"""Module to analyze Python source code; for syntax coloring tools.

Interface:
    tags = fontify(pytext, searchfrom, searchto)

The 'pytext' argument is a string containing Python source code.
The (optional) arguments 'searchfrom' and 'searchto' may contain a slice in pytext.
The returned value is a list of tuples, formatted like this:
    [('keyword', 0, 6, None), ('keyword', 11, 17, None), ('comment', 23, 53, None), etc. ]
The tuple contents are always like this:
    (tag, startindex, endindex, sublist)
tag is one of 'keyword', 'string', 'comment' or 'identifier'
sublist is not used, hence always None.
"""

# Based on FontText.py by Mitchell S. Chapman,
# which was modified by Zachary Roadhouse,
# then un-Tk'd by Just van Rossum.
# Many thanks for regular expression debugging & authoring are due to:
#   Tim (the-incredib-ly y'rs) Peters and Cristian Tismer
# So, who owns the copyright? ;-) How about this:
# Copyright 1996-2001:
#   Mitchell S. Chapman,
#   Zachary Roadhouse,
#   Tim Peters,
#   Just van Rossum

__version__ = "0.4"

import string
import re

# First a little helper, since I don't like to repeat things. (Tismer speaking)
import string
def replace(where, what, with26):
    return string.join(string.split(where, what), with26)

# This list of keywords is taken from ref/node13.html of the
# Python 1.3 HTML documentation. ("access" is intentionally omitted.)
keywordsList = [
    "as", "assert", "exec",
    "del", "from", "lambda", "return",
    "and", "elif", "global", "not", "try",
    "break", "else", "if", "or", "while",
    "class", "except", "import", "pass",
    "continue", "finally", "in", "print",
    "def", "for", "is", "raise", "yield"]

# Build up a regular expression which will match anything
# interesting, including multi-line triple-quoted strings.
commentPat = r"#[^\n]*"

pat = r"q[^\\q\n]*(\\[\000-\377][^\\q\n]*)*q"
quotePat = replace(pat, "q", "'") + "|" + replace(pat, 'q', '"')

# Way to go, Tim!
pat = r"""
    qqq
    [^\\q]*
    (
        (   \\[\000-\377]
        |   q
            (   \\[\000-\377]
            |   [^\q]
            |   q
                (   \\[\000-\377]
                |   [^\\q]
                )
            )
        )
        [^\\q]*
    )*
    qqq
"""
pat = string.join(string.split(pat), '')    # get rid of whitespace
tripleQuotePat = replace(pat, "q", "'") + "|" + replace(pat, 'q', '"')

# Build up a regular expression which matches all and only
# Python keywords. This will let us skip the uninteresting
# identifier references.
# nonKeyPat identifies characters which may legally precede
# a keyword pattern.
nonKeyPat = r"(^|[^a-zA-Z0-9_.\"'])"

keyPat = nonKeyPat + "(" + string.join(keywordsList, "|") + ")" + nonKeyPat

matchPat = commentPat + "|" + keyPat + "|" + tripleQuotePat + "|" + quotePat
matchRE = re.compile(matchPat)

idKeyPat = "[ \t]*[A-Za-z_][A-Za-z_0-9.]*"  # Ident w. leading whitespace.
idRE = re.compile(idKeyPat)


def fontify(pytext, searchfrom = 0, searchto = None):
    if searchto is None:
        searchto = len(pytext)
    # Cache a few attributes for quicker reference.
    search = matchRE.search
    idSearch = idRE.search

    tags = []
    tags_append = tags.append
    commentTag = 'comment'
    stringTag = 'string'
    keywordTag = 'keyword'
    identifierTag = 'identifier'

    start = 0
    end = searchfrom
    while 1:
        m = search(pytext, end)
        if m is None:
            break   # EXIT LOOP
        start = m.start()
        if start >= searchto:
            break   # EXIT LOOP
        match = m.group(0)
        end = start + len(match)
        c = match[0]
        if c not in "#'\"":
            # Must have matched a keyword.
            if start <> searchfrom:
                # there's still a redundant char before and after it, strip!
                match = match[1:-1]
                start = start + 1
            else:
                # this is the first keyword in the text.
                # Only a space at the end.
                match = match[:-1]
            end = end - 1
            tags_append((keywordTag, start, end, None))
            # If this was a defining keyword, look ahead to the
            # following identifier.
            if match in ["def", "class"]:
                m = idSearch(pytext, end)
                if m is not None:
                    start = m.start()
                    if start == end:
                        match = m.group(0)
                        end = start + len(match)
                        tags_append((identifierTag, start, end, None))
        elif c == "#":
            tags_append((commentTag, start, end, None))
        else:
            tags_append((stringTag, start, end, None))
    return tags


def test(path):
    f = open(path)
    text = f.read()
    f.close()
    tags = fontify(text)
    for tag, start, end, sublist in tags:
        print tag, `text[start:end]`
