/******************************************************************************
 *
 * Component: OGDI Driver Support Library
 * Purpose: Generic SQL WHERE Expression Implementation.
 * Author: Frank Warmerdam <warmerdam@pobox.com>
 * 
 ******************************************************************************
 * Copyright (C) 2001 Information Interoperability Institute (3i)
 * Permission to use, copy, modify and distribute this software and
 * its documentation for any purpose and without fee is hereby granted,
 * provided that the above copyright notice appear in all copies, that
 * both the copyright notice and this permission notice appear in
 * supporting documentation, and that the name of 3i not be used 
 * in advertising or publicity pertaining to distribution of the software 
 * without specific, written prior permission.  3i makes no
 * representations about the suitability of this software for any purpose.
 * It is provided "as is" without express or implied warranty.
 ******************************************************************************
 *
 * $Log: swq.c,v $
 * Revision 1.2  2001/06/26 00:59:39  warmerda
 * fixed strcasecmp on WIN32
 *
 * Revision 1.1  2001/06/19 15:46:30  warmerda
 * New
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "swq.h"

#ifndef SWQ_MALLOC
#define SWQ_MALLOC(x) malloc(x)
#define SWQ_FREE(x) free(x)
#endif

#ifndef TRUE
#  define TRUE 1
#endif

#ifndef FALSE
#  define FALSE 0
#endif

#ifdef WIN32
#  define strcasecmp stricmp
#endif

char	swq_error[1024];

/************************************************************************/
/*                           swq_isalphanum()                           */
/*                                                                      */
/*      Is the passed character in the set of things that could         */
/*      occur in an alphanumeric token, or a number?                    */
/************************************************************************/

static int swq_isalphanum( char c )

{

    if( (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z')
        || (c >= '0' && c <= '9') || c == '.' || c == '+' || c == '-'
        || c == '_' )
        return TRUE;
    else
        return FALSE;
}

/************************************************************************/
/*                             swq_token()                              */
/************************************************************************/

static char *swq_token( const char *expression, char **next )

{
    char	*token;
    int		i_token;

    while( *expression == ' ' || *expression == '\t' )
        expression++;

    if( *expression == '\0' )
    {
        *next = (char *) expression;
        return NULL; 
    }

/* -------------------------------------------------------------------- */
/*      Handle string constants.                                        */
/* -------------------------------------------------------------------- */
    if( *expression == '"' )
    {
        expression++;

        token = (char *) SWQ_MALLOC(strlen(expression)+1);
        i_token = 0;

        while( *expression != '\0' )
        {
            if( *expression == '\\' && expression[1] == '"' )
                expression++;
            else if( *expression == '"' )
            {
                expression++;
                break;
            }
            
            token[i_token++] = *(expression++);
        }
        token[i_token] = '\0';
    }

/* -------------------------------------------------------------------- */
/*      Handle alpha-numerics.                                          */
/* -------------------------------------------------------------------- */
    else if( swq_isalphanum( *expression ) )
    {
        token = (char *) SWQ_MALLOC(strlen(expression)+1);
        i_token = 0;

        while( swq_isalphanum( *expression ) )
        {
            token[i_token++] = *(expression++);
        }

        token[i_token] = '\0';
    }

/* -------------------------------------------------------------------- */
/*      Handle special tokens.                                          */
/* -------------------------------------------------------------------- */
    else
    {
        token = (char *) SWQ_MALLOC(3);
        token[0] = *expression;
        token[1] = '\0';
        expression++;

        /* special logic to group stuff like '>=' into one token. */

        if( (*token == '<' || *token == '>' || *token == '=' || *token == '!')
           && (*expression == '<' || *expression == '>' || *expression == '='))
        {
            token[1] = *expression;
            token[2] = '\0';
            expression++;
        }
    }

    *next = (char *) expression;

    return token;
}

/************************************************************************/
/*                         swq_identify_field()                         */
/************************************************************************/

static swq_op swq_identify_op( const char *token )

{
    if( strcasecmp(token,"OR") == 0 )
        return SWQ_OR;
    
    if( strcasecmp(token,"AND") == 0 )
        return SWQ_AND;
    
    if( strcasecmp(token,"NOT") == 0 )
        return SWQ_NOT;
    
    if( strcasecmp(token,"<=") == 0 )
        return SWQ_LE;

    if( strcasecmp(token,">=") == 0 )
        return SWQ_GE;
    
    if( strcasecmp(token,"=") == 0 )
        return SWQ_EQ;
    
    if( strcasecmp(token,"!=") == 0 )
        return SWQ_NE;
    
    if( strcasecmp(token,"<>") == 0 )
        return SWQ_NE;
    
    if( strcasecmp(token,"<") == 0 )
        return SWQ_LT;
    
    if( strcasecmp(token,">") == 0 )
        return SWQ_GT;

    return SWQ_UNKNOWN;
}

/************************************************************************/
/*                         swq_op_is_logical()                          */
/************************************************************************/

static int swq_op_is_logical( swq_op op )

{
    return op == SWQ_OR || op == SWQ_AND || op == SWQ_NOT;
}


/************************************************************************/
/*                         swq_identify_field()                         */
/************************************************************************/

static int swq_identify_field( const char *token,
                               int field_count,
                               char **field_list, 
                               swq_field_type *field_types, 
                               swq_field_type *this_type )

{
    int	i;

    for( i = 0; i < field_count; i++ )
    {
        if( strcasecmp( field_list[i], token ) == 0 )
        {
            if( field_types != NULL )
                *this_type = field_types[i];
            else
                *this_type = SWQ_OTHER;
            
            return i;
        }
    }

    *this_type = SWQ_OTHER;
    return -1;
}

/************************************************************************/
/*                        swq_subexpr_compile()                         */
/************************************************************************/

static const char *
swq_subexpr_compile( char **tokens,
                     int field_count,
                     char **field_list, 
                     swq_field_type *field_types, 
                     swq_expr **expr_out,
                     int *tokens_consumed )

{
    swq_expr	*op;
    const char  *error;

    *tokens_consumed = 0;
    *expr_out = NULL;

    if( tokens[0] == NULL || tokens[1] == NULL )
    {
        sprintf( swq_error, "Not enough tokens to complete expression." );
        return swq_error;
    }
    
    op = (swq_field_op *) SWQ_MALLOC(sizeof(swq_field_op));
    memset( op, 0, sizeof(swq_field_op) );
    op->field_index = -1;

    if( strcmp(tokens[0],"(") == 0 )
    {
        int	sub_consumed = 0;

        error = swq_subexpr_compile( tokens + 1, field_count, field_list, 
                                     field_types, 
                                     (swq_expr **) &(op->first_sub_expr), 
                                     &sub_consumed );
        if( error != NULL )
        {
            swq_expr_free( op );
            return error;
        }

        if( strcmp(tokens[sub_consumed+1],")") != 0 )
        {
            swq_expr_free( op );
            sprintf(swq_error,"Unclosed brackets, or incomplete expression.");
            return swq_error;
        }

        *tokens_consumed += sub_consumed + 2;

        /* If we are at the end of the tokens, we should return our subnode */
        if( tokens[*tokens_consumed] == NULL
            || strcmp(tokens[*tokens_consumed],")") == 0 )
        {
            *expr_out = (swq_expr *) op->first_sub_expr;
            op->first_sub_expr = NULL;
            swq_expr_free( op );
            return NULL;
        }
    }
    else
    {
        op->field_index = 
            swq_identify_field( tokens[*tokens_consumed], 
                                field_count, field_list, field_types, 
                                &(op->field_type) );

        if( op->field_index < 0 )
        {
            swq_expr_free( op );
            sprintf( swq_error, "Failed to identify field:" );
            strncat( swq_error, tokens[*tokens_consumed], 
                     sizeof(swq_error) - strlen(swq_error) - 1 );
            return swq_error;
        }

        (*tokens_consumed)++;
    }

    /*
    ** Identify the operation.
    */
    if( tokens[*tokens_consumed] == NULL || tokens[*tokens_consumed+1] == NULL)
    {
        sprintf( swq_error, "Not enough tokens to complete expression." );
        return swq_error;
    }
    
    op->operation = swq_identify_op( tokens[*tokens_consumed] );
    if( op->operation == SWQ_UNKNOWN )
    {
        swq_expr_free( op );
        sprintf( swq_error, "Failed to identify operation:" );
        strncat( swq_error, tokens[*tokens_consumed], 
                 sizeof(swq_error) - strlen(swq_error) - 1 );
        return swq_error;
    }

    if( swq_op_is_logical( op->operation ) && op->first_sub_expr == NULL )
    {
        swq_expr_free( op );
        strcpy( swq_error, "Used logical operation with non-logical operand.");
        return swq_error;
    }

    if( op->field_index != -1 && op->field_type == SWQ_STRING
        && (op->operation != SWQ_EQ && op->operation != SWQ_NE) )
    {
        sprintf( swq_error, 
            "Attempt to use STRING field `%s' with numeric comparison `%s'.",
            field_list[op->field_index], tokens[*tokens_consumed] );
        swq_expr_free( op );
        return swq_error;
    }

    (*tokens_consumed)++;

    /*
    ** Collect the second operand as a subexpression.
    */
    
    if( tokens[*tokens_consumed] == NULL )
    {
        sprintf( swq_error, "Not enough tokens to complete expression." );
        return swq_error;
    }
    
    if( swq_op_is_logical( op->operation ) )
    {
        int	sub_consumed = 0;

        error = swq_subexpr_compile( tokens + *tokens_consumed, 
                                     field_count, field_list, field_types, 
                                     (swq_expr **) &(op->second_sub_expr), 
                                     &sub_consumed );
        if( error != NULL )
        {
            swq_expr_free( op );
            return error;
        }

        *tokens_consumed += sub_consumed;
    }

    /*
    ** Otherwise collect it as a literal value.
    */
    else
    {
        op->string_value = (char *) 
            SWQ_MALLOC(strlen(tokens[*tokens_consumed])+1);
        strcpy( op->string_value, tokens[*tokens_consumed] );
        op->int_value = atoi(op->string_value);
        op->float_value = atof(op->string_value);
        
        if( op->field_index != -1 
            && (op->field_type == SWQ_INTEGER || op->field_type == SWQ_FLOAT) 
            && op->string_value[0] != '-'
            && op->string_value[0] != '+'
            && op->string_value[0] != '.'
            && (op->string_value[0] < '0' || op->string_value[0] > '9') )
        {
            sprintf( swq_error, 
                     "Attempt to compare numeric field `%s' to non-numeric"
                     " value `%s' is illegal.", 
                     field_list[op->field_index], op->string_value );
            swq_expr_free( op );
            return swq_error;
        }

        (*tokens_consumed)++;
    }

    *expr_out = op;
    op = NULL;

    /*
    ** Are we part of an unparantized logical expression chain?  If so, 
    ** grab the remainder of the expression at "this level" and add to the
    ** local tree. 
    */
    if( tokens[*tokens_consumed] != NULL
        && swq_op_is_logical(swq_identify_op( tokens[*tokens_consumed] )) )
    {
        swq_expr *remainder = NULL;
        swq_expr *parent;
        int	 sub_consumed;

        error = swq_subexpr_compile( tokens + *tokens_consumed + 1, 
                                     field_count, field_list, field_types, 
                                     &remainder, &sub_consumed );
        if( error != NULL )
        {
            swq_expr_free( *expr_out );
            *expr_out = NULL;
            return error;
        }

        parent = (swq_field_op *) SWQ_MALLOC(sizeof(swq_field_op));
        memset( parent, 0, sizeof(swq_field_op) );
        parent->field_index = -1;

        parent->first_sub_expr = (struct swq_node_s *) *expr_out;
        parent->second_sub_expr = (struct swq_node_s *) remainder;
        parent->operation = swq_identify_op( tokens[*tokens_consumed] );

        *expr_out = parent;

        *tokens_consumed += sub_consumed + 1;
    }
    
    return NULL;
}



/************************************************************************/
/*                          swq_expr_compile()                          */
/************************************************************************/

const char *swq_expr_compile( const char *where_clause, 
                              int field_count,
                              char **field_list, 
                              swq_field_type *field_types, 
                              swq_expr **expr_out )

{
#define MAX_TOKEN 1024
    char	*token_list[MAX_TOKEN], *rest_of_expr;
    int		token_count = 0;
    int		tokens_consumed, i;
    const char *error;
    
    /*
    ** Collect token array.
    */
    rest_of_expr = (char *) where_clause;
    while( token_count < MAX_TOKEN )
    {
        token_list[token_count] = swq_token( rest_of_expr, &rest_of_expr );
        if( token_list[token_count] == NULL )
            break;

        token_count++;
    }
    token_list[token_count] = NULL;
    
    /*
    ** Parse the expression.
    */
    *expr_out = NULL;
    error = 
        swq_subexpr_compile( token_list, field_count, field_list, field_types, 
                             expr_out, &tokens_consumed );

    for( i = 0; i < token_count; i++ )
        SWQ_FREE( token_list[i] );

    if( error != NULL )
        return error;

    if( tokens_consumed < token_count )
    {
        swq_expr_free( *expr_out );
        *expr_out = NULL;
        sprintf( swq_error, "Syntax error, %d extra tokens", 
                 token_count - tokens_consumed );
        return swq_error;
    }

    return NULL;
}

/************************************************************************/
/*                           swq_expr_free()                            */
/************************************************************************/

void swq_expr_free( swq_expr *expr )

{
    if( expr == NULL )
        return;

    if( expr->first_sub_expr != NULL )
        swq_expr_free( (swq_expr *) expr->first_sub_expr );
    if( expr->second_sub_expr != NULL )
        swq_expr_free( (swq_expr *) expr->second_sub_expr );

    if( expr->string_value != NULL )
        SWQ_FREE( expr->string_value );

    SWQ_FREE( expr );
}

/************************************************************************/
/*                         swq_expr_evaluate()                          */
/************************************************************************/

int swq_expr_evaluate( swq_expr *expr, swq_op_evaluator fn_evaluator, 
                       void *record_handle )

{
    if( expr->operation == SWQ_OR )
    {
        return swq_expr_evaluate( (swq_expr *) expr->first_sub_expr, 
                                  fn_evaluator, 
                                  record_handle) 
            || swq_expr_evaluate( (swq_expr *) expr->second_sub_expr, 
                                  fn_evaluator, 
                                  record_handle);
    }
    else if( expr->operation == SWQ_AND )
    {
        return swq_expr_evaluate( (swq_expr *) expr->first_sub_expr, 
                                  fn_evaluator, 
                                  record_handle) 
            && swq_expr_evaluate( (swq_expr *) expr->second_sub_expr, 
                                  fn_evaluator, 
                                  record_handle);
    }
    else
    {
        return fn_evaluator( expr, record_handle );
    }

    return FALSE;
}

/************************************************************************/
/*                           swq_expr_dump()                            */
/************************************************************************/

void swq_expr_dump( swq_expr *expr, FILE * fp, int depth )

{
    char	spaces[60];
    int		i;
    const char  *op_name = "unknown";

    for( i = 0; i < depth*2 && i < sizeof(spaces); i++ )
        spaces[i] = ' ';
    spaces[i] = '\0';

    /*
    ** first term.
    */
    if( expr->first_sub_expr != NULL )
        swq_expr_dump( (swq_expr *) expr->first_sub_expr, fp, depth + 1 );
    else
        fprintf( fp, "%s  Field %d\n", spaces, expr->field_index );

    /*
    ** Operation.
    */
    if( expr->operation == SWQ_OR )
        op_name = "OR";
    if( expr->operation == SWQ_AND )
        op_name = "AND";
    if( expr->operation == SWQ_NOT)
        op_name = "NOT";
    if( expr->operation == SWQ_GT )
        op_name = ">";
    if( expr->operation == SWQ_LT )
        op_name = "<";
    if( expr->operation == SWQ_EQ )
        op_name = "=";
    if( expr->operation == SWQ_NE )
        op_name = "!=";
    if( expr->operation == SWQ_GE )
        op_name = ">=";
    if( expr->operation == SWQ_LE )
        op_name = "<=";

    fprintf( fp, "%s%s\n", spaces, op_name );

    /*
    ** Second term.
    */
    if( expr->second_sub_expr != NULL )
        swq_expr_dump( (swq_expr *) expr->second_sub_expr, fp, depth + 1 );
    else
        fprintf( fp, "%s  %s\n", spaces, expr->string_value );
}


