/**
 * Hysteretic music-state selector: turns a continuous intensity signal (nearby threat,
 * alert count, chase proximity) into a stable theme id. The engine can already crossfade
 * a soundtrack; this decides *when*, without the flapping a bare threshold produces when
 * one enemy walks in and out of range.
 */
export interface MusicTier {
    id: string;
    /** Theme id passed to `ctx.game.audio.music`; null silences the soundtrack in this tier. */
    theme: string | null;
    /** Intensity at or above which this tier may be entered. */
    enter: number;
    /** Minimum time in this tier before it may drop to a lower one. Default 0. */
    holdMs?: number;
}
/** The tier ladder plus the release margin that keeps a hovering intensity from flapping between tiers. */
export interface MusicStateConfig {
    /** Ordered or unordered; the highest `enter` at or below the intensity wins. */
    tiers: readonly MusicTier[];
    /** Intensity must fall this far below a tier's `enter` before leaving it. Default 0.2. */
    release?: number;
}
/** Which tier is playing and when it was entered, on the caller's clock. Serialisable. */
export interface MusicStateSnapshot {
    tierId: string | null;
    /** Timestamp the current tier was entered, on the caller's clock. */
    sinceMs: number;
}
/** The current intensity signal and clock reading for one resolve. */
export interface MusicStateInput {
    intensity: number;
    nowMs: number;
}
/** Next state, the theme that should be playing, and whether this advance is the one that changed it. */
export interface MusicStateResult {
    state: MusicStateSnapshot;
    theme: string | null;
    /** True only on the advance the tier changed — the caller's cue to crossfade. */
    changed: boolean;
}
/** Fresh state with no tier entered, so the first resolve always settles and reports `changed`. */
export declare function createMusicState(): MusicStateSnapshot;
/**
 * Pick the theme for the current intensity. Escalation is immediate; de-escalation waits for the
 * tier's `holdMs` and needs the intensity to fall a `release` margin below the tier it is leaving.
 */
export declare function resolveMusicState(state: MusicStateSnapshot, input: MusicStateInput, config: MusicStateConfig): MusicStateResult;