Add PK & FKs to the table model

FKs is not fully functional.
Blocked by #15

DbSeeder/Schema/ForeignKey.cs

@@ -0,0 +1,7 @@
+namespace DbSeeder.Schema;
+
+public record ForeignKey(
+    Table Table,
+    Column Column,
+    Table RefTable,
+    Column RefColumn);

DbSeeder/Schema/PrimaryKey.cs

@@ -0,0 +1,5 @@
+namespace DbSeeder.Schema;
+
+public record PrimaryKey(
+    Table Table,
+    Column Column);

DbSeeder/Schema/SqlSchema.cs

@@ -3,10 +3,12 @@
 public class SqlSchema
 {
     private readonly List<Table> _tables = [];
+
     public IReadOnlyList<Table> Tables => _tables;
 
     public void AddTable(Table table)
-    {
-        _tables.Add(table);
-    }
+        => _tables.Add(table);
+
+    public Table? GetTableByName(string tableName)
+        => _tables.FirstOrDefault(t => t.Name.Equals(tableName, StringComparison.OrdinalIgnoreCase));
 }

DbSeeder/Schema/SqlSchemaBuilder.cs

@@ -54,21 +54,19 @@ private void TraverseCreateStatement(SyntaxTreeNode createStatementNode)
     private Table CreateTable(SyntaxTreeNode tableRoot)
     {
         var tableName = tableRoot.Value;
-        var table = new Table(tableName);
+        var table = new Table(tableName, _sqlSchema!);
 
         // Actually, now we expect that table root contains only cols, but in the future more sub-nodes can be added,
         // so we have to be sure that we're working exactly with a node that contains cols.
         var colsRoot = tableRoot.Children.First(x => x?.Type is SyntaxTreeNodeType.TableColumns);
         var cols = ParseColumns(colsRoot!);
-        table.Columns.AddRange(cols);
+        table.AddColumns(cols);
 
         return table;
     }
 
     private IEnumerable<Column> ParseColumns(SyntaxTreeNode colsRoot)
-    {
-        return colsRoot.Children.Select(GetColumn!).ToList();
-    }
+        => colsRoot.Children.Select(GetColumn!).ToList();
 
     private Column GetColumn(SyntaxTreeNode columnNode)
     {

DbSeeder/Schema/Table.cs

@@ -1,7 +1,74 @@
 namespace DbSeeder.Schema;
 
-public class Table(string name)
+public class Table(string name, SqlSchema schema)
 {
+    private readonly List<Column> _columns = [];
+    private readonly List<ForeignKey> _foreignKeys = [];
+
+    // There are some rules how to deal if PK is not defined
+    // ex: find the first attribute with NOT NULL & UNIQUE constraints
+    public PrimaryKey? PrimaryKey { get; private set; }
     public string Name { get; } = name;
-    public List<Column> Columns { get; } = [];
+    public IReadOnlyList<Column> Columns => _columns;
+    public IReadOnlyList<ForeignKey> ForeignKeys => _foreignKeys;
+
+    public void AddColumns(IEnumerable<Column> columns)
+    {
+        foreach (var column in columns)
+        {
+            AddColumn(column);
+        }
+    }
+
+    private void AddColumn(Column column)
+    {
+        ArgumentNullException.ThrowIfNull(column);
+        _columns.Add(column);
+
+        if (column.IsPrimaryKey)
+        {
+            SetTablePrimaryKey(column);
+        }
+        else if (column.IsForeignKey)
+        {
+            SetTableForeignKey(column);
+        }
+    }
+
+    private void SetTablePrimaryKey(Column column)
+    {
+        if (PrimaryKey != null)
+        {
+            throw new ArgumentException("Table can not contains more that one PRIMARY KEY");
+        }
+
+        PrimaryKey = new PrimaryKey(this, column);
+    }
+
+    private void SetTableForeignKey(Column column)
+    {
+        ArgumentNullException.ThrowIfNull(column.ForeignKeyRef);
+
+        var refTable = schema.GetTableByName(column.ForeignKeyRef.TableName);
+        if (refTable is null)
+        {
+            throw new InvalidOperationException($"Referenced table {column.ForeignKeyRef.TableName} is not exists " +
+                                                $"in current schema. Validate the order of the create statements, " +
+                                                $"it's matter");
+        }
+
+        var refColumn = refTable.GetColumnByName(column.ForeignKeyRef.ColumnName);
+        if (refColumn is null)
+        {
+            throw new InvalidOperationException($"Referenced table {column.ForeignKeyRef.TableName} is not exists " +
+                                                $"in current schema. Validate the order of the create statements, " +
+                                                $"it's matter");
+        }
+
+        var fk = new ForeignKey(this, column, refTable, refColumn);
+        _foreignKeys.Add(fk);
+    }
+
+    private Column? GetColumnByName(string columnName)
+        => Columns.FirstOrDefault(c => c.Name.Equals(columnName, StringComparison.Ordinal));
 }