app/theme.py

"""Single source of truth for OncoDSL viewer presentation.

Holds the MSI palette + order used by every chart, and registers (and enables) a
custom Altair theme `oncodsl` for a calm, consistent chart look. Importing this
module is enough to activate the theme.
"""

from __future__ import annotations

import altair as alt

# MSI-H is the warm highlight; MSS recedes into a cool grey-blue. Indeterminate
# and NA are quieter neutrals so they don't compete for attention.
MSI_COLORS: dict[str, str] = {
    "MSI-H":             "#BC6B2E",
    "MSI-Indeterminate": "#A7B6BE",
    "MSS":               "#6E7F8C",
    "NA":                "#D9D5CE",
}

MSI_ORDER: list[str] = ["MSI-H", "MSI-Indeterminate", "MSS", "NA"]

# Single muted colour for charts that aren't split by MSI.
MUTED: str = "#6E7F8C"

_FONT = "Helvetica Neue, Helvetica, Arial, sans-serif"


def _oncodsl_theme() -> dict:
    return {
        "config": {
            "background": "transparent",
            "view": {"stroke": None},
            "axis": {
                "gridColor":    "#ECEAE4",
                "domainColor":  "#D8D5CE",
                "tickColor":    "#D8D5CE",
                "labelColor":   "#5A6670",
                "titleColor":   "#23303A",
                "labelFontSize": 12,
                "titleFontSize": 12,
                "labelFont":    _FONT,
                "titleFont":    _FONT,
            },
            "legend": {
                "labelColor": "#5A6670",
                "titleColor": "#23303A",
                "labelFont":  _FONT,
                "titleFont":  _FONT,
                "labelFontSize": 12,
                "titleFontSize": 12,
            },
            "title": {
                "color":    "#23303A",
                "font":     _FONT,
                "fontSize": 13,
            },
        }
    }


def msi_color_scale(*, include_na: bool = True) -> alt.Scale:
    """An Altair colour scale that maps every MSI bucket to its themed colour."""
    domain = MSI_ORDER if include_na else [k for k in MSI_ORDER if k != "NA"]
    return alt.Scale(domain=domain, range=[MSI_COLORS[k] for k in domain])


# Register + enable on import.
alt.themes.register("oncodsl", _oncodsl_theme)
alt.themes.enable("oncodsl")