Problem Statement

Write reconcile_payment(payment, invoices) to pair a payment with an invoice when its memo directly names an invoice ID.

A memo can contain either "paying for: invoice-id" or "Paying off: invoice-id", without regard to letter casing. Obtain that invoice ID and locate the corresponding invoice.

Example

Input:

payment = "payment-014, 750, PAYING FOR: inv-842"

invoices = [
    "inv-731, 2024-06-18, 750",
    "inv-842, 2024-05-09, 750",
    "inv-963, 2024-04-27, 300"
]

Output:

"Payment payment-014 paid 750 for invoice inv-842 due on 2024-05-09"

Requirements

• Split the payment value into its payment ID, amount, and memo fields.
• Inspect the memo for an invoice-ID reference, such as "paying for: inv-842".
• Compare the extracted ID against the supplied invoices.
• Produce the required formatted result.
• Handle a memo that refers to an invoice ID absent from the list.

Edge Cases to Consider

• The memo's invoice ID is not present among the invoices.
• The invoice array contains several entries, but only one should be selected.
• Memo wording and capitalization may vary.
• The payment string might be incomplete or incorrectly formatted.

Problem Statement

Enhance the solution for payments whose memos do not name a particular invoice. If the memo does not yield an invoice ID, find an invoice whose amount equals the payment amount exactly.

When several invoices have that amount, use the one with the earliest due date.

ID-based behavior from Part 1 must remain supported, and an ID match must be attempted before an amount match.

Example

Input:

payment = "payment-027, 600, Service renewal"

invoices = [
    "inv-110, 2024-07-14, 900",
    "inv-220, 2024-05-16, 600",
    "inv-330, 2024-06-03, 600",
    "inv-440, 2024-04-08, 600"
]

Output:

"Payment payment-027 paid 600 for invoice inv-440 due on 2024-04-08"

Note: inv-440 wins because it is due first among the invoices totaling 600.

Requirements

• First look for an invoice reference in the memo, following Part 1.
• If the memo does not contain an ID, find invoices equal to the payment amount.
• If multiple exact amount candidates exist, pick the one due soonest.
• Parse and compare dates in chronological order.
• Return the "could not be matched" message when no equal-amount invoice exists.

Clarification Questions to Ask

• Must an invoice selected by ID also have the same amount as the payment?
• What should happen if two invoices have both the same amount and the same due date?
• Which date representation is guaranteed or expected?
• Are zero or negative payment amounts valid?

Problem Statement

Wire transfers can lose value to fees or differ slightly because of rounding. For instance, an invoice may be for $100, but a $2 bank charge can mean that only $98 arrives. Reconcile these close, rather than identical, values.

Introduce a third strategy: amount matching with a forgiveness threshold. Extend the function signature to reconcile_payment(payment, invoices, forgiveness=0), where forgiveness is the additional threshold parameter. If no exact amount candidate exists, consider invoices whose total falls within ±forgiveness of the received payment. If several invoices meet that condition, choose the one with the earliest due date.

Matching Priority:

1. Invoice ID match (Part 1)
2. Exact amount match (Part 2)
3. Forgiveness-range amount match (Part 3)

Example

Input:

payment = "payment-038, 118, Client remittance"

invoices = [
    "inv-510, 2024-06-21, 120",
    "inv-620, 2024-05-12, 118",
    "inv-730, 2024-04-04, 122"
]

forgiveness = 5

Output:

"Payment payment-038 paid 118 for invoice inv-620 due on 2024-05-12"

Note: inv-620 is an exact amount match, so it is preferred to inv-510, even though that invoice also lies inside the forgiveness range.

Another Example with Fuzzy Match:

payment = "payment-049, 76, Client remittance"

invoices = [
    "inv-510, 2024-06-21, 80",
    "inv-730, 2024-04-04, 78"
]

forgiveness = 5

Output:

"Payment payment-049 paid 76 for invoice inv-730 due on 2024-04-04"

Note: Both invoices differ from 76 by no more than 5, so inv-730 is chosen because its due date comes earlier.

Requirements

• Take forgiveness as one more function parameter.
• Use the three-level priority order: ID, then exact amount, then fuzzy amount.
• A fuzzy candidate must have an amount in [payment_amount - forgiveness, payment_amount + forgiveness].
• For multiple candidates at the same priority level, select the earliest due date.
• An exact amount result must outrank a fuzzy result even if the fuzzy candidate is due earlier.

Testing Considerations

When building tests, make sure that:

• Tests establish that each tier is evaluated in the intended priority sequence.
• An ID-based match wins even when its amount is different.
• An exact amount match wins over an in-range fuzzy match.
• Fuzzy matching is attempted only after exact matching finds nothing.
• The exact boundary of the forgiveness interval is covered, such as forgiveness=5 with a difference of 5.
• Multiple matches in one tier are resolved using the earliest due date.