import type { TimelineEvent, TimelineToken } from "atom.io"

import {
	ingestAtomUpdateEvent,
	ingestCreationEvent,
	ingestDisposalEvent,
	ingestSelectorUpdateEvent,
	ingestTransactionOutcomeEvent,
} from "../events/index.ts"
import type { Store } from "../store/index.ts"

export function timeTravel(
	store: Store,
	action: `redo` | `undo`,
	token: TimelineToken<any>,
): void {
	store.logger.info(
		action === `redo` ? `⏩` : `⏪`,
		`timeline`,
		token.key,
		action,
	)
	const timelineData = store.timelines.get(token.key)
	if (!timelineData) {
		store.logger.error(
			`🐞`,
			`timeline`,
			token.key,
			`Failed to ${action}. This timeline has not been initialized.`,
		)
		return
	}

	if (
		(action === `redo` && timelineData.at === timelineData.history.length) ||
		(action === `undo` && timelineData.at === 0)
	) {
		store.logger.warn(
			`💁`,
			`timeline`,
			token.key,
			`Failed to ${action} at the ${
				action === `redo` ? `end` : `beginning`
			} of timeline "${token.key}". There is nothing to ${action}.`,
		)
		return
	}

	timelineData.timeTraveling = action === `redo` ? `into_future` : `into_past`
	let nextIndex = timelineData.at
	let events: TimelineEvent<any>[]
	switch (action) {
		case `undo`:
			--nextIndex
			while (
				nextIndex !== 0 &&
				timelineData.history[nextIndex].checkpoint !== true
			) {
				--nextIndex
			}
			events = timelineData.history.slice(nextIndex, timelineData.at).reverse()

			break
		case `redo`:
			++nextIndex
			events = timelineData.history.slice(timelineData.at, nextIndex)
	}
	timelineData.at = nextIndex

	const applying = action === `redo` ? `newValue` : `oldValue`

	for (const event of events) {
		switch (event.type) {
			case `atom_creation`: {
				ingestCreationEvent(store, event, applying)
				break
			}
			case `atom_disposal`: {
				ingestDisposalEvent(store, event, applying)
				break
			}
			case `atom_update`: {
				ingestAtomUpdateEvent(store, event, applying)
				break
			}
			case `selector_update`: {
				ingestSelectorUpdateEvent(store, event, applying)
				break
			}
			case `transaction_outcome`: {
				ingestTransactionOutcomeEvent(store, event, applying)
				break
			}
		}
	}

	timelineData.subject.next({
		type: `timeline_update`,
		event: action,
		at: timelineData.at,
		length: timelineData.history.length,
	})
	timelineData.timeTraveling = null
	store.logger.info(
		`⏸️`,
		`timeline`,
		token.key,
		`"${token.key}" is now at ${timelineData.at} / ${timelineData.history.length}`,
	)
}