Python / FastAPI

1mkdir seshn-fastapi && cd seshn-fastapi
2python -m venv .venv && source .venv/bin/activate
3pip install fastapi uvicorn httpx

1import os
2import httpx
3
4BASE_URL = "https://api.seshn.net"
5API_KEY = os.environ["SESHN_API_KEY"]
6
7client = httpx.AsyncClient(
8    base_url=BASE_URL,
9    headers={
10        "Authorization": f"Bearer {API_KEY}",
11        "Content-Type": "application/json",
12    },
13)
14
15
16async def get_availability(service_id: str, from_date: str, to_date: str) -> list[dict]:
17    """Query available slots for a service within a date range."""
18    resp = await client.get(
19        "/v1/availability",
20        params={"serviceId": service_id, "from": from_date, "to": to_date},
21    )
22    resp.raise_for_status()
23    return resp.json()["data"]
24
25
26async def create_booking(slot_id: str, contact_id: str, seats: int = 1) -> dict:
27    """Create a new booking for a slot."""
28    resp = await client.post(
29        "/v1/bookings",
30        json={"slotId": slot_id, "contactId": contact_id, "seats": seats},
31    )
32    resp.raise_for_status()
33    return resp.json()["booking"]
34
35
36async def confirm_booking(booking_id: str) -> dict:
37    """Confirm a pending or held booking."""
38    resp = await client.post(f"/v1/bookings/{booking_id}/confirm", json={})
39    resp.raise_for_status()
40    return resp.json()["booking"]

1import hashlib
2import hmac
3import os
4
5from fastapi import FastAPI, Request, HTTPException
6from pydantic import BaseModel
7
8from seshn_client import get_availability, create_booking, confirm_booking
9
10app = FastAPI()
11
12WEBHOOK_SECRET = os.environ.get("SESHN_WEBHOOK_SECRET", "")
13
14
15# ── Schemas ──────────────────────────────────────────────────
16
17class BookRequest(BaseModel):
18    slot_id: str
19    contact_id: str
20    seats: int = 1
21
22
23# ── GET /availability ────────────────────────────────────────
24
25@app.get("/availability")
26async def availability(service_id: str, from_date: str, to_date: str):
27    slots = await get_availability(service_id, from_date, to_date)
28    return {"slots": slots, "count": len(slots)}
29
30
31# ── POST /book ───────────────────────────────────────────────
32
33@app.post("/book")
34async def book(body: BookRequest):
35    booking = await create_booking(body.slot_id, body.contact_id, body.seats)
36    confirmed = await confirm_booking(booking["id"])
37    return confirmed
38
39
40# ── POST /webhooks ───────────────────────────────────────────
41
42@app.post("/webhooks")
43async def webhooks(request: Request):
44    signature = request.headers.get("x-webhook-signature", "")
45    event = request.headers.get("x-webhook-event", "")
46    payload = await request.body()
47
48    if not verify_signature(payload, signature, WEBHOOK_SECRET):
49        raise HTTPException(status_code=401, detail="Invalid signature")
50
51    data = await request.json()
52
53    match event:
54        case "booking.confirmed":
55            # Send confirmation email, sync calendar, etc.
56            pass
57        case "booking.cancelled":
58            # Process refund, notify staff, etc.
59            pass
60        case "payment.succeeded":
61            # Update your records
62            pass
63
64    return {"received": True}
65
66
67# ── Signature verification ───────────────────────────────────
68
69def verify_signature(payload: bytes, header: str, secret: str) -> bool:
70    """Verify the HMAC-SHA256 signature from Seshn webhooks."""
71    expected = "sha256=" + hmac.new(
72        secret.encode(),
73        payload,
74        hashlib.sha256,
75    ).hexdigest()
76
77    return hmac.compare_digest(header, expected)

1SESHN_API_KEY=sk_test_... uvicorn main:app --reload --port 3001

1# Check availability
2curl "http://localhost:3001/availability?service_id=svc_yoga_class&from_date=2026-03-20&to_date=2026-03-27"
3
4# Create a booking
5curl -X POST http://localhost:3001/book \
6  -H "Content-Type: application/json" \
7  -d '{"slot_id": "slot_...", "contact_id": "ct_jane_doe", "seats": 1}'

1pip install datamodel-code-generator
2datamodel-codegen --url https://api.seshn.net/openapi.json --output models.py