Read the money out of an 835 without a TR3 open on your desk.

import { parseX12, get835 } from "@cosyte/x12";

const raw = `ISA*00*          *00*          *ZZ*MEDICARE       *ZZ*SUBMITTER      *260601*1200*^*00501*000000001*0*P*:~
GS*HP*MEDICARE*SUBMITTER*20260601*1200*1*X*005010X221A1~
ST*835*0001~
BPR*I*450.00*C*ACH*CCP*01*123456789*DA*987654321*1512345678**01*111111111*DA*222222222*20260601~
TRN*1*0012345*1512345678~
DTM*405*20260601~
N1*PR*MEDICARE PART A~
N3*123 PAYER WAY~
N4*BALTIMORE*MD*21244~
PER*BL*JANE COORDINATOR*TE*5551234567~
N1*PE*SAMPLE CLINIC INC~
N3*456 PROVIDER LN~
N4*CLEVELAND*OH*44113~
REF*TJ*123456789~
LX*1~
CLP*PT-ACCT-001*1*500.00*450.00*50.00*MC*PAYER-CLAIM-001*11*1~
NM1*QC*1*PATIENT*TEST*A***MI*MEMBER001~
NM1*82*2*RENDERING PROVIDER INC*****XX*1234567890~
DTM*232*20260501~
DTM*233*20260501~
SVC*HC:99213*500.00*450.00**1~
DTM*472*20260501~
CAS*PR*1*50.00~
REF*6R*LINE-CTRL-001~
SE*23*0001~
GE*1*1~
IEA*1*000000001~`;

const ix = parseX12(raw);
const tx = ix.groups[0]?.transactions.find((t) => t.st.elements[1] === "835");
if (tx === undefined) throw new Error("no 835 in this interchange");
const remit = get835(ix.delimiters, tx);
if (remit === undefined) throw new Error("not an 835");

// The payment, the claim's split, and who owes the difference and why.
const claim = remit.claims[0];
const adjustment = claim?.serviceLines[0]?.adjustments[0];
console.log("paid", remit.payment.totalActualPayment?.toString(), "by", remit.payment.method);
console.log("claim", claim?.patientControlNumber, "charged", claim?.totalChargeAmount?.toString());
console.log("patient owes", claim?.patientResponsibilityAmount?.toString());
console.log("reason", adjustment?.groupCode, adjustment?.reasonCode, adjustment?.reasonDescription);
console.log("warnings", ix.warnings.length);

// The values printed above, which the test suite asserts on every run:
remit.payment.totalActualPayment?.toString(); // => "450.00"
claim?.totalChargeAmount?.toString(); // => "500.00"
claim?.patientResponsibilityAmount?.toString(); // => "50.00"
adjustment?.groupCode; // => "PR"
adjustment?.reasonCode; // => "1"
adjustment?.reasonDescription; // => "Deductible Amount"
ix.warnings; // => []