#!/usr/bin/python
# -*- coding:utf-8 -*-
############################################################################
#
# MODULE:       v.sample.class.py
#
# AUTHOR(S):    M. Cannata, M. Molinari (IST-SUPSI www.istgis.ist.supsi.ch:8001/GEOMATICA)
#
# PURPOSE:      Field values calculator
#
# COPYRIGHT:    (c) 2007 The GRASS Development Team
#
#               This program is free software under the GNU General Public
#               License (>=v2). Read the file COPYING that comes with GRASS
#               for details.
#
############################################################################
#%Module
#% description:  Field values calculator
#% keywords: vector, field, calculator
#%end
#%option
#% key: input
#% type: string
#% gisprompt: old,vector,vector
#% key_desc : name
#% description: input
#% required : yes
#%end
#%option
#% key: field
#% type: string
#% key_desc : name
#% description: field to store results
#% required : yes
#%end
#%option
#% key: exp
#% type: string
#% key_desc : operation
#% description: expression to execute
#% required : yes
#%end
#%option
#%  key: where
#%  type: string
#%  key_desc : expression
#%  description: where condition to execute
#%  required : no
#%end

import os,sys,subprocess,string,random,math,tempfile,time,re

def main(): 

    table = os.getenv('GIS_OPT_input').split('@')[0]
    field = os.getenv('GIS_OPT_field')
    exp = os.getenv('GIS_OPT_exp')
    wherest = os.getenv('GIS_OPT_where')

    #Get vector fields name
    cmdargs0=["db.columns","table=%s" %table, "--q"]
    proc0 = subprocess.Popen(cmdargs0, stdout=subprocess.PIPE,stderr=subprocess.PIPE)
    colnames = proc0.communicate()[0].split("\n")

    #print "cols:\n"
    #for item in colnames: # print each item
    #    print item + "\n"

    #Parse operation expression
    spe = re.split("([\[\]])", exp)

    #Check exp field names validity and get required field list
    expfields = []
    for i in range(len(spe)):
        if(spe[i]=="["):
            if spe[i+1] not in colnames:
                print "FATAL ERROR: field " + spe[i+1] + " not found in table " + table + "\n"
                print "tried SQL: " + spe[i+1] + " not found in table " + table + "\n"
                return -1
            else:
                expfields.append(spe[i+1])

    #Get unique list of required fields
    uf = list(set(expfields))

    #Prepare query statement
    lf = ", ".join(uf)
    sel = "SELECT cat"
    if len(uf)>0:
        sel = sel + "," + lf
    sel = sel  + " from " + table
    if wherest:
        sel = sel + " WHERE " + wherest

    #Execute query
    cmdargs1=["db.select","sql=%s" %sel, "--q", "-c"]
    proc1 = subprocess.Popen(cmdargs1, stdout=subprocess.PIPE,stderr=subprocess.PIPE)
    lines = proc1.communicate()[0].split("\n")

    #print "query: " + sel

    #print "unique list:\n"
    #for item in uf: # print each item
    #    print item + "\n" 

    #print "selection:\n"
    #for item in lines: # print each item
    #    print item + "\n" 

    #Check query results
    if len(lines) == 1:
        print "WARNING: no record selected\n"
        print "executed query: " + sel + "\n"
        return -1
    #Process and UPDATE
    else:
        print "please wait while updating values...."
        #process lines
        for l in range(0,len(lines)-1):
            #if l%10==0:
            #    sys.stdout.write(".")
            cols = lines[l].split("|")
            evalexp = exp
            for i in range(len(uf)):
                evalexp = evalexp.replace("["+uf[i]+"]",cols[i+1])
            try:
                #print evalexp + "\n"            
                value = eval(str(evalexp))
            #except ArithmeticError, e:
            except StandardError, e:
                print "\n%s\nIn command: %s" % (repr(e), str(evalexp))
                return -1

            #print value           
            updst = "UPDATE " + table + " SET " + field + "=" + str(value) + " WHERE cat=" + cols[0]
            #print updst
            cmdargs2=["map=%s"%table,"col=%s"%field,"val=%s"%str(value),"where=cat=%s"%cols[0],"--q"]     
            os.spawnvp(os.P_WAIT,"v.db.update", ["v.db.update"] + cmdargs2)
        print "....DONE"
    return

if __name__ == "__main__":
    if ( len(sys.argv) <= 1 or sys.argv[1] != "@ARGS_PARSED@" ):
        os.execvp("g.parser", [sys.argv[0]] + sys.argv)
    else:
	main();