Bidirectional MT ↔ MX translation for ISO 20022 messages.

This crate translates between SWIFT MT FIN messages and their corresponding ISO 20022 MX (XML) representations. It provides:

• A SWIFT MT message parser ([mt]) that decomposes a raw MT message into its block structure (blocks 1, 2, 3, 4, 5) and then into typed field structs ([mt::fields::mt103::Mt103], [mt::fields::mt202::Mt202], [mt::fields::mt940::Mt940]).
• Translation helpers in [mappings] that convert each parsed MT struct into the corresponding pacs / camt Document from mx20022-model, and back.
• A [mappings::charset] module covering SWIFT FIN character-set conversion and SWIFT-MT line-wrapping.
• Translation result and error types ([mappings::TranslationResult], [mappings::TranslationError]) that distinguish hard failures from data-loss warnings ([mappings::TranslationWarning]).

Supported message-type pairs

Other MT message types (MT202COV, MT900, MT910, MT942) and other pacs / camt versions are not yet wired up.

Quick start: MT103 → pacs.008.001.13

use mx20022_translate::mappings::mt103_to_pacs008::mt103_to_pacs008;
use mx20022_translate::mt::{self, fields::mt103::parse_mt103};

let raw = "\
{1:F01BANKBEBBAXXX0000000000}\
{2:I103BANKDEFFXXXXN}\
{3:{108:MYREF}}\
{4:\n\
:20:REF123\n\
:23B:CRED\n\
:32A:230615EUR1000,00\n\
:50K:ACME CORP\n\
:59:JANE SMITH\n\
:71A:SHA\n\
-}\
{5:{CHK:ABCDEF1234}}";

// Step 1: parse the raw MT into block structure.
let msg = mt::parse(raw).unwrap();
assert_eq!(msg.message_type(), Some("103"));

// Step 2: parse Block 4 into typed MT103 fields.
let mt103 = parse_mt103(&msg.block4).unwrap();
assert_eq!(mt103.senders_reference, "REF123");

// Step 3: translate to pacs.008.001.13.
let result = mt103_to_pacs008(&mt103, "MSG-1", "2023-06-15T10:00:00").unwrap();
let doc = &result.message;
let tx = &doc.fi_to_fi_cstmr_cdt_trf.cdt_trf_tx_inf[0];
assert_eq!(tx.intr_bk_sttlm_amt.value.0, "1000.00");
assert_eq!(tx.intr_bk_sttlm_amt.ccy.0, "EUR");

// result.warnings carries any data-loss notes, e.g. when an MT
// field has no clean pacs.008 equivalent.
for w in &result.warnings.warnings {
    eprintln!("{}: {}", w.field, w.message);
}

Quick start: pacs.008.001.13 → MT103

pacs008_to_mt103 requires the source pacs.008 to carry a BICFI or party name on DbtrAgt and CdtrAgt (the BICs that go into the MT message header). The fixture below adds :52A: and :57A: to the source MT103 so the round-trip carries that data through.

# use mx20022_translate::mappings::{mt103_to_pacs008::mt103_to_pacs008, pacs008_to_mt103::pacs008_to_mt103};
# use mx20022_translate::mt::{self, fields::mt103::parse_mt103};
# let raw = "{1:F01BANKBEBBAXXX0000000000}{2:I103BANKDEFFXXXXN}{3:{108:R}}{4:\n:20:R\n:23B:CRED\n:32A:230615EUR1,00\n:52A:BANKBEBBAXXX\n:50K:A\n:57A:BANKDEFFXXXX\n:59:B\n:71A:SHA\n-}{5:{CHK:0}}";
# let mt103 = parse_mt103(&mt::parse(raw).unwrap().block4).unwrap();
# let doc = mt103_to_pacs008(&mt103, "M", "2023-06-15T10:00:00").unwrap().message;
let result = pacs008_to_mt103(&doc).unwrap();
assert!(result.message.contains(":20:"));
assert!(result.message.contains(":32A:"));

See the roundtrip and translate_mt103 examples in the umbrella mx20022 crate for end-to-end demos that include XML serialization.