Mini Shell

"""Object representations for debugging purposes. Unlike the default
repr, these expose more information and produce HTML instead of ASCII.

Together with the CSS and JavaScript of the debugger this gives a
colorful and more compact output.
"""
import codecs
import re
import sys
import typing as t
from collections import deque
from html import escape
from traceback import format_exception_only

missing = object()
_paragraph_re = re.compile(r"(?:\r\n|\r|\n){2,}")
RegexType = type(_paragraph_re)

HELP_HTML = """\
<div class=box>
  <h3>%(title)s</h3>
  <pre class=help>%(text)s</pre>
</div>\
"""
OBJECT_DUMP_HTML = """\
<div class=box>
  <h3>%(title)s</h3>
  %(repr)s
  <table>%(items)s</table>
</div>\
"""


def debug_repr(obj: object) -> str:
    """Creates a debug repr of an object as HTML string."""
    return DebugReprGenerator().repr(obj)


def dump(obj: object = missing) -> None:
    """Print the object details to stdout._write (for the interactive
    console of the web debugger.
    """
    gen = DebugReprGenerator()
    if obj is missing:
        rv = gen.dump_locals(sys._getframe(1).f_locals)
    else:
        rv = gen.dump_object(obj)
    sys.stdout._write(rv)  # type: ignore


class _Helper:
    """Displays an HTML version of the normal help, for the interactive
    debugger only because it requires a patched sys.stdout.
    """

    def __repr__(self) -> str:
        return "Type help(object) for help about object."

    def __call__(self, topic: t.Optional[t.Any] = None) -> None:
        if topic is None:
            sys.stdout._write(f"<span class=help>{self!r}</span>")  # type: ignore
            return
        import pydoc

        pydoc.help(topic)
        rv = sys.stdout.reset()  # type: ignore
        if isinstance(rv, bytes):
            rv = rv.decode("utf-8", "ignore")
        paragraphs = _paragraph_re.split(rv)
        if len(paragraphs) > 1:
            title = paragraphs[0]
            text = "\n\n".join(paragraphs[1:])
        else:
            title = "Help"
            text = paragraphs[0]
        sys.stdout._write(HELP_HTML % {"title": title, "text": text})  # type: ignore


helper = _Helper()


def _add_subclass_info(
    inner: str, obj: object, base: t.Union[t.Type, t.Tuple[t.Type, ...]]
) -> str:
    if isinstance(base, tuple):
        for base in base:
            if type(obj) is base:
                return inner
    elif type(obj) is base:
        return inner
    module = ""
    if obj.__class__.__module__ not in ("__builtin__", "exceptions"):
        module = f'<span class="module">{obj.__class__.__module__}.</span>'
    return f"{module}{type(obj).__name__}({inner})"


def _sequence_repr_maker(
    left: str, right: str, base: t.Type, limit: int = 8
) -> t.Callable[["DebugReprGenerator", t.Iterable, bool], str]:
    def proxy(self: "DebugReprGenerator", obj: t.Iterable, recursive: bool) -> str:
        if recursive:
            return _add_subclass_info(f"{left}...{right}", obj, base)
        buf = [left]
        have_extended_section = False
        for idx, item in enumerate(obj):
            if idx:
                buf.append(", ")
            if idx == limit:
                buf.append('<span class="extended">')
                have_extended_section = True
            buf.append(self.repr(item))
        if have_extended_section:
            buf.append("</span>")
        buf.append(right)
        return _add_subclass_info("".join(buf), obj, base)

    return proxy


class DebugReprGenerator:
    def __init__(self) -> None:
        self._stack: t.List[t.Any] = []

    list_repr = _sequence_repr_maker("[", "]", list)
    tuple_repr = _sequence_repr_maker("(", ")", tuple)
    set_repr = _sequence_repr_maker("set([", "])", set)
    frozenset_repr = _sequence_repr_maker("frozenset([", "])", frozenset)
    deque_repr = _sequence_repr_maker(
        '<span class="module">collections.</span>deque([', "])", deque
    )

    def regex_repr(self, obj: t.Pattern) -> str:
        pattern = repr(obj.pattern)
        pattern = codecs.decode(pattern, "unicode-escape", "ignore")  # type: ignore
        pattern = f"r{pattern}"
        return f're.compile(<span class="string regex">{pattern}</span>)'

    def string_repr(self, obj: t.Union[str, bytes], limit: int = 70) -> str:
        buf = ['<span class="string">']
        r = repr(obj)

        # shorten the repr when the hidden part would be at least 3 chars
        if len(r) - limit > 2:
            buf.extend(
                (
                    escape(r[:limit]),
                    '<span class="extended">',
                    escape(r[limit:]),
                    "</span>",
                )
            )
        else:
            buf.append(escape(r))

        buf.append("</span>")
        out = "".join(buf)

        # if the repr looks like a standard string, add subclass info if needed
        if r[0] in "'\"" or (r[0] == "b" and r[1] in "'\""):
            return _add_subclass_info(out, obj, (bytes, str))

        # otherwise, assume the repr distinguishes the subclass already
        return out

    def dict_repr(
        self,
        d: t.Union[t.Dict[int, None], t.Dict[str, int], t.Dict[t.Union[str, int], int]],
        recursive: bool,
        limit: int = 5,
    ) -> str:
        if recursive:
            return _add_subclass_info("{...}", d, dict)
        buf = ["{"]
        have_extended_section = False
        for idx, (key, value) in enumerate(d.items()):
            if idx:
                buf.append(", ")
            if idx == limit - 1:
                buf.append('<span class="extended">')
                have_extended_section = True
            buf.append(
                f'<span class="pair"><span class="key">{self.repr(key)}</span>:'
                f' <span class="value">{self.repr(value)}</span></span>'
            )
        if have_extended_section:
            buf.append("</span>")
        buf.append("}")
        return _add_subclass_info("".join(buf), d, dict)

    def object_repr(
        self, obj: t.Optional[t.Union[t.Type[dict], t.Callable, t.Type[list]]]
    ) -> str:
        r = repr(obj)
        return f'<span class="object">{escape(r)}</span>'

    def dispatch_repr(self, obj: t.Any, recursive: bool) -> str:
        if obj is helper:
            return f'<span class="help">{helper!r}</span>'
        if isinstance(obj, (int, float, complex)):
            return f'<span class="number">{obj!r}</span>'
        if isinstance(obj, str) or isinstance(obj, bytes):
            return self.string_repr(obj)
        if isinstance(obj, RegexType):
            return self.regex_repr(obj)
        if isinstance(obj, list):
            return self.list_repr(obj, recursive)
        if isinstance(obj, tuple):
            return self.tuple_repr(obj, recursive)
        if isinstance(obj, set):
            return self.set_repr(obj, recursive)
        if isinstance(obj, frozenset):
            return self.frozenset_repr(obj, recursive)
        if isinstance(obj, dict):
            return self.dict_repr(obj, recursive)
        if isinstance(obj, deque):
            return self.deque_repr(obj, recursive)
        return self.object_repr(obj)

    def fallback_repr(self) -> str:
        try:
            info = "".join(format_exception_only(*sys.exc_info()[:2]))
        except Exception:
            info = "?"
        return (
            '<span class="brokenrepr">'
            f"&lt;broken repr ({escape(info.strip())})&gt;</span>"
        )

    def repr(self, obj: object) -> str:
        recursive = False
        for item in self._stack:
            if item is obj:
                recursive = True
                break
        self._stack.append(obj)
        try:
            try:
                return self.dispatch_repr(obj, recursive)
            except Exception:
                return self.fallback_repr()
        finally:
            self._stack.pop()

    def dump_object(self, obj: object) -> str:
        repr = None
        items: t.Optional[t.List[t.Tuple[str, str]]] = None

        if isinstance(obj, dict):
            title = "Contents of"
            items = []
            for key, value in obj.items():
                if not isinstance(key, str):
                    items = None
                    break
                items.append((key, self.repr(value)))
        if items is None:
            items = []
            repr = self.repr(obj)
            for key in dir(obj):
                try:
                    items.append((key, self.repr(getattr(obj, key))))
                except Exception:
                    pass
            title = "Details for"
        title += f" {object.__repr__(obj)[1:-1]}"
        return self.render_object_dump(items, title, repr)

    def dump_locals(self, d: t.Dict[str, t.Any]) -> str:
        items = [(key, self.repr(value)) for key, value in d.items()]
        return self.render_object_dump(items, "Local variables in frame")

    def render_object_dump(
        self, items: t.List[t.Tuple[str, str]], title: str, repr: t.Optional[str] = None
    ) -> str:
        html_items = []
        for key, value in items:
            html_items.append(f"<tr><th>{escape(key)}<td><pre class=repr>{value}</pre>")
        if not html_items:
            html_items.append("<tr><td><em>Nothing</em>")
        return OBJECT_DUMP_HTML % {
            "title": escape(title),
            "repr": f"<pre class=repr>{repr if repr else ''}</pre>",
            "items": "\n".join(html_items),
        }