package stdio

import (
	"bytes"
	"encoding/json"
	"fmt"
	"strings"
)

// Callers is a module's trusted list of who may call a verb of its (novox/hq ADR 0459 §2, ADR 0563 §8), as the mesh
// writes a list setting into a file the module reads: `{"callers": [...]}`. An entry is a module's name (that module on
// any machine), exactly <machine>.<module>, or exactly person.<name>. Each caller is the runtime's proof (CallerOf), never
// an argument; nobody beyond the list is granted, a wildcard is no entry, and an unproven caller never matches.
type Callers []string

// ParseCallers reads a callers file: the list under `callers`, and nothing else.
func ParseCallers(raw []byte) (Callers, error) {
	var f struct {
		Callers Callers `json:"callers"`
	}
	dec := json.NewDecoder(bytes.NewReader(raw))
	dec.DisallowUnknownFields()
	if err := dec.Decode(&f); err != nil {
		return nil, fmt.Errorf("the callers setting is not a list of callers: %v", err)
	}
	return f.Callers, nil
}

// Allows says whether caller, as the runtime proved it, is one the list names.
func (c Callers) Allows(caller string) bool {
	if caller == "" || caller == Unproven {
		return false
	}
	for _, entry := range c {
		if entry == "" || strings.ContainsAny(entry, "*> ") {
			continue
		}
		if entry == caller {
			return true
		}
		if !strings.Contains(entry, ".") {
			if _, module, ok := strings.Cut(caller, "."); ok && module == entry && !strings.HasPrefix(caller, "person.") {
				return true
			}
		}
	}
	return false
}