# Policy Engine Development
The policy engine is implemented using [Common Expressions Languages](https://cel.dev).
This development document is ONLY for Policy v2, internally represented
as Filter V2 for naming consistency.
## Enum Constants
Protobuf enums are exposed as integer values in CEL. To improve policy readability, we generate enum constant maps that allow using symbolic names instead of integers.
**Example usage in policies:**
```cel
// Instead of: p.project.type == 1
p.project.type == ProjectSourceType.GITHUB
// Instead of: pkg.ecosystem == 2
pkg.ecosystem == Ecosystem.NPM
```
**How it works:**
- `pkg/analyzer/filterv2/enums.go` registers enums via `RegisteredEnums` by referencing protobuf-generated `Type_value` maps
- `pkg/analyzer/filterv2/enumgen/` generates `enums_generated.go` with constant maps
- Run `go generate ./pkg/analyzer/filterv2/` to regenerate after adding new enums
**Adding new enums:**
1. Add entry to `RegisteredEnums` in `pkg/analyzer/filterv2/enums.go`:
```go
{
Name: "SeverityRisk",
Prefix: "RISK_",
ValueMap: vulnerabilityv1.Severity_Risk_value,
}
```
2. Declare the enum variable in `pkg/analyzer/filterv2/eval.go` `NewEvaluator()`:
```go
cel.Variable("SeverityRisk", cel.MapType(cel.StringType, cel.IntType))
```
3. Run `go generate ./pkg/analyzer/filterv2/`
The generator automatically strips prefixes (e.g., `RISK_CRITICAL` → `CRITICAL`) and keeps enums synchronized with protobuf definitions.
