String> contentTypes;
        try {
            contentTypes = configurationProviderInfo.get().getContentTypes();
        } catch (ConfigurationProviderException e) {
            logger.warn("Unable to initialize content type information.", e);
            return Response.status(500).build();
        }
        try {
            objectMapper.writerWithDefaultPrettyPrinter().writeValue(byteArrayOutputStream, contentTypes);
        } catch (IOException e) {
            logger.warn("Unable to write configuration providers to output stream.", e);
            return Response.status(500).build();
        }
        return Response.ok().type(MediaType.APPLICATION_JSON_TYPE).entity(byteArrayOutputStream.toByteArray()).build();
    }

    @GET
    public Response getConfig(@Context HttpServletRequest request, @Context HttpHeaders httpHeaders, @Context UriInfo uriInfo) {
        try {
            authorizer.authorize(SecurityContextHolder.getContext().getAuthentication(), uriInfo);
        } catch (AuthorizationException e) {
            logger.warn(HttpRequestUtil.getClientString(request) + " not authorized to access " + uriInfo, e);
            return Response.status(403).build();
        }
        Map<String, List<String>> parameters = new HashMap<>();
        for (Map.Entry<String, List<String>> entry : uriInfo.getQueryParameters().entrySet()) {
            parameters.put(entry.getKey(), entry.getValue());
        }
        List<MediaType> acceptValues = httpHeaders.getAcceptableMediaTypes();
        boolean defaultAccept = false;
        if (acceptValues.size() == 0) {
            acceptValues = Arrays.asList(MediaType.WILDCARD_TYPE);
            defaultAccept = true;
        }
        if (logger.isDebugEnabled()) {
            StringBuilder builder = new StringBuilder("Handling request from ")
                    .append(HttpRequestUtil.getClientString(request))
                    .append(" with parameters ")
                    .append(parameters)
                    .append(" and Accept");
            if (defaultAccept) {
                builder = builder.append(" default value");
            }
            builder = builder.append(": ")
                    .append(acceptValues.stream().map(Object::toString).collect(Collectors.joining(", ")));
            logger.debug(builder.toString());
        }

        try {
            ConfigurationProviderValue configurationProviderValue = configurationCache.get(new ConfigurationProviderKey(acceptValues, parameters));
            Configuration configuration = configurationProviderValue.getConfiguration();
            Response.ResponseBuilder ok = Response.ok();
            ok = ok.header("X-Content-Version", configuration.getVersion());
            ok = ok.type(configurationProviderValue.getMediaType());
            byte[] buffer = new byte[1024];
            int read;
            try (InputStream inputStream = configuration.getInputStream();
                 ByteArrayOutputStream outputStream = new ByteArrayOutputStream()) {
                MessageDigest md5 = MessageDigest.getInstance("MD5");
                MessageDigest sha256 = MessageDigest.getInstance("SHA-256");
                while ((read = inputStream.read(buffer)) >= 0) {
                    outputStream.write(buffer, 0, read);
                    md5.update(buffer, 0, read);
                    sha256.update(buffer, 0, read);
                }
                ok = ok.header("Content-MD5", bytesToHex(md5.digest()));
                ok = ok.header("X-Content-SHA-256", bytesToHex(sha256.digest()));
                ok = ok.entity(outputStream.toByteArray());
            } catch (ConfigurationProviderException | IOException | NoSuchAlgorithmException e) {
                logger.error("Error reading or checksumming configuration file", e);
                throw new WebApplicationException(500);
            }
            return ok.build();
        } catch (AuthorizationException e) {
            logger.warn(HttpRequestUtil.getClientString(request) + " not authorized to access " + uriInfo, e);
            return Response.status(403).build();
        } catch (InvalidParameterException e) {
            logger.info(HttpRequestUtil.getClientString(request) + " made invalid request with " + HttpRequestUtil.getQueryString(request), e);
            return Response.status(400).entity("Invalid request.").build();
        } catch (ConfigurationProviderException e) {
            logger.warn("Unable to get configuration.", e);
            return Response.status(500).build();
        } catch (ExecutionException|UncheckedExecutionException e) {
            Throwable cause = e.getCause();
            if (cause instanceof WebApplicationException) {
                throw (WebApplicationException) cause;
            }
            logger.error(HttpRequestUtil.getClientString(request) + " made request with " + HttpRequestUtil.getQueryString(request) + " that caused error.", cause);
            return Response.status(500).entity("Internal error").build();
        }
    }

    // see: https://stackoverflow.com/questions/15429257/how-to-convert-byte-array-to-hexstring-in-java#answer-15429408
    protected static String bytesToHex(byte[] in) {
        final StringBuilder builder = new StringBuilder();
        for (byte b : in) {
            builder.append(String.format("%02x", b));
        }
        return builder.toString();
    }

    private Pair<MediaType, ConfigurationProvider> getProvider(List<MediaType> acceptValues) throws ConfigurationProviderException {
        List<Pair<MediaType, ConfigurationProvider>> mediaTypeList;
        try {
            mediaTypeList = this.configurationProviderInfo.get().getMediaTypeList();
        } catch (ConfigurationProviderException.Wrapper e) {
            throw e.unwrap();
        }
        for (MediaType accept : acceptValues) {
            for (Pair<MediaType, ConfigurationProvider> pair : mediaTypeList) {
                MediaType mediaType = pair.getFirst();
                if (accept.isCompatible(mediaType)) {
                    return new Pair<>(mediaType, pair.getSecond());
                }
            }
        }

        throw new WebApplicationException(Response.status(406).entity("Unable to find configuration provider for " +
                "\"Accept: " + acceptValues.stream().map(Object::toString).collect(Collectors.joining(", ")) + "\" supported media types are " +
                mediaTypeList.stream().map(Pair::getFirst).map(Object::toString).collect(Collectors.joining(", "))).build());
    }
}