Split Tender Transactions Part 1 - Basic Split Tendering

Complete the source function process_events in the editor below. FastPrep exposes the language-adapted method name processEvents.

Function Parameters

string events[n]: lines for each event in chronological order. Lines have a format defined by one of three schemas:

timestamp,ADD_GIFTCARD,customer_id,card_id,amount,valid_before
timestamp,CHARGE,charge_id,customer_id,amount,zip_code
timestamp,REFUND,charge_id,refund_amount

string surcharge_rates[m]: a list of non-overlapping ZIP-code ranges mapped to a surcharge percentage in the format start_zip-end_zip:rate, where start and end are inclusive. Example: 90000-99999:0.05 (representing 5%).

Part 1 practice adapter: the judged Part 1 input contains only ADD_GIFTCARD and CHARGE events and therefore exposes only events. The source-wide surcharge_rates parameter and REFUND schema are retained above for fidelity but belong to later parts.

Returns. string[n]: an array of strings, one per input event, in the same order. For CHARGE events, return the formatted charge string using the schema below. For all other event types, return an empty string "". The length of the output array must exactly match the length of the input events array.

CC_CHARGE_AMOUNT,GIFT_CARD_ID_1:AMOUNT_USED,GIFT_CARD_ID_2:AMOUNT_USED

Part 1: Basic split tendering

For Part 1, process ADD_GIFTCARD and CHARGE events. All customer balances start at 0.

When an ADD_GIFTCARD event is received, add the specified amount to the designated customer's total gift card balance. Return an empty string "".

When a CHARGE event is received, attempt to cover the transaction cost using the customer's available gift card balance first.

• If the gift card balance is greater than or equal to the charge amount, deduct the charge amount from the gift card balance. The credit card charge is 0.
• If the charge amount exceeds the gift card balance, drain the entire gift card balance to 0. The remaining unpaid amount becomes the credit card charge.

Output Format for CHARGE

Return a string starting with the credit card charge, followed by a comma-separated list of the gift cards debited and their amounts (CARD_ID:AMOUNT). If no gift cards were debited, output only the credit card charge.

CC_CHARGE_AMOUNT,GIFT_CARD_ID_1:AMOUNT_USED,GIFT_CARD_ID_2:AMOUNT_USED

Note

In Part 1, each customer will hold at most one active gift card at a time. You do not need to implement card prioritization or sorting logic until Part 2.

Later-Part Context from the Related Caption (Not Judged)

The related caption explains that later parts remove expired cards, prioritize earlier expiration dates and then card IDs, apply a ZIP-code credit-card surcharge, record the actual credit-card portion for refunds, and turn any refund beyond that portion into a new never-expiring gift card. It also suggests heaps for avoiding repeated gift-card sorting and sorting only the gift cards actually used for output. None of those later-part rules changes the judged Part 1 behavior above.

Source Example

Suppose we receive the following events in order. Example 1 below reproduces the source input and output.