import { App, Notice, TFile } from 'obsidian';
import type { Task } from './types';
import { DAILY_NOTE_TASKS_HEADING } from './constants';

// obsidian-daily-notes-interface re-exports moment from Obsidian's bundle.
// We import it this way so esbuild treats moment as external.
declare const moment: (date?: unknown) => {
  format(fmt: string): string;
};

interface DailyNotesInterface {
  appHasDailyNotesPluginLoaded(app: App): boolean;
  getDailyNote(
    date: ReturnType<typeof moment>,
    notes: Record<string, TFile>
  ): TFile | null;
  createDailyNote(date: ReturnType<typeof moment>): Promise<TFile>;
  getAllDailyNotes(): Record<string, TFile>;
}

let dni: DailyNotesInterface | null = null;

async function getDni(): Promise<DailyNotesInterface> {
  if (!dni) {
    dni = await import('obsidian-daily-notes-interface') as unknown as DailyNotesInterface;
  }
  return dni;
}

/**
 * Append a completed task (and its notes) to the `#### Tasks` section
 * of today's daily note, creating the section and/or the note if needed.
 */
export async function appendTaskToDailyNote(task: Task, app: App): Promise<void> {
  const lib = await getDni();

  if (!lib.appHasDailyNotesPluginLoaded(app)) {
    new Notice(
      'YAOTP: Daily Notes plugin is not enabled. ' +
        'Please enable it in Settings → Core plugins.'
    );
    return;
  }

  const all = lib.getAllDailyNotes();
  // moment is available as a global in Obsidian's runtime
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  const today = (window as any).moment();
  let file: TFile | null = lib.getDailyNote(today, all);

  if (!file) {
    file = await lib.createDailyNote(today);
  }

  const existing = await app.vault.read(file);
  const appended = buildAppendedContent(existing, task);
  await app.vault.modify(file, appended);
}

function buildAppendedContent(existing: string, task: Task): string {
  const taskLine = `- [x] ${task.text}`;
  const notesBlock =
    task.notes.length > 0 ? '\n\n' + task.notes.join('\n') : '';
  const entry = taskLine + notesBlock;

  const headingIndex = existing.lastIndexOf(DAILY_NOTE_TASKS_HEADING);

  if (headingIndex === -1) {
    // Section doesn't exist — append it at the end
    const base = existing.trimEnd();
    return base + (base.length > 0 ? '\n\n' : '') + DAILY_NOTE_TASKS_HEADING + '\n\n' + entry + '\n';
  }

  // Section exists — insert after heading and any existing items
  const afterHeading = existing.slice(headingIndex + DAILY_NOTE_TASKS_HEADING.length);
  // Find where the next same-or-higher-level heading starts (if any)
  const nextHeadingMatch = afterHeading.match(/\n#{1,4} /);
  const insertionRelative = nextHeadingMatch?.index ?? afterHeading.length;

  const before = existing.slice(0, headingIndex + DAILY_NOTE_TASKS_HEADING.length);
  const sectionContent = afterHeading.slice(0, insertionRelative).trimEnd();
  const after = afterHeading.slice(insertionRelative);

  return before + sectionContent + '\n\n' + entry + (after.length > 0 ? '\n' + after : '\n');
}