package sessionbroker

import (
	"fmt"

	sessioncontracts "github.com/example/remote-access-platform/backend/pkg/contracts/session"
)

var allowedTransitions = map[sessioncontracts.State]map[sessioncontracts.State]struct{}{
	sessioncontracts.StateStarting: {
		sessioncontracts.StateActive:     {},
		sessioncontracts.StateFailed:     {},
		sessioncontracts.StateTerminated: {},
	},
	sessioncontracts.StateActive: {
		sessioncontracts.StateDetached:     {},
		sessioncontracts.StateReconnecting: {},
		sessioncontracts.StateFailed:       {},
		sessioncontracts.StateTerminated:   {},
	},
	sessioncontracts.StateDetached: {
		sessioncontracts.StateReconnecting: {},
		sessioncontracts.StateTerminated:   {},
		sessioncontracts.StateFailed:       {},
	},
	sessioncontracts.StateReconnecting: {
		sessioncontracts.StateActive:     {},
		sessioncontracts.StateDetached:   {},
		sessioncontracts.StateFailed:     {},
		sessioncontracts.StateTerminated: {},
	},
}

func validateTransition(from, to sessioncontracts.State) error {
	if from == to {
		return nil
	}
	if allowed, ok := allowedTransitions[from]; ok {
		if _, ok := allowed[to]; ok {
			return nil
		}
	}
	return fmt.Errorf("invalid session state transition: %s -> %s", from, to)
}