package org.opendaylight.controller.sal.rest.impl;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URI;
import java.util.Map.Entry;
import java.util.Set;

import org.opendaylight.controller.sal.restconf.impl.CompositeNodeWrapper;
import org.opendaylight.controller.sal.restconf.impl.SimpleNodeWrapper;

import com.google.common.collect.Lists;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.google.gson.JsonPrimitive;

class JsonReader {

    public CompositeNodeWrapper read(InputStream entityStream) throws UnsupportedJsonFormatException {
        JsonParser parser = new JsonParser();
        
        JsonElement rootElement = parser.parse(new InputStreamReader(entityStream));
        if (!rootElement.isJsonObject()) {
            throw new UnsupportedJsonFormatException("Root element of Json has to be Object");
        }
        
        Set<Entry<String, JsonElement>> entrySetsOfRootJsonObject = rootElement.getAsJsonObject().entrySet();
        if (entrySetsOfRootJsonObject.size() != 1) {
            throw new UnsupportedJsonFormatException("Json Object should contain one element");
        } else {
            Entry<String, JsonElement> childEntry = Lists.newArrayList(entrySetsOfRootJsonObject).get(0);
            String firstElementName = childEntry.getKey();
            JsonElement firstElementType = childEntry.getValue();
            if (firstElementType.isJsonObject()) { // container in yang
                return createStructureWithRoot(firstElementName, firstElementType.getAsJsonObject());
            }
            if (firstElementType.isJsonArray()) { // list in yang
                if (firstElementType.getAsJsonArray().size() == 1) {
                    JsonElement firstElementInArray = firstElementType.getAsJsonArray().get(0);
                    if (firstElementInArray.isJsonObject()) {
                        return createStructureWithRoot(firstElementName, firstElementInArray.getAsJsonObject());
                    }
                    throw new UnsupportedJsonFormatException("Array as the first element in Json Object can have only Object element");
                }
            }
            throw new UnsupportedJsonFormatException("First element in Json Object has to be \"Object\" or \"Array with one Object element\". Other scenarios are not supported yet.");
        }
    }
    
    private CompositeNodeWrapper createStructureWithRoot(String rootObjectName, JsonObject rootObject) {
        CompositeNodeWrapper firstNode = new CompositeNodeWrapper(getNamespaceFrom(rootObjectName),
                getLocalNameFrom(rootObjectName));
        for (Entry<String, JsonElement> childOfFirstNode : rootObject.entrySet()) {
            addChildToParent(childOfFirstNode.getKey(), childOfFirstNode.getValue(), firstNode);
        }
        return firstNode;
    }
    
    private void addChildToParent(String childName, JsonElement childType, CompositeNodeWrapper parent) {
        if (childType.isJsonObject()) {
            CompositeNodeWrapper child = new CompositeNodeWrapper(getNamespaceFrom(childName),
                    getLocalNameFrom(childName));
            parent.addValue(child);
            for (Entry<String, JsonElement> childOfChild : childType.getAsJsonObject().entrySet()) {
                addChildToParent(childOfChild.getKey(), childOfChild.getValue(), child);
            }
        } else if (childType.isJsonArray()) {
            for (JsonElement childOfChildType : childType.getAsJsonArray()) {
                addChildToParent(childName, childOfChildType, parent);
            }
        } else if (childType.isJsonPrimitive()) {
            JsonPrimitive childPrimitive = childType.getAsJsonPrimitive();
            String value = childPrimitive.getAsString();
            SimpleNodeWrapper child = null;
            if (value.equals("[null]")) {
                child = new SimpleNodeWrapper(getNamespaceFrom(childName), getLocalNameFrom(childName), null);
            } else {
                child = new SimpleNodeWrapper(getNamespaceFrom(childName), getLocalNameFrom(childName), value);
            }
            parent.addValue(child);
        }
    }

    private URI getNamespaceFrom(String jsonElementName) {
        int indexOfDelimeter = jsonElementName.lastIndexOf(':');
        if (indexOfDelimeter == -1) {
            return null;
        }
        return URI.create(jsonElementName.substring(0, indexOfDelimeter));
    }

    private String getLocalNameFrom(String jsonElementName) {
        int indexOfDelimeter = jsonElementName.lastIndexOf(':');
        if (indexOfDelimeter == -1) {
            return jsonElementName;
        }
        return jsonElementName.substring(indexOfDelimeter + 1, jsonElementName.length());
    }

}