from collections import namedtuple

from utils.xml import StringToTree, FileToTree, subelement, TreeToFile, prettyPrint

class Brdf(object):
    def __init__(self, reflect, alpha, ior=1.0):
        self.reflect= reflect
        self.alpha = alpha
        self.ior = ior
    
def materialsAsXml(materials):
    tree = StringToTree('<root/>')
    
    for matname, m in materials.items():
        e = subelement(tree.getroot(), 'brdf', attribs={'type': 'basic', 'name': matname})
        reflect, alpha, ior = m.reflect, m.alpha, m.ior
            
        subelement(e, 'reflect', attribs={'value': reflect})
        subelement(e, 'alpha', attribs={'value': alpha})
        subelement(e, 'ior', attribs={'value': ior})
    return tree

def loadMaterialsFromTree(tree):
    materials = {}
    for e in tree.getroot().xpath('brdf'):
        try:
            reflect = float(e.xpath('string(reflect/@value)'))
            alpha = float(e.xpath('string(alpha/@value)'))
            ior = float(e.xpath('string(ior/@value)'))
        except Exception:
            print 'cannot load material %s' % e.attrib.get('name')
            reflect, alpha, ior = 0.5, 0.5, 1.0
            
        materials[e.attrib['name']] = Brdf(reflect, alpha, ior)
    return materials
    
def loadMaterialsFromString(materialsxml):
    return loadMaterialsFromTree(StringToTree(materialsxml))
    
def loadMaterials(materials_file):
    return loadMaterialsFromTree(FileToTree(materials_file))