session-mcp/src/tools/relations.ts

// Task relations: dependencies and checklists

import { query, queryOne, execute } from '../db.js';

interface TaskLinkArgs {
  from_id: string;
  to_id: string;
  link_type: string;
}

interface ChecklistAddArgs {
  task_id: string;
  item: string;
}

interface ChecklistToggleArgs {
  item_id: number;
  checked: boolean;
}

/**
 * Create a dependency between tasks
 */
export async function taskLink(args: TaskLinkArgs): Promise<string> {
  const { from_id, to_id, link_type } = args;

  try {
    await execute(
      `INSERT INTO task_links (from_task_id, to_task_id, link_type)
       VALUES ($1, $2, $3)
       ON CONFLICT (from_task_id, to_task_id, link_type) DO NOTHING`,
      [from_id, to_id, link_type]
    );

    return `Linked: ${from_id} ${link_type} ${to_id}`;
  } catch (error) {
    return `Error creating link: ${error}`;
  }
}

/**
 * Add a checklist item to a task
 */
export async function checklistAdd(args: ChecklistAddArgs): Promise<string> {
  const { task_id, item } = args;

  // Get next position
  const result = await queryOne<{ max: number }>(
    `SELECT COALESCE(MAX(position), 0) + 1 as max
     FROM task_checklist WHERE task_id = $1`,
    [task_id]
  );

  const position = result?.max || 1;

  await execute(
    `INSERT INTO task_checklist (task_id, item, position)
     VALUES ($1, $2, $3)`,
    [task_id, item, position]
  );

  return `Added to ${task_id}: ${item}`;
}

/**
 * Toggle a checklist item
 */
export async function checklistToggle(args: ChecklistToggleArgs): Promise<string> {
  const { item_id, checked } = args;

  const result = await execute(
    `UPDATE task_checklist SET checked = $1 WHERE id = $2`,
    [checked, item_id]
  );

  if (result === 0) {
    return `Checklist item not found: ${item_id}`;
  }

  return `${checked ? 'Checked' : 'Unchecked'}: item #${item_id}`;
}