# 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, Paul McGuire
#
from pyparsing import Literal, CaselessLiteral, Word, Upcase, delimitedList, Optional, \
    Combine, Group, alphas, nums, alphanums, ParseException, Forward, oneOf, quotedString, \
    ZeroOrMore, restOfLine, Keyword

def test( str ):
    print(str,"->")
    try:
        tokens = simpleSQL.parseString( str )
        print("tokens = ",        tokens)
        print("tokens.columns =", tokens.columns)
        print("tokens.tables =",  tokens.tables)
        print("tokens.where =", tokens.where)
    except ParseException as err:
        print(" "*err.loc + "^\n" + err.msg)
        print(err)
    print()


# define SQL tokens
selectStmt = Forward()
selectToken = Keyword("select", caseless=True)
fromToken   = Keyword("from", caseless=True)

ident          = Word( alphas, alphanums + "_$" ).setName("identifier")
columnName     = Upcase( delimitedList( ident, ".", combine=True ) )
columnNameList = Group( delimitedList( columnName ) )
tableName      = Upcase( delimitedList( ident, ".", combine=True ) )
tableNameList  = Group( delimitedList( tableName ) )

whereExpression = Forward()
and_ = Keyword("and", caseless=True)
or_ = Keyword("or", caseless=True)
in_ = Keyword("in", caseless=True)

E = CaselessLiteral("E")
binop = oneOf("= != < > >= <= eq ne lt le gt ge", caseless=True)
arithSign = Word("+-",exact=1)
realNum = Combine( Optional(arithSign) + ( Word( nums ) + "." + Optional( Word(nums) )  |
                                                         ( "." + Word(nums) ) ) + 
            Optional( E + Optional(arithSign) + Word(nums) ) )
intNum = Combine( Optional(arithSign) + Word( nums ) + 
            Optional( E + Optional("+") + Word(nums) ) )

columnRval = realNum | intNum | quotedString | columnName # need to add support for alg expressions
whereCondition = Group(
    ( columnName + binop + columnRval ) |
    ( columnName + in_ + "(" + delimitedList( columnRval ) + ")" ) |
    ( columnName + in_ + "(" + selectStmt + ")" ) |
    ( "(" + whereExpression + ")" )
    )
whereExpression << whereCondition + ZeroOrMore( ( and_ | or_ ) + whereExpression ) 

# define the grammar
selectStmt      << ( selectToken + 
                   ( '*' | columnNameList ).setResultsName( "columns" ) + 
                   fromToken + 
                   tableNameList.setResultsName( "tables" ) + 
                   Optional( Group( CaselessLiteral("where") + whereExpression ), "" ).setResultsName("where") )

simpleSQL = selectStmt

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


test( "SELECT * from XYZZY, ABC" )
test( "select * from SYS.XYZZY" )
test( "Select A from Sys.dual" )
test( "Select A,B,C from Sys.dual" )
test( "Select A, B, C from Sys.dual" )
test( "Select A, B, C from Sys.dual, Table2   " )
test( "Xelect A, B, C from Sys.dual" )
test( "Select A, B, C frox Sys.dual" )
test( "Select" )
test( "Select &&& frox Sys.dual" )
test( "Select A from Sys.dual where a in ('RED','GREEN','BLUE')" )
test( "Select A from Sys.dual where a in ('RED','GREEN','BLUE') and b in (10,20,30)" )
test( "Select A,b from table1,table2 where table1.id eq table2.id -- test out comparison operators" )

"""
Test output:
>pythonw -u simpleSQL.py
SELECT * from XYZZY, ABC ->
tokens =  ['select', '*', 'from', ['XYZZY', 'ABC']]
tokens.columns = *
tokens.tables = ['XYZZY', 'ABC']

select * from SYS.XYZZY ->
tokens =  ['select', '*', 'from', ['SYS.XYZZY']]
tokens.columns = *
tokens.tables = ['SYS.XYZZY']

Select A from Sys.dual ->
tokens =  ['select', ['A'], 'from', ['SYS.DUAL']]
tokens.columns = ['A']
tokens.tables = ['SYS.DUAL']

Select A,B,C from Sys.dual ->
tokens =  ['select', ['A', 'B', 'C'], 'from', ['SYS.DUAL']]
tokens.columns = ['A', 'B', 'C']
tokens.tables = ['SYS.DUAL']

Select A, B, C from Sys.dual ->
tokens =  ['select', ['A', 'B', 'C'], 'from', ['SYS.DUAL']]
tokens.columns = ['A', 'B', 'C']
tokens.tables = ['SYS.DUAL']

Select A, B, C from Sys.dual, Table2    ->
tokens =  ['select', ['A', 'B', 'C'], 'from', ['SYS.DUAL', 'TABLE2']]
tokens.columns = ['A', 'B', 'C']
tokens.tables = ['SYS.DUAL', 'TABLE2']

Xelect A, B, C from Sys.dual ->
^
Expected 'select'
Expected 'select' (0), (1,1)

Select A, B, C frox Sys.dual ->
               ^
Expected 'from'
Expected 'from' (15), (1,16)

Select ->
      ^
Expected '*'
Expected '*' (6), (1,7)

Select &&& frox Sys.dual ->
       ^
Expected '*'
Expected '*' (7), (1,8)

>Exit code: 0
"""