# This file is part of Indico.
# Copyright (C) 2002 - 2021 CERN
#
# Indico is free software; you can redistribute it and/or
# modify it under the terms of the MIT License; see the
# LICENSE file for more details.

import string
from collections import namedtuple

from sqlalchemy.ext.declarative import declared_attr

from indico.core.db import db
from indico.util.decorators import strict_classproperty


class ColorTuple(namedtuple('ColorTuple', ('text', 'background'))):
    """A tuple that contains text and background color.

    Both colors are unified to 'rrggbb' notation (in case 'rgb' is
    passed) and leading ``#`` is stripped.

    When a text/background color is specifie, the other color needs
    to be specified too.  If no color is specified, the ColorTuple
    is falsy.
    """

    def __new__(cls, text, background):
        colors = [text or '', background or '']
        for i, color in enumerate(colors):
            if color.startswith('#'):
                color = color[1:]
            if len(color) == 3:
                color = ''.join(x * 2 for x in color)
            colors[i] = color.lower()
        if any(colors):
            if not all(colors):
                raise ValueError('Both colors must be specified')
            if not all(len(x) == 6 for x in colors):
                raise ValueError('Colors must be be `rgb` or `rrggbb`')
            if not all(c in string.hexdigits for color in colors for c in color):
                raise ValueError('Colors must only use hex digits')
        return super().__new__(cls, *colors)

    def __nonzero__(self):
        return all(self)

    @property
    def css(self):
        return f'color: #{self.text} !important; background: #{self.background} !important'


class ColorMixin:
    """Mixin to store text+background colors in a model.

    For convenience (e.g. for WTForms integrations when selecting both
    colors at the same time from a palette or in a compound field) it
    provides a `colors` property which returns/accepts a `ColorTuple`
    holding text color and background color.
    """

    #: Whether all objects must have a color set. Disallows removing
    #: color information and adds a CHECK constraint to ensure that
    #: the colors are set.  Otherwise there is only a CHECK to ensure
    #: that both or no colors are set.
    colors_required = True
    #: The default colors when not specifying anything.
    default_colors = None

    @strict_classproperty
    @classmethod
    def __auto_table_args(cls):
        checks = [db.CheckConstraint("(text_color = '') = (background_color = '')", 'both_or_no_colors')]
        if cls.colors_required:
            checks.append(db.CheckConstraint("text_color != '' AND background_color != ''", 'colors_not_empty'))
        return tuple(checks)

    @declared_attr
    def text_color(cls):
        return db.Column(
            db.String,
            nullable=False,
            default='' if not cls.default_colors else cls.default_colors[0]
        )

    @declared_attr
    def background_color(cls):
        return db.Column(
            db.String,
            nullable=False,
            default='' if not cls.default_colors else cls.default_colors[1]
        )

    @property
    def colors(self):
        """The current set of colors or None if no colors are set."""
        colors = ColorTuple(self.text_color, self.background_color)
        return colors or self.default_colors

    @colors.setter
    def colors(self, value):
        if value is None:
            value = '', ''
        self.text_color, self.background_color = ColorTuple(*value)
