/** Inactive and active hex shades of one colour in one theme. */
export interface IPaletteEntry {
    inactive: string;
    active: string;
}
/** Shades per colour id for a single theme. */
export type ThemePalette = {
    [colourId: string]: IPaletteEntry;
};
/** The full palette: shades for both themes. */
export interface IPalette {
    light: ThemePalette;
    dark: ThemePalette;
}
/** Divider contrast magnitude selectable in settings. */
export type DividerContrast = 'low' | 'medium' | 'high';
/**
 * Target contrast ratio per magnitude. Retuned one notch subtler after live
 * use (the 1.1.14 ladder read too strong): high is the original 4.0:1
 * strength, medium the WCAG non-text minimum, and low a deliberate hairline
 * BELOW that floor - the divider is an aesthetic aid, not text, so subtlety
 * on explicit user choice outranks the guideline. Must stay identical to the
 * dividerContrast enum in schema/plugin.json - the anti-drift test pins the
 * two together.
 */
export declare const CONTRAST_TARGETS: {
    [K in DividerContrast]: number;
};
/**
 * The value if it is a known contrast magnitude, otherwise 'medium'. Guards
 * the raw settings value the same way mergePalette guards the palette.
 * Membership is derived from CONTRAST_TARGETS so a new magnitude added there
 * is accepted without touching this guard.
 *
 * @param value - the raw dividerContrast value from the setting registry
 */
export declare function asDividerContrast(value: unknown): DividerContrast;
/**
 * The canonical palette. Must stay identical to the variable values in
 * style/base.css and the settings schema defaults - the anti-drift test in
 * src/__tests__/dynamicStyle.spec.ts pins all three copies together.
 */
export declare const DEFAULT_PALETTE: IPalette;
/**
 * Deep-merge user settings data over DEFAULT_PALETTE, field by field.
 *
 * A user value replaces the default only when it is a 6-digit hex string;
 * anything else (missing, malformed, wrong type) leaves that field's default
 * in place. Unknown colour keys are ignored. Never throws, whatever shape the
 * settings hand over.
 *
 * @param user - the raw palette value from the setting registry
 */
export declare function mergePalette(user: unknown): IPalette;
/**
 * The CSS for the injected style element: variable redefinitions for both
 * themes and, when enabled, the same-colour divider rules.
 *
 * The divider grey is computed from the palette at runtime (never hardcoded)
 * so user palette edits keep their contrast: darker than the tab colour in the
 * light theme, brighter in the dark theme, targeting the configured ratio
 * (CONTRAST_TARGETS[contrast]) against the inactive shade only - the divider
 * separates pairs of inactive tabs, never the active tab (DEF-7).
 *
 * @param palette - the merged palette to emit
 * @param dynamicDivider - whether to emit the divider rules
 * @param contrast - divider contrast magnitude; default 'medium' (3.0:1)
 */
export declare function buildDynamicCss(palette: IPalette, dynamicDivider: boolean, contrast?: DividerContrast): string;
/**
 * Upsert the injected <style id="jp-colourful-tab-dynamic-style"> element in
 * <head> and set its content. No-op outside a browser (node-env jest).
 *
 * @param css - the stylesheet content, as built by buildDynamicCss
 */
export declare function applyDynamicStyle(css: string): void;