import { useContext, useMemo, useSyncExternalStore } from 'react'
import { type FocusMove, type SelectionState, shiftAnchor } from '../../core/selection.js'
import StdinContext from '../components/StdinContext.js'
import instances from '../instances.js'

/**
 * Access to text selection operations on the Ink instance (fullscreen only).
 * Returns no-op functions when fullscreen mode is disabled.
 */
export function useSelection(): {
	copySelection: () => string
	copySelectionNoClear: () => string
	clearSelection: () => void
	hasSelection: () => boolean
	getState: () => SelectionState | null
	subscribe: (cb: () => void) => () => void
	shiftAnchor: (dRow: number, minRow: number, maxRow: number) => void
	shiftSelection: (dRow: number, minRow: number, maxRow: number) => void
	moveFocus: (move: FocusMove) => void
	captureScrolledRows: (firstRow: number, lastRow: number, side: 'above' | 'below') => void
	setSelectionBgColor: (color: string) => void
} {
	useContext(StdinContext)
	const ink = instances.get(process.stdout)
	return useMemo(() => {
		if (!ink) {
			return {
				copySelection: () => '',
				copySelectionNoClear: () => '',
				clearSelection: () => {},
				hasSelection: () => false,
				getState: () => null,
				subscribe: () => () => {},
				shiftAnchor: () => {},
				shiftSelection: () => {},
				moveFocus: () => {},
				captureScrolledRows: () => {},
				setSelectionBgColor: () => {},
			}
		}
		return {
			copySelection: () => ink.copySelection(),
			copySelectionNoClear: () => ink.copySelectionNoClear(),
			clearSelection: () => ink.clearTextSelection(),
			hasSelection: () => ink.hasTextSelection(),
			getState: () => ink.selection,
			subscribe: (cb: () => void) => ink.subscribeToSelectionChange(cb),
			shiftAnchor: (dRow: number, minRow: number, maxRow: number) =>
				shiftAnchor(ink.selection, dRow, minRow, maxRow),
			shiftSelection: (dRow: number, minRow: number, maxRow: number) =>
				ink.shiftSelectionForScroll(dRow, minRow, maxRow),
			moveFocus: (move: FocusMove) => ink.moveSelectionFocus(move),
			captureScrolledRows: (firstRow: number, lastRow: number, side: 'above' | 'below') =>
				ink.captureScrolledRows(firstRow, lastRow, side),
			setSelectionBgColor: (color: string) => ink.setSelectionBgColor(color),
		}
	}, [ink])
}

const NO_SUBSCRIBE = () => () => {}
const ALWAYS_FALSE = () => false

/**
 * Reactive selection-exists state.
 */
export function useHasSelection(): boolean {
	useContext(StdinContext)
	const ink = instances.get(process.stdout)
	return useSyncExternalStore(
		ink ? ink.subscribeToSelectionChange : NO_SUBSCRIBE,
		ink ? ink.hasTextSelection : ALWAYS_FALSE,
	)
}