import { Section } from '../types'

const MAX_HISTORY = 50

export interface UndoRedoState {
  past: Section[][]
  present: Section[]
  future: Section[][]
}

export function createUndoRedoState(initial: Section[]): UndoRedoState {
  return {
    past: [],
    present: initial,
    future: [],
  }
}

export function pushState(state: UndoRedoState, next: Section[]): UndoRedoState {
  const past = [...state.past, state.present]
  if (past.length > MAX_HISTORY) {
    past.shift()
  }
  return {
    past,
    present: next,
    future: [],
  }
}

export function undo(state: UndoRedoState): UndoRedoState {
  if (state.past.length === 0) return state
  const previous = state.past[state.past.length - 1]
  const newPast = state.past.slice(0, -1)
  return {
    past: newPast,
    present: previous,
    future: [state.present, ...state.future],
  }
}

export function redo(state: UndoRedoState): UndoRedoState {
  if (state.future.length === 0) return state
  const next = state.future[0]
  const newFuture = state.future.slice(1)
  return {
    past: [...state.past, state.present],
    present: next,
    future: newFuture,
  }
}

export function canUndo(state: UndoRedoState): boolean {
  return state.past.length > 0
}

export function canRedo(state: UndoRedoState): boolean {
  return state.future.length > 0
}