55 lines
1.7 KiB
TypeScript
55 lines
1.7 KiB
TypeScript
/**
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* Pure math utilities for timeline drag operations.
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* Extracted from useTimelineDrag to make the conversion logic testable
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* and reusable across different drag modes.
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*/
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/** Convert a pixel delta to a number of whole days based on cell width. */
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export function pixelsToDays(deltaX: number, cellWidth: number): number {
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if (!Number.isFinite(cellWidth) || cellWidth <= 0) {
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return 0;
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}
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return Math.round(deltaX / cellWidth);
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}
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/**
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* Shift a date by a given number of days, returning a new Date.
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* Does not mutate the input.
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*/
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export function shiftDate(date: Date, daysDelta: number): Date {
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const result = new Date(date);
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result.setDate(result.getDate() + daysDelta);
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return result;
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}
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/**
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* Compute new start/end dates for a drag operation.
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* Handles move, resize-start, and resize-end modes with clamping
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* to prevent start from crossing past end (or vice versa).
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*/
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export function computeDragDates(
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mode: "move" | "resize-start" | "resize-end",
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originalStart: Date,
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originalEnd: Date,
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daysDelta: number,
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): { start: Date; end: Date } {
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const newStart = new Date(originalStart);
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const newEnd = new Date(originalEnd);
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if (mode === "move") {
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newStart.setDate(newStart.getDate() + daysDelta);
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newEnd.setDate(newEnd.getDate() + daysDelta);
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} else if (mode === "resize-start") {
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newStart.setDate(newStart.getDate() + daysDelta);
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// Clamp: allow same-day but prevent crossing
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if (newStart > newEnd) newStart.setTime(newEnd.getTime());
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} else {
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// resize-end
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newEnd.setDate(newEnd.getDate() + daysDelta);
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// Clamp: allow same-day but prevent crossing
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if (newEnd < newStart) newEnd.setTime(newStart.getTime());
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}
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return { start: newStart, end: newEnd };
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}
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