#!/usr/bin/env python
# A hack to transform xyz column data (traveltime, velocity) to
# the very strange claritas .nmo format.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU program General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the GNU
# program General Public License for more details.
#
# You should have received a copy of the GNU program General Public
# License along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307	USA
#
#
# TODO: add option (with optparse) to shift traveltimes (other than the first).
# this will make it easy to handle the OBS style 1/2 way traveltime.  Also add
# option to write out trace numbers instead of offset (cause Claritas cracks under
# the pressure of using offsets).

import sys
import fileinput
from string import *

if len(sys.argv) != 3:
	print """
	Error: usage is 'zelt_vm2claritas.py [input] [output]'.

	Used to convert 'offset(km), traveltime(s), velocity(km/s)' 
	ascii column data to a claritas .nmo format.  Can handle 
	non xyz headers.
	"""
	#print len(sys.argv)
	sys.exit()

inFile, outFile = sys.argv[1:3]
inputData = []
resultData = []

# Checking of input data, should be 3 columns of numbers (offset, depth[or tt], velocity),
for line in fileinput.input(inFile):
	fields = line.split()
	if len(fields) != 3:
		continue
	try:
		fields = map(float, (fields))
	except ValueError:
		continue
	inputData.append(fields)



allProfiles = []
singleProfile = []
# assigning each offset to its seperate list inside a larger list (list in a list)
for point in range(0, len(inputData)):
	currentOffset = inputData[point][0]
	prevOffset = inputData[point - 1][0]

	if currentOffset == prevOffset:
		singleProfile.append(inputData[point])
	# if its a different offset, start a new sub-list and put values in it
	else:
		singleProfile = []
		singleProfile.append(inputData[point])
		allProfiles.append(singleProfile)

# if there was only one offset, then it should still be appended to the superlist
# for simplicity later on.
if len(allProfiles) == 0:
	allProfiles.append(singleProfile)

# # Delete every 3rd, 5th, 7th, ..., nth element, because they are not useful in the 
# # .nmo file.
# for profile in allProfiles:
# 	i = 1
# 	while 1:
# 		i += 1
# 		if i < len(profile):
# 			del profile[i]
# 		else:
# 			break



outFileObj = open(outFile, "w")

# Write out the .nmo header fluff
# if the first column of the input file doesn't represent offset, this should
# be changed accordingly.
outFileObj.write("""NMO
PRIMARY KEY : OFFSET
SECONDARY KEY : ???
INTERPOLATION KEY : Interpolate/End
Created:
|KEYVAL|{T1     |V1}     |{T2     |V2}     |{T3     |V3}     |{T4     |V4}...  |
""")

# # Taking the average velocity of each layer.  Perhaps unnecessary, so excluded.
# for i in range(len(inputData) - 1):
#     inputData[i][1] = (inputData[i][1] + inputData[i + 1][1]) / 2

# For each clump of 4 lines in the input file, write them to one line 
# in the output file.
for profile in allProfiles:
	inputLen = len(profile)

	step = 4
	for i in range(0, inputLen, step):
		# Have to skip offsets of exactly "-1", because Claritas is to pie crusts what a 
		# porsche is to cars.
		if int(profile[i][0]) == -1:
			continue

		# For the first line only, write out the "cdp" (or offset), else write an equal 
		# amount of space.
		if i == 0:
			offset = str(int(profile[i][0]))
			whiteSpace = abs(7 - len(offset))
			# must stick in some blank space so everything is alligned vertically
			# Changed 'offset' from an int to a float, because Claritas can handle it.
			# changing everything to strings, so its left justified.
			outFileObj.write(" %s%s" %(offset, " " * whiteSpace))
		else:
			# sticking in space to fill in the column in which offset isn't written. - crazy format.
			outFileObj.write("        ")
		for j in range(step):
			if i + j < inputLen:
				#print "depth (or time):", profile[i + j][1]*1000, "velocity:", profile[i + j][2]*1000
				# Writing of the nmo format, columns have to be left justified, and therefore
				# have to be converted to strings, hence the ugly syntax.
				outFileObj.write("%s   %s   " %((str(int(profile[i + j][1]*1000))).ljust(6),\
											(str(int(profile[i + j][2]*1000))).ljust(6)))
		outFileObj.write("\n")


outFileObj.close()