package role

type GrantChange struct {
	Key  string `json:"key"`
	From Scope  `json:"from"`
	To   Scope  `json:"to"`
}

type GrantDiff struct {
	Added   []Grant       `json:"added"`
	Removed []Grant       `json:"removed"`
	Changed []GrantChange `json:"changed"`
}

func (d GrantDiff) Empty() bool {
	return len(d.Added) == 0 && len(d.Removed) == 0 && len(d.Changed) == 0
}

func DiffGrants(before []Grant, after []Grant) GrantDiff {
	diff := GrantDiff{Added: []Grant{}, Removed: []Grant{}, Changed: []GrantChange{}}
	previous := scopesByKey(before)
	current := scopesByKey(after)
	for _, grant := range after {
		held, present := previous[grant.Key]
		if !present {
			diff.Added = append(diff.Added, grant)
		} else if held != grant.Scope {
			diff.Changed = append(diff.Changed, GrantChange{Key: grant.Key, From: held, To: grant.Scope})
		}
	}
	for _, grant := range before {
		if _, present := current[grant.Key]; !present {
			diff.Removed = append(diff.Removed, grant)
		}
	}
	return diff
}

func scopesByKey(grants []Grant) map[string]Scope {
	scopes := make(map[string]Scope, len(grants))
	for _, grant := range grants {
		scopes[grant.Key] = grant.Scope
	}
	return scopes
}