pyvconv.py

   1 import libxml2
   2 import re
   3
   4 class Variable:
   5     def __init__(self, namestr, defaultstr, exprstr):
   6         self.namestr = namestr
   7         self.defaultstr = defaultstr
   8         self.exprstr = exprstr
   9
  10     def __str__(self):
  11         return self.namestr
  12
  13     def has_value(self):
  14         return self.defaultstr != None
  15
  16     def evaluate(self):
  17         return self.exprstr
  18
  19 class OptionalSetting:
  20     def __init__(self, namestr, exprstr):
  21         self.namestr = namestr
  22         self.exprstr = exprstr
  23
  24     def get_name(self):
  25         return self.namestr
  26
  27     def evaluate(self, var_list):
  28         instr = self.exprstr
  29         for var in var_list:
  30             if var_list[var].has_value():
  31                 p = re.compile( '\$\{' + var + '\}')
  32                 instr = p.sub( var_list[var].get_value(), instr)
  33         if instr.find("$") != -1:
  34             instr = "" # if not all variables were found, return empty option
  35         return instr
  36
  37 class RenderCommand:
  38     def __init__(self, namestr, callstr, var_list, optset_list):
  39         self.namestr = namestr
  40         self.callstr = callstr
  41         self.var_list = var_list
  42         self.optset_list = optset_list
  43
  44     def get_name(self):
  45         return self.namestr
  46
  47     def evaluate(self):
  48         instr = self.callstr
  49
  50         p = re.compile("\$\[(\w+)\]")
  51         for o in p.findall(instr):
  52             if o not in self.optset_list:
  53                 raise "Error: Optional variable not defined"
  54             instr = p.sub(self.optset_list[o].evaluate(self.var_list), instr)
  55
  56         p = re.compile("\$\{(\w+)\}")
  57         for o in p.findall(instr):
  58             instr = p.sub(self.var_list[o].evaluate(), instr)
  59
  60         if instr.find("$") != -1:
  61             raise "Error: all variables were not expanded"
  62         return instr
  63
  64 class RenderCommands:
  65     def __init__(self):
  66         self.cmdcall_dict = {}
  67         self._read_config()
  68
  69     def _read_properties(self, propnode, mand_propnames, opt_propnames = []):
  70         propdict = {}
  71
  72         for p in propnode:
  73             if p.name in mand_propnames:
  74                 propdict[p.name] = str(p.content)
  75             elif p.name != "text" and p.name not in opt_propnames:
  76                 raise "Error parsing XML: only name and call are accepted properties in the element command, found " + str(p.name)
  77
  78         if len(mand_propnames) != len(propdict.keys()):
  79                 raise "Error parsing XML: must supply both name and call in element command"
  80
  81         for p in propnode:
  82             if p.name in opt_propnames:
  83                 propdict[p.name] = str(p.content)
  84             elif p.name != "text" and p.name not in mand_propnames:
  85                 raise "Error parsing XML: only name and call are accepted properties in the element command, found " + str(p.name)
  86
  87         return propdict
  88
  89     def _read_config(self):
  90         doc = libxml2.parseFile("rendercommands.xml")
  91         cmd_xmllist = doc.xpathEval( '//command')
  92
  93         # read all commands from XML description
  94         for cmdnode in cmd_xmllist:
  95             if cmdnode.type == "element" and cmdnode.name == "command":
  96
  97                 if cmdnode.children:
  98                     for varsetnode in cmdnode.children:
  99                         var_list = {}
 100                         optset_list = {}
 101
 102                         if varsetnode.type == "element" and varsetnode.name == "variable":
 103                             props =  self._read_properties(varsetnode.properties, ["name", "expr"], ["default"])
 104                             defprop = None
 105                             if "default" in props:
 106                                 defprop = props["default"]
 107                             var_list[props["name"]] = Variable(props["name"], defprop, props["expr"])
 108
 109                         elif varsetnode.type == "element" and varsetnode.name == "optionalsetting":
 110                             props = self._read_properties(varsetnode.properties, ["name", "expr"])
 111                             optset_list[props["name"]] = OptionalSetting(props["name"], props["expr"])
 112
 113                         elif varsetnode.name != "text":
 114                             raise "Error parsing XML: only variable and optionalsetting elements allowed in command"
 115
 116                 props = self._read_properties(cmdnode.properties, ["name", "call"])
 117                 self.cmdcall_dict[props["name"]] = RenderCommand(props["name"], props["call"], var_list, optset_list)
 118
 119             else:
 120                 raise "Error parsing XML: only command elements are supported"
 121
 122         print self.cmdcall_dict
 123
 124 def main():
 125     commands = RenderCommands()
 126
 127 if __name__ == "__main__":
 128     main()
 129