'''Update a symlink hierachy to match the tag collection values.'''

import sys
import os
from lib.tagfiles import TagCollection
from lib.relpath import relpath

def create_target_links(basepath, dirpath, targets, our_files, msgs):
    '''Create links for targets in dirpath. Add link names to our_files.'''
    
    for target in targets:
        if os.path.isdir(os.path.join(basepath, target)):
            # Just the last part for directories
            tname = target.split('/')[-1]
        else:
            # Directory and filename
            tname = '-'.join(target.split('/')[-2:])
        
        tyear = target.split('/')[0]
        linkname = tyear + '-' + tname
        linkpath = os.path.join(dirpath, linkname)
        targetpath = relpath(dirpath, os.path.join(basepath, target))
        our_files.add(linkpath)
        
        if os.path.islink(linkpath) and os.readlink(linkpath) == targetpath:
            # Nothing to do
            continue
        
        # Only remove links, do not remove real files
        if os.path.lexists(linkpath):
            if os.path.islink(linkpath):
                os.unlink(linkpath)
            else:
                msgs.append('File already exists: ' + linkpath)
                continue
        
        os.symlink(targetpath, linkpath)

def remove_unnecessary(linkdir, our_files, msgs):
    '''Remove empty directories and symlinks from file system if they are
    not in our_files.'''
    
    def onerror(error):
        '''Add notes to msgs for errors from os.walk.'''
        msgs.append('Directory traversal error: ' + str(error))
    
    for dirpath, dirnames, filenames in os.walk(linkdir, False, onerror):
        for filename in filenames:
            filename = os.path.join(dirpath, filename)
            if filename not in our_files:
                if os.path.islink(filename):
                    os.remove(filename)
                else:
                    msgs.append('Unknown file: ' + filename)

        for dirname in dirnames:
            dirname = os.path.join(dirpath, dirname)
            for filename in our_files:
                if filename.startswith(dirname):
                    break
            else:
                if os.path.islink(dirname):
                    os.remove(dirname) # Our link
                elif not os.listdir(dirname):
                    os.rmdir(dirname) # Empty dir
                else:
                    msgs.append('Non-empty unnecessary directory: ' + dirname)

def update_symlinks(basepath, linkdir, tagcollection, msgs):
    '''Remove any tags and symlinks that no-longer exist in the collection.
    Add any missing symlinks and tags to filesystem.'''
    
    # Check that all tags are in place
    our_files = set()
    for tag, targets in tagcollection.tags.items():
        # Verify that the tag directory exists
        dirpath = os.path.join(linkdir, tag)
        our_files.add(dirpath)
        if not os.path.isdir(dirpath):
            try:
                os.makedirs(dirpath, 0755)
            except os.error, ex:
                msgs.append('Could not create directory ' +
                    dirpath + ': ' + str(ex))
                continue
    
        create_target_links(basepath, dirpath, targets, our_files, msgs)
    
    remove_unnecessary(linkdir, our_files, msgs)

def main(path):
    tc = TagCollection()
    tc.import_recursively(path, 'Merkinnat.txt')
    
    if tc.msgs:
        print "Import messages (%d):" % len(tc.msgs)
        for msg in tc.msgs:
            print msg
            print '-' * 20
        
        print "Symlinks were not updated."
        return False
    
    msgs = []
    update_symlinks(path, os.path.join(path, 'Luokiteltuna'), tc, msgs)
    
    if msgs:
        print "Symlink creation messages (%d):" % len(msgs)
        for msg in msgs:
            print msg
            print '-' * 20
        return False
    
    return True

if __name__ == '__main__':
    sys.exit(int(not main(os.getcwd())))