package conversation

import (
	"errors"
	"fmt"
)

type Status string

const (
	StatusPreparing     Status = "PREPARING"
	StatusRoomIssued    Status = "ROOM_ISSUED"
	StatusStartingAgent Status = "STARTING_AGENT"
	StatusActive        Status = "ACTIVE"
	StatusStopping      Status = "STOPPING"
	StatusCompleted     Status = "COMPLETED"
	StatusFailed        Status = "FAILED"
	StatusExpired       Status = "EXPIRED"
)

var ErrInvalidTransition = errors.New("invalid conversation state transition")

var transitions = map[Status]map[Status]struct{}{
	StatusPreparing:     {StatusRoomIssued: {}, StatusFailed: {}},
	StatusRoomIssued:    {StatusStartingAgent: {}, StatusExpired: {}},
	StatusStartingAgent: {StatusActive: {}, StatusStopping: {}, StatusFailed: {}},
	StatusActive:        {StatusStopping: {}},
	StatusStopping:      {StatusCompleted: {}},
}

func ValidateTransition(from, to Status) error {
	if from == to && IsKnown(from) {
		return nil
	}
	if _, allowed := transitions[from][to]; !allowed {
		return fmt.Errorf("%w: %s -> %s", ErrInvalidTransition, from, to)
	}
	return nil
}

func IsTerminal(status Status) bool {
	return status == StatusCompleted || status == StatusFailed || status == StatusExpired
}

func IsKnown(status Status) bool {
	switch status {
	case StatusPreparing, StatusRoomIssued, StatusStartingAgent, StatusActive, StatusStopping, StatusCompleted, StatusFailed, StatusExpired:
		return true
	default:
		return false
	}
}