import {
    ScrollListAction,
    ScrollListScrollAction,
    ScrollListUpdateAction,
    ScrollListJumpAction,
    SCROLL_LIST_SCROLL,
    SCROLL_LIST_UPDATE,
    SCROLL_LIST_JUMP,
} from './actions'

export interface ScrollListsState {
    [key: string]: ScrollListState
}
export interface ScrollListState {
    scroll: ScrollListScrollState
    height: number
    childHeight: number
    childrenVisible: number
    jumped: number | false
}

export interface ScrollListScrollState {
    scrollTop: number
    idx: number
    skip: number
}

export interface ScrollListItem {
    [id: string]: any
}

export const initialScrollListState: ScrollListsState = {}

export const scrollListReducer = (state = initialScrollListState,
                                  action: ScrollListAction): ScrollListsState => {
    switch (action.type) {
        case SCROLL_LIST_SCROLL: {
            return scrollListScroll(state, action)
        }
        case SCROLL_LIST_UPDATE: {
            return scrollListUpdate(state, action)
        }
        case SCROLL_LIST_JUMP: {
            return scrollListJump(state, action)
        }
        default: {
            return state
        }
    }
}

const updateScrollList = (state: ScrollListsState,
                          id: string,
                          fn: (a: ScrollListState) => Partial<ScrollListState>) => ({
    ...state,
    [id]: {
        ...state[id],
        ...fn(state[id]),
    },
})

const scrollListScroll = (state: ScrollListsState, action: ScrollListScrollAction) =>
    updateScrollList(state, action.id, (scrollList: ScrollListState) => ({
        scroll: action.scroll,
    }))

const scrollListUpdate = (state: ScrollListsState, action: ScrollListUpdateAction) =>
    updateScrollList(state, action.id, () => action.scrollList)

const scrollListJump = (state: ScrollListsState, action: ScrollListJumpAction) =>
    updateScrollList(state, action.id, (scrollList: ScrollListState) => ({
        scroll: {
            idx: action.idx,
            scrollTop: action.idx > 0 ? scrollList.childHeight : 0,
            skip: Math.max(action.idx - 1, 0),
        },
        jumped: action.idx,
    }))