# Alap Expression Parser — Rust
[Alap](https://github.com/DanielSmith/alap) is a JavaScript library that turns links into dynamic menus with multiple curated targets. This is the server-side Rust port of the expression parser, enabling expression resolution in Rust servers without a Node.js sidecar.
## What's included
- **`alap` crate** — Recursive descent parser for the Alap expression grammar, macro expansion, regex search, config merging, URL sanitization, regex validation
## What's NOT included
This is the server-side subset of `alap/core`. It covers expression parsing, config merging, URL sanitization, and regex validation — everything a server needs to resolve cherry-pick and query requests.
Browser-side concerns (DOM rendering, menu positioning, event handling) are handled by the JavaScript client and are not ported here.
## Supported expression syntax
```
item1, item2 # item IDs (comma-separated)
.coffee # tag query
.nyc + .bridge # AND (intersection)
(.nyc | .sf) + .open # parenthesized grouping
@favorites # macro expansion
/mypattern/ # regex search (by pattern key)
/mypattern/lu # regex with field options
```
## Usage
```rust
use alap::{Config, ExpressionParser, resolve, cherry_pick, merge_configs, sanitize_url};
let config: Config = serde_json::from_str(r#"{
"allLinks": {
"item1": { "label": "Example", "url": "https://example.com", "tags": ["demo"] },
"item2": { "label": "Other", "url": "https://other.com", "tags": ["demo", "test"] }
},
"macros": {
"all": { "linkItems": ".demo" }
}
}"#).unwrap();
// Low-level: get matching IDs
let mut parser = ExpressionParser::new(&config);
let ids = parser.query(".demo", ""); // ["item1", "item2"]
let ids = parser.query(".demo - .test", ""); // ["item1"]
// Resolve: expression → full link objects (URLs sanitized)
let results = resolve(&config, ".demo");
// Cherry-pick: expression → HashMap<id, Link> (URLs sanitized)
let subset = cherry_pick(&config, ".test");
// Merge multiple configs
let merged = merge_configs(&[&config1, &config2]);
// URL sanitization (standalone)
let safe = sanitize_url("javascript:alert(1)"); // "about:blank"
```
## Installation
Add to your `Cargo.toml`:
```toml
[dependencies]
alap = "0.1"
```
## Tests
```bash
cargo test
cargo clippy
```
35 tests across 8 tiers: operands, commas, operators, chaining, macros, parentheses, edge cases, and URL sanitization.
## Example Server
- [axum-sqlite](https://github.com/DanielSmith/alap/tree/main/examples/servers/axum-sqlite) — Rust + Axum + rusqlite, all 7 endpoints