package filter

// BuildFromScripts builds a basic compact block filter from script elements and
// returns its BIP158 serialization.
//
// It removes empty scripts and exact duplicate scripts before building, which
// matches the BIP158 rule that nil elements are excluded and the basic filter
// element set is a set. It does not attempt to identify OP_RETURN scripts or to
// parse transactions: the caller must supply the basic filter element set,
// namely the previous output scripts spent by non-coinbase inputs plus the
// scriptPubKeys of all outputs except OP_RETURN outputs.
//
// The block hash is used in internal (little-endian) order, as for Build.
func BuildFromScripts(scripts [][]byte, blockHash [32]byte) []byte {
	items := make([][]byte, 0, len(scripts))
	seen := make(map[string]struct{}, len(scripts))
	for _, script := range scripts {
		if len(script) == 0 {
			continue
		}
		if _, ok := seen[string(script)]; ok {
			continue
		}
		seen[string(script)] = struct{}{}
		items = append(items, script)
	}
	return Build(items, blockHash)
}