feat: added getAddressAtIndex method and API

[andreabadesso]

Motivation

Currently the getAddressAtIndex method in the wallet service facade is broken since it expects this.seed to have the seed loaded and we don't keep it in memory, so it derives an address from an empty Mnemonic:

https://github.com/HathorNetwork/hathor-wallet-lib/blob/652b94e72021dd11cd0372d3a5b750d9d83f0e29/src/wallet/wallet.ts#L991

We could ask for the user's PIN and use his seed to derive the address at an index, but that would also force us to also ask the PIN on the fullnode facade, which is something we don't want to do.

Acceptance Criteria

• We should be able to fetch an address by its index
• We should include flake.nix, flake.lock and direnv files to setup a working nodejs14 environment using nix flakes

Security Checklist

• Make sure you do not include new dependencies in the project unless strictly necessary and do not include dev-dependencies as production ones. More dependencies increase the possibility of one of them being hijacked and affecting us.

[codecov]

Codecov Report

Merging #425 (a3a71a4) into master (196e53f) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #425      +/-   ##
==========================================
+ Coverage   95.56%   95.60%   +0.03%     
==========================================
  Files          40       40              
  Lines        2436     2458      +22     
  Branches      274      278       +4     
==========================================
+ Hits         2328     2350      +22     
  Misses        108      108              

Impacted Files	Coverage Δ
src/api/utils.ts	96.66% <ø> (ø)
src/types.ts	98.65% <ø> (ø)
src/api/addresses.ts	98.24% <100.00%> (+0.62%)	⬆️
src/api/errors.ts	100.00% <100.00%> (ø)
src/db/index.ts	99.67% <100.00%> (+<0.01%)	⬆️

[luislhl]

If this file accepts comments, I think we should explain what this is.

Maybe also mention in the README (or some other doc that we would link in the README) that we have these configs and how to use them.

[andreabadesso]

Done in 5c9ab39

[luislhl]

Why this change was needed?

[tuliomir]

I'm uncertain if this change should be made here. I feel that having it in its own PR would make it easy for future developers to understand that:

1. No other changes on the application were necessary (in case of a one-line PR), or
2. What changes had to be made with this lib update

[andreabadesso]

We have both mysql and mysql2 on the project, mysql2 is used by sequelize during migrations

Both OkPacket are exactly the same on both libraries, I changed this because I needed a type from mysql2 but ended up not using it and forgot to rollback to mysql instead of mysql2

Changed mysql2 to mysql in 79b8d38

[luislhl]

For an address to be available in this table, we need to have had a transaction involving the address, right?

I'm asking this because, if this is true, then this new API you're building won't be able to actually derive a new address at an index, right?

I don't know how this API will be used to evaluate whether this is a limitation or not

[andreabadesso]

You're partially correct

We also make sure that the wallet always have at least MAX_GAP addresses starting from the last used index

So you're correct that this API won't be able to actually derive a new address at an index, but that's the expected behavior since this is exactly what the old facade does, so this is definetly a limitation but is not a problem for our use case

I added a notice in the API docs in 724fde2

[tuliomir]

I'm uncertain if this change should be made here. I feel that having it in its own PR would make it easy for future developers to understand that:

1. No other changes on the application were necessary (in case of a one-line PR), or
2. What changes had to be made with this lib update