/**
 * Copyright 2014 IBM Corp.
 *
 * 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.
 **/

module.exports = function(RED) {
    "use strict";
    var ExifImage = require('exif').ExifImage;
    
    function convertDegreesMinutesSecondsToDecimals(degrees, minutes, seconds) {
        var result;
        result = degrees + (minutes / 60) + (seconds / 3600);
        return result;
    }
    
    /***
     * Extracts GPS location information from Exif data. If enough information is
     * provided, convert the Exif data into a pair of single floating point number
     * latitude/longitude data pairs. Populates msg.location with these.
     * Assumes that the msg object will always have exifData available as msg.exif.
     * Assume that the GPS data saved into Exif provides a valid value
     */
    function addMsgLocationDataFromExifGPSData(msg) {
        if(msg.exif.gps) {
            var gpsData = msg.exif.gps; // declaring variable purely to make checks more readable
            if(gpsData.GPSAltitude) {
                if(!msg.location) {
                    msg.location = {};
                }
                msg.location.alt = gpsData.GPSAltitude;
            }
            if(gpsData.GPSLatitudeRef && gpsData.GPSLatitude && gpsData.GPSLongitudeRef && gpsData.GPSLongitude) { // location can be determined, OK
                // The data provided in Exif is in degrees, minutes, seconds, this is to be converted into a single floating point degree
                if(gpsData.GPSLatitude.length === 3) { // OK to convert latitude
                    if(gpsData.GPSLongitude.length === 3) { // OK to convert longitude
                        var latitude = convertDegreesMinutesSecondsToDecimals(gpsData.GPSLatitude[0], gpsData.GPSLatitude[1], gpsData.GPSLatitude[2]);
                        latitude = Math.round(latitude * 100000)/100000;
                        
                        // (N)orth means positive latitude
                        // (S)outh means negative latitude
                        // (E)ast means positive longitude
                        // (W)est means negative longitude
                        if(gpsData.GPSLatitudeRef.toString() === 'S' || gpsData.GPSLatitudeRef.toString() === 's') {
                            latitude = latitude * -1;
                        }
                        
                        var longitude = convertDegreesMinutesSecondsToDecimals(gpsData.GPSLongitude[0], gpsData.GPSLongitude[1], gpsData.GPSLongitude[2]);
                        longitude = Math.round(longitude * 100000)/100000;
                        
                        if(gpsData.GPSLongitudeRef.toString() === 'W' || gpsData.GPSLongitudeRef.toString() === 'w') {
                            longitude = longitude * -1;
                        }
                        if(!msg.location) {
                            msg.location = {};
                        }
                        msg.location.lat = latitude;
                        msg.location.lon = longitude;
                        return;
                    } else {
                        node.log("Invalid longitude data, no location information has been added to the message.");
                    }
                } else {
                    node.log("Invalid latitude data, no location information has been added to the message.");
                }
            } else {
                node.log("The location of this image cannot be determined safely so no location information has been added to the message.");
            }
        } else {
            node.log("No location info found in this image.");
        }
    }

    function ExifNode(n) {
        RED.nodes.createNode(this,n);
        var node = this;
        this.on("input", function(msg) {
            try {
                
                if(msg.payload) {
                    var isBuffer = Buffer.isBuffer(msg.payload);
                    if(isBuffer === true) {
                        new ExifImage({ image : msg.payload }, function (error, exifData) {
                                if (error) {
                                    node.error('Failed to extract Exif data from image.');
                                    node.log('Failed to extract Exif data from image. '+ error);
                                } else {
                                    //msg.payload remains the same buffer
                                    if(exifData) {
                                        msg.exif = exifData;
                                        addMsgLocationDataFromExifGPSData(msg);
                                    } else {
                                        node.warn("The incoming buffer did not contain Exif data, nothing to do. ");
                                    }
                                }
                                node.send(msg);
                            });
                    } else {
                        node.error("Invalid payload received, the Exif node cannot proceed, no messages sent.");
                        return;
                    }
                } else {
                    node.error("No payload received, the Exif node cannot proceed, no messages sent.");
                    return;
                }
            } catch (error) {
                node.error("An error occurred while extracting Exif information. Please check the log for details.");
                node.log('Error: '+error.message);
                return;
            }
        });
    }
    RED.nodes.registerType("exif",ExifNode);
}