/**
 * Snippet Library — the left pane (spec §02).
 *
 * M1 scope: the always-visible list with a pinned "Create New Snippet" item,
 * selection/highlight, and delete. Search, sort controls, the metadata panel,
 * status/dataset indicators, and the storage monitor arrive in later milestones.
 */

import { useShallow } from 'zustand/react/shallow';
import { useSnippetStore } from '../stores/SnippetStore';
import styles from './SnippetLibrary.module.css';

/** Compact relative date for the list (full date formatting lands in M5). */
function relativeDate(iso: string): string {
  const then = new Date(iso);
  const now = new Date();
  const startOfToday = new Date(now.getFullYear(), now.getMonth(), now.getDate());
  const dayMs = 24 * 60 * 60 * 1000;
  const days = Math.floor(
    (startOfToday.getTime() -
      new Date(then.getFullYear(), then.getMonth(), then.getDate()).getTime()) /
      dayMs,
  );
  if (days <= 0) return 'Today';
  if (days === 1) return 'Yesterday';
  if (days < 7) return `${days}d ago`;
  return then.toLocaleDateString();
}

export function SnippetLibrary() {
  const snippets = useSnippetStore(useShallow((s) => s.snippets));
  const activeId = useSnippetStore((s) => s.activeSnippetId);
  const createSnippet = useSnippetStore((s) => s.createSnippet);
  const selectSnippet = useSnippetStore((s) => s.selectSnippet);
  const removeSnippet = useSnippetStore((s) => s.removeSnippet);

  // Default ordering: newest-modified first (spec §02 → Sort).
  const ordered = [...snippets].sort((a, b) => b.modified.localeCompare(a.modified));

  const handleDelete = (id: string, name: string) => {
    // TODO: M1 stopgap — route destructive confirms through the modal coordinator
    // (docs/architecture/03) when the modal system lands, and surface a deletion
    // toast (spec §02), instead of the native window.confirm.
    if (window.confirm(`Delete "${name}"? This cannot be undone.`)) removeSnippet(id);
  };

  return (
    <div className={styles.library}>
      <button className={styles.createNew} onClick={() => createSnippet()}>
        + Create New Snippet
      </button>

      <ul className={styles.list}>
        {ordered.length === 0 && <li className={styles.empty}>No snippets found</li>}
        {ordered.map((s) => (
          <li
            key={s.id}
            className={`${styles.item} ${s.id === activeId ? styles.active : ''}`}
            aria-current={s.id === activeId}
            onClick={() => selectSnippet(s.id)}
          >
            <div className={styles.itemMain}>
              <span className={styles.name}>{s.name}</span>
              <span className={styles.date}>{relativeDate(s.modified)}</span>
            </div>
            <button
              className={styles.delete}
              aria-label={`Delete ${s.name}`}
              title="Delete snippet"
              onClick={(e) => {
                e.stopPropagation();
                handleDelete(s.id, s.name);
              }}
            >
              ✕
            </button>
          </li>
        ))}
      </ul>
    </div>
  );
}