# simpleSQL.py
#
# simple demo of using the parsing library to do simple-minded SQL parsing
# could be extended to include where clauses etc.
#
# Copyright (c) 2003,2016, Paul McGuire
#
from pyparsing import Word, delimitedList, Optional, \
    Group, alphas, alphanums, Forward, oneOf, quotedString, \
    infixNotation, opAssoc, \
    ZeroOrMore, restOfLine, CaselessKeyword, pyparsing_common as ppc

# define SQL tokens
selectStmt = Forward()
SELECT, FROM, WHERE, AND, OR, IN, IS, NOT, NULL = map(CaselessKeyword, 
    "select from where and or in is not null".split())
NOT_NULL = NOT + NULL

ident          = Word( alphas, alphanums + "_$" ).setName("identifier")
columnName     = delimitedList(ident, ".", combine=True).setName("column name")
columnName.addParseAction(ppc.upcaseTokens)
columnNameList = Group( delimitedList(columnName))
tableName      = delimitedList(ident, ".", combine=True).setName("table name")
tableName.addParseAction(ppc.upcaseTokens)
tableNameList  = Group(delimitedList(tableName))

binop = oneOf("= != < > >= <= eq ne lt le gt ge", caseless=True)
realNum = ppc.real()
intNum = ppc.signed_integer()

columnRval = realNum | intNum | quotedString | columnName # need to add support for alg expressions
whereCondition = Group(
    ( columnName + binop + columnRval ) |
    ( columnName + IN + Group("(" + delimitedList( columnRval ) + ")" )) |
    ( columnName + IN + Group("(" + selectStmt + ")" )) |
    ( columnName + IS + (NULL | NOT_NULL))
    )

whereExpression = infixNotation(whereCondition,
    [
        (NOT, 1, opAssoc.RIGHT),
        (AND, 2, opAssoc.LEFT),
        (OR, 2, opAssoc.LEFT),
    ])

# define the grammar
selectStmt <<= (SELECT + ('*' | columnNameList)("columns") +
                FROM + tableNameList( "tables" ) +
                Optional(Group(WHERE + whereExpression), "")("where"))

simpleSQL = selectStmt

# define Oracle comment format, and ignore them
oracleSqlComment = "--" + restOfLine
simpleSQL.ignore( oracleSqlComment )

if __name__ == "__main__":
    simpleSQL.runTests("""\

        # multiple tables
        SELECT * from XYZZY, ABC

        # dotted table name
        select * from SYS.XYZZY

        Select A from Sys.dual

        Select A,B,C from Sys.dual

        Select A, B, C from Sys.dual, Table2

        # FAIL - invalid SELECT keyword
        Xelect A, B, C from Sys.dual

        # FAIL - invalid FROM keyword
        Select A, B, C frox Sys.dual

        # FAIL - incomplete statement
        Select

        # FAIL - incomplete statement
        Select * from

        # FAIL - invalid column
        Select &&& frox Sys.dual

        # where clause
        Select A from Sys.dual where a in ('RED','GREEN','BLUE')

        # compound where clause
        Select A from Sys.dual where a in ('RED','GREEN','BLUE') and b in (10,20,30)

        # where clause with comparison operator
        Select A,b from table1,table2 where table1.id eq table2.id
        """)