Change and draft types

import type {
  GanttBeforeChangeHandler,
  GanttChangeType,
  GanttDependencyChange,
  GanttReorderChange,
  GanttTaskChange,
  GanttTaskDraft,
} from '@jaeungkim/gantt-chart';

/** What a gesture is about to write */
export type GanttChangeType = 'move' | 'resize' | 'progress';

/**
 * The mutation a finished gesture wants to commit
 *
 * Handed to `onBeforeTaskChange` before anything is written, so a host can send it to a
 * server and answer with a veto.
 */
export interface GanttTaskChange {
  type: GanttChangeType;
  /** The bar the user grabbed */
  task: Task;
  /** Only the tasks this gesture rewrites - dragging a summary bar carries its whole subtree */
  changedTasks: Task[];
  /** Those same tasks as they were before the gesture, in the same order */
  previousTasks: Task[];
  /** The full array the chart would hand to `onTasksChange` */
  tasks: Task[];
  /** Which edge moved - `resize` only */
  edge?: 'start' | 'end';
}

/**
 * Runs before a gesture is committed and can cancel it
 *
 * Returning `false`, a promise resolving to `false`, or a rejected promise rolls the bar
 * back to where it started. Anything else commits. While the promise is pending the bar
 * stays where it was dropped, so the UI never blocks on the round trip.
 */
export type GanttBeforeChangeHandler = (
  change: GanttTaskChange
) => boolean | void | Promise<boolean | void>;

/**
 * What a row drag committed - everything needed to persist the move
 *
 * Returning `false` from the callback cancels the drop: nothing is written to the chart and
 * `onTasksChange` does not fire.
 */
export interface GanttReorderChange {
  /** The moved task, already carrying its new parentId and sequence */
  task: Task;
  /** The new parent (null = root) */
  parentId: string | null;
  /** The parent the task had in the incoming data, untouched by normalization */
  previousParentId: string | null;
  /** Zero-based position among the new parent's children */
  index: number;
  /** The moved task's new dotted sequence */
  sequence: string;
  /** The whole updated array - the same one onTasksChange receives */
  tasks: Task[];
}

/** The link the user drew, handed to `onDependencyCreate` before anything is committed */
export interface GanttDependencyChange {
  /** Task the drag started on */
  predecessorId: string;
  /** Task the drag was dropped on - the one whose `dependencies` gains the entry */
  successorId: string;
  type: DependencyType;
}

/** The task the user drew, handed to `onTaskCreate` - nothing is committed by the chart */
export interface GanttTaskDraft {
  /** UTC ISO string, snapped to the current scale */
  startDate: string;
  endDate: string;
  /** Id of the task whose row the range was drawn on, null when the row has none */
  rowTaskId: string | null;
}