# Base64 Codec Review

Date: 2026-06-10
Issue: #55
Branch: `feat/issue-55-base64`

## Scope

Add focused Base64 codec primitives to `bluetape-rs-codec`:

- standard alphabet, padded and unpadded variants
- URL-safe alphabet, padded and unpadded variants
- project-owned typed decode error
- README and README.ko examples
- `base64` crate dependency through workspace dependencies

Base58 and Base62 are intentionally excluded and tracked by #63.

## 7-Tier Review

| Tier | Verdict | Evidence |
|---|---|---|
| 1. Public API / Contract | PASS | Public names make alphabet and padding policy explicit: standard vs URL-safe, padded vs `_unpadded`. Decode returns `Result<Vec<u8>, Base64DecodeError>`. |
| 2. Architecture / Boundary | PASS | The change stays inside `crates/codec` plus workspace dependency and README wiring. No compression, serde, Base58, or Base62 scope is mixed into #55. |
| 3. Rust API Shape | PASS | APIs use `impl AsRef<[u8]>` for encode input, `impl AsRef<str>` for decode input, owned output values, and a non-exhaustive error enum. No unsafe code or runtime state is introduced. |
| 4. Tests | PASS | Unit tests cover empty input, standard and URL-safe alphabets, padded and unpadded round trips, alphabet rejection, missing/extra padding rejection, invalid length, and diagnostic formatting. |
| 5. Static / Docs | PASS | Rustdoc examples compile under `RUSTDOCFLAGS="-D warnings"`; README and README.ko expose matching Base64 examples. |
| 6. Release / Cargo | PASS | `base64 = "0.22.1"` is added as a workspace dependency and consumed only by `bluetape-rs-codec`. `Cargo.lock` is refreshed. |
| 7. Evidence Integrity | PASS | The implementation was validated against the upstream `base64` 0.22.1 padding modes: `RequireCanonical` for padded engines and `RequireNone` for no-padding engines. Staged graph review analyzed 10 files with risk score 0.00 and test gaps 0. |

## P0/P1 Gate

P0=0 P1=0

Native review lanes:

- `code-reviewer`: PASS, P0=0 P1=0. Checked API scope, Rust surface, README parity, tests, cargo gates, and no unsafe/debug/secret patterns.
- `verifier`: PASS for local implementation, P0=0 P1=0. End-to-end workflow remains partial until PR/CI/post-PR gates complete.

No P2/P3 follow-up is required for #55. PR #62 is still open, so this branch may
need a rebase after #62 merges because both PRs touch codec README/Rustdoc
surface area.

## Validation

- `cargo test -p bluetape-rs-codec base64::tests:: --all-features --locked`: PASS
- `git diff --check`: PASS
- `cargo fmt --all --check`: PASS
- `cargo test -p bluetape-rs-codec --all-features --locked`: PASS
- `cargo test --workspace --all-features --locked`: PASS
- `cargo clippy --workspace --all-targets --all-features --locked -- -D warnings`: PASS
- `RUSTDOCFLAGS="-D warnings" cargo doc --workspace --all-features --no-deps --locked`: PASS
