Integrating Visualforce and Google Charts

1/* This class contains the encoding algorithm for use with the 
2   Google chartAPI. */
3   
4public class GoogleDataEncoding { 
5    // Exceptions to handle any erroneous data
6    public class EncodingException extends Exception {}
7    public class UnsupportedEncodingTypeException 
8           extends Exception {}  
9
10    /* The encoding map which takes an integer key and returns the 
11       respective encoding value as defined by Google. 
12       This map is initialized in init() */
13      private Map<Integer, String> encodingMap { get; set; }
14    
15   /* The maximum encoding value supported for the given encoding 
16      type. This value is set during init() */
17    private Integer encodingMax { get; set; }
18    
19    /* The minimum encoding value supported for the given encoding 
20       type. This value is set during init() */
21    private Integer encodingMin { get; set; }
22    
23    /* The encoding type according to Google's API. Only SIMPLE 
24       is implemented. */
25    public enum EncodingType { TEXT, SIMPLE, EXTENDED }
26    
27    /* The minimum value to use in the generation of an encoding 
28       value. */
29    public Integer min { get; private set; }
30    
31    /* The maximum value to use in the generation of an encoding 
32       value. */
33    public Integer max { get; private set; }
34    
35    // The encoding type according to the API defined by Google
36    public EncodingType eType { get; private set; }       
37    
38    // Corresponds to the data set provided by the page 
39    public String dataSet { get; set; }
40    
41    // Corresponds to the type of graph selected on the page 
42    public String graph { get; set; }
43    
44    // The URL that renders the Google Chart
45    public String chartURL { get; set; }  
46
47    // Indicates whether the chart should be displayed 
48    public Boolean displayChart { get; set; }
49    
50    public GoogleDataEncoding() {
51        min = 0;
52        max = 61;
53        eType = EncodingType.SIMPLE;
54        displayChart = false;
55        init();
56    } 
57    
58    public PageReference create() {
59        String[] dataSetList = dataSet.split(',', 0);
60        String mappedValue = 'chd=s:';
61        
62        chartURL = 'http://chart.apis.google.com/chart?chs=600x300'
63         + '&amp;chtt=Time+vs|Distance&amp;chxt=x,y,x,y' 
64         + '&amp;chxr=0,0,10,1|1,0,65,5'
65         + '&amp;chxl=2:|Seconds|3:|Meters';
66        
67        if (graph.compareTo('barChart') == 0)
68        {
69            chartURL += '&amp;cht=bvs';
70        }
71        else if (graph.compareTo('lineChart') == 0)
72        {
73            chartURL += '&amp;cht=ls';
74        }
75        else
76        {
77            throw new EncodingException('An unsupported chart type' 
78                + 'was selected: ' + graph + ' does not exist.');
79        }
80        
81        for(String dataPoint : dataSetList)
82        {
83            mappedValue += 
84               getEncode(Integer.valueOf(dataPoint.trim()));
85        }
86        
87        chartURL += '&amp;' + mappedValue;
88        displayChart = true;
89        return null;
90    }
91
92    
93    /* This method returns the encoding type parameter value that 
94       matches the specified encoding type. */
95   public static String getEncodingDescriptor(EncodingType t) {
96        if(t == EncodingType.TEXT) return 't';
97        else if(t == EncodingType.SIMPLE) return 's';
98        else if(t == EncodingType.EXTENDED) return 'e';
99        else return '';
100    }  
101    
102    /* This method takes a given number within the declared 
103       range of the encoding class and encodes it according to the 
104       encoding type. If the value provided fall outside of the 
105       declared range, an EncodingException is thrown. */
106    public String getEncode(Integer d) {    
107        if(d > max || d < min) {
108            throw new EncodingException('Value provided ' + d 
109                + ' was outside the declared min/max range (' 
110                + min + '/' + max + ')');         
111        } 
112        else {
113            return encodingMap.get(d);
114        }
115    }  
116    
117    /* This method initializes the encoding map which is then 
118       stored for expected repetitious use to minimize statement 
119       invocation. */
120    private void init() {
121        if(eType == EncodingType.SIMPLE) {
122            encodingMax = 61;
123            encodingMin = 0;
124            encodingMap = new Map<Integer, String>();
125            encodingMap.put(0,'A');
126            encodingMap.put(1,'B');
127            encodingMap.put(2,'C');
128            encodingMap.put(3,'D');
129            encodingMap.put(4,'E');
130            encodingMap.put(5,'F');
131            encodingMap.put(6,'G');
132            encodingMap.put(7,'H');
133            encodingMap.put(8,'I');
134            encodingMap.put(9,'J');
135            encodingMap.put(10,'K');
136            encodingMap.put(11,'L');
137            encodingMap.put(12,'M');
138            encodingMap.put(13,'N');
139            encodingMap.put(14,'O');
140            encodingMap.put(15,'P');
141            encodingMap.put(16,'Q');
142            encodingMap.put(17,'R');
143            encodingMap.put(18,'S');
144            encodingMap.put(19,'T');
145            encodingMap.put(20,'U');
146            encodingMap.put(21,'V');
147            encodingMap.put(22,'W');
148            encodingMap.put(23,'X');
149            encodingMap.put(24,'Y');
150            encodingMap.put(25,'Z');
151            encodingMap.put(26,'a');
152            encodingMap.put(27,'b');
153            encodingMap.put(28,'c');
154            encodingMap.put(29,'d');
155            encodingMap.put(30,'e');
156            encodingMap.put(31,'f');
157            encodingMap.put(32,'g');
158            encodingMap.put(33,'h');
159            encodingMap.put(34,'i');
160            encodingMap.put(35,'j');
161            encodingMap.put(36,'k');
162            encodingMap.put(37,'l');
163            encodingMap.put(38,'m');
164            encodingMap.put(39,'n');
165            encodingMap.put(40,'o');
166            encodingMap.put(41,'p');
167            encodingMap.put(42,'q');
168            encodingMap.put(43,'r');
169            encodingMap.put(44,'s');
170            encodingMap.put(45,'t');
171            encodingMap.put(46,'u');
172            encodingMap.put(47,'v');
173            encodingMap.put(48,'w');
174            encodingMap.put(49,'x');
175            encodingMap.put(50,'y');
176            encodingMap.put(51,'z');
177            encodingMap.put(52,'0');
178            encodingMap.put(53,'1');
179            encodingMap.put(54,'2');
180            encodingMap.put(55,'3');
181            encodingMap.put(56,'4');
182            encodingMap.put(57,'5');
183            encodingMap.put(58,'6');
184            encodingMap.put(59,'7');
185            encodingMap.put(60,'8');
186            encodingMap.put(61,'9');
187        }
188    } 
189}