package agentprotocol

import (
	"errors"
	"strings"
	"time"
)

const Version = "v1"

type Capability struct {
	ID       string `json:"id"`
	Version  string `json:"version"`
	ReadOnly bool   `json:"readOnly"`
}
type Hello struct {
	Protocol     string       `json:"protocol"`
	AgentID      string       `json:"agentId"`
	ObservedAt   time.Time    `json:"observedAt"`
	Capabilities []Capability `json:"capabilities"`
}

func (h Hello) Validate(now time.Time) error {
	if h.Protocol != Version {
		return errors.New("unsupported agent protocol")
	}
	if strings.TrimSpace(h.AgentID) == "" || len(h.AgentID) > 120 {
		return errors.New("invalid agent id")
	}
	if h.ObservedAt.IsZero() || h.ObservedAt.After(now.Add(time.Minute)) {
		return errors.New("invalid agent observation time")
	}
	if len(h.Capabilities) > 50 {
		return errors.New("too many agent capabilities")
	}
	for _, capability := range h.Capabilities {
		if strings.TrimSpace(capability.ID) == "" || capability.Version == "" || !capability.ReadOnly {
			return errors.New("agent capability must be explicit and read-only")
		}
	}
	return nil
}