import { CircularProgress, List, ListItem, Box, useTheme, Pagination } from "@mui/material";
import { useEffect, useState } from "react";
import { apiRequestHandler } from "../../utils/api/apiRequestHandler";
import { ApiError, Ticket } from "../../utils/api/types";
import TicketCard from "./TicketCard";
import { useSnackbar } from "notistack";


const TICKETS_PER_PAGE = 10;

export default function TicketList() {
    const theme = useTheme();
    const { enqueueSnackbar } = useSnackbar();
    const [tickets, setTickets] = useState<Ticket[]>([]);
    const [ticketCount, setTicketCount] = useState<number | null>(null);
    const [currentPage, setCurrentPage] = useState<number>(0);
    const [isLoading, setIsLoading] = useState<boolean>(false);

    useEffect(function fetchTickets() {
        setIsLoading(true);
        const abortController = new AbortController();

        apiRequestHandler.getTickets({ amt: TICKETS_PER_PAGE, page: currentPage, srch: "", status: "open" }, abortController.signal)
            .then(result => {
                if (result instanceof ApiError) {
                    enqueueSnackbar(`Error: ${result.message}`);
                    return;
                } else if (result instanceof Error) {
                    console.log(result);
                    return;
                }
                setTickets(result.data);
                setTicketCount(result.count);
                setIsLoading(false);
            });

        return () => {
            abortController.abort();
        };
    }, [currentPage, enqueueSnackbar]);

    useEffect(function subscribeToTickets() {
        const unsubscribe = apiRequestHandler.subscribeToAllTickets({
            onMessage: event => {
                console.log("SSE received:", event.data);
                const newTicket = event.data;
                if (typeof newTicket === "string") return;
                const existingTicketIndex = tickets.findIndex(ticket => ticket.id === newTicket.id);
                if (existingTicketIndex !== -1) {
                    setTickets(prevTickets => {
                        const newTickets = prevTickets.slice();
                        newTickets.splice(existingTicketIndex, 1, newTicket);
                        return newTickets;
                    });
                    return;
                }
                setTickets(prevTickets => [newTicket, ...prevTickets.slice(0, TICKETS_PER_PAGE - 1)]);
            },
            onError: event => {
                console.log("SSE Error:", event);
            }
        });

        return () => {
            unsubscribe();
        };
    }, [tickets]);

    return (
        <Box sx={{
            display: "flex",
            gap: "40px",
            flexDirection: "column",
        }}>
            <List sx={{
                p: 0,
                display: "flex",
                flexDirection: "column",
                gap: "40px",
                opacity: isLoading ? 0.4 : 1,
                transitionProperty: "opacity",
                transitionDuration: "200ms",
            }}>
                {tickets.map(ticket =>
                    <ListItem key={ticket.id} disablePadding>
                        <TicketCard
                            name={ticket.title}
                            body={ticket.top_message.message}
                            time={new Date(ticket.updated_at).toLocaleDateString()}
                            ticketId={ticket.id}
                        />
                    </ListItem>
                )}
                {isLoading &&
                    <Box sx={{
                        position: "absolute",
                        width: "100%",
                        height: "100%",
                        minHeight: "80px",
                        display: "flex",
                        alignItems: "center",
                        justifyContent: "center",
                    }}>
                        <CircularProgress sx={{ color: theme.palette.brightPurple.main }} size={60} />
                    </Box>
                }
            </List>
            {ticketCount !== null && ticketCount > TICKETS_PER_PAGE &&
                <Pagination
                    count={Math.ceil(ticketCount / TICKETS_PER_PAGE)}
                    page={currentPage + 1}
                    onChange={(e, value) => setCurrentPage(value - 1)}
                    sx={{ alignSelf: "center" }}
                />
            }
        </Box>
    );
}