cratestack-core 0.2.3

# cratestack-core

Core types, traits, and error handling shared across the CrateStack workspace.

## Overview

`cratestack-core` provides the foundational types that the rest of the workspace depends on:

- **Error handling**: `CoolError` with HTTP status mapping and operator vs. public message split
- **Auth context**: `CoolContext`, `PrincipalContext`, `CoolAuthIdentity`, `AuthProvider`
- **Schema AST**: `Schema`, `Model`, `Field`, `Procedure`, `MixinDecl`, `TypeDecl`, `EnumDecl`
- **Audit**: `AuditEvent`, `AuditOperation`, `AuditActor`, `AuditSink`, `NoopAuditSink`, `MulticastAuditSink`
- **Signed envelope**: `HmacEnvelope` (HS256), `KeyProvider`, `StaticKeyProvider`, `NonceStore`, `InMemoryNonceStore`
- **Codec/envelope traits**: `CoolCodec`, `CoolEnvelope`, `NoEnvelope`
- **Event bus**: `CoolEventBus`, `ModelEvent<T>`, `ModelEventKind`, `CoolEventEnvelope`
- **Transaction isolation**: `TransactionIsolation`
- **Decimal scalar**: `Decimal` (compile-time backend)
- **Validators**: `validate_length`, `validate_range_i64`, `validate_range_decimal`, `validate_email`, `validate_uri`, `validate_iso4217`

## Installation

```toml
[dependencies]
cratestack-core = "0.2.2"
```

A `Decimal` backend feature must be selected. `decimal-rust-decimal` is the default; `decimal-bigdecimal` is reserved and not yet implemented (selecting it today is a compile error).

## Error Handling

`CoolError` returns a safe public message to clients while keeping operator-only detail for tracing.

```rust
use cratestack_core::CoolError;
use http::StatusCode;

let err = CoolError::BadRequest("missing query parameter".to_owned());
assert_eq!(err.status_code(), StatusCode::BAD_REQUEST);
assert_eq!(err.public_message(), "missing query parameter");

// 5xx variants return a fixed canned public message; the inner string flows to `detail` only.
let err = CoolError::Database("connection refused".to_owned());
assert_eq!(err.public_message(), "internal error");
assert_eq!(err.detail(), Some("connection refused"));
```

Variants: `BadRequest`, `NotAcceptable`, `Unauthorized`, `UnsupportedMediaType`, `Forbidden`, `NotFound`, `Conflict`, `Validation`, `PreconditionFailed`, `Codec`, `Database`, `Internal`. The codec/database/internal variants are 5xx-mapped.

## Auth Context

`CoolContext` carries the authenticated principal and arbitrary host-provided extensions.

```rust
use cratestack_core::{CoolContext, Value};

let ctx = CoolContext::anonymous();

let ctx = CoolContext::from_principal(Some(serde_json::json!({
    "id": "usr_123",
    "role": "admin",
    "tenant": { "id": "org_456" }
})))?;

assert_eq!(ctx.auth_field("id"), Some(&Value::String("usr_123".to_owned())));
assert_eq!(ctx.tenant_id(), Some("org_456"));
```

### AuthProvider

Host applications implement `AuthProvider` to resolve auth from HTTP requests:

```rust
use cratestack_core::{AuthProvider, CoolContext, CoolError, RequestContext};

#[derive(Clone)]
struct MyAuthProvider;

impl AuthProvider for MyAuthProvider {
    type Error = CoolError;

    async fn authenticate(&self, request: &RequestContext<'_>) -> Result<CoolContext, Self::Error> {
        let token = request.headers
            .get("authorization")
            .and_then(|v| v.to_str().ok())
            .ok_or_else(|| CoolError::Unauthorized("missing token".to_owned()))?;
        // Validate and project into CoolContext...
        Ok(CoolContext::anonymous())
    }
}
```

`AuthProvider` is also implemented blanket for any `Fn(&HeaderMap) -> Result<CoolContext, E>` closure.

## Audit Events

```rust
use cratestack_core::{AuditEvent, AuditOperation, AuditActor};
use chrono::Utc;

let event = AuditEvent {
    event_id: uuid::Uuid::new_v4(),
    schema_name: "banking".to_owned(),
    model: "Account".to_owned(),
    operation: AuditOperation::Update,
    primary_key: serde_json::json!({"id": "acc_123"}),
    actor: AuditActor {
        id: Some("usr_456".to_owned()),
        claims: Default::default(),
        ip: Some("192.168.1.1".to_owned()),
    },
    tenant: None,
    before: Some(serde_json::json!({"balance": 1000})),
    after: Some(serde_json::json!({"balance": 900})),
    request_id: Some("trace-abc".to_owned()),
    occurred_at: Utc::now(),
};
```

`AuditSink` is an async trait. The bundled implementations are `NoopAuditSink` and `MulticastAuditSink`. The in-database table written by `cratestack-sqlx` is treated as the canonical record; sinks are best-effort projections.

## Decimal Backend

```toml
[dependencies]
cratestack-core = { version = "0.2.2", features = ["decimal-rust-decimal"] }
```

```rust
use cratestack_core::Decimal;

let amount: Decimal = "123.45".parse()?;
```

## Transaction Isolation

```rust
use cratestack_core::TransactionIsolation;

let isolation = TransactionIsolation::parse("serializable")?;
assert_eq!(isolation.as_sql(), "SERIALIZABLE");
```

Accepts `read_committed` / `read committed`, `repeatable_read` / `repeatable read`, and `serializable`.

## Signed Envelope (HMAC-SHA-256)

`HmacEnvelope<K: KeyProvider>` implements `CoolEnvelope` for HS256-signed messages. Production multi-replica deployments back the `NonceStore` with Redis so replay rejection holds cluster-wide.

## See Also

- [Auth Provider guide](https://cratestack.dev/guides/auth-provider)
- [Audit Log guide](https://cratestack.dev/guides/audit-log)
- [Transaction Isolation guide](https://cratestack.dev/guides/transaction-isolation)
- [Validators guide](https://cratestack.dev/guides/validators)

## License

MIT