"""Simple water flow example using ANUGA

Water flowing down a channel with changing boundary conditions
"""

#------------------------------------------------------------------------------
# Import necessary modules
#------------------------------------------------------------------------------
import anuga

def generate_domain():
    #--------------------------------------------------------------------------
    # Setup computational domain
    #--------------------------------------------------------------------------
    length = 10.
    width = 5.
    dx = dy = 1.           # Resolution: Length of subdivisions on both axes
    
    points, vertices, boundary = anuga.rectangular_cross(int(length/dx),
                                    int(width/dy), len1=length, len2=width)
                                            
    domain = anuga.Domain(points, vertices, boundary)   
    domain.set_name('channel2')                 # Output name
    
    #--------------------------------------------------------------------------
    # Setup initial conditions
    #--------------------------------------------------------------------------
    def topography(x,y):
        return -x/10                             # linear bed slope
    
    domain.set_quantity('elevation', topography) # Use function for elevation
    domain.set_quantity('friction', 0.01)        # Constant friction 
    domain.set_quantity('stage',
                        expression='elevation')  # Dry initial condition
    
    #--------------------------------------------------------------------------
    # Setup boundary conditions
    #--------------------------------------------------------------------------
    Bi = anuga.Dirichlet_boundary([0.4, 0, 0])   # Inflow
    Br = anuga.Reflective_boundary(domain)       # Solid reflective wall
    Bo = anuga.Dirichlet_boundary([-5, 0, 0])    # Outflow
    
    domain.set_boundary({'left': Bi, 'right': Br, 'top': Br, 'bottom': Br})
    import sys
    if len(sys.argv) > 1 and "gpu" in sys.argv:
        domain.using_gpu = True
    else:
        domain.using_gpu = False
    print sys.argv, "gpu" in sys.argv
    return domain

def evolve_domain(domain):
    #--------------------------------------------------------------------------
    # Evolve system through time
    #--------------------------------------------------------------------------
    for t in domain.evolve(yieldstep=0.2, finaltime=40.0):
        print domain.timestepping_statistics()
    
        if domain.get_quantity('stage').\
               get_values(interpolation_points=[[5, 2.5]]) > 0:        
            print 'Stage > 0: Changing to outflow boundary'
            domain.set_boundary({'top': Bo})
            
if __name__ == '__main__':
    domain = generate_domain()
    evolve_domain(domain)