# Agent Notes
This crate parses Synapse (`.syn`) files with Pest and builds the AST used by the cFS code generator.
## Commands
From the workspace root:
```bash
cargo test -p synapse-parser
cargo run -p synapse-parser --example parse_synapse -- synapse-parser/examples/sample.syn
```
From this crate:
```bash
cargo test
cargo run --example parse_synapse -- examples/sample.syn
```
## Files
- `synapse.pest`: Pest PEG grammar.
- `src/lib.rs`: exposes `SynapseParser` and parser tests.
- `src/ast.rs`: converts Pest pairs into the public AST.
- `examples/parse_synapse.rs`: parser debugging CLI.
- `examples/sample.syn`: sample language file.
## Language Shape
Top-level items are `namespace`, `import`, `const`, `enum`, `struct`, `command`, `telemetry`, `table`, and legacy `message`.
Use `struct` for plain reusable ABI-shaped data. Use `command` for cFS Software Bus command packets; generators add `CFE_MSG_CommandHeader_t`. Use `telemetry` for cFS Software Bus telemetry packets; generators add `CFE_MSG_TelemetryHeader_t`. Use `table` for cFS Table Services payload data; generators do not add a Software Bus header. Legacy `message` remains accepted as a generic Software Bus packet.
Types include Rust-style primitives (`f32`, `f64`, `i8` through `i64`, `u8` through `u64`, `bool`, `bytes`), `string`, and user-defined refs such as `Point` or `geometry::Point`.
Array suffixes are:
- `[]`: dynamic
- `[N]`: fixed-size
- `[<=N]`: bounded dynamic
For `string`, `string[<=N]` means a bounded-length string, not an array of strings.
## Pest Ordering Rules
Pest ordered choice uses the first successful branch, so keep these grammar orderings intact:
- `base_type`: `string_type` before `primitive_type` before `type_ref`.
- `literal`: `float_lit` before `hex_lit` before `int_lit` before identifiers.
These prevent keywords and partial numeric literals from being parsed as broader fallback rules.