ld_demo.py

import os
import time

from dotenv import load_dotenv
import ldclient
from ldclient.config import Config
from ldclient import Context

# ── SDK setup ─────────────────────────────────────────────────────────────────
load_dotenv()

SDK_KEY = os.environ.get("LAUNCHDARKLY_SDK_KEY")
if not SDK_KEY:
    raise SystemExit("Set LAUNCHDARKLY_SDK_KEY in your .env file.")

ldclient.set_config(Config(SDK_KEY))
client = ldclient.get()

# ── User pool for rollout demos ────────────────────────────────────────────────
# Segment membership is managed in LaunchDarkly — no custom attributes needed.
# Carol (ak_user-003) and Grace (ak_user-007) are in the "premium-users" segment.
ROLLOUT_USERS = [
    {"key": "ak_user-001", "name": "Alice"},
    {"key": "ak_user-002", "name": "Bob"},
    {"key": "ak_user-003", "name": "Carol"},   # in segment: premium-users
    {"key": "ak_user-004", "name": "David"},
    {"key": "ak_user-005", "name": "Eva"},
    {"key": "ak_user-006", "name": "Frank"},
    {"key": "ak_user-007", "name": "Grace"},   # in segment: premium-users
    {"key": "ak_user-008", "name": "Henry"},
    {"key": "ak_user-009", "name": "Iris"},
    {"key": "ak_user-010", "name": "James"},
]


def build_context(user: dict) -> Context:
    # Context only needs kind + key — segment membership is evaluated server-side in LD.
    return (
        Context.builder(user["key"])
        .kind("user")
        .name(user["name"])
        .build()
    )


def choose_user():
    print("1  Early Access User  (in segment: premium-users)")
    print("2  General User       (not in segment)")
    choice = input("Choose (1 or 2): ").strip()

    if choice == "1":
        user = {"key": "ak_user-003", "name": "Carol"}
    else:
        user = {"key": "ak_user-001", "name": "Alice"}

    return build_context(user), user


# ── Demo 1: targeting ──────────────────────────────────────────────────────────
def demo_targeting(context: Context, user: dict) -> None:
    print(f"\nContext: key={user['key']}  name={user['name']}")

    # Evaluate the flag for this context.
    # Fallback (False) is returned only if the SDK can't reach LaunchDarkly.
    result = client.variation("disable-payments", context, False)

    # Toggle this flag ON in LaunchDarkly to simulate an incident response.
    # true  = server blocks payment, returns 503 maintenance response
    # false = server processes payment normally
    print(f"disable-payments → {result}  ({'BLOCKED — returning 503' if result else 'ENABLED — processing payment'})")


# ── Demo 2: percentage rollout ─────────────────────────────────────────────────
def demo_percentage_rollout() -> None:
    # Set the flag's default rule to a percentage rollout in LaunchDarkly,
    # then press Enter. Each user key hashes to a 0–99 bucket — deterministic.
    print("\nGo to LaunchDarkly → release-checkout-redesign → set default rule to a % rollout → save")
    input("Press Enter when done — script will read the live value from LD: ")

    print(f"\n{'Name':<10} {'Segment':<16} {'Result'}")
    print("-" * 42)

    new_count = 0
    for user in ROLLOUT_USERS:
        context   = build_context(user)
        gets_new  = client.variation("release-checkout-redesign", context, False)
        segment   = "premium-users" if user["key"] in ("ak_user-003", "ak_user-007") else "—"
        print(f"{user['name']:<10} {segment:<16} {'new UI' if gets_new else 'old UI'}")
        if gets_new:
            new_count += 1

    total = len(ROLLOUT_USERS)
    print(f"\n{new_count}/{total} users on new UI")


# ── Demo 3: gradual rollout ────────────────────────────────────────────────────
def demo_gradual_rollout() -> None:
    steps = [
        ("10%  — canary",      "Go to LaunchDarkly → set default rule to 10% → save"),
        ("50%  — broad beta",  "Go to LaunchDarkly → increase to 50% → save"),
        ("100% — full launch", "Go to LaunchDarkly → increase to 100% → save"),
    ]

    for label, instruction in steps:
        print(f"\n{label}")
        print(f"  Action: {instruction}")
        input("  Press Enter when done — script will read the live value from LD: ")

        new_count = 0
        reached   = []
        for user in ROLLOUT_USERS:
            context  = build_context(user)
            gets_new = client.variation("release-checkout-redesign", context, False)
            if gets_new:
                new_count += 1
                reached.append(user["name"])

        total = len(ROLLOUT_USERS)
        print(f"{new_count}/{total} users on new UI — {', '.join(reached) if reached else 'none yet'}")

    # After 7 days at 100%, flag status becomes "Launched" in LD →
    # signal to remove the flag wrapper from code and archive the flag.
    print("\nRollout complete. Next: remove flag from code, archive in LaunchDarkly.")


# ── Main menu ──────────────────────────────────────────────────────────────────
def run_demo() -> None:
    time.sleep(1)  # allow SDK to fully initialize

    if not client.is_initialized():
        print("WARNING: SDK not initialized — check your SDK key.")

    print("\n1  Targeting  (evaluate flag for a chosen user)")
    print("2  Percentage rollout  (evaluate across 10 users)")
    print("3  Gradual rollout  (step through 10% → 50% → 100%)")
    choice = input("\nChoose (1 / 2 / 3): ").strip()

    if choice == "2":
        demo_percentage_rollout()
    elif choice == "3":
        demo_gradual_rollout()
    else:
        # Flag: disable-payments
        # Type: Boolean  |  true = block payment, return 503  |  false = process normally
        # Toggle ON/OFF in LaunchDarkly during the demo — no redeploy needed
        context, user = choose_user()
        demo_targeting(context, user)


if __name__ == "__main__":
    try:
        run_demo()
    finally:
        client.close()