Adds prototype NFT Ownership flow for use in demo

[krhoda]

Description

Adds a prototype NFT Ownership Verification flow. The implementation will likely change subsequently to it's use in a demo.

Notes on the nature of the changes to come are found in the comments and documentation. Until a final version of the NFT Ownership flow lands, Gitbook has been skipped. The documentation primarily says don't rely on it.

Type

• New feature (non-breaking change which adds functionality)

Diligence Checklist

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas.

[krhoda]

Need to finish adding to the docs and squashing commits before removing WIP.

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View logs

[krhoda]

WIP Closed, ready for review.

[sbihel]

I don't understand

[krhoda]

I want to modify them in the loop. I re-assign based on the first iteration.

[sbihel]

page_key is assigned and then directly used, so you don't need it to be "global", you can just do

let page_key = res.next_page.clone();

[krhoda]

res is used after the loop, how do I do that? I tried returning from the loop, but that seems to return out of the function:

     let res = loop {
            let inner_res = self
                .process_page(&client, next_u.clone(), &proof.statement.contract_address)
                .await?;

            if inner_res.found {
                return inner_res;
            }

            let page_key = inner_res.next_page.clone();
            match page_key {
                None => return inner_res,
                Some(s) => {
                    next_u = u.join(&format!("&pageKey={}", s)).map_err(|_e| {
                        FlowError::BadLookup("Could not follow paginated results".to_string())
                    })?;
                }
            }
        };

gets:

warning: unreachable statement
 --> src/flow/nft_ownership.rs:190:9
  |
170 |           let res = loop {
  |  ___________________-
171 | |             let inner_res = self
172 | |                 .process_page(&client, next_u.clone(), &proof.statement.contract_address)
173 | |                 .await?;
...   |
187 | |             }
188 | |         };
  | |_________- any code following this expression is unreachable

And:

error[E0308]: mismatched types
  --> src/flow/nft_ownership.rs:176:24
   |
176 |                 return inner_res;

[sbihel]

You can do break inner_res

[sbihel]

Don't use a mut, return from the loop

[krhoda]

How do I modify these values between iterations of the loop?

[sbihel]

Like page_key, res is assigned and used in the same loop, so I would do

     let res = loop {
            let res = self
                .process_page(&client, next_u.clone(), &proof.statement.contract_address)
                .await?;

            if res.found {
                break;
            }

            page_key = res.next_page.clone();
            match page_key {
                None => break res,
                Some(s) => {
                    next_u = u.join(&format!("&pageKey={}", s)).map_err(|_e| {
                        FlowError::BadLookup("Could not follow paginated results".to_string())
                    })?;
                }
            }
        };

[krhoda]

What about next_u?

[sbihel]

In that case it's fine because it's changed in one iteration of the loop and used in the next one. But actually, is this correct? Because it just keeps adding &pageKey={} to the URL?

[krhoda]

If you look close, I keep using the url that next_u is cloned from. I never modify the original url, just use it to generate next_u.

[sbihel]

indeed! 😪