Email to Todo Converter

AI Prompts to Build This

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1. 1. Inbound Email + User Addressing

   Create a Next.js 14 App Router app with Resend Inbound email routing.
   
   DNS setup:
   - Register task.product.com as a Resend domain.
   - Add MX records pointing to Resend inbound servers.
   - Configure catch-all routing: all inbox.*@task.product.com → https://product.com/api/inbound webhook.
   
   Schema:
   - users(id, email, inbox_slug, plan, stripe_customer_id, created_at)
   - destinations(id, user_id, type ENUM[todoist,notion,linear,things,email_digest], oauth_access_token_encrypted, oauth_refresh_token_encrypted, config JSONB)
   - emails_processed(id, user_id, from_address, subject, received_at, llm_tokens_used, status ENUM[pending,processed,failed])
   - tasks_extracted(id, email_id, title, due_date, priority, owner, context_snippet, pushed_to_destinations JSONB)
   - usage_monthly(id, user_id, month, emails_processed_count, llm_cost_cents)
   
   On user signup:
   - Generate inbox_slug as hex(random(3)) + '.' + slugify(first_name) + hex(random(2)) → e.g. 'a8b2.jeff.c4d1'. Collision check; retry.
   - Store on users.inbox_slug. User's forwarding address is {inbox_slug}@task.product.com.
   
   /api/inbound endpoint:
   - Verify Resend signature header.
   - Parse payload: from, to (extract inbox_slug), subject, text, html, attachments.
   - Find user by inbox_slug. If not found, 404 (prevents random address spam).
   - Enforce monthly rate limit via Upstash: if over, reply to sender with friendly upgrade message.
   - Enqueue processing job (Vercel Cron or QStash).
   
   Return 200 fast (< 5s); do LLM work async.

2. 2. AI Task Extraction

   Implement the email-to-task extraction with Claude Haiku 4.5.
   
   Prompt construction:
   - User context: their timezone, default priority preference, typical working hours.
   - Email: from, subject, body (strip signatures, HTML tags, quoted thread history).
   - Today's date in ISO.
   
   System prompt:
   "You extract actionable tasks from a single email. Return strict JSON matching this schema:
   {
    thread_summary: 'one sentence of what the email is about',
    tasks: [
    {
    title: 'imperative verb + object, max 80 chars',
    due_date: 'ISO date or null, inferred from phrases like by Friday, EOD, next Monday',
    priority: 'low' | 'medium' | 'high' based on urgency language and explicit markers,
    owner: 'the person the task is for — null if ambiguous, or the user email if clearly a personal ask',
    context_snippet: '15-30 word quote from the email that establishes the ask'
    }
    ],
    sender_urgency: 'low' | 'medium' | 'high' — the overall tone
   }
   
   Rules:
   - Only include tasks that are real action items. Informational content ('FYI') is NOT a task.
   - If the email has 0 tasks, return tasks: [].
   - 'by Friday' relative to today's date. 'next week' = Monday through Sunday of next calendar week.
   - Priority 'high' if words like 'urgent', 'asap', 'blocker', 'production down' appear. 'low' if casual/FYI language. Default 'medium'.
   - Never hallucinate due dates. If unclear, due_date: null.
   
   Today is {today}. User timezone: {tz}."
   
   Call Claude via Anthropic SDK with response_format: {type: 'json_schema'}. Validate structure; if malformed, log and retry once with simpler prompt. On success, write tasks_extracted rows.
   
   Fan out to destinations: call each destination adapter's pushTasks(tasks). If destination fails (e.g., OAuth token expired), log to emails_processed.status = 'failed_destination' and email user.

3. 3. Destination Adapters (Todoist + Notion)

   Build destination adapters with a common interface: export async function pushTasks(tasks: Task[], config: Config): Promise.
   
   Todoist adapter (destinations/todoist.ts):
   - OAuth flow: user clicks 'Connect Todoist', redirect to https://todoist.com/oauth/authorize?client_id=X&scope=data:read_write&state=user_id. Callback at /api/destinations/todoist/callback exchanges code for token.
   - Store access_token encrypted + project_id where tasks should go (default Inbox).
   - pushTasks: for each task, POST to https://api.todoist.com/rest/v2/tasks with body:
    {
    content: task.title,
    description: task.context_snippet,
    due_date: task.due_date,
    priority: task.priority === 'high' ? 4 : task.priority === 'medium' ? 3 : 2,
    project_id: config.project_id
    }
   - Handle rate limit: 450 tasks/15min. Batch with Promise.all, max 5 concurrent.
   
   Notion adapter (destinations/notion.ts):
   - OAuth flow: user authorizes a Notion integration scoped to a specific database.
   - Store access_token + database_id.
   - pushTasks: for each task, POST to https://api.notion.com/v1/pages:
    {
    parent: { database_id: config.database_id },
    properties: {
    Name: { title: [{ text: { content: task.title } }] },
    'Due Date': task.due_date ? { date: { start: task.due_date } } : null,
    Priority: { select: { name: task.priority } },
    Context: { rich_text: [{ text: { content: task.context_snippet } }] }
    }
    }
   - User must pre-create database with these property names; show schema doc on connect.
   
   Digest email adapter (destinations/email_digest.ts):
   - Collect tasks across the day; send one digest email at user-configured time (default 6pm local).
   - React Email template with checkboxes, priorities color-coded, tappable add-to-calendar links.
   
   Error handling: on 401, mark OAuth token as expired, email user to reconnect. Never push tasks to a stale destination.