from gvsig import *
from geom import *

def main(*args):
    """ Convert polygon layer to line layer with one line sort by a field """
    
    ### INITIAL DATA
    path = "/home/oscm/temp/layer_ex5_01.shp"
    sortByField = "DISTANCE"
    
    ### LAYERS
    layer = currentLayer() # active layer

    ### PROCESS
    # New layer with new schema
    newSchema = createSchema()
    newSchema.append("ID", "INTEGER", size=10)
    newSchema.append("GEOMETRY", "GEOMETRY")
    CRS = currentView().getProjection()
    output = createShape(newSchema, path, CRS=CRS,
                         geometryType=LINE)
                         
    # Calculate lines and distance
    # Access to the points witho spatial orden (DISTANCE field)
    newLine = createLine()
    for feature in layer.features(sortBy=sortByField):
        geom = feature.geometry().centroid()
        newLine.addVertex(geom)
    values = {"ID":1, "GEOMETRY":newLine}
    output.append(values) # add values to output layer
    
    #Add layer to currentView. Commit changes
    output.commit()
    currentView().addLayer(output)