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import type { Bookmark, TimelineTrack } from "@/lib/timeline";
import { TIMELINE_CONSTANTS } from "@/constants/timeline-constants";
import { BOOKMARK_TIME_EPSILON } from "@/lib/timeline/bookmarks";
import { getElementKeyframes } from "@/lib/animation";
export interface SnapPoint {
time: number;
type: "element-start" | "element-end" | "playhead" | "bookmark" | "keyframe";
elementId?: string;
trackId?: string;
}
export interface SnapResult {
snappedTime: number;
snapPoint: SnapPoint | null;
snapDistance: number;
}
const DEFAULT_SNAP_THRESHOLD_PX = 10;
export function findSnapPoints({
tracks,
playheadTime,
excludeElementId,
bookmarks = [],
excludeBookmarkTime,
enableElementSnapping = true,
enablePlayheadSnapping = true,
enableBookmarkSnapping = true,
enableKeyframeSnapping = true,
}: {
tracks: Array<TimelineTrack>;
playheadTime: number;
excludeElementId?: string;
bookmarks?: Array<Bookmark>;
excludeBookmarkTime?: number;
enableElementSnapping?: boolean;
enablePlayheadSnapping?: boolean;
enableBookmarkSnapping?: boolean;
enableKeyframeSnapping?: boolean;
}): SnapPoint[] {
const snapPoints: SnapPoint[] = [];
for (const track of tracks) {
for (const element of track.elements) {
if (element.id === excludeElementId) continue;
if (enableElementSnapping) {
snapPoints.push(
{
time: element.startTime,
type: "element-start",
elementId: element.id,
trackId: track.id,
},
{
time: element.startTime + element.duration,
type: "element-end",
elementId: element.id,
trackId: track.id,
},
);
}
if (enableKeyframeSnapping) {
for (const keyframe of getElementKeyframes({
animations: element.animations,
})) {
snapPoints.push({
time: element.startTime + keyframe.time,
type: "keyframe",
elementId: element.id,
trackId: track.id,
});
}
}
}
}
if (enablePlayheadSnapping) {
snapPoints.push({ time: playheadTime, type: "playhead" });
}
if (enableBookmarkSnapping) {
for (const bookmark of bookmarks) {
if (
excludeBookmarkTime != null &&
Math.abs(bookmark.time - excludeBookmarkTime) < BOOKMARK_TIME_EPSILON
) {
continue;
}
snapPoints.push({ time: bookmark.time, type: "bookmark" });
}
}
return snapPoints;
}
export function snapToNearestPoint({
targetTime,
snapPoints,
zoomLevel,
snapThreshold = DEFAULT_SNAP_THRESHOLD_PX,
}: {
targetTime: number;
snapPoints: Array<SnapPoint>;
zoomLevel: number;
snapThreshold?: number;
}): SnapResult {
const pixelsPerSecond = TIMELINE_CONSTANTS.PIXELS_PER_SECOND * zoomLevel;
const thresholdInSeconds = snapThreshold / pixelsPerSecond;
let closestSnapPoint: SnapPoint | null = null;
let closestDistance = Infinity;
for (const snapPoint of snapPoints) {
const distance = Math.abs(targetTime - snapPoint.time);
if (distance < thresholdInSeconds && distance < closestDistance) {
closestDistance = distance;
closestSnapPoint = snapPoint;
}
}
return {
snappedTime: closestSnapPoint ? closestSnapPoint.time : targetTime,
snapPoint: closestSnapPoint,
snapDistance: closestDistance,
};
}
export function snapElementEdge({
targetTime,
elementDuration,
tracks,
playheadTime,
zoomLevel,
excludeElementId,
snapToStart = true,
bookmarks = [],
}: {
targetTime: number;
elementDuration: number;
tracks: Array<TimelineTrack>;
playheadTime: number;
zoomLevel: number;
excludeElementId?: string;
snapToStart?: boolean;
bookmarks?: Array<Bookmark>;
}): SnapResult {
const snapPoints = findSnapPoints({
tracks,
playheadTime,
excludeElementId,
bookmarks,
});
const effectiveTargetTime = snapToStart
? targetTime
: targetTime + elementDuration;
const snapResult = snapToNearestPoint({
targetTime: effectiveTargetTime,
snapPoints,
zoomLevel,
});
if (!snapToStart && snapResult.snapPoint) {
snapResult.snappedTime = snapResult.snappedTime - elementDuration;
}
return snapResult;
}
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