import ast
import codegen
import logging
import os.path
import bb.utils, bb.data
from itertools import chain
from pysh import pyshyacc, pyshlex, sherrors


logger = logging.getLogger('BitBake.CodeParser')
PARSERCACHE_VERSION = 2

try:
    import cPickle as pickle
except ImportError:
    import pickle
    logger.info('Importing cPickle failed.  Falling back to a very slow implementation.')


def check_indent(codestr):
    """If the code is indented, add a top level piece of code to 'remove' the indentation"""

    i = 0
    while codestr[i] in ["\n", "\t", " "]:
        i = i + 1

    if i == 0:
        return codestr

    if codestr[i-1] == "\t" or codestr[i-1] == " ":
        return "if 1:\n" + codestr

    return codestr

pythonparsecache = {}
shellparsecache = {}

def parser_cachefile(d):
    cachedir = (bb.data.getVar("PERSISTENT_DIR", d, True) or
                bb.data.getVar("CACHE", d, True))
    if cachedir in [None, '']:
        return None
    bb.utils.mkdirhier(cachedir)
    cachefile = os.path.join(cachedir, "bb_codeparser.dat")
    logger.debug(1, "Using cache in '%s' for codeparser cache", cachefile)
    return cachefile

def parser_cache_init(d):
    global pythonparsecache
    global shellparsecache

    cachefile = parser_cachefile(d)
    if not cachefile:
        return

    try:
        p = pickle.Unpickler(file(cachefile, "rb"))
        data, version = p.load()
    except:
        return

    if version != PARSERCACHE_VERSION:
        return

    pythonparsecache = data[0]
    shellparsecache = data[1]

def parser_cache_save(d):
    cachefile = parser_cachefile(d)
    if not cachefile:
        return

    lf = bb.utils.lockfile(cachefile + ".lock")

    try:
        p = pickle.Unpickler(file(cachefile, "rb"))
        data, version = p.load()
    except IOError, EOFError:
        data, version = None, None

    if version == PARSERCACHE_VERSION:
        for h in data[0]:
            if h not in pythonparsecache:
                pythonparsecache[h] = data[0][h]
        for h in data[1]:
            if h not in pythonparsecache:
                shellparsecache[h] = data[1][h]

    p = pickle.Pickler(file(cachefile, "wb"), -1)
    p.dump([[pythonparsecache, shellparsecache], PARSERCACHE_VERSION])
    bb.utils.unlockfile(lf)

class PythonParser():
    class ValueVisitor():
        """Visitor to traverse a python abstract syntax tree and obtain
        the variables referenced via bitbake metadata APIs, and the external
        functions called.
        """

        getvars = ("d.getVar", "bb.data.getVar", "data.getVar")
        expands = ("d.expand", "bb.data.expand", "data.expand")
        execs = ("bb.build.exec_func", "bb.build.exec_task")

        @classmethod
        def _compare_name(cls, strparts, node):
            """Given a sequence of strings representing a python name,
            where the last component is the actual Name and the prior
            elements are Attribute nodes, determine if the supplied node
            matches.
            """

            if not strparts:
                return True

            current, rest = strparts[0], strparts[1:]
            if isinstance(node, ast.Attribute):
                if current == node.attr:
                    return cls._compare_name(rest, node.value)
            elif isinstance(node, ast.Name):
                if current == node.id:
                    return True
            return False

        @classmethod
        def compare_name(cls, value, node):
            """Convenience function for the _compare_node method, which
            can accept a string (which is split by '.' for you), or an
            iterable of strings, in which case it checks to see if any of
            them match, similar to isinstance.
            """

            if isinstance(value, basestring):
                return cls._compare_name(tuple(reversed(value.split("."))),
                                         node)
            else:
                return any(cls.compare_name(item, node) for item in value)

        def __init__(self, value):
            self.var_references = set()
            self.var_execs = set()
            self.direct_func_calls = set()
            self.var_expands = set()
            self.value = value

        @classmethod
        def warn(cls, func, arg):
            """Warn about calls of bitbake APIs which pass a non-literal
            argument for the variable name, as we're not able to track such
            a reference.
            """

            try:
                funcstr = codegen.to_source(func)
                argstr = codegen.to_source(arg)
            except TypeError:
                logger.debug(2, 'Failed to convert function and argument to source form')
            else:
                logger.debug(1, "Warning: in call to '%s', argument '%s' is "
                                "not a literal", funcstr, argstr)

        def visit_Call(self, node):
            if self.compare_name(self.getvars, node.func):
                if isinstance(node.args[0], ast.Str):
                    self.var_references.add(node.args[0].s)
                else:
                    self.warn(node.func, node.args[0])
            elif self.compare_name(self.expands, node.func):
                if isinstance(node.args[0], ast.Str):
                    self.warn(node.func, node.args[0])
                    self.var_expands.update(node.args[0].s)
                elif isinstance(node.args[0], ast.Call) and \
                     self.compare_name(self.getvars, node.args[0].func):
                    pass
                else:
                    self.warn(node.func, node.args[0])
            elif self.compare_name(self.execs, node.func):
                if isinstance(node.args[0], ast.Str):
                    self.var_execs.add(node.args[0].s)
                else:
                    self.warn(node.func, node.args[0])
            elif isinstance(node.func, ast.Name):
                self.direct_func_calls.add(node.func.id)
            elif isinstance(node.func, ast.Attribute):
                # We must have a qualified name.  Therefore we need
                # to walk the chain of 'Attribute' nodes to determine
                # the qualification.
                attr_node = node.func.value
                identifier = node.func.attr
                while isinstance(attr_node, ast.Attribute):
                    identifier = attr_node.attr + "." + identifier
                    attr_node = attr_node.value
                if isinstance(attr_node, ast.Name):
                    identifier = attr_node.id + "." + identifier
                self.direct_func_calls.add(identifier)

    def __init__(self):
        #self.funcdefs = set()
        self.execs = set()
        #self.external_cmds = set()
        self.references = set()

    def parse_python(self, node):

        h = hash(str(node))

        if h in pythonparsecache:
            self.references = pythonparsecache[h]["refs"]
            self.execs = pythonparsecache[h]["execs"]
            return

        code = compile(check_indent(str(node)), "<string>", "exec",
                       ast.PyCF_ONLY_AST)

        visitor = self.ValueVisitor(code)
        for n in ast.walk(code):
            if n.__class__.__name__ == "Call":
                visitor.visit_Call(n)

        self.references.update(visitor.var_references)
        self.references.update(visitor.var_execs)
        self.execs = visitor.direct_func_calls

        pythonparsecache[h] = {}
        pythonparsecache[h]["refs"] = self.references
        pythonparsecache[h]["execs"] = self.execs

class ShellParser():
    def __init__(self):
        self.funcdefs = set()
        self.allexecs = set()
        self.execs = set()

    def parse_shell(self, value):
        """Parse the supplied shell code in a string, returning the external
        commands it executes.
        """

        h = hash(str(value))

        if h in shellparsecache:
            self.execs = shellparsecache[h]["execs"]
            return self.execs

        try:
            tokens, _ = pyshyacc.parse(value, eof=True, debug=False)
        except pyshlex.NeedMore:
            raise sherrors.ShellSyntaxError("Unexpected EOF")

        for token in tokens:
            self.process_tokens(token)
        self.execs = set(cmd for cmd in self.allexecs if cmd not in self.funcdefs)

        shellparsecache[h] = {}
        shellparsecache[h]["execs"] = self.execs

        return self.execs

    def process_tokens(self, tokens):
        """Process a supplied portion of the syntax tree as returned by
        pyshyacc.parse.
        """

        def function_definition(value):
            self.funcdefs.add(value.name)
            return [value.body], None

        def case_clause(value):
            # Element 0 of each item in the case is the list of patterns, and
            # Element 1 of each item in the case is the list of commands to be
            # executed when that pattern matches.
            words = chain(*[item[0] for item in value.items])
            cmds  = chain(*[item[1] for item in value.items])
            return cmds, words

        def if_clause(value):
            main = chain(value.cond, value.if_cmds)
            rest = value.else_cmds
            if isinstance(rest, tuple) and rest[0] == "elif":
                return chain(main, if_clause(rest[1]))
            else:
                return chain(main, rest)

        def simple_command(value):
            return None, chain(value.words, (assign[1] for assign in value.assigns))

        token_handlers = {
            "and_or": lambda x: ((x.left, x.right), None),
            "async": lambda x: ([x], None),
            "brace_group": lambda x: (x.cmds, None),
            "for_clause": lambda x: (x.cmds, x.items),
            "function_definition": function_definition,
            "if_clause": lambda x: (if_clause(x), None),
            "pipeline": lambda x: (x.commands, None),
            "redirect_list": lambda x: ([x.cmd], None),
            "subshell": lambda x: (x.cmds, None),
            "while_clause": lambda x: (chain(x.condition, x.cmds), None),
            "until_clause": lambda x: (chain(x.condition, x.cmds), None),
            "simple_command": simple_command,
            "case_clause": case_clause,
        }

        for token in tokens:
            name, value = token
            try:
                more_tokens, words = token_handlers[name](value)
            except KeyError:
                raise NotImplementedError("Unsupported token type " + name)

            if more_tokens:
                self.process_tokens(more_tokens)

            if words:
                self.process_words(words)

    def process_words(self, words):
        """Process a set of 'words' in pyshyacc parlance, which includes
        extraction of executed commands from $() blocks, as well as grabbing
        the command name argument.
        """

        words = list(words)
        for word in list(words):
            wtree = pyshlex.make_wordtree(word[1])
            for part in wtree:
                if not isinstance(part, list):
                    continue

                if part[0] in ('`', '$('):
                    command = pyshlex.wordtree_as_string(part[1:-1])
                    self.parse_shell(command)

                    if word[0] in ("cmd_name", "cmd_word"):
                        if word in words:
                            words.remove(word)

        usetoken = False
        for word in words:
            if word[0] in ("cmd_name", "cmd_word") or \
               (usetoken and word[0] == "TOKEN"):
                if "=" in word[1]:
                    usetoken = True
                    continue

                cmd = word[1]
                if cmd.startswith("$"):
                    logger.debug(1, "Warning: execution of non-literal "
                                    "command '%s'", cmd)
                elif cmd == "eval":
                    command = " ".join(word for _, word in words[1:])
                    self.parse_shell(command)
                else:
                    self.allexecs.add(cmd)
                break
