# Strict Hex Codec Review

## Scope

- Issue: #54
- Branch: `feat/issue-54-strict-hex`
- Reviewed diff: strict hex primitives in `bluetape-rs-codec`, public README
  examples, and focused unit/Rustdoc coverage.

## Findings

- P0: 0
- P1: 0
- P2: 0
- P3: 0

No blocker findings.

## Review Notes

- API shape is Rust-native: byte slices are accepted through `AsRef<[u8]>`,
  decode accepts `AsRef<str>`, encode returns owned `String`, and decode returns
  `Result<Vec<u8>, HexDecodeError>`.
- Error contract is typed and diagnostic enough for service logs:
  `OddLength { len }` and `InvalidCharacter { index, byte }`.
- The decoder is strict: no prefixes, whitespace, separators, or non-ASCII
  digits are accepted.
- No dependency was added for hex encoding. The implementation is small enough
  to keep first-party and avoids adding a wrapper dependency for #54.
- Tests cover empty input, binary bytes, lowercase/uppercase output, mixed-case
  decode, odd length, invalid high/low nibble positions, non-ASCII input, and
  error formatting.

## Validation

| Check | Status | Evidence |
| --- | --- | --- |
| Diff whitespace | PASS | `git diff --check` |
| Format | PASS | `cargo fmt --all --check` |
| Issue acceptance test | PASS | `cargo test -p bluetape-rs-codec --all-features --locked` |
| Workspace tests | PASS | `cargo test --workspace` |
| Clippy | PASS | `cargo clippy --workspace --all-targets --all-features -- -D warnings` |

## Verdict

PASS. P0=0 P1=0.
