#!/usr/bin/python

'''Minify XHTML

Simple filter.

This simple XHTML minifier removes only indentation and comments. The reason
I wrote this is that the other HTML minifiers caused validation errors.
'''

#import sys

no_minify = [
    ('<pre', '</pre>')          # Start/stop patterns.
]

def engine(get_input, set_output):
    '''get_input is a function that returns a string (one line) with a
    trailing newline.
    set_output is a function that takes one argument: string.
    
    Returns when get_input returns empty string.
    '''
    nop_mode = False
    comment = False
    in_str = get_input()
    if not in_str:
        return
    #Comment
    #   Leave?
    #No comment
    #   Does a comment begin on this line?
    #   nop_mode
    #           Leave nop_mode?
    #   normal mode
    #           Enter nop_mode?
    #   Did a comment begin on this line?
    while True:
        # Get input it before the loop and in the end, simplifies
        # nop_mode changes.
        if comment:
            # Leave comment mode?
            ptr = in_str.find('-->')
            if ptr >= 0:
                in_str = in_str[ptr + 3:]
                comment = False
                continue
        else:
            # Does a comment begin on this line?
            comment_ptr = in_str.find('<!--')
            if comment_ptr >= 0:
                comment = True
                in_str,comment_str = in_str[:comment_ptr],in_str[comment_ptr:]
            if nop_mode:
                # Input must not be modified.
                
                # Get back to normal mode?
                ptrs = filter(lambda x: x >= 0,
                            [in_str.find(stop) for start, stop in no_minify])
                if not len(ptrs):
                    set_output(in_str)
                else:
                    set_output(in_str[:min(ptrs)])
                    in_str = in_str[min(ptrs):]
                    nop_mode = False
                    # Make it believe it came from a new line.
                    continue
            else:
                # Preserve the newline and remove all leading whitespace.
                
                # Get into NOP mode?
                ptrs = filter(lambda x: x >= 0,
                            [in_str.find(start) for start, stop in no_minify])
                if not len(ptrs):
                    for ptr, c in enumerate(in_str):
                        if c not in ' \t':
                            set_output(in_str[ptr:])
                            break
                else:
                    for ptr, c in enumerate(in_str):
                        if c not in ' \t':
                            set_output(in_str[ptr:min(ptrs)])
                            break
                    in_str = in_str[min(ptrs):]
                    nop_mode = True
                    continue
            # Did a comment begin on this line?
            if comment:
                # Loop in comment mode using the rest of the string instead
                # of a new line.
                in_str = comment_str
                continue
        in_str = get_input()
        if not in_str:
            break

if __name__ == '__main__':
    import sys
    engine(sys.stdin.readline, sys.stdout.write)