from __future__ import division, print_function
##############################################################################
#
# Copyright (c) 2009-2018 by The University of Queensland
# http://www.uq.edu.au
#
# Primary Business: Queensland, Australia
# Licensed under the Apache License, version 2.0
# http://www.apache.org/licenses/LICENSE-2.0
#
# Development until 2012 by Earth Systems Science Computational Center (ESSCC)
# Development 2012-2013 by School of Earth Sciences
# Development from 2014 by Centre for Geoscience Computing (GeoComp)
#
##############################################################################

__copyright__="""Copyright (c) 2009-2018 by The University of Queensland
http://www.uq.edu.au
Primary Business: Queensland, Australia"""
__license__="""Licensed under the Apache License, version 2.0
http://www.apache.org/licenses/LICENSE-2.0"""
__url__="https://launchpad.net/escript-finley"

############################################################FILE HEADER
# example07a.py
# Antony Hallam
# Acoustic Wave Equation Simulation using displacement solution

#######################################################EXTERNAL MODULES
import matplotlib
matplotlib.use('agg') #It's just here for automated testing
from esys.escript import *
from esys.finley import Rectangle
from esys.weipa import saveVTK
import sys
import os
# smoothing operator 
from esys.escript.pdetools import Projector, Locator
from esys.escript.unitsSI import *
import numpy as np
import pylab as pl
import matplotlib.cm as cm
from esys.escript.linearPDEs import LinearPDE

try:
    # This imports the rectangle domain function 
    from esys.finley import Rectangle
    HAVE_FINLEY = True
except ImportError:
    print("Finley module not available")
    HAVE_FINLEY = False
########################################################MPI WORLD CHECK
if getMPISizeWorld() > 1:
        import sys
        print("This example will not run in an MPI world.")
        sys.exit(0)

if HAVE_FINLEY:
    #################################################ESTABLISHING VARIABLES
    # where to save output data
    savepath = "data/example07a"
    mkDir(savepath)
    #Geometric and material property related variables.
    mx = 1000. # model lenght
    my = 1000. # model width
    ndx = 400 # steps in x direction 
    ndy = 400 # steps in y direction
    xstep=mx/ndx # calculate the size of delta x
    ystep=my/ndy # calculate the size of delta y

    c=380.0*m/sec  # velocity of sound in air
    csq=c*c #square of c
    # Time related variables.
    testing=True
    if testing:
            print('The testing end time is currently selected. This severely limits the number of time iterations.')
            print("Try changing testing to False for more iterations.")
            tend=0.004
    else:
            tend=1.5    # end time

    h=0.001     # time step
    # data recording times
    rtime=0.0 # first time to record
    rtime_inc=tend/20.0 # time increment to record
    #Check to make sure number of time steps is not too large.
    print("Time step size= ",h, "Expected number of outputs= ",tend/h)

    U0=0.005 # amplitude of point source
    # want a spherical source in the middle of area
    xc=[500,500] # with reference to mx,my this is the source location

    ####################################################DOMAIN CONSTRUCTION
    mydomain=Rectangle(l0=mx,l1=my,n0=ndx, n1=ndy) # create the domain
    x=mydomain.getX() # get the node locations of the domain

    ##########################################################ESTABLISH PDE
    mypde=LinearPDE(mydomain) # create pde
    mypde.setSymmetryOn() # turn symmetry on
    mypde.setValue(D=1.) # set the value of D in the general form to 1.

    ############################################FIRST TIME STEPS AND SOURCE
    # define small radius around point xc
    src_radius = 30
    print("src_radius = ",src_radius)
    # set initial values for first two time steps with source terms
    u=U0*(cos(length(x-xc)*3.1415/src_radius)+1)*whereNegative(length(x-xc)-src_radius)
    u_m1=u
    #plot source shape
    cut_loc=[] #where the cross section of the source along x will be
    src_cut=[] #where the cross section of the source will be
    # create locations for source cross section
    for i in range(ndx//2-ndx//10,ndx//2+ndx//10):
        cut_loc.append(xstep*i)
        src_cut.append([xstep*i,xc[1]])
    # locate the nearest nodes to the points in src_cut
    src=Locator(mydomain,src_cut)
    src_cut=src.getValue(u) #retrieve the values from the nodes
    # plot the x locations vs value and save the figure
    pl.plot(cut_loc,src_cut)
    pl.axis([xc[0]-src_radius*3,xc[0]+src_radius*3,0.,2.*U0])
    pl.savefig(os.path.join(savepath,"source_line.png"))

    ####################################################ITERATION VARIABLES
    n=0 # iteration counter
    t=0 # time counter
    ##############################################################ITERATION
    while t<tend:
        g=grad(u); pres=csq*h*h*g # get current pressure
        mypde.setValue(X=-pres,Y=(2.*u-u_m1)) # set values in pde
        u_p1 = mypde.getSolution() # get the new displacement
        u_m1=u; u=u_p1 # shift values back one time step for next iteration
            # save current displacement, acceleration and pressure
        if (t >= rtime):
            saveVTK(os.path.join(savepath,"ex07a.%i.vtu"%n),displacement=length(u),tensor=pres)
            rtime=rtime+rtime_inc #increment data save time
        # increment loop values
        t=t+h; n=n+1
        print("time step %d, t=%s"%(n,t))