terom@16: 
terom@16: """
terom@16:     Parsing trees of node stored using a python-like syntax.
terom@16: 
terom@16:     A file consists of a number of lines, and each line consists of indenting whitespace and data. Each line has a parent
terom@16: """
terom@16: 
terom@17: class TreeParseError (Exception) :
terom@17:     """
terom@17:         Error parsing a tree file
terom@17:     """
terom@17: 
terom@17:     pass
terom@17: 
terom@16: def _read_lines (path, stop_tokens='') :
terom@16:     """
terom@16:         Reads lines from the given path, ignoring empty lines, and yielding (line_number, indent, line) tuples, where 
terom@16:         line_number is the line number, indent counts the amount of leading whitespace, and line is the actual line
terom@16:         data with whitespace stripped.
terom@16: 
terom@16:         Stop tokens is a list of chars to stop counting indentation on - if such a line begins with such a char, its
terom@16:         indentation is taken as zero.
terom@16:     """
terom@16: 
terom@16:     for line_number, line in enumerate(open(path, 'rb')) :
terom@16:         indent = 0
terom@16: 
terom@16:         # count indent
terom@16:         for char in line :
terom@16:             # tabs break things
terom@16:             assert char != '\t'
terom@16:             
terom@16:             # increment up to first non-space char
terom@16:             if char == ' ' :
terom@16:                 indent += 1
terom@16:             
terom@16:             elif char in stop_tokens :
terom@16:                 # consider line as not having any indentation at all
terom@16:                 indent = 0
terom@16:                 break
terom@16: 
terom@16:             else :
terom@16:                 break
terom@16:         
terom@16:         # strip whitespace
terom@16:         line = line.strip()
terom@16: 
terom@16:         # ignore empty lines
terom@16:         if not line :
terom@16:             continue
terom@16: 
terom@16:         # yield
terom@16:         yield line_number + 1, indent, line
terom@16: 
terom@16: def parse (path, stop_tokens='') :
terom@16:     """
terom@16:         Reads and parses the file at the given path, returning a list of (line_number, line, children) tuples.
terom@16:     """
terom@16: 
terom@16:     # stack of (indent, PageInfo) items
terom@16:     stack = []
terom@16: 
terom@16:     # the root item
terom@16:     root = None
terom@16: 
terom@16:     # the previous item processed, None for first one
terom@16:     prev = None
terom@16:     
terom@16:     # read lines
terom@16:     for line_number, indent, line in _read_lines(path, stop_tokens) :
terom@16:         # create item
terom@16:         item = (line_number, line, [])
terom@16: 
terom@16:         # are we the first item?
terom@16:         if not prev :
terom@16:             # root node does not have a parent
terom@16:             parent = None
terom@16:             
terom@16:             # set root
terom@16:             root = item
terom@16: 
terom@16:             # initialize stack
terom@16:             stack.append((0, root))
terom@16:             
terom@16:         else :
terom@16:             # peek stack
terom@16:             stack_indent, stack_parent = stack[-1]
terom@16: 
terom@16:             # new indent level?
terom@16:             if indent > stack_indent :
terom@16:                 # set parent to previous item, and push new indent level + parent to stack
terom@16:                 parent = prev
terom@16: 
terom@16:                 # push new indent level + its parent
terom@16:                 stack.append((indent, parent))
terom@16: 
terom@16:             # same indent level as previous
terom@16:             elif indent == stack_indent :
terom@16:                 # parent is the one of the current stack level, stack doesn't change
terom@16:                 parent = stack_parent
terom@16:             
terom@16:             # unravel stack
terom@16:             elif indent < stack_indent :
terom@16:                 while True :
terom@16:                     # remove current stack level
terom@16:                     stack.pop(-1)
terom@16: 
terom@16:                     # peek next level
terom@16:                     stack_indent, stack_parent = stack[-1]
terom@16:                     
terom@16:                     # found the level to return to?
terom@16:                     if stack_indent == indent :
terom@16:                         # restore prev
terom@16:                         parent = stack_parent
terom@16: 
terom@16:                         break
terom@16: 
terom@16:                     elif stack_indent < indent :
terom@17:                         raise TreeParseError("Bad unindent on %s:%d, %d < %d" % (path, line_number, stack_indent, indent))
terom@16:         
terom@16:         # add to parent?
terom@16:         if parent :
terom@16:             parent[2].append(item)
terom@16: 
terom@16:         # update prev
terom@16:         prev = item
terom@16:     
terom@16:     # return the root
terom@16:     return root
terom@16: