Change a Lesson’s Duration

Like moving, this comes in a one-week flavor and a standing flavor — and the standing flavor involves money.

One week only (no money)

In the weekly calendar’s lesson modal, the Length select (30/60/90/120) changes that occurrence alone — “This week only — the standing booking keeps its own length.” The only check is a conflict sweep: lengthening a lesson into the next booking is refused. No ledger entry is ever posted for a single-occurrence change.

The standing length (with a ledger adjustment)

Changing Length in the reservation edit modal on the schedule grid behaves differently depending on status:

• Pending reservation — the duration just changes. No lessons exist yet and nothing has been charged, so there is nothing to reconcile. When the reservation is later confirmed, the lesson fee for the new length is what gets charged.
• Confirmed reservation — the family was already charged for the old length, so the save is intercepted and the admin is taken to the Duration Change Accounting screen before anything is written.

The accounting screen

/admin/duration_change_accounting.php shows the whole calculation and lets the admin adjust it before posting:

• Lesson progress — total lessons, used, remaining. “Used” counts attended and cancelled lessons (the family was still charged for a cancelled week); a lesson marked missed counts as remaining. One-off lessons are excluded entirely.
• Refund — the original semester fee for the old length, divided by the semester’s lessons_per_semester to get a per-lesson cost; the refund is the original fee minus (per-lesson × used).
• New charge — the new length’s per-lesson cost × lessons remaining.

Both amounts are editable before posting, which is the point of the screen: the formula prices against the full-semester fee even when the reservation generated fewer lessons (a mid-semester start, say), and integer division drops sub-cent remainders — so the admin is shown the math and can round it to what’s fair.

Post Entries & Update Duration then:

1. Posts up to two ledger rows, dated today: a credit (“Duration change refund: 30→60 min”, entry type other) and a debit (“Duration change charge: 30→60 min”, entry type lessons). Zero amounts post nothing.
2. Updates the reservation’s duration, which re-runs the full conflict sweep and moves the future lessons to the new length in place.

Things to watch

• Post-then-update ordering: if the new, longer duration collides with the next booking, the duration update fails after the ledger rows are already posted. The error is shown, but the adjustment is on the ledger for a change that didn’t happen — reverse it with a custom ledger entry, fix the schedule, and retry.
• No dedupe: re-submitting the accounting screen posts a second pair of entries.
• A status change made in the same modal save as a length change is dropped — the save exits into the accounting flow before the status is applied. Change status and length in two separate saves.