sjansen/mecha

package main

import (
    "fmt"
    "log"

    "github.com/google/cel-go/cel"
    "github.com/google/cel-go/checker/decls"
)

// https://github.com/google/cel-spec

func main() {
    env, err := cel.NewEnv(cel.Declarations(
        decls.NewConst("name", decls.String, nil),
        decls.NewVar("group", decls.String),
    ))
    if err != nil {
        log.Fatalf("env construction error: %s", err)
    }

    parsed, issues := env.Parse(`name.startsWith("/groups/" + group)`)
    if issues != nil && issues.Err() != nil {
        log.Fatalf("parse error: %s", issues.Err())
    }

    checked, issues := env.Check(parsed)
    if issues != nil && issues.Err() != nil {
        log.Fatalf("type-check error: %s", issues.Err())
    }

    prg, err := env.Program(checked)
    if err != nil {
        log.Fatalf("program construction error: %s", err)
    }

    out, details, err := prg.Eval(map[string]interface{}{
        "name":  "/groups/acme.co/documents/secret-stuff",
        "group": "acme.co",
    })
    if err != nil {
        log.Fatalf("program evaluation error: %s", err)
    }
    fmt.Println(out)
    fmt.Printf("%#v\n", details)
}