import itertools

import Util
from ShCommands import Command, Pipeline, Seq

class ShLexer:
    def __init__(self, data, win32Escapes = False):
        self.data = data
        self.pos = 0
        self.end = len(data)
        self.win32Escapes = win32Escapes

    def eat(self):
        c = self.data[self.pos]
        self.pos += 1
        return c

    def look(self):
        return self.data[self.pos]

    def maybe_eat(self, c):
        """
        maybe_eat(c) - Consume the character c if it is the next character,
        returning True if a character was consumed. """
        if self.data[self.pos] == c:
            self.pos += 1
            return True
        return False

    def lex_arg_fast(self, c):
        # Get the leading whitespace free section.
        chunk = self.data[self.pos - 1:].split(None, 1)[0]
        
        # If it has special characters, the fast path failed.
        if ('|' in chunk or '&' in chunk or 
            '<' in chunk or '>' in chunk or
            "'" in chunk or '"' in chunk or
            '\\' in chunk):
            return None
        
        self.pos = self.pos - 1 + len(chunk)
        return chunk
        
    def lex_arg_slow(self, c):
        if c in "'\"":
            str = self.lex_arg_quoted(c)
        else:
            str = c
        while self.pos != self.end:
            c = self.look()
            if c.isspace() or c in "|&":
                break
            elif c in '><':
                # This is an annoying case; we treat '2>' as a single token so
                # we don't have to track whitespace tokens.

                # If the parse string isn't an integer, do the usual thing.
                if not str.isdigit():
                    break

                # Otherwise, lex the operator and convert to a redirection
                # token.
                num = int(str)
                tok = self.lex_one_token()
                assert isinstance(tok, tuple) and len(tok) == 1
                return (tok[0], num)                    
            elif c == '"':
                self.eat()
                str += self.lex_arg_quoted('"')
            elif not self.win32Escapes and c == '\\':
                # Outside of a string, '\\' escapes everything.
                self.eat()
                if self.pos == self.end:
                    Util.warning("escape at end of quoted argument in: %r" % 
                                 self.data)
                    return str
                str += self.eat()
            else:
                str += self.eat()
        return str

    def lex_arg_quoted(self, delim):
        str = ''
        while self.pos != self.end:
            c = self.eat()
            if c == delim:
                return str
            elif c == '\\' and delim == '"':
                # Inside a '"' quoted string, '\\' only escapes the quote
                # character and backslash, otherwise it is preserved.
                if self.pos == self.end:
                    Util.warning("escape at end of quoted argument in: %r" % 
                                 self.data)
                    return str
                c = self.eat()
                if c == '"': # 
                    str += '"'
                elif c == '\\':
                    str += '\\'
                else:
                    str += '\\' + c
            else:
                str += c
        Util.warning("missing quote character in %r" % self.data)
        return str
    
    def lex_arg_checked(self, c):
        pos = self.pos
        res = self.lex_arg_fast(c)
        end = self.pos

        self.pos = pos
        reference = self.lex_arg_slow(c)
        if res is not None:
            if res != reference:
                raise ValueError,"Fast path failure: %r != %r" % (res, reference)
            if self.pos != end:
                raise ValueError,"Fast path failure: %r != %r" % (self.pos, end)
        return reference
        
    def lex_arg(self, c):
        return self.lex_arg_fast(c) or self.lex_arg_slow(c)
        
    def lex_one_token(self):
        """
        lex_one_token - Lex a single 'sh' token. """

        c = self.eat()
        if c in ';!':
            return (c,)
        if c == '|':
            if self.maybe_eat('|'):
                return ('||',)
            return (c,)
        if c == '&':
            if self.maybe_eat('&'):
                return ('&&',)
            if self.maybe_eat('>'): 
                return ('&>',)
            return (c,)
        if c == '>':
            if self.maybe_eat('&'):
                return ('>&',)
            if self.maybe_eat('>'):
                return ('>>',)
            return (c,)
        if c == '<':
            if self.maybe_eat('&'):
                return ('<&',)
            if self.maybe_eat('>'):
                return ('<<',)
            return (c,)

        return self.lex_arg(c)

    def lex(self):
        while self.pos != self.end:
            if self.look().isspace():
                self.eat()
            else:
                yield self.lex_one_token()

###
 
class ShParser:
    def __init__(self, data, win32Escapes = False):
        self.data = data
        self.tokens = ShLexer(data, win32Escapes = win32Escapes).lex()
    
    def lex(self):
        try:
            return self.tokens.next()
        except StopIteration:
            return None
    
    def look(self):
        next = self.lex()
        if next is not None:
            self.tokens = itertools.chain([next], self.tokens)
        return next
    
    def parse_command(self):
        tok = self.lex()
        if not tok:
            raise ValueError,"empty command!"
        if isinstance(tok, tuple):
            raise ValueError,"syntax error near unexpected token %r" % tok[0]
        
        args = [tok]
        redirects = []
        while 1:
            tok = self.look()

            # EOF?
            if tok is None:
                break

            # If this is an argument, just add it to the current command.
            if isinstance(tok, str):
                args.append(self.lex())
                continue

            # Otherwise see if it is a terminator.
            assert isinstance(tok, tuple)
            if tok[0] in ('|',';','&','||','&&'):
                break
            
            # Otherwise it must be a redirection.
            op = self.lex()
            arg = self.lex()
            if not arg:
                raise ValueError,"syntax error near token %r" % op[0]
            redirects.append((op, arg))

        return Command(args, redirects)

    def parse_pipeline(self):
        negate = False
        if self.look() == ('!',):
            self.lex()
            negate = True

        commands = [self.parse_command()]
        while self.look() == ('|',):
            self.lex()
            commands.append(self.parse_command())
        return Pipeline(commands, negate)
            
    def parse(self):
        lhs = self.parse_pipeline()

        while self.look():
            operator = self.lex()
            assert isinstance(operator, tuple) and len(operator) == 1

            if not self.look():
                raise ValueError, "missing argument to operator %r" % operator[0]
            
            # FIXME: Operator precedence!!
            lhs = Seq(lhs, operator[0], self.parse_pipeline())

        return lhs

###

import unittest

class TestShLexer(unittest.TestCase):
    def lex(self, str, *args, **kwargs):
        return list(ShLexer(str, *args, **kwargs).lex())

    def test_basic(self):
        self.assertEqual(self.lex('a|b>c&d<e'),
                         ['a', ('|',), 'b', ('>',), 'c', ('&',), 'd', 
                          ('<',), 'e'])

    def test_redirection_tokens(self):
        self.assertEqual(self.lex('a2>c'),
                         ['a2', ('>',), 'c'])
        self.assertEqual(self.lex('a 2>c'),
                         ['a', ('>',2), 'c'])
        
    def test_quoting(self):
        self.assertEqual(self.lex(""" 'a' """),
                         ['a'])
        self.assertEqual(self.lex(""" "hello\\"world" """),
                         ['hello"world'])
        self.assertEqual(self.lex(""" "hello\\'world" """),
                         ["hello\\'world"])
        self.assertEqual(self.lex(""" "hello\\\\world" """),
                         ["hello\\world"])
        self.assertEqual(self.lex(""" he"llo wo"rld """),
                         ["hello world"])
        self.assertEqual(self.lex(""" a\\ b a\\\\b """),
                         ["a b", "a\\b"])
        self.assertEqual(self.lex(""" "" "" """),
                         ["", ""])
        self.assertEqual(self.lex(""" a\\ b """, win32Escapes = True),
                         ['a\\', 'b'])

class TestShParse(unittest.TestCase):
    def parse(self, str):
        return ShParser(str).parse()

    def test_basic(self):
        self.assertEqual(self.parse('echo hello'),
                         Pipeline([Command(['echo', 'hello'], [])], False))
        self.assertEqual(self.parse('echo ""'),
                         Pipeline([Command(['echo', ''], [])], False))

    def test_redirection(self):
        self.assertEqual(self.parse('echo hello > c'),
                         Pipeline([Command(['echo', 'hello'], 
                                           [((('>'),), 'c')])], False))
        self.assertEqual(self.parse('echo hello > c >> d'),
                         Pipeline([Command(['echo', 'hello'], [(('>',), 'c'),
                                                     (('>>',), 'd')])], False))
        self.assertEqual(self.parse('a 2>&1'),
                         Pipeline([Command(['a'], [(('>&',2), '1')])], False))

    def test_pipeline(self):
        self.assertEqual(self.parse('a | b'),
                         Pipeline([Command(['a'], []),
                                   Command(['b'], [])],
                                  False))

        self.assertEqual(self.parse('a | b | c'),
                         Pipeline([Command(['a'], []),
                                   Command(['b'], []),
                                   Command(['c'], [])],
                                  False))

        self.assertEqual(self.parse('! a'),
                         Pipeline([Command(['a'], [])],
                                  True))

    def test_list(self):        
        self.assertEqual(self.parse('a ; b'),
                         Seq(Pipeline([Command(['a'], [])], False),
                             ';',
                             Pipeline([Command(['b'], [])], False)))

        self.assertEqual(self.parse('a & b'),
                         Seq(Pipeline([Command(['a'], [])], False),
                             '&',
                             Pipeline([Command(['b'], [])], False)))

        self.assertEqual(self.parse('a && b'),
                         Seq(Pipeline([Command(['a'], [])], False),
                             '&&',
                             Pipeline([Command(['b'], [])], False)))

        self.assertEqual(self.parse('a || b'),
                         Seq(Pipeline([Command(['a'], [])], False),
                             '||',
                             Pipeline([Command(['b'], [])], False)))

        self.assertEqual(self.parse('a && b || c'),
                         Seq(Seq(Pipeline([Command(['a'], [])], False),
                                 '&&',
                                 Pipeline([Command(['b'], [])], False)),
                             '||',
                             Pipeline([Command(['c'], [])], False)))

if __name__ == '__main__':
    unittest.main()