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from validator.contextgenerator import ContextGenerator


class ChromeManifest(object):
    """This class enables convenient parsing and iteration of
chrome.manifest files."""

    def __init__(self, data, path):
        self.context = ContextGenerator(data)
        self.lines = data.split("\n")

        # Extract the data from the triples in the manifest
        triples = []
        counter = 0

        for line in self.lines:
            line = line.strip()

            counter += 1

            # Skip weird lines.
            if line.startswith("#"):
                continue

            triple = line.split(None, 2)
            if not triple:
                continue
            elif len(triple) == 2:
                triple.append("")
            if len(triple) < 3:
                continue

            triples.append({"subject": triple[0],
                            "predicate": triple[1],
                            "object": triple[2],
                            "line": counter,
                            "filename": path,
                            "context": self.context})

        self.triples = triples

    def get_value(self, subject=None, predicate=None, object_=None):
        """Returns the first triple value matching the given subject,
predicate, and/or object"""

        for triple in self.triples:

            # Filter out non-matches
            if (subject and triple["subject"] != subject) or \
               (predicate and triple["predicate"] != predicate) or \
               (object_ and triple["object"] != object_): # pragma: no cover
                continue

            # Return the first found.
            return triple

        return None

    def get_objects(self, subject=None, predicate=None):
        """Returns a generator of objects that correspond to the
specified subjects and predicates."""

        for triple in self.triples:

            # Filter out non-matches
            if (subject and
                triple["subject"] != subject) or \
               (predicate and
                triple["predicate"] != predicate): # pragma: no cover
                continue

            yield triple["object"]

    def get_triples(self, subject=None, predicate=None, object_=None):
        """Returns triples that correspond to the specified subject,
predicates, and objects."""

        for triple in self.triples:

            # Filter out non-matches
            if subject is not None and triple["subject"] != subject:
                continue
            if predicate is not None and triple["predicate"] != predicate:
                continue
            if object_ is not None and triple["object"] != object_:
                continue

            yield triple

    def get_applicable_overlays(self, error_bundle):
        """
Given an error bundle, a list of overlays that are present in the
current package or subpackage are returned.
"""

        content_paths = self.get_triples(subject="content")
        if not content_paths:
            return set()

        # Create some variables that will store where the applicable content
        # instruction path references and where it links to.
        chrome_path = ""
        content_root_path = "/"

        # Look through each of the listed packages and paths.
        for path in content_paths:
            chrome_name = path["predicate"]
            if not path["object"]:
                continue
            path_location = path["object"].strip().split()[0]

            # Handle jarred paths differently.
            if path_location.startswith("jar:"):
                if not error_bundle.is_nested_package():
                    continue

                # Parse out the JAR and it's location within the chrome.
                split_jar_url = path_location[4:].split("!", 2)
                # Ignore invalid/unsupported JAR URLs.
                if len(split_jar_url) != 2:
                    continue

                # Unpack the JAR URL.
                jar_path, package_path = split_jar_url

                # Ignore the instruction if the JAR it points to doesn't match
                # up with the current subpackage tree.
                if jar_path != error_bundle.package_stack[0]:
                    continue
                chrome_path = self._url_chunk_join(chrome_name, package_path)
                # content_root_path stays at the default: /

                break
            else:
                # If we're in a subpackage, a content instruction referring to
                # the root of the package obviously doesn't apply.
                if error_bundle.is_nested_package():
                    continue

                chrome_path = self._url_chunk_join(chrome_name, "content")
                content_root_path = "/%s/" % path_location.strip("/")
                break

        if not chrome_path:
            return set()

        applicable_overlays = set()
        chrome_path = "chrome://%s" % self._url_chunk_join(chrome_path + "/")

        for overlay in self.get_triples(subject="overlay"):
            if not overlay["object"]:
                error_bundle.error(
                    err_id=("chromemanifest", "get_applicable_overalys",
                            "object"),
                    error="Overlay instruction missing a property.",
                    description="When overlays are registered in a chrome "
                                "manifest file, they require a namespace and "
                                "a chrome URL at minimum.",
                    filename=overlay["filename"],
                    line=overlay["line"],
                    context=self.context) #TODO(basta): Update this!
                continue
            overlay_url = overlay["object"].split()[0]
            if overlay_url.startswith(chrome_path):
                overlay_relative_path = overlay_url[len(chrome_path):]
                applicable_overlays.add("/%s" %
                        self._url_chunk_join(content_root_path,
                                             overlay_relative_path))

        return applicable_overlays

    def reverse_lookup(self, state, path):
        """
Returns a chrome URL for a given path, given the current package depth
in an error bundle.

State may either be an error bundle or the actual package stack.
"""

        # Make sure the path starts with a forward slash.
        if not path.startswith("/"):
            path = "/%s" % path

        # If the state is an error bundle, extract the package stack.
        if not isinstance(state, list):
            state = state.package_stack

        content_paths = self.get_triples(subject="content")
        for content_path in content_paths:
            chrome_name = content_path["predicate"]
            if not content_path["object"]:
                continue
            path_location = content_path["object"].split()[0]

            if path_location.startswith("jar:"):
                if not state:
                    continue

                # Parse out the JAR and it's location within the chrome.
                split_jar_url = path_location[4:].split("!", 2)
                # Ignore invalid/unsupported JAR URLs.
                if len(split_jar_url) != 2:
                    continue

                # Unpack the JAR URL.
                jar_path, package_path = split_jar_url

                if jar_path != state[0]:
                    continue

                return "chrome://%s" % self._url_chunk_join(chrome_name,
                                                            package_path,
                                                            path)
            else:
                if state:
                    continue

                path_location = "/%s/" % path_location.strip("/")
                if not path.startswith(path_location):
                    continue

                sliced_path = "/%s" % path[len(path_location):]

                return "chrome://%s" % self._url_chunk_join(chrome_name,
                                                            sliced_path)

        return None

    def _url_chunk_join(self, *args):
        """Join the arguments together to form a predictable URL chunk."""
        # Strip slashes from either side of each path piece.
        pathlets = map(lambda s: s.strip("/"), args)
        # Remove empty pieces.
        pathlets = filter(None, pathlets)
        url = "/".join(pathlets)
        # If this is a directory, add a trailing slash.
        if args[-1].endswith("/"):
            url = "%s/" % url
        return url

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