# Concatenate two MuseScore3 .mscx files (scores) into album format.
# Both scores must have same instrumentation and number of staves.
# The staff layout and instrumentation of the first score is applied
# to both scores. Any title-page text box(es) in the second score will
# be deleted.
#
# The first file may itself be an .mscx album file produced by this
# program; this allows for concatenation of three or more scores.
#
# The result is written out as an .mscx file which may be loaded
# into MuseScore3 and written out in standard .mscz format.
#
# Written for python3.
# Last mod: 2021 Dec 16

import re    # regular expression module

# Edit the lines below with the actual file paths/names:

inputfile1 = '/home/homeuser/Desktop/OrchFragment3-MS3.mscx'
inputfile2 = '/home/homeuser/Desktop/OrchFragment8-MS3.mscx'
outputfile = '/home/homeuser/Desktop/album_temp.mscx'


# find next line with string  s  in a score & return its line index, or -1 if not found
def find_next(datalines, s, init_index):
    j = next((i for i in enumerate(datalines[init_index+1:-1]) if s in i[1]),[-1,-1])[0]
    if j < 0:
        return -1
    return init_index+1+j

# find the next '<Staff id="*">' and return the value and the line index
# call with init_index = -1 or the returned index from the prev call
# returns  id, index  as a tuple
def find_next_staff_id(datalines, init_index):
    index = init_index+1+next((i for i in enumerate(datalines[init_index+1:-1]) if "Staff id" in i[1]),[-1,-1])[0]
    id = int(re.findall('\d+', datalines[index])[0])
    return id, index

# get the number of staves = largest staff id in a score = datalines
# return (maxid, id, index) with maxid = number of staves, id = 1,
# and index pointing to the '<Staff id="1">' line preceding the first measure
def get_num_staves(datalines):
    maxid = -1
    index = -1
    while True:
        id, index = find_next_staff_id(datalines, index)
        if id < maxid:
            break
        else:
            maxid = id
    return maxid, id, index

# splice list2 in between the i-1'th and i'th elements of list1, return result
# (if i is less than the length of list1, the result is an insertion;
#  if i is equal or greater, the result is an append to the end of list1;
#  if i is negative, it is taken as a count back from the end of list1) )
def splice(list1, list2, i):
    return list1[0:i] + list2 + list1[i:]

with open(inputfile1) as f:
    file1data = f.readlines()

with open(inputfile2) as g:
    file2data = g.readlines()

# check that both files have the same number of staves

ns, id1, ix1 = get_num_staves(file1data)
n2, id2, ix2 = get_num_staves(file2data)

if ns == n2:
     print("Both files have " + str(ns) + " staves.")
else:
     print("Different numbers of staves in files; exiting.")
     exit()

while id1 <= ns:  # loop over staves

   if id1 == ns:
       jx1 = find_next(file1data, '</Score>', ix1)  # end of final staff
       jx2 = find_next(file2data, '</Score>', ix2)
   else:
       jd1, jx1 = find_next_staff_id(file1data, ix1)  # point to next '<Staff id="*">'
       jd2, jx2 = find_next_staff_id(file2data, ix2)  # shd have jd1 = jd2 = id1+1

   if id1 == 1:  # special actions for staff 1

       i = jx1 - 1     # insert section break in last measure of staff 1
       while '<Measure>' not in file1data[i]:
           i = i - 1   # back up to start of final measure
       i = i + 1       # insert after '<Measure>'
       file1data = splice(file1data,
           ['        <LayoutBreak>\n','          <subtype>section</subtype>\n','           </LayoutBreak>\n'], i)

       jx1 = jx1 + 3   # correct the index for length of spliced-in segment

       # remove any text box(es) from file2data[ix2:jx2] and correct jx2
       while True:
           i = find_next(file2data[0:jx2], '<VBox>', ix2)
           if i < 0:
               break   # not found
           j = find_next(file2data[0:jx2], '</VBox>', i+1)
           file2data = file2data[0:i] + file2data[j+1: ]  # cut out VBox
           jx2 = jx2 - (j+1-i)

   # done with special actions for staff 1

   # now splice the current staff segment from file 2 into file 1
           
   file1data = splice(file1data, file2data[ix2+1:jx2-1], jx1-1)
   ix1 = jx1 + jx2 - ix2  # add length of spliced-in segment
   ix2 = jx2
   id1 = id1 + 1

# write out file1data as the "album" in .mscx format

with open(outputfile, 'w') as h:
    h.writelines(file1data)
print('wrote file  ' + outputfile)