package domain

import (
	"errors"
	"fmt"
)

var ErrInvalidStatusFacts = errors.New("invalid app status facts")

// AppStatusFacts are IO-free observations used to derive one visible state.
type AppStatusFacts struct {
	Operation        AppStatus
	Running          bool
	RecoveryPending  bool
	Incompatible     bool
	InstalledVersion string
	CatalogVersion   string
}

// ResolveAppStatus derives the single user-visible state from local and
// background-operation facts.
func ResolveAppStatus(facts AppStatusFacts) (AppStatus, error) {
	if facts.RecoveryPending {
		return StatusRollbackPending, nil
	}
	if facts.Operation != "" {
		if !validOperationStatus(facts.Operation) {
			return "", fmt.Errorf(
				"%w: operation %q",
				ErrInvalidStatusFacts,
				facts.Operation,
			)
		}
		return facts.Operation, nil
	}
	if facts.Running {
		return StatusRunning, nil
	}
	if facts.Incompatible {
		return StatusIncompatible, nil
	}
	if facts.InstalledVersion == "" {
		return StatusNotInstalled, nil
	}
	if _, err := ParseSemVer(facts.InstalledVersion); err != nil {
		return "", fmt.Errorf("%w: installed version: %v", ErrInvalidStatusFacts, err)
	}
	if facts.CatalogVersion == "" {
		return StatusInstalled, nil
	}
	comparison, err := CompareSemVer(facts.InstalledVersion, facts.CatalogVersion)
	if err != nil {
		return "", fmt.Errorf("%w: catalog version: %v", ErrInvalidStatusFacts, err)
	}
	if comparison < 0 {
		return StatusUpdateAvailable, nil
	}
	return StatusInstalled, nil
}

func validOperationStatus(status AppStatus) bool {
	switch status {
	case StatusQueued,
		StatusDownloading,
		StatusVerifying,
		StatusExtracting,
		StatusInstalling,
		StatusFailed:
		return true
	default:
		return false
	}
}