package inventory

import "fmt"

// CatalogStatus represents the lifecycle stage of a cataloged hardware item.
// Stored as the catalog_status custom field value in NetBox.
type CatalogStatus string

const (
	StatusDraft         CatalogStatus = "draft"
	StatusIndexed       CatalogStatus = "indexed"
	StatusNeedsResearch CatalogStatus = "needs_research"
	StatusResearched    CatalogStatus = "researched"
	StatusComplete      CatalogStatus = "complete"
)

// validTransitions defines the allowed state machine transitions.
// No backward transitions are permitted (lifecycle is forward-only).
var validTransitions = map[CatalogStatus][]CatalogStatus{
	StatusDraft:         {StatusIndexed},
	StatusIndexed:       {StatusNeedsResearch, StatusResearched},
	StatusNeedsResearch: {StatusResearched},
	StatusResearched:    {StatusComplete},
	StatusComplete:      {}, // terminal — no further transitions
}

// CanTransitionTo returns true if transitioning from s to next is permitted.
func (s CatalogStatus) CanTransitionTo(next CatalogStatus) bool {
	allowed, ok := validTransitions[s]
	if !ok {
		return false
	}
	for _, a := range allowed {
		if a == next {
			return true
		}
	}
	return false
}

// Transition attempts to move from current to next status.
// Returns the new status on success, or an error describing the invalid transition.
func Transition(current, next CatalogStatus) (CatalogStatus, error) {
	if !current.CanTransitionTo(next) {
		return "", fmt.Errorf("invalid transition: %s → %s (not in valid transitions map)", current, next)
	}
	return next, nil
}

// ParseCatalogStatus parses a string to a CatalogStatus.
// Returns error for unknown status values.
func ParseCatalogStatus(s string) (CatalogStatus, error) {
	cs := CatalogStatus(s)
	if _, ok := validTransitions[cs]; ok {
		return cs, nil
	}
	return "", fmt.Errorf("unknown catalog status: %q (valid: draft, indexed, needs_research, researched, complete)", s)
}

// AllStatuses returns all valid catalog statuses in lifecycle order.
func AllStatuses() []CatalogStatus {
	return []CatalogStatus{
		StatusDraft, StatusIndexed, StatusNeedsResearch, StatusResearched, StatusComplete,
	}
}