Implement CsvFieldIndexer.

Fixes #2

CsvLib.Tests/CsvFieldIndexerTests.cs

@@ -0,0 +1,142 @@
+using CsvLib;
+
+namespace CvsLib;
+
+public class CsvFieldIndexerTests
+{
+    #region GenerateIndex
+    
+    [Fact]
+    public void GenerateIndex__Empty()
+    {
+        // --- Arrange
+        StringReader sr = new(string.Empty);
+        
+        // --- Act
+        CsvFieldIndexer indexer = new();
+        indexer.GenerateIndex(sr);
+        
+        // --- Assert
+        
+        Assert.Single(indexer.Index);
+        
+        Assert.Equal(0, indexer.Index[0]);
+        Assert.Empty(indexer.FieldIndex);
+    }
+    
+    [Fact]
+    public void GenerateIndex__PlainText__OneRow()
+    {
+        // --- Arrange
+        StringReader sr = new("Hello World");
+        
+        // --- Act
+        CsvFieldIndexer indexer = new();
+        indexer.GenerateIndex(sr);
+        
+        // --- Assert
+        
+        Assert.Equal(2, indexer.Index.Count);
+        Assert.Equal(0, indexer.Index[0]);
+        Assert.Equal(12, indexer.Index[1]);
+        
+        Assert.Single(indexer.FieldIndex);
+        Assert.Equal(0, indexer.FieldIndex[0][0]);
+        Assert.Equal(10, indexer.FieldIndex[0][1]);
+    }
+
+    [Fact]
+    public void GenerateIndex__TwoLinesOfPainText__TwoRows()
+    {
+        // --- Arrange
+        StringReader sr = new("""
+                                Hello World
+                                Hello World
+                                """);
+        
+        // --- Act
+        CsvFieldIndexer indexer = new();
+        indexer.GenerateIndex(sr);
+        
+        // --- Assert
+        
+        Assert.Equal(3, indexer.Index.Count);
+        Assert.Equal(0, indexer.Index[0]);
+        Assert.Equal(12, indexer.Index[1]);
+        Assert.Equal(24, indexer.Index[2]);
+        
+        Assert.Equal(2, indexer.FieldIndex.Count);
+        Assert.Equal(2, indexer.FieldIndex[0].Count);
+        Assert.Equal(0, indexer.FieldIndex[0][0]);
+        Assert.Equal(10, indexer.FieldIndex[0][1]);
+        Assert.Equal(2, indexer.FieldIndex[1].Count);
+        Assert.Equal(12, indexer.FieldIndex[1][0]);
+        Assert.Equal(22, indexer.FieldIndex[1][1]);
+    }
+
+    [Fact]
+    public void GenerateIndex__TwoLinesOfQuotedText__TwoRows()
+    {
+        // --- Arrange
+        StringReader sr = new("""
+                                "Hello World"
+                                "Hello World"
+                                """);
+        
+        // --- Act
+        CsvFieldIndexer indexer = new();
+        indexer.GenerateIndex(sr);
+        
+        // --- Assert
+        
+        Assert.Equal(3, indexer.Index.Count);
+        Assert.Equal(0, indexer.Index[0]);
+        Assert.Equal(14, indexer.Index[1]);
+        Assert.Equal(28, indexer.Index[2]);
+        
+        Assert.Equal(2, indexer.FieldIndex.Count);
+        Assert.Equal(2, indexer.FieldIndex[0].Count);
+        Assert.Equal(1, indexer.FieldIndex[0][0]);
+        Assert.Equal(11, indexer.FieldIndex[0][1]);
+        Assert.Equal(2, indexer.FieldIndex[1].Count);
+        Assert.Equal(15, indexer.FieldIndex[1][0]);
+        Assert.Equal(25, indexer.FieldIndex[1][1]);
+    }
+
+    [Fact]
+    public void GenerateIndex__TwoLinesWithTwoQuotedColumns__TwoRowsTwoFields()
+    {
+        // --- Arrange
+        StringReader sr = new("""
+                                "Hello","World"
+                                "Hello","World"
+                                """);
+        
+        // --- Act
+        CsvFieldIndexer indexer = new();
+        indexer.GenerateIndex(sr);
+        
+        // --- Assert
+        
+        Assert.Equal(3, indexer.Index.Count);
+        Assert.Equal(0, indexer.Index[0]);
+        Assert.Equal(16, indexer.Index[1]);
+        Assert.Equal(32, indexer.Index[2]);
+        
+        Assert.Equal(2, indexer.FieldIndex.Count);
+        Assert.Equal(4, indexer.FieldIndex[0].Count);
+        Assert.Equal(1, indexer.FieldIndex[0][0]);
+        Assert.Equal(5, indexer.FieldIndex[0][1]);
+        Assert.Equal(9, indexer.FieldIndex[0][2]);
+        Assert.Equal(13, indexer.FieldIndex[0][3]);
+        Assert.Equal(4, indexer.FieldIndex[1].Count);
+        Assert.Equal(17, indexer.FieldIndex[1][0]);
+        Assert.Equal(21, indexer.FieldIndex[1][1]);
+        Assert.Equal(25, indexer.FieldIndex[1][2]);
+        Assert.Equal(29, indexer.FieldIndex[1][3]);
+    }
+
+    
+    
+    #endregion GenerateIndex
+}