/**
 * Pure UTC calendar projections for the lane timeline.
 *
 * The year fold gives every month equal screen width, then divides that cell
 * by the month's maximum Gregorian day count. This aligns wall dates across
 * years and leaves an implicit Feb 29 ghost gap in common years. The accepted
 * trade-off is that one day is slightly wider in February than in January.
 */
export type FoldProjection = {
    rowKey: string;
    rowIndex: number;
    rowLabel: string;
    phase0: number;
    phase1: number;
    ghost?: boolean;
};
export interface TemporalProjector {
    readonly id: string;
    project(tMs: number): FoldProjection | null;
}
export type CalendarPrecisionUnit = "year" | "month" | "day" | "hour" | "minute";
/** Source precision, kept distinct from the event's representative instant. */
export type TemporalPrecision = {
    readonly kind: "calendar";
    readonly unit: CalendarPrecisionUnit;
} | {
    readonly kind: "uncertainty";
    readonly beforeYears: number;
    readonly afterYears: number;
};
export type PrecisionEvent = {
    readonly tMs?: unknown;
    readonly precision?: TemporalPrecision;
};
export type PrecisionWindow = readonly [startMs: number, endMs: number];
export type FoldWindowFragment = {
    rowIndex: number;
    phase0: number;
    phase1: number;
    full: boolean;
};
export type FoldId = "millennium" | "century" | "decade" | "year" | "month" | "week" | "day" | "hour";
/**
 * Return an event's exact timestamp after applying ECMAScript Date's TimeClip.
 * Approximate `y` coordinates deliberately have no fallback here: calendar
 * folds must not invent a month or day from a years-before-present value.
 */
export declare function evTimestampMs(event: unknown): number | null;
/**
 * Construct the half-open UTC calendar cycle containing an event's instant.
 * Epistemic uncertainty deliberately returns null: it remains on the
 * continuous axis and must not acquire invented calendar coordinates.
 */
export declare function precisionWindow(event: PrecisionEvent): PrecisionWindow | null;
/**
 * UTC year fold with twelve equal-width month cells. Each cell uses the
 * month's maximum Gregorian day count, keeping wall dates aligned across
 * years and leaving a ghost Feb 29 slot in common years.
 */
export declare const foldYearProjector: TemporalProjector;
/** Decimal year folds; rows contain 10 years, 10 decades, or 10 centuries. */
export declare const foldDecadeProjector: TemporalProjector;
export declare const foldCenturyProjector: TemporalProjector;
export declare const foldMillenniumProjector: TemporalProjector;
/** month fold: one row per calendar month, 31 max-day slots */
export declare const foldMonthProjector: TemporalProjector;
/** week fold: one row per Monday-start UTC week, 7 weekday slots.
 *  Rows are keyed by their Monday's date (avoids ISO week-year edge cases). */
export declare const foldWeekProjector: TemporalProjector;
/** day fold: one row per UTC date, 24 hour slots */
export declare const foldDayProjector: TemporalProjector;
/** hour fold: one row per UTC hour, 60 minute slots */
export declare const foldHourProjector: TemporalProjector;
/**
 * Project a half-open instant window into consecutive fold-row fragments.
 * The caller owns viewport clipping and must bound wide windows before using
 * a fine fold; this pure helper intentionally has no internal row cap.
 * Invalid, empty, or partially unrepresentable windows are rejected as an
 * empty fragment list.
 */
export declare function projectWindow(foldId: FoldId, startMs: number, endMs: number): FoldWindowFragment[];
/** the start instant of a fold row — inverse of project()'s rowIndex */
export declare function foldRowStartMs(foldId: string, rowIndex: number): number;
/** nominal period length of a fold row (ms) — for scale-continuous mapping */
export declare const FOLD_PERIOD_MS: Record<string, number>;
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