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docs: design for dynamic global pricing configuration

2026-03-06 13:18:47 -06:00

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Dynamic Global Pricing Configuration

Date: 2026-03-06 Status: Approved Author: System Design

Overview

Add superadmin UI to dynamically modify global billing defaults (free device count and price per device) with automatic Stripe Price creation and subscription migration. Update default pricing from $1 to $2/device/month.

Goals

Allow superadmins to change global pricing without code deployment
Automatically create new Stripe Prices and migrate active subscriptions
Update marketing materials to reflect $2/device/month pricing
Maintain per-organization override capability
Provide audit trail and migration reporting

Design Decisions

Storage Strategy (Hybrid Approach)

ApplicationSettings entries:

default_free_devices (integer): Number of free devices (default: 10)
default_price_per_device (string): Price per device/month USD (default: "2.00")
stripe_price_id (string): Current Stripe Price object ID

Fallback behavior:

Check ApplicationSettings first
Fall back to module attributes if not set
Stripe Price ID falls back to env var STRIPE_PRICE_ID

Stripe Integration

Price changes trigger:

Create new Stripe Price object at new unit amount
Update stripe_price_id in ApplicationSettings
Migrate all active subscriptions to new Price (best-effort)
Report successes/failures

Migration behavior:

Update subscriptions with proration_behavior: "none" (change at next billing cycle)
Best-effort: continue on individual failures, report at end
Failed migrations logged for manual review

UI Placement

Location: /admin/organizations page Component: "Global Billing Defaults" card at top of organization list

Workflow:

Superadmin clicks "Edit Defaults"
Modal shows form with current values
On save → confirmation dialog: "This will update X active subscriptions. Continue?"
After confirmation → updates DB + Stripe + migrates subscriptions
Success message shows migration results (e.g., "Updated 45/47 subscriptions, 2 failed")

Safety & Audit

Confirmation dialog:

Shows current values vs new values
Shows count of active subscriptions that will be affected
Requires explicit confirmation before execution

Audit logging:

Action: "global_pricing_updated"
Metadata includes:
- Old/new values for free devices and price
- Migration results (succeeded/failed counts)
- Failed organization IDs and error reasons
IP address and superuser ID captured

Data Model

New ApplicationSettings Records

INSERT INTO application_settings (id, key, value, value_type, description, inserted_at, updated_at)
VALUES
  (gen_random_uuid(), 'default_free_devices', '10', 'integer',
   'Number of free devices included in all subscriptions', NOW(), NOW()),
  (gen_random_uuid(), 'default_price_per_device', '2.00', 'string',
   'Price per device per month (USD) after free tier', NOW(), NOW());

Note: stripe_price_id will be populated on first price update via admin UI.

Schema Changes

No schema changes required. Uses existing application_settings table.

Implementation Components

1. Billing Module Updates

New functions:

default_free_devices/0 - Get from Settings or fallback
default_price_per_device/0 - Get from Settings or fallback
stripe_price_id/0 - Get from Settings or fallback to env var
migrate_all_subscriptions_to_price/1 - Migrate subscriptions with reporting

Updated functions:

effective_free_device_count/1 - Use default_free_devices/0
effective_price_per_device/1 - Use default_price_per_device/0

Module attribute updates:

Change @default_price_per_device from Decimal.new("1.00") to Decimal.new("2.00")

2. StripeClient Updates

New functions:

create_price/1 - Create metered billing Price object
update_subscription_price/2 - Switch subscription to new Price
list_active_subscriptions/1 - Paginated list of active subs

Price creation parameters:

unit_amount_decimal: e.g., "2.00" for $2/device/month
recurring.usage_type: "metered"
recurring.aggregate_usage: "max" (bill for max devices in period)
billing_scheme: "per_unit"

3. Admin Context

New function:

Admin.update_global_pricing/3 - Orchestrates full update

Flow:

Validate new values (positive numbers, reasonable ranges)
Get count of active subscriptions for confirmation
If price changed: create new Stripe Price
Update ApplicationSettings
If price changed: migrate subscriptions
Create audit log with results
Return migration report

4. Admin LiveView UI

Location: lib/towerops_web/live/admin/org_live/index.ex

New components:

Global Defaults card with current values
Edit modal with form
Confirmation dialog with impact preview
Success/error messages with migration results

Validation:

default_free_devices: integer, 1-10000
default_price_per_device: decimal, 0.01-999.99

5. Marketing Updates

Files to update:

lib/towerops_web/controllers/page_html/home.html.heex: Change $3 → $2
lib/towerops_web/controllers/user_registration_html/new.html.heex: Update copy

Error Handling

Partial Migration Failures

Scenario: Stripe API fails for some subscriptions

Behavior:

Continue migrating remaining subscriptions
Collect failed org IDs and error messages
Return summary: %{total: 50, succeeded: 48, failed: 2, failures: [...]}
Display warning in UI with failure details
Log failures in audit_logs for manual follow-up

Failed subscriptions:

Remain on old price until manually updated
No disruption to billing
Superadmin can retry migration or update individually

Complete Failures

Scenario: Stripe Price creation fails