import { get, writable } from "svelte/store";
import { debounce, WEEKDAYS } from "../utils";
import { taskToThing } from "../models/task";
import {
  getThingAll,
  saveSolidDatasetAt,
  setThing,
  removeThing,
} from "@inrupt/solid-client";
import { fetch } from "@inrupt/solid-client-authn-browser";
import podInfo from "./podInfoStore";
import { addToast } from "./toastStore";
import { DateTime } from "luxon";

const DEBOUNCE_TIME_SYNC = 2000;

const taskStore = writable<Task[]>([]);
const { update, set, subscribe } = taskStore;

const addTask = (task: Omit<Task, "id">) => {
  const podUrl = get(podInfo).podUrl;
  update(tasks => [
    ...tasks,
    { ...task, id: `${podUrl}/tasks/default#${Date.now()}` },
  ]);
};

const updateTask = (taskId: string, taskUpdate: Partial<Task>) => {
  update(tasks =>
    tasks.map(task => {
      if (task.id === taskId) return { ...task, ...taskUpdate };
      return task;
    })
  );

  if (taskUpdate.done) {
    const task = get(taskStore).find(item => item.id === taskId);
    const now = DateTime.now();
    const datetime = task?.dueDate
      ? DateTime.fromJSDate(task.dueDate)
      : now
    let weekday = WEEKDAYS[task?.byDay as string];
    let dueDate: DateTime | null = null;
    if (task?.byDay && !task.byMonthWeek) {
      dueDate = datetime.set({ weekday });
      if (dueDate <= now) dueDate = dueDate.plus({ week: 1 })
    }
    else if (task?.byMonthDay) {
      dueDate = datetime.set({ day: task.byMonthDay })
      if (dueDate <= now) dueDate = dueDate.plus({ month: 1 })
    }
    else if (task?.byDay && task?.byMonthWeek) {
      dueDate = datetime.set({ weekday, weekNumber: task.byMonthWeek })
      if (dueDate <= now) dueDate = dueDate.plus({ month: 1 })
    }

    if (dueDate) {
      console.log(`Tâche replanifiée pour le ${dueDate.toISODate()}`)
      addTask({ ...task, dueDate: dueDate.toJSDate(), done: false, endTime: undefined });
    }
  }
};

const deleteTask = (taskId: string) => {
  update(tasks => tasks.filter(task => task.id !== taskId));
};

// Sync tasks with pod data
let init = false;
subscribe(
  debounce(async (tasks: Task[]) => {
    if (!init) return (init = true);

    let taskDataset = get(podInfo).tasksDataset;
    if (!taskDataset) throw new Error("No tasks dataset. Can't write to pod.");

    const currentDatasetThings = getThingAll(taskDataset);
    const updatedDatasetThings = tasks.map(taskToThing);

    // Add task things to dataset
    for (const taskThing of updatedDatasetThings) {
      taskDataset = setThing(taskDataset, taskThing);
    }

    // Remove deleted tasks from dataset
    const removedThings = currentDatasetThings.filter(
      thing => !updatedDatasetThings.find(thg => thg.url === thing.url)
    );
    for (const removedThing of removedThings) {
      taskDataset = removeThing(taskDataset, removedThing);
    }

    const podUrl = get(podInfo).podUrl;
    const savedSolidDataset = await saveSolidDatasetAt(
      `${podUrl}/tasks/default`,
      taskDataset,
      { fetch: fetch }
    );
    podInfo.update(store => ({ ...store, tasksDataset: savedSolidDataset }));
    addToast("Tâches enregistrées vers le pod.");
  }, DEBOUNCE_TIME_SYNC)
);

export default { set, update, subscribe, addTask, updateTask, deleteTask };