CS 351: Design of Large Programs
                --------------------------------

               Assignment # 4, Due Date  11/10/01
               ----------------------------------


The goal of this assignment is to extract information from an XML document 
and save it on disk. The XML document contains customer information and
purchase orders accumulated over a period of about a week. Each week a new
document containing fresh orders will be received and new information
needs to be extracted and added to the already saved purchase orders
on disk.
Extra Credit Part only:
In addition, it should be possible to query the database for information
on sales of specific items and/or customer purchases over a period (such
as the first quarter of 2001, etc.)

Background:
-----------

There are at least two types of parsers used to parse XML documents.
The first is based on the Document Object Model (DOM). This requires 
that the entire document be loaded into memory before it can be used.
Another commonly used type of parser is the SAX (Simple API for XML)
parser that you will use for this assignment. A SAX parser reads the 
document in stages and issues "callbacks" to user-written code as 
different conditions occur such as the start of an element, or the 
occurence of a string of characters between the start and end tags
of an element.

Assignment Specifics:
---------------------

First, follow the instructions in Denys' handout related to installing 
the libxml2 library on your system. Then, make sure you can run the 
sample program handed out in class.

The program below (a modification of the program handed out in class)
(1) defines five callback functions (start/end of document, start/end
    of element, string occurence between start and end tags of an 
    element).
(2) creates an instance of the callback structure and initializes the 
    callback function pointers.
(3) creates a state structure which saves state information between
    callbacks.
(4) creates a parser and passes it pointers to the callback structure 
    and to the state structure
(5) starts the parser and
(6) performs clean-up operations after the parser terminates.


Study the program below since you will need to use most of the 
statements therein for this assignment.


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

#include <libxml/parser.h>
#include <libxml/parserInternals.h>

typedef enum { parse_start_s=0, parse_finish_s,
               parse_item_id_s, parse_quantity_s,
               parse_price_s, parse_discount_s,
               parse_other_s}    Parse_state;

typedef struct {
          Parse_state pstate;
          Parse_state discount;
          } State_struc;

static xmlSAXHandler callbacks;

static void start_document(void *ctx)
{
    State_struc  *state_ptr;
    state_ptr = (State_struc *) ctx;
    state_ptr->pstate = parse_start_s; 
    state_ptr->discount = parse_start_s; 
    printf("Document started!!!\n");
}

static void end_document(void *ctx)
{
    printf("Document ended!!!\n");

}

static void start_element( void *ctx, const xmlChar *name, const xmlChar **attrs)
{
    State_struc  *state_ptr;
    state_ptr = (State_struc *) ctx;
    if( strcmp((const char *)name, "item_id")==0 ) 
          state_ptr->pstate = parse_item_id_s; 
   else if( strcmp((const char *)name, "price")==0 )  
          state_ptr->pstate = parse_price_s; 
   else if( strcmp((const char *)name, "quantity")==0 )  
          state_ptr->pstate = parse_quantity_s; 
   else if( strcmp((const char *)name, "discount")==0 ) { 
          state_ptr->pstate = parse_discount_s;
          state_ptr->discount = parse_discount_s;
   }
   else state_ptr->pstate = parse_other_s;
       
}

static void end_element( void *ctx, const xmlChar *name)
{
    printf("Element %s ended\n", name);
}

static void chars_found( void *ctx, const char *chars, int len )
{
    char buff[len+1];
    State_struc  *state_ptr;
    state_ptr = (State_struc *) ctx;
    
    strncpy(buff, chars, len);
    buff[len] = '\0';

    switch( state_ptr->pstate) {
     case parse_item_id_s  :
      printf("\t i_id=%s", buff);
      state_ptr->pstate = parse_other_s;
      break;   
     case parse_discount_s  :
      printf("\t  disc=%s", buff);  
      state_ptr->pstate = parse_other_s;   
      break;   
     case parse_price_s  :
      if ((state_ptr->discount) != parse_discount_s) printf("\t\t");
      state_ptr->discount = parse_other_s;
      printf("\t  pr=%s", buff);  
      state_ptr->pstate = parse_other_s;   
      break;   
     case parse_quantity_s  :
      printf("\t  Quan=%s\n", buff);
      state_ptr->pstate = parse_other_s;   
      break;   
     case parse_other_s  :
      break;
     default:
      break;
    }
}    


int main()
{
    xmlParserCtxtPtr ctxt_ptr;
    State_struc  state;
   
    memset( &callbacks, sizeof(xmlSAXHandler), 0);
    callbacks.startDocument= start_document;
    callbacks.endDocument= end_document;
    callbacks.startElement= start_element;
    callbacks.endElement= end_element;
    callbacks.characters=(void (*)(void *, const xmlChar *, int)) chars_found;

    ctxt_ptr= xmlCreateFileParserCtxt("sales.xml");
    if( !ctxt_ptr ) {
	printf("Failed to create file parser  !!!\n");
	return -1;
    }
    
    ctxt_ptr->sax= &callbacks;
    ctxt_ptr->userData= &state;
    xmlParseDocument(ctxt_ptr);

    if( !ctxt_ptr->wellFormed ) {
	printf("Document is not well formed!!!\n");
    }
    
    ctxt_ptr->sax= NULL;
    xmlFreeParserCtxt(ctxt_ptr);
    printf("Parsing complete!!! \n");
    return -1;
}

******************************************************************

The POs that comprise the document your program will receive are
defined by the DTD (Document Type Definition) below.


<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>

<!DOCTYPE orders [

<!ELEMENT orders (order+) >
<!ELEMENT order (date, customer, items, total, payment ) >
<!ATTLIST order order_id CDATA #REQUIRED>
<!ELEMENT customer (cust_name, address ) >
<!ATTLIST customer cust_id CDATA #REQUIRED>
<!ELEMENT address (block, city, zip, phone+, fax*, mobile?) >
<!ELEMENT items (item+ ) >
<!ELEMENT item (item_name, discount?, price, quantity, subtotal ) >
<!ATTLIST item item_id CDATA #REQUIRED>
<!ELEMENT payment ( cash | credit)>
<!ELEMENT cash (amount_paid, change)>  
<!ELEMENT credit (card_type, card_owner, card_number, expiration_date)>
                            

<!ELEMENT date (#PCDATA) >
<!ELEMENT total (#PCDATA) >
<!ELEMENT cust_name (#PCDATA) >
<!ELEMENT block (#PCDATA) >
<!ELEMENT city (#PCDATA) >
<!ELEMENT zip (#PCDATA) >
<!ELEMENT phone (#PCDATA) >
<!ELEMENT fax (#PCDATA) >
<!ELEMENT mobile (#PCDATA) >
<!ELEMENT item_name (#PCDATA) >
<!ELEMENT discount (#PCDATA) >
<!ELEMENT price (#PCDATA) >
<!ELEMENT quantity (#PCDATA) >
<!ELEMENT subtotal (#PCDATA) >
<!ELEMENT type (#PCDATA) >
<!ELEMENT amount_paid (#PCDATA) >
<!ELEMENT change (#PCDATA) >
<!ELEMENT card_type (#PCDATA) >
<!ELEMENT card_owner (#PCDATA) >
<!ELEMENT card_number (#PCDATA) >
<!ELEMENT expiration_date (#PCDATA) >

]>

******************************************************************

A sample XML document of POs is shown below.

<orders>
   <order order_id="789">
     <date>10/22/2001</date>
     <customer cust_id="5432">
	 <cust_name>John</cust_name>
	 <address>
            <block>1010 Main</block>
	    <city>Albuquerque</city>
	    <zip>87131</zip>
	    <phone>1234567</phone>
       	    <fax>2347654</fax>
	 </address>
     </customer>	 
     <items>
	    <item item_id="472">
		<item_name>shoes</item_name>
		<price>5.00</price>
		<quantity>1</quantity>
		<subtotal>5.00</subtotal>
	    </item>
	    <item item_id="290">
		<item_name>sugar</item_name>
                <discount>15</discount>
		<price>2.00</price>
		<quantity>2</quantity>
		<subtotal>4.00</subtotal>
	    </item>
      </items>     
      <total>9.00</total>
      <payment>
	     <cash>
	        <amount_paid>10.00</amount_paid>
	        <change>1.00</change>
	     </cash>
      </payment>
   </order>

   <order order_id="799">
     <date>10/24/2001</date>
     <customer cust_id="2411">
	 <cust_name>Mary</cust_name>
	 <address>
            <block>2643 Bronze</block>
	    <city>New York</city>
	    <zip>88131</zip>
	    <phone>2345678</phone>
	    <phone>5678234</phone>
       	    <fax>4765411</fax>
	 </address>
     </customer>
     <items>
	    <item item_id="307">
		<item_name>ink</item_name>
		<price>1.00</price>
		<quantity>5</quantity>
		<subtotal>5.00</subtotal>
	    </item>
     </items>
     <total>5.00</total>
     <payment>
            <credit>
               <card_type>VISA</card_type>
               <card_owner>Mary</card_owner>
               <card_number>1234567890</card_number>
               <expiration_date>07/03</expiration_date>
            </credit>
     </payment>
   </order> 
								   
   <order order_id="889">
     <date>10/24/2001</date>
     <customer cust_id="3790">
	 <cust_name>Steve</cust_name>
	 <address>
            <block>7432 Silver</block>
	    <city>Greenbelt</city>
	    <zip>89131</zip>
	    <phone>2345678</phone>
            <mobile>4320659</mobile>
	 </address>
     </customer>
     <items>
	    <item item_id="687">
		<item_name>tooth paste</item_name>
		<price>2.50</price>
		<quantity>2</quantity>
		<subtotal>5.00</subtotal>
	    </item>
	    <item item_id="285">
		<item_name>tooth brush</item_name>
		<price>1.00</price>
		<quantity>2</quantity>
		<subtotal>2.00</subtotal>
	    </item>
     </items>
     <total>7.00</total>
     <payment>
	     <cash>
	        <amount_paid>10.00</amount_paid>
	        <change>3.00</change>
	     </cash>
     </payment>
     </order>


   <order order_id="989">
     <date>10/25/2001</date>
     <customer cust_id="1834">
	 <cust_name>John</cust_name>
	 <address>
            <block>5103 Gold</block>
	    <city>Round Rock</city>
	    <zip>90131</zip>
	    <phone>1234567</phone>
	 </address>
     </customer>
     <items>
	    <item item_id="554">
		<item_name>TV set</item_name>
                <discount>10</discount>
		<price>150.00</price>
		<quantity>1</quantity>
		<subtotal>150.00</subtotal>
	    </item>
     </items>	
          <total>150.00</total>
          <payment>
 	     <cash>
	        <amount_paid>150.00</amount_paid>
	        <change>0.00</change>
 	     </cash>
	  </payment>
    </order>

</orders>

******************************************************************


What should your program do?
----------------------------

Your program should support the folowing interaction with the user. In
what follows, user responses are underlined.

   Enter name of your (local) file: menezes
                                    -------
Use your name since we will need to inspect your file later and we 
should know which group created which file. (Last names in CS 351
are unique, so it's best you use that for the file that stores 
all the information extracted from the XML files processed.) 
The response of your program should be either
   menezes does not exist
      OR
   Loading menezes

   Enter xml filename:  xyz.xml
                        -------

Parsing of xyz.xml should then commence and your program should store
the PO information in container(s) designed by you.
When done, the following should be displayed:

   xyz.xml parsing over

Then the program should prompt the user for a command and the expected 
response is one of the following four:
   Enter Command: d
                  -
OR
   Enter Command: d*
                  --
OR
   Enter Command: d <date1> <date2>
                  -----------------
OR
   Enter Command: s
                  -

The first command should cause the program to display each PO
extracted from xyz.xml in the format described below. 

The second command should cause the program to display each PO
in menezes followed by each PO in xyz.xml.

The third command should cause the program to display each PO
extracted from xyz.xml that has been placed between <date1>
and <date2>.

The fourth command should append the orders extracted from xyz.xml
to menezes and save menezes on disk if menezes already existed. If
menezes does not yet exist, it should be created and the new POs
extracted from xyz.xml should be saved in it. 

The format for display of each PO is:


Date:______	Order #: _________	Customer: _____________________
Address: ______________________________________________________________
Phone: __________	Fax: ____________	Mobile: ___________

Item#	ItemDesc	Disc	Price	Quantity	SubTotal
-----   --------        ----    -----   --------        --------
 ...	 ...		...	 ...	 ...		 ...
 ...	 ...		...	 ...	 ...		 ...
 ...	 ...		...	 ...	 ...		 ...

Total: ___________________________
Payment: __________________________________________________


This interaction can be repeated without limit, each time adding
fresh POs to file menezes.

Note:

(1) Customers, POs and items are each uniquely identified by their
    respective id's.

(2) Your implementation should store information efficiently. This
    means that you may wish to use two containers -- one to store
    customer information and the other to store PO information. 

(3) Customer details (address, phone numbers, etc.) may change over 
    time. For the extra-credit part, which involves queries related
    to, among other things, customer information, the latest
    information should be displayed.

(4) Design your display function so that it appears one screen-full
    at a time.