public static Query Parse(Benumerator <char> en)
{
var s = en.Save();
en.MoveNext();
if (en.Current == ' ')
{
en.MoveNext();
}
if (en.Current == 'C')
{
return(CreateTable.Parse(s));
}
else if (en.Current == 'F')
{
return(Get.Parse(s));
}
else if (en.Current == 'I')
{
return(Insert.Parse(s));
}
else
{
throw new Exception("Unrecognized first command");
}
}
public static new Get Parse(Benumerator <char> en)
{
// Skipping first whitespace and failing if empty
if (!en.MoveNext() || en.Current == ' ' && !en.MoveNext())
{
throw new Exception("failed to parse. No Input");
}
var from = From.Parse(en);
var select = Select.Parse(en);
if (from != null && select.columns.Length > 0)
{
return(new Get
{
from = from,
columns = select.columns,
select = select
});
}
else
{
return(null);
}
}
public static void SkipWhitespace(Benumerator <char> en)
{
if (en.Current == ' ')
{
en.MoveNext();
}
}
public static bool HasValue(Benumerator <char> en, string value)
{
foreach (Char c in value)
{
if (en.Current != c)
{
return(false);
}
en.MoveNext();
}
return(true);
}
public static From Parse(Benumerator <char> en)
{
if (en.Current != 'F' || !en.MoveNext() ||
en.Current != 'R' || !en.MoveNext() ||
en.Current != 'O' || !en.MoveNext() ||
en.Current != 'M' || !en.MoveNext() ||
en.Current != ' '
)
{
throw new Exception("failed to parse FROM. Expected FROM keyword");
}
List <char> tableName = new List <char>();
while (en.MoveNext() && en.Current != ' ')
{
tableName.Add(en.Current);
}
if (!en.MoveNext())
{
throw new Exception("failed to parse FROM. Unexpected end up input");
}
return(new From {
table = new string(tableName.ToArray())
});
}
public static string ParseWord(Benumerator <char> en, bool possiblyAtEnd = false)
{
Parser.SkipWhitespace(en);
List <char> work = new List <char>();
do
{
work.Add(en.Current);
}while (en.MoveNext() && en.Current != ' ' && en.Current != ',' && en.Current != '(' && en.Current != ')');
return(new String(work.ToArray()));
}
public static ColumnDefinition Parse(Benumerator <char> en)
{
ColumnDefinition colDef = new ColumnDefinition();
List <char> col;
while (en.Current == ' ' || en.Current == ',')
{
en.MoveNext();
}
// get name
col = new List <char>();
while (en.Current != ' ' && en.Current != ',')
{
col.Add(en.Current);
en.MoveNext();
}
colDef.name = new string(col.ToArray()).Trim();
if (en.Current == ',')
{
throw new Exception("Failed parsing Column Definition. Missing type");
}
en.MoveNext();
col = new List <char>();
while (en.Current != ' ' && en.Current != ',')
{
col.Add(en.Current);
en.MoveNext();
}
colDef.type = new string(col.ToArray()).Trim();
return(colDef);
}
public static IEnumerable <SelectColumn> Parse(Benumerator <char> en, bool possiblyAtEnd = false)
{
do
{
Parser.SkipWhitespace(en);
string columnName = Parser.ParseWord(en, possiblyAtEnd);
if (!string.IsNullOrWhiteSpace(columnName))
{
yield return(new SelectColumn
{
columnName = columnName
});
}
Parser.SkipWhitespace(en);
}while (en.Current == ',' && en.MoveNext());
}
private static IEnumerable <SelectColumn> _Parse(Benumerator <char> en)
{
// Next value MUST be "SELECT "
if (en.Current != 'S' || !en.MoveNext() ||
en.Current != 'E' || !en.MoveNext() ||
en.Current != 'L' || !en.MoveNext() ||
en.Current != 'E' || !en.MoveNext() ||
en.Current != 'C' || !en.MoveNext() ||
en.Current != 'T' || !en.MoveNext() ||
en.Current != ' ' || !en.MoveNext()
)
{
throw new Exception("failed to parse SELECT. Expecting SELECT keyword");
}
// I am very lazily forcing the use of * for now
foreach (var col in SelectColumn.Parse(en, true))
{
yield return(col);
}
}
public static new CreateTable Parse(Benumerator <char> en)
{
if (!en.MoveNext() || en.Current == ' ' && !en.MoveNext())
{
throw new Exception("failed to parse. No Input");
}
if (en.Current != 'C' || !en.MoveNext() ||
en.Current != 'R' || !en.MoveNext() ||
en.Current != 'E' || !en.MoveNext() ||
en.Current != 'A' || !en.MoveNext() ||
en.Current != 'T' || !en.MoveNext() ||
en.Current != 'E' || !en.MoveNext() ||
en.Current != ' ' || !en.MoveNext() ||
en.Current != 'T' || !en.MoveNext() ||
en.Current != 'A' || !en.MoveNext() ||
en.Current != 'B' || !en.MoveNext() ||
en.Current != 'L' || !en.MoveNext() ||
en.Current != 'E' || !en.MoveNext() ||
en.Current != ' '
)
{
throw new Exception("failed to parse CREATE. Expected 'CREATE TABLE '");
}
List <char> tableName = new List <char>();
while (en.MoveNext() && en.Current != ' ')
{
tableName.Add(en.Current);
}
if (!en.MoveNext())
{
throw new Exception("failed to parse CREATE. Unexpected end up input");
}
if (en.Current != '(' || !en.MoveNext())
{
throw new Exception("failed to parse CREATE. Ending ')' is missing");
}
var colDefs = new List <ColumnDefinition>();
do
{
colDefs.Add(ColumnDefinition.Parse(en));
} while (en.Current == ',');
if (en.Current == ' ')
{
en.MoveNext();
}
if (en.Current != ')')
{
throw new Exception("failed to parse CREATE. Ending ')' is missing");
}
return(new CreateTable
{
tableName = new string(tableName.ToArray()).Trim(),
columns = colDefs.ToArray()
});
}
public static new Insert Parse(Benumerator <char> en)
{
if (!en.MoveNext() || en.Current == ' ' && !en.MoveNext())
{
throw new Exception("failed to parse. No Input");
}
if (!Parser.HasValue(en, "INSERT INTO "))
{
throw new Exception("failed to parse INSERT. Expecting 'INSERT INTO '");
}
var tableName = Parser.ParseWord(en);
Parser.SkipWhitespace(en);
if (!Parser.HasValue(en, "("))
{
throw new Exception("failed to parse INSERT. Expecting '('");
}
var columns = SelectColumn.Parse(en).ToArray();
Parser.SkipWhitespace(en);
if (!Parser.HasValue(en, ")"))
{
throw new Exception("failed to parse INSERT. Expecting ')'");
}
Parser.SkipWhitespace(en);
if (!Parser.HasValue(en, "VALUES"))
{
throw new Exception("failed to parse INSERT. Expecting ')'");
}
List <SelectColumn[]> rows = new List <SelectColumn[]>();
do
{
Parser.SkipWhitespace(en);
if (!Parser.HasValue(en, "("))
{
throw new Exception("failed to parse INSERT. Expecting ')'");
}
Parser.SkipWhitespace(en);
var values = SelectColumn.Parse(en).ToArray();
if (values.Length != columns.Length)
{
throw new Exception("failed to parse INSERT. Number of values do not match number of columns");
}
rows.Add(values);
Parser.SkipWhitespace(en);
if (!Parser.HasValue(en, ")"))
{
throw new Exception("failed to parse INSERT. Expecting ')'");
}
Parser.SkipWhitespace(en);
} while (Parser.HasValue(en, ","));
return(new Insert
{
tableName = tableName,
columns = columns,
rows = rows
});
}