package stdio

import (
	"reflect"
	"regexp"
	"sync"
	"unsafe"
)

// Unproven is the caller of a call the runtime named no caller for: one that arrived on the subject that names
// none, or from a runtime that names none (novox/hq issue 365). Said as a word, never left empty, so a record
// shows it was not proven.
const Unproven = "unproven"

// MetaCaller is where in a `tools/call`'s `_meta` the runtime names the caller: the bus user that published the
// call, which the runtime takes from the subject the call arrived on — that subject's last token, which the
// bus lets each user publish with its own name alone (novox/hq issue 365, by ADR 0259 §3's precedent). The
// runtime writes `_meta`; a caller writes only `arguments`, so no caller can name another.
const MetaCaller = "mesh/caller"

// busUser is the shape of a bus user's name: `<node>.<module>`, `person.<name>`, `controller` — names whose
// parts are safe in a subject. Anything else the runtime named is not a caller and reads as Unproven.
var busUser = regexp.MustCompile(`^[A-Za-z0-9_-]+(\.[A-Za-z0-9_-]+)*$`)

// calls holds the caller of every call while its tool runs, by the arguments map that call was handed.
var calls sync.Map // unsafe.Pointer → string

func argsKey(args map[string]any) unsafe.Pointer {
	return reflect.ValueOf(args).UnsafePointer()
}

// CallerOf is who called the tool that was handed args, as the runtime proved it: the bus user that
// published the call, or Unproven. Read from the runtime, never from the arguments' contents — a `caller`
// argument names nobody. Valid while the tool runs; arguments no call was handed have no caller.
func CallerOf(args map[string]any) string {
	if args == nil {
		return Unproven
	}
	if c, ok := calls.Load(argsKey(args)); ok {
		return c.(string)
	}
	return Unproven
}

// callerIn is the caller a `tools/call`'s `_meta` names, or Unproven.
func callerIn(meta map[string]any) string {
	if s, ok := meta[MetaCaller].(string); ok && busUser.MatchString(s) {
		return s
	}
	return Unproven
}

// runAs runs a tool with the caller held for its arguments for as long as it runs.
func runAs(t Tool, caller string, args map[string]any) (any, error) {
	key := argsKey(args)
	calls.Store(key, caller)
	defer calls.Delete(key)
	return t.Run(args)
}