import type { EventChangeArg, EventDropArg, EventSourceInput, PluginDef } from "@fullcalendar/core";
import froca from "../../services/froca.js";
import ViewMode, { type ViewModeArgs } from "./view_mode.js";
import type FNote from "../../entities/fnote.js";
import server from "../../services/server.js";
import ws from "../../services/ws.js";
import { t } from "../../services/i18n.js";
import options from "../../services/options.js";

const TPL = `
<div class="calendar-view">
    <style>
    .calendar-view {
        overflow: hidden;
        position: relative;
        height: 100%;
        user-select: none;
        padding: 10px;
    }

    .calendar-view a {
        color: unset;
    }

    .calendar-container {
        height: 100%;
    }

    .calendar-container .fc-toolbar.fc-header-toolbar {
        margin-bottom: 0.5em;
    }

    .calendar-container .fc-toolbar-title {
        font-size: 1.3rem;
        font-weight: normal;
    }

    .calendar-container .fc-button {
        padding: 0.2em 0.5em;
    }
    </style>

    <div class="calendar-container">
    </div>
</div>
`;

export default class CalendarView extends ViewMode {

    private $root: JQuery<HTMLElement>;
    private $calendarContainer: JQuery<HTMLElement>;
    private noteIds: string[];

    constructor(args: ViewModeArgs) {
        super(args);

        this.$root = $(TPL);
        this.$calendarContainer = this.$root.find(".calendar-container");
        this.noteIds = args.noteIds;
        args.$parent.append(this.$root);
    }

    async renderList(): Promise<JQuery<HTMLElement> | undefined> {
        const editable = true;

        const { Calendar } = await import("@fullcalendar/core");
        const plugins: PluginDef[] = [];
        plugins.push((await import("@fullcalendar/daygrid")).default);

        if (editable) {
            plugins.push((await import("@fullcalendar/interaction")).default);
        }

        const calendar = new Calendar(this.$calendarContainer[0], {
            plugins,
            initialView: "dayGridMonth",
            events: await CalendarView.#buildEvents(this.noteIds),
            editable,
            eventChange: (e) => this.#onEventMoved(e),
            buttonText: {
                today: t("calendar_view.today"),
                month: t("calendar_view.month"),
                week: t("calendar_view.week"),
                day: t("calendar_view.day"),
                list: t("calendar_view.list")
            },
            firstDay: options.getInt("firstDayOfWeek") ?? 0
        });
        calendar.render();

        return this.$root;
    }

    async #onEventMoved(e: EventChangeArg) {
        const startDate = CalendarView.#formatDateToLocalISO(e.event.start);
        let endDate = CalendarView.#formatDateToLocalISO(e.event.end);
        const noteId = e.event.extendedProps.noteId;

        // Fullcalendar end date is exclusive, not inclusive but we store it the other way around.
        if (endDate) {
            const endDateParsed = new Date(endDate);
            endDateParsed.setDate(endDateParsed.getDate() - 1);
            endDate = CalendarView.#formatDateToLocalISO(endDateParsed);
        }

        // Don't store the end date if it's empty.
        if (endDate === startDate) {
            endDate = undefined;
        }

        // Update start date
        const note = await froca.getNote(noteId);
        if (!note) {
            return;
        }

        CalendarView.#setAttribute(note, "label", "startDate", startDate);
        CalendarView.#setAttribute(note, "label", "endDate", endDate);
    }

    static async #buildEvents(noteIds: string[]) {
        const notes = await froca.getNotes(noteIds);
        const events: EventSourceInput = [];

        for (const note of notes) {
            const startDate = note.getAttributeValue("label", "startDate");
            const customTitle = note.getAttributeValue("label", "calendar:title");

            if (!startDate) {
                continue;
            }

            const titles = await CalendarView.#parseCustomTitle(customTitle, note);
            for (const title of titles) {
                const eventData: typeof events[0] = {
                    title: title,
                    start: startDate,
                    url: `#${note.noteId}`,
                    noteId: note.noteId
                };

                const endDate = new Date(note.getAttributeValue("label", "endDate") ?? startDate);
                if (endDate) {
                    // Fullcalendar end date is exclusive, not inclusive.
                    endDate.setDate(endDate.getDate() + 1);
                    eventData.end = CalendarView.#formatDateToLocalISO(endDate);
                }

                events.push(eventData);
            }
        }

        return events;
    }

    static async #parseCustomTitle(customTitleValue: string | null, note: FNote, allowRelations = true): Promise<string[]> {
        if (customTitleValue) {
            const attributeName = customTitleValue.substring(1);
            if (customTitleValue.startsWith("#")) {
                const labelValue = note.getAttributeValue("label", attributeName);
                if (labelValue) {
                    return [ labelValue ];
                }
            } else if (allowRelations && customTitleValue.startsWith("~")) {
                const relations = note.getRelations(attributeName);
                if (relations.length > 0) {
                    const noteIds = relations.map((r) => r.targetNoteId);
                    const notesFromRelation = await froca.getNotes(noteIds);
                    const titles = [];

                    for (const targetNote of notesFromRelation) {
                        const targetCustomTitleValue = targetNote.getAttributeValue("label", "calendar:title");
                        const targetTitles = await CalendarView.#parseCustomTitle(targetCustomTitleValue, targetNote, false);
                        titles.push(targetTitles.flat());
                    }

                    return titles.flat();
                }
            }
        }

        return [ note.title ];
    }

    static async #setAttribute(note: FNote, type: "label" | "relation", name: string, value: string | null | undefined) {
        if (value) {
            // Create or update the attribute.
            await server.put(`notes/${note.noteId}/set-attribute`, { type, name, value });
        } else {
            // Remove the attribute if it exists on the server but we don't define a value for it.
            const attributeId = note.getAttribute(type, name)?.attributeId;
            if (attributeId) {
                await server.remove(`notes/${note.noteId}/attributes/${attributeId}`);
            }
        }
        await ws.waitForMaxKnownEntityChangeId();
    }

    static #formatDateToLocalISO(date: Date | null | undefined) {
        if (!date) {
            return undefined;
        }

        const offset = date.getTimezoneOffset();
        const localDate = new Date(date.getTime() - offset * 60 * 1000);
        return localDate.toISOString().split('T')[0];
    }

}