Normalize labelhash for ENSRainbow Heal request

[tk-o]

@lightwalker-eth suggested

Suggest to define some utility function for normalizeLabelhash that takes the provided labelhash and then "normalizes" it into the format expected by the the ENSRainbow heal API.

Of course, normalizeLabelhash should throw an error if the provided labelhash cannot be normalized. This error should flow through the heal function being defined here. In the JSDoc comment on the heal function suggest documenting a @throws for the case that labelhash is not a valid labelhash.

[lightwalker-eth]

This goal should be implemented in the ENSRainbow SDK and NOT inside ENSRainbow.

[djstrong]

Some implementation is here: https://github.com/namehash/ens-utils/blob/64d9ad1e46c949fc85ce71f74a41095b1d58f7c5/src/hashutils.ts#L65

[lightwalker-eth]

Here's a more general description of the goals of this issue:

We should define a function parseEncodedLabelhash that takes as input a param called maybeEncodedLabelhash of type string and returns a validated and normalized labelhash value.

We should also define a function parseLabelhash that takes as input a param called maybeLabelhash of type string and returns a validated and normalized labelhash value.

parseEncodedLabelhash should:

1. Validate that the provided maybeEncodedLabelhash begins with "[" and ends with "]". If it does, it should strip those characters and pass the remainder to parseLabelhash. If it doesn't, it should throw an error.

parseLabelHash should:

1. Add 0x as a prefix to the input if the input doesn't begin with 0x.
2. Validate that all characters in the input (other than an optional 0x prefix) are valid hex digits (uppercase or lowercase).
3. If the number of hex digits is odd, add an implied 0 hex digit such that there are an even number of hex digits.
4. Validate that there are the expected number of hex digits for a labelhash.
5. Throw an error if any of the requirements described above fail.

Expected outcomes of parseEncodedLabelHash include:

1. 0000000000000000000000000000000000000000000000000000000000000000 throws error.
2. [0000000000000000000000000000000000000000000000000000000000000000 throws error.
3. 0000000000000000000000000000000000000000000000000000000000000000] throws error.
4. [00000000000000000000000000000000000000000000000000000000000000] throws error.
5. [00000000000000000000000000000000000000000000000000000000000000000] throws error.
6. [0000000000000000000000000000000000000000000000000000000000000000] returns 0x0000000000000000000000000000000000000000000000000000000000000000
7. [000000000000000000000000000000000000000000000000000000000000000] returns 0x0000000000000000000000000000000000000000000000000000000000000000.
8. [0x0000000000000000000000000000000000000000000000000000000000000000] returns 0x0000000000000000000000000000000000000000000000000000000000000000.
9. [0x000000000000000000000000000000000000000000000000000000000000000] returns 0x0000000000000000000000000000000000000000000000000000000000000000.
10. [0X0000000000000000000000000000000000000000000000000000000000000000] throws error.
11. [A000000000000000000000000000000000000000000000000000000000000000] returns 0xa000000000000000000000000000000000000000000000000000000000000000.
12. [A00000000000000000000000000000000000000000000000000000000000000] returns 0x0a000000000000000000000000000000000000000000000000000000000000000.

Then, inside the implementation of heal in the ENSRainbow SDK API client, it should attempt both parseEncodedLabelhash and parseLabelhash on the string value it is provided, such that we are maximally generous with the inputs it is able to accept and use successfully.