'''
Generic combinatorial name-matching subsystem

Config files are expected to have names matching the following spec:

.. code-block:: sh

    <style>-<scheme>.<config_pathname>

- ``config_pathname``: refers to a concrete filename, typically that which is expected by
  the target app (e.g., ``kitty.conf``). In the context of ``config_map`` in the registry,
  however, it merely serves as an identifier, as it can be mapped onto any path.
- ``scheme``: indicates the lightness mode ("light" or "dark")
- ``style``: general identifier capturing the stylizations applied to the config file.
  This is typically of the form ``<variant>-<palette>``, i.e., including a reference to a
  particular color palette. 

For example

.. code-block:: sh

    soft-gruvbox-dark.kitty.conf

gets mapped to 

.. code-block:: sh

    style    -> "soft-gruvbox"
    scheme   -> "dark"
    pathname -> "kitty.conf"
'''
from pathlib import Path

from symconf import util


class FilePart:
    def __init__(self, path: str | Path):
        self.path = util.absolute_path(path)
        self.pathname = self.path.name

        parts = str(self.pathname).split('.')
        if len(parts) < 2:
            raise ValueError(f'Filename "{pathname}" incorrectly formatted, ignoring')

        self.theme = parts[0]
        self.conf  = '.'.join(parts[1:])

        theme_split = self.theme.split('-')
        self.scheme = theme_split[-1]
        self.style  = '-'.join(theme_split[:-1])

        self.index = -1

    def set_index(self, idx: int):
        self.index = idx


class Matcher:
    def get_file_parts(
        self, 
        paths: list[str | Path],
    ) -> list[FilePart]:
        '''
        Split pathnames into parts for matching.

        Pathnames should be of the format

        .. code-block:: sh

            <style>-<scheme>.<config_pathname>

        where ``style`` is typically itself of the form ``<variant>-<palette>``.
        '''
        file_parts = []
        for path in paths:
            try:
                config_file = FilePart(path)
                file_parts.append(config_file)
            except ValueError as e:
                print(f'Filename "{pathname}" incorrectly formatted, ignoring')

        return file_parts

    def prefix_order(
        self, 
        scheme,
        style,
        strict=False,
    ) -> list[tuple[str, str]]:
        '''
        Determine the order of concrete config pathname parts to match, given the
        ``scheme`` and ``style`` inputs.

        There is a unique preferred match order when ``style``, ``scheme``, both, or none
        are ``any``. In general, when ``any`` is provided for a given factor, it is
        best matched by a config file that expresses indifference under that factor.
        '''
        # explicit cases are the most easily managed here, even if a little redundant
        if strict:
            theme_order = [
                (style, scheme),
            ]
        else:
            # inverse order of match relaxation; intention being to overwrite with
            # results from increasingly relevant groups given the conditions
            if style == 'any' and scheme == 'any':
                # prefer both be "none", with preference for specific scheme
                theme_order = [
                    (style , scheme),
                    (style , 'none'),
                    ('none'  , scheme),
                    ('none'  , 'none'),
                ]
            elif style == 'any':
                # prefer style to be "none", then specific, then relax specific scheme
                # to "none"
                theme_order = [
                    (style , 'none'),
                    ('none'  , 'none'),
                    (style , scheme),
                    ('none'  , scheme),
                ]
            elif scheme == 'any':
                # prefer scheme to be "none", then specific, then relax specific style
                # to "none"
                theme_order = [
                    ('none'  , scheme),
                    ('none'  , 'none'),
                    (style , scheme),
                    (style , 'none'),
                ]
            else:
                # neither component is any; prefer most specific
                theme_order = [
                    ('none'  , 'none'),
                    ('none'  , scheme),
                    (style , 'none'),
                    (style , scheme),
                ]

        return theme_order

    def match_paths(
        self, 
        paths: list[str | Path],
        prefix_order: list[tuple[str, str]],
    ) -> list[FilePart]:
        '''
        Find and return FilePart matches according to the provided prefix order.

        The prefix order specifies all valid style-scheme combos that can be considered as
        "consistent" with some user input (and is computed external to this method). For
        example, it could be

        .. code-block:: python

            [
                ('none', 'none')
                ('none', 'dark')
            ]

        indicating that either ``none-none.<config>`` or ``none-dark.<config>`` would be
        considered matching pathnames, with the latter being preferred.

        This method exists because we need a way to allow any of the combos in the prefix
        order to match the candidate files. We don't know a priori how good of a match
        will be available, so we consider each file for each of the prefixes, and take the
        latest/best match for each unique config pathname (allowing for a "soft" match).
        
        .. admonition:: Checking for matches

            When thinking about how best to structure this method, it initially felt like
            indexing factors of the FileParts would make the most sense, preventing the
            inner loop that needs to inspect each FilePart for each element of the prefix
            order. But indexing the file parts and checking against prefixes isn't so
            straightforward, as we'd still need to check matches by factor. For instance,
            if we index by style-scheme, either are allowed to be "any," so we'd need to
            check for the 4 valid combos and join the matching lists. If we index by both
            factors individually, we may have several files associated with a given key,
            and then need to coordinate the checks across both to ensure they belong to
            the same file.

            In any case, you should be able to do this in a way that's a bit more
            efficient, but the loop and the simple conditionals is just much simpler to
            follow. We're also talking about at most 10s of files, so it really doesn't
            matter.

        Parameters:
            pathnames:
            scheme:
            style:
            prefix_order:
            strict:
        '''
        file_parts = self.get_file_parts(paths)

        ordered_matches = []
        for i, (style_prefix, scheme_prefix) in enumerate(prefix_order):
            for fp in file_parts:
                style_match  = style_prefix == fp.style or style_prefix == 'any'
                scheme_match = scheme_prefix == fp.scheme or scheme_prefix == 'any'

                if style_match and scheme_match:
                    fp.set_index(i+1)
                    ordered_matches.append(fp)

        return ordered_matches

    def relaxed_match(
        self,
        match_list: list[FilePart]
    ) -> list[FilePart]:
        '''
        Isolate the best match in a match list and find its relaxed variants.

        This method allows us to use the ``match_paths()`` method for matching templates
        rather than direct user config files. In the latter case, we want to symlink the
        single best config file match for each stem, across all stems with matching
        prefixes (e.g., ``none-dark.config.a`` and ``solarized-dark.config.b`` have two
        separate stems with prefixes that could match ``scheme=dark, style=any`` query).
        We can find these files by just indexing the ``match_path`` outputs (i.e., all
        matches) by config pathname and taking the one that appears latest (under the
        prefix order) for each unique value.

        In the template matching case, we want only a single best file match, period
        (there's really no notion of "config stems," it's just the prefixes). Once that
        match has been found, we can then "relax" either the scheme or style (or both) to
        ``none``, and if the corresponding files exist, we use those as parts of the
        template keys. For example, if we match ``solarized-dark.toml``, we would also
        consider the values in ``none-dark.toml`` if available. The TOML values that are
        defined in the most specific (i.e., better under the prefix order) match are
        loaded "on top of" those less specific matches, overwriting keys when there's a
        conflict. ``none-dark.toml``, for instance, might define a general dark scheme
        background color, but a more specific definition in ``solarized-dark.toml`` would
        take precedent. These TOML files would be stacked before using the resulting
        dictionary to populate config templates.
        '''
        if not match_list:
            return []

        relaxed_map = {}
        match = match_list[-1]

        for fp in match_list:
            style_match  = fp.style  == match.style  or fp.style  == 'none'
            scheme_match = fp.scheme == match.scheme or fp.scheme == 'none'

            if style_match and scheme_match:
                relaxed_map[fp.pathname] = fp

        return list(relaxed_map.values())