import { ChangeOperation } from "../../interfaces/dataUnit.js";
import { LoadDataRequest } from "../../loading/LoadDataRequest.js";
import { PaginationInfo } from "../../loading/PaginationInfo.js";
import { Action } from "../action/DataUnitAction.js";
import StateManager, { ActionReducer, StateAction } from "../StateManager.js";

class LoadingControlReducerImpl implements ActionReducer {

    public sliceName: string = "loadingControl";

    public reduce(stateManager: StateManager, currentState: LoadingControlState, action: StateAction): LoadingControlState {
        switch (action.type) {
            case Action.LOADING_DATA :
                return {...currentState, lastRequest: action.payload};
            case Action.DATA_LOADED:
                return {...currentState, paginationInfo: action.payload?.paginationInfo};
            case Action.PAGINATION_UPDATED:
                return {...currentState, paginationInfo: action.payload};
            case Action.DATA_SAVED:
                return {...currentState, paginationInfo: updatePaginationInfo(stateManager, action.payload)};

        }
        return currentState;
    }
}

export const LoadingControlReducer = new LoadingControlReducerImpl();

export const getPaginationInfo = (stateManager: StateManager): PaginationInfo|undefined => {
    const state: LoadingControlState = stateManager.select(LoadingControlReducer.sliceName, (state: LoadingControlState) => state);
    return state ? state.paginationInfo : undefined;
};

export const getCurrentRequest = (stateManager: StateManager): LoadDataRequest|undefined => {
    const state: LoadingControlState = stateManager.select(LoadingControlReducer.sliceName, (state: LoadingControlState) => state);
    return state ? state.lastRequest : undefined;
};

export const getCurrentPage = (stateManager: StateManager): number => {
    const paginationInfo = getPaginationInfo(stateManager);
    return paginationInfo ? paginationInfo.currentPage : 0;
};

export const getLastPage = (stateManager: StateManager, pageSize: number): number => {
    const paginationInfo = getPaginationInfo(stateManager);
    return paginationInfo ? Math.ceil((paginationInfo.total||paginationInfo.count||0) / pageSize) : 0;
};

export const hasMorePages = (stateManager: StateManager): boolean => {
    const paginationInfo = getPaginationInfo(stateManager);
    if(paginationInfo && paginationInfo.hasMore){
        return true;
    }
    return false;
}

export const hasPreviousPages = (stateManager: StateManager): boolean => {
    const paginationInfo = getPaginationInfo(stateManager);
    return paginationInfo ? paginationInfo.currentPage > 0 : false;
}

const updatePaginationInfo = (stateManager: StateManager, payload: Payload): PaginationInfo =>{
    const paginationInfo = getPaginationInfo(stateManager);
    let { records, changes } = payload;

    if(!records || !changes || !paginationInfo || !validateNewRecordOperation(changes)) return paginationInfo as PaginationInfo;
    
    const { count, firstRecord, lastRecord, total } = paginationInfo;

    return {
        ...paginationInfo,
        count: (count ?? 0) + records.length,
        firstRecord: firstRecord === 0 && records.length > 0 ? 1 : firstRecord,
        lastRecord: lastRecord + records.length,
        total: (total ?? 0) + records.length
    }
    
}

const validateNewRecordOperation = (changes: Array<Change>): boolean => {
    return changes.every(change => isNewRecordOperation(change._operation));
};

const isNewRecordOperation = (operation: string): operation is ChangeOperation => {
    return ["INSERT", "COPY"].includes(operation);
};

interface LoadingControlState{
    lastRequest: LoadDataRequest;
    paginationInfo: PaginationInfo;
}

interface Change {
    dataUnit: string;
    record: Record<string, any>;
    updatingFields: Record<string, any>;
    _operation: string;
}

interface Payload {
    changes: Change[];
    records: Record<string, any>[];
}