Below is the answer by Stuart in discord:
The specs for parsing transactions are here:
https://github.com/radixdlt/radixdlt/blob/develop/docs/transaction-specs/specs/parsing.md.
I implemented the spec to create my own parser but there is a Rust example here:
https://github.com/radixdlt/radixdlt/tree/develop/docs/transaction-specs/test/parser
The new core-api has a parse function that will take an unsigned or signed transaction blob and return the component parts.
Ref:
Thank, if the transaction is not existed yet (just in prepare step and not in the finalize step yet), can we do the parse with new core-api?
Yes, there is an “signed” option in the api call which you can just set to false and it will parse the unsigned transaction hex blob.
Thanks, I will try this soon.