from __future__ import generators
import sys
import inspect, tokenize
import py
cpy_compile = compile 

# DON'T IMPORT PY HERE

class Source(object):
    """ a mutable object holding a source code fragment,
        possibly deindenting it.
    """
    def __init__(self, *parts, **kwargs):
        self.lines = lines = []
        de = kwargs.get('deindent', True)
        rstrip = kwargs.get('rstrip', True) 
        for part in parts:
            if not part: 
                partlines = []
            if isinstance(part, Source):
                partlines = part.lines
            elif isinstance(part, (unicode, str)):
                partlines = part.split('\n')
                if rstrip:
                    while partlines: 
                        if partlines[-1].strip(): 
                            break
                        partlines.pop()
            else:
                partlines = getsource(part, deindent=de).lines
            if de:
                partlines = deindent(partlines)
            lines.extend(partlines)

    def __eq__(self, other): 
        try:
            return self.lines == other.lines 
        except AttributeError: 
            if isinstance(other, str): 
                return str(self) == other 
            return False 

    def __getitem__(self, key):
        if isinstance(key, int):
            return self.lines[key]
        else:
            if key.step not in (None, 1):
                raise IndexError("cannot slice a Source with a step")
            return self.__getslice__(key.start, key.stop)

    def __len__(self): 
        return len(self.lines) 

    def __getslice__(self, start, end):
        newsource = Source()
        newsource.lines = self.lines[start:end]
        return newsource

    def strip(self):
        """ return new source object with trailing
            and leading blank lines removed.
        """
        start, end = 0, len(self)
        while start < end and not self.lines[start].strip():
            start += 1
        while end > start and not self.lines[end-1].strip():
            end -= 1
        source = Source()
        source.lines[:] = self.lines[start:end]
        return source

    def putaround(self, before='', after='', indent=' ' * 4): 
        """ return a copy of the source object with 
            'before' and 'after' wrapped around it. 
        """
        before = Source(before)
        after = Source(after)
        newsource = Source()
        lines = [ (indent + line) for line in self.lines]
        newsource.lines = before.lines + lines +  after.lines
        return newsource

    def indent(self, indent=' ' * 4): 
        """ return a copy of the source object with 
            all lines indented by the given indent-string. 
        """
        newsource = Source()
        newsource.lines = [(indent+line) for line in self.lines]
        return newsource

    def getstatement(self, lineno):
        """ return Source statement which contains the
            given linenumber (counted from 0).
        """
        start, end = self.getstatementrange(lineno)
        return self[start:end]

    def getstatementrange(self, lineno):
        """ return (start, end) tuple which spans the minimal 
            statement region which containing the given lineno.
        """
        # XXX there must be a better than these heuristic ways ...
        # XXX there may even be better heuristics :-)
        if not (0 <= lineno < len(self)):
            raise IndexError("lineno out of range")

        # 1. find the start of the statement
        from codeop import compile_command
        for start in range(lineno, -1, -1):
            trylines = self.lines[start:lineno+1]
            # quick hack to indent the source and get it as a string in one go
            trylines.insert(0, 'def xxx():')
            trysource = '\n '.join(trylines)
            #              ^ space here
            try:
                compile_command(trysource)
            except (SyntaxError, OverflowError, ValueError):
                pass
            else:
                break   # got a valid or incomplete statement

        # 2. find the end of the statement
        for end in range(lineno+1, len(self)+1):
            trysource = self[start:end]
            if trysource.isparseable():
                break

        return start, end

    def getblockend(self, lineno):
        # XXX
        lines = [x + '\n' for x in self.lines[lineno:]]
        blocklines = inspect.getblock(lines)
        #print blocklines
        return lineno + len(blocklines) - 1

    def deindent(self, offset=None):
        """ return a new source object deindented by offset.
            If offset is None then guess an indentation offset from
            the first non-blank line.  Subsequent lines which have a
            lower indentation offset will be copied verbatim as
            they are assumed to be part of multilines.
        """
        # XXX maybe use the tokenizer to properly handle multiline
        #     strings etc.pp?
        newsource = Source()
        newsource.lines[:] = deindent(self.lines, offset)
        return newsource

    def isparseable(self, deindent=True):
        """ return True if source is parseable, heuristically
            deindenting it by default. 
        """
        import parser
        if deindent:
            source = str(self.deindent())
        else:
            source = str(self)
        try:
            parser.suite(source+'\n')
        except (parser.ParserError, SyntaxError):
            return False
        else:
            return True

    def __str__(self):
        return "\n".join(self.lines)

    def compile(self, filename=None, mode='exec',
                flag=generators.compiler_flag, dont_inherit=0):
        """ return compiled code object. if filename is None
            invent an artificial filename which displays
            the source/line position of the caller frame.
        """
        if not filename or py.path.local(filename).check(file=0): 
            frame = sys._getframe(1) # the caller
            filename = '%s<%s:%d>' % (filename, frame.f_code.co_filename,
                                      frame.f_lineno)
        source = "\n".join(self.lines) + '\n'
        try:
            co = cpy_compile(source, filename, mode, flag)
        except SyntaxError, ex:
            # re-represent syntax errors from parsing python strings
            msglines = self.lines[:ex.lineno]
            if ex.offset:
                msglines.append(" "*ex.offset + '^')
            msglines.append("syntax error probably generated here: %s" % filename)
            newex = SyntaxError('\n'.join(msglines))
            newex.offset = ex.offset
            newex.lineno = ex.lineno
            newex.text = ex.text
            raise newex
        else:
            co_filename = MyStr(filename)
            co_filename.__source__ = self
            return py.code.Code(co).new(rec=1, co_filename=co_filename) 
            #return newcode_withfilename(co, co_filename)

#
# public API shortcut functions
#

def compile_(source, filename=None, mode='exec', flags=
            generators.compiler_flag, dont_inherit=0):
    """ compile the given source to a raw code object,
        which points back to the source code through
        "co_filename.__source__".  All code objects
        contained in the code object will recursively
        also have this special subclass-of-string
        filename.
    """
    s = Source(source)
    co = s.compile(filename, mode, flags)
    return co


#
# various helper functions
#
class MyStr(str):
    """ custom string which allows to add attributes. """

def getsource(obj, **kwargs):
    if hasattr(obj, 'func_code'):
        obj = obj.func_code
    elif hasattr(obj, 'f_code'):
        obj = obj.f_code
    try:
        fullsource = obj.co_filename.__source__
    except AttributeError:
        try:
            strsrc = inspect.getsource(obj)
        except IndentationError:
            strsrc = "\"Buggy python version consider upgrading, cannot get source\""
        assert isinstance(strsrc, str)
        return Source(strsrc, **kwargs)
    else:
        lineno = obj.co_firstlineno - 1
        end = fullsource.getblockend(lineno)
        return fullsource[lineno:end+1]


def deindent(lines, offset=None):
    if offset is None:
        for line in lines:
            line = line.expandtabs()
            s = line.lstrip()
            if s:
                offset = len(line)-len(s)
                break
        else:
            offset = 0
    if offset == 0:
        return list(lines)
    newlines = []
    def readline_generator(lines):
        for line in lines:
            yield line + '\n'
        while True:
            yield ''
            
    readline = readline_generator(lines).next

    try:
        for _, _, (sline, _), (eline, _), _ in tokenize.generate_tokens(readline):
            if sline > len(lines):
                break # End of input reached
            if sline > len(newlines):
                line = lines[sline - 1].expandtabs()
                if line.lstrip() and line[:offset].isspace():
                    line = line[offset:] # Deindent
                newlines.append(line)

            for i in range(sline, eline):
                # Don't deindent continuing lines of
                # multiline tokens (i.e. multiline strings)
                newlines.append(lines[i])
    except (IndentationError, tokenize.TokenError):
        pass
    # Add any lines we didn't see. E.g. if an exception was raised.
    newlines.extend(lines[len(newlines):])
    return newlines
