Interpret type codes

[barszcz]

Bai2 Version: 0.1.0

03 (Account Identifier) and 16 (Transaction Detail) records contain three-digit "type codes" that denote the type(s) of data the record contains. These are key to interpreting the data in the BAI2 file; therefore it makes sense that this library should return relevant information about them.

Type codes come in three broad categories:

• Account Status: Pretty self explanatory, these describe things like ledger balance, available balance and float position. These show up in 03 records (and their continuations).
• Activity Summary: These are summaries of credit and debit activity on the account. Again, these appear in 03 records (and their continuations).
• Transaction Detail: These describe individual debits and credits on an account. As the name suggests, they show up on 16 records (and I assume their continuations, but the spec is mum on this).

Summary and Detail types also denote whether they refer to a debit or credit. The spec PDF has a large table detailing all the codes and their meanings. A kind person has helpfully transcribed them all into a CSV already.

We can probably convert that CSV into a hardcoded map without much difficulty. Something like

type TypeCode struct {
	TypeCode string // not int as leading zeros are significant
	Transaction string // "CR" "DB" or "NA"
	Level string // "Status" "Summary" or "Detail"
	Description string
}

var TypeCodes := map[string]TypeCode{
	"010": {
		TypeCode: "010",
		Transaction: "NA",
		Level: "Status",
		Description: "Opening Ledger",
	},
	// ...
}

Then it would be an easy lookup. We could also make type-aliased string enums for transaction and level, but unsure if it's really necessary.

In 03 records, we can also determine whether a type code should have item count and funds type by whether it's a status or summary type code, which may help in parsing that.

[barszcz]

I could whip something up later this week to generate a Go file with the map from the CSV. Shouldn't be too bad to do with Go templates.

[adamdecaf]

Sounds good. If they don't change often we could just generate the code once. If you need examples there are a few in other codebases.

https://github.com/moov-io/ach/blob/master/internal/iso4217/iso4217_gen.go