Textual Theme Manger

theme_manager.py

"""Theme manager for Textual"""

import os
from typing import Dict, List, Literal, Optional, TypeAlias

import simplejson as json
from textual.design import ColorSystem

ThemeMode: TypeAlias = Literal["dark", "light"]
ThemeModes: List[ThemeMode] = ["dark", "light"]
Theme: TypeAlias = Dict[ThemeMode, ColorSystem]
Themes: TypeAlias = Dict[str, Theme]


class InvalidThemeError(Exception):
    """Raised when an invalid theme is provided."""

    def __init__(self, theme_name: str):
        """Initialize the exception with the invalid theme name."""
        self.theme_name = theme_name
        super().__init__(f"Invalid theme: {theme_name}")


class ThemeModeError(InvalidThemeError):
    """Raised when a theme does not have at least one of 'dark' or 'light' modes."""

    def __init__(self, theme_name: str):
        """Initialize the exception with the invalid theme name."""
        super().__init__(
            f"Theme '{theme_name}' does not have at least one of 'dark' or 'light' modes."
        )


class ThemeManager:
    """Theme manager for Textual"""

    themes: Themes
    theme_folder: str

    def __init__(self, theme_folder: Optional[str] = None) -> None:
        """Initialize the theme manager"""
        self.theme_folder = theme_folder or f"{os.getcwd()}/parllama/themes"
        self.themes = self.load_themes()

    def load_theme(self, theme_name: str) -> Theme:
        """Load textual theme from json file"""
        theme: Theme = {}
        theme_name = os.path.basename(theme_name)
        with open(f"{self.theme_folder}/{theme_name}", "r", encoding="utf-8") as f:
            theme_def = json.load(f)
            if "dark" not in theme_def and "light" not in theme_def:
                raise ThemeModeError(theme_name)

            for mode in ThemeModes:
                if mode in theme_def:
                    theme[mode] = ColorSystem(**theme_def[mode])
        return theme

    def load_themes(self) -> Themes:
        """Load textual themes from json files"""
        themes: Themes = {}
        for file in os.listdir(self.theme_folder):
            if file.lower().endswith(".json"):
                theme_name = os.path.splitext(file)[0]
                themes[theme_name] = self.load_theme(f"{self.theme_folder}/{file}")
        return themes

    def get_theme(self, theme_name: str) -> Theme:
        """Get theme by name"""
        return self.themes[theme_name]

    def list_themes(self) -> List[str]:
        """Get list of themes"""
        return list(self.themes.keys())

    def theme_has_dark(self, theme_name: str) -> bool:
        """Check if theme has dark mode"""
        return "dark" in self.themes[theme_name]

    def theme_has_light(self, theme_name: str) -> bool:
        """Check if theme has light mode"""
        return "light" in self.themes[theme_name]

    def get_color_system_for_theme_mode(
        self, theme_name: str, dark: bool
    ) -> ColorSystem:
        """Get color system for theme mode"""
        theme = self.themes[theme_name]

        if dark:
            if "dark" in theme:
                return theme["dark"]
            return theme["light"]

        if "light" in theme:
            return theme["light"]
        return theme["dark"]

theme_manager = ThemeManager()

# use the following method in your App class
def get_css_variables(self) -> dict[str, str]:
    """Get a mapping of variables used to pre-populate CSS.

    May be implemented in a subclass to add new CSS variables.

    Returns:
        A mapping of variable name to value.
    """
    return theme_manager.get_color_system_for_theme_mode(
        self.theme, self.dark
    ).generate()

json theme files take the following format

{
  "dark": {
    "primary": "#e49500",
    "secondary": "#6e4800",
    "warning": "#ffa62b",
    "error": "#ba3c5b",
    "success": "#4EBF71",
    "accent": "#6e4800",
    "panel": "#111",
    "surface":"#1e1e1e",
    "background":"#121212",
    "dark": true
  },
  "light": {
    "primary": "#004578",
    "secondary": "#ffa62b",
    "warning": "#ffa62b",
    "error": "#ba3c5b",
    "success": "#4EBF71",
    "accent": "#0178D4",
    "background":"#efefef",
    "surface":"#f5f5f5",
    "dark": false
  }
}