markdown_it/ruler.py

"""
class Ruler

Helper class, used by [[MarkdownIt#core]], [[MarkdownIt#block]] and
[[MarkdownIt#inline]] to manage sequences of functions (rules):

- keep rules in defined order
- assign the name to each rule
- enable/disable rules
- add/replace rules
- allow assign rules to additional named chains (in the same)
- cacheing lists of active rules

You will not need use this class directly until write plugins. For simple
rules control use [[MarkdownIt.disable]], [[MarkdownIt.enable]] and
[[MarkdownIt.use]].
"""
from typing import Callable, Dict, List, Optional, Union
import attr


class StateBase:
    def __init__(self, src: str, md, env):
        self.src = src
        self.env = env
        self.md = md


RuleFunc = Callable[[StateBase], None]


@attr.s(slots=True)
class Rule:
    name: str = attr.ib()
    enabled: bool = attr.ib()
    fn: RuleFunc = attr.ib(repr=False)
    alt: List[str] = attr.ib()


class Ruler:
    def __init__(self):
        # List of added rules.
        self.__rules__: List[Rule] = []
        # Cached rule chains.
        # First level - chain name, '' for default.
        # Second level - diginal anchor for fast filtering by charcodes.
        self.__cache__: Optional[Dict[str, RuleFunc]] = None

    def __find__(self, name: str) -> int:
        """Find rule index by name"""
        for i, rule in enumerate(self.__rules__):
            if rule.name == name:
                return i
        return -1

    def __compile__(self):
        """Build rules lookup cache"""
        chains = {""}
        # collect unique names
        for rule in self.__rules__:
            if not rule.enabled:
                continue
            for name in rule.alt:
                chains.add(name)
        self.__cache__ = {}
        for chain in chains:
            self.__cache__[chain] = []
            for rule in self.__rules__:
                if not rule.enabled:
                    continue
                if chain and (chain not in rule.alt):
                    continue
                self.__cache__[chain].append(rule.fn)

    def at(self, ruleName: str, fn: RuleFunc, options=None):
        """Replace rule by name with new function & options.

        :param name: rule name to replace.
        :param fn: new rule function.
        :param options: new rule options (not mandatory).
        :raises: KeyError if name not found
        """
        index = self.__find__(ruleName)
        options = options or {}
        if index == -1:
            raise KeyError(f"Parser rule not found: {ruleName}")
        self.__rules__[index].fn = fn
        self.__rules__[index].alt = options["alt"] or []
        self.__cache__ = None

    def before(self, beforeName: str, ruleName: str, fn: RuleFunc, options=None):
        """Add new rule to chain before one with given name.

        :param beforeName: new rule will be added before this one.
        :param ruleName: new rule will be added before this one.
        :param fn: new rule function.
        :param options: new rule options (not mandatory).
        :raises: KeyError if name not found
        """
        index = self.__find__(beforeName)
        options = options or {}
        if index == -1:
            raise KeyError(f"Parser rule not found: {beforeName}")
        self.__rules__.insert(index, Rule(ruleName, True, fn, options.get("alt", [])))
        self.__cache__ = None

    def after(self, afterName: str, ruleName: str, fn: RuleFunc, options=None):
        """Add new rule to chain after one with given name.

        :param beforeName: new rule will be added before this one.
        :param ruleName: new rule will be added before this one.
        :param fn: new rule function.
        :param options: new rule options (not mandatory).
        :raises: KeyError if name not found
        """
        index = self.__find__(afterName)
        options = options or {}
        if index == -1:
            raise KeyError(f"Parser rule not found: {afterName}")
        self.__rules__.insert(
            index + 1, Rule(ruleName, True, fn, options.get("alt", []))
        )
        self.__cache__ = None

    def push(self, ruleName: str, fn: RuleFunc, options=None):
        """Push new rule to the end of chain.

        :param ruleName: new rule will be added before this one.
        :param fn: new rule function.
        :param options: new rule options (not mandatory).

        """
        self.__rules__.append(Rule(ruleName, True, fn, (options or {}).get("alt", [])))
        self.__cache__ = None

    def enable(self, names: Union[str, List[str]], ignoreInvalid: bool = False):
        """Enable rules with given names.

        :param names: name or list of rule names to enable.
        :param ignoreInvalid: ignore errors when rule not found
        :raises: KeyError if name not found and not ignoreInvalid
        :return: list of found rule names
        """
        if isinstance(names, str):
            names = [names]
        result = []
        for name in names:
            idx = self.__find__(name)
            if (idx < 0) and ignoreInvalid:
                continue
            if (idx < 0) and not ignoreInvalid:
                raise KeyError(f"Rules manager: invalid rule name {name}")
            self.__rules__[idx].enabled = True
            result.append(name)
        self.__cache__ = None
        return result

    def enableOnly(self, names: Union[str, List[str]], ignoreInvalid: bool = False):
        """Enable rules with given names, and disable everything else.

        :param names: name or list of rule names to enable.
        :param ignoreInvalid: ignore errors when rule not found
        :raises: KeyError if name not found and not ignoreInvalid
        :return: list of found rule names
        """
        if isinstance(names, str):
            names = [names]
        for rule in self.__rules__:
            rule.enabled = False
        self.enable(names, ignoreInvalid)

    def disable(self, names: Union[str, List[str]], ignoreInvalid: bool = False):
        """Disable rules with given names.

        :param names: name or list of rule names to enable.
        :param ignoreInvalid: ignore errors when rule not found
        :raises: KeyError if name not found and not ignoreInvalid
        :return: list of found rule names
        """
        if isinstance(names, str):
            names = [names]
        result = []
        for name in names:
            idx = self.__find__(name)
            if (idx < 0) and ignoreInvalid:
                continue
            if (idx < 0) and not ignoreInvalid:
                raise KeyError(f"Rules manager: invalid rule name {name}")
            self.__rules__[idx].enabled = False
            result.append(name)
        self.__cache__ = None
        return result

    def getRules(self, chainName: str) -> List[RuleFunc]:
        """Return array of active functions (rules) for given chain name.
        It analyzes rules configuration, compiles caches if not exists and returns result.

        Default chain name is `''` (empty string). It can't be skipped.
        That's done intentionally, to keep signature monomorphic for high speed.

        """
        if self.__cache__ is None:
            self.__compile__()
        # Chain can be empty, if rules disabled. But we still have to return Array.
        return self.__cache__.get(chainName, []) or []

    def get_active_rules(self) -> List[str]:
        """Return the active rule names."""
        return [r.name for r in self.__rules__ if r.enabled]