package catalogue

import (
	"regexp"
)

// settingRef is how a definition asks for an operator's value: ${setting:<key>}.
var settingRef = regexp.MustCompile(`\$\{setting:([a-z0-9][a-z0-9_.-]*)\}`)

// settingsUsed is every key a file's content asks for, once each, in order of first use.
func settingsUsed(content string) []string {
	var keys []string
	seen := map[string]bool{}
	for _, m := range settingRef.FindAllStringSubmatch(content, -1) {
		if !seen[m[1]] {
			seen[m[1]] = true
			keys = append(keys, m[1])
		}
	}
	return keys
}