package vm import ( "context" "fmt" "regexp" "git.defalsify.org/festive/state" ) var ( inputRegexStr = "^[a-zA-Z0-9].*$" inputRegex = regexp.MustCompile(inputRegexStr) ctrlRegexStr = "^[<>_]$" ctrlRegex = regexp.MustCompile(inputRegexStr) symRegexStr = "^[a-zA-Z0-9][a-zA-Z0-9_]+$" symRegex = regexp.MustCompile(inputRegexStr) ) // CheckInput validates the given byte string as client input. func ValidInput(input []byte) error { if !inputRegex.Match(input) { return fmt.Errorf("Input '%s' does not match input format /%s/", input, inputRegexStr) } return nil } // control characters for relative navigation. func validControl(input []byte) error { if !ctrlRegex.Match(input) { return fmt.Errorf("Input '%s' does not match 'control' format /%s/", input, ctrlRegexStr) } return nil } // CheckSym validates the given byte string as a node symbol. func ValidSym(input []byte) error { if !symRegex.Match(input) { return fmt.Errorf("Input '%s' does not match 'sym' format /%s/", input, symRegexStr) } return nil } // false if target is not valid func valid(target []byte) bool { var ok bool if len(target) == 0 { return false } err := ValidSym(target) if err == nil { ok = true } if !ok { err = validControl(target) if err == nil { ok = true } } return ok } // CheckTarget tests whether the navigation state transition is available in the current state. // // Fails if target is formally invalid, or if navigation is unavailable. func CheckTarget(target []byte, st *state.State) (bool, error) { ok := valid(target) if !ok { return false, fmt.Errorf("invalid target: %x", target) } switch target[0] { case '_': topOk, err := st.Top() if err!= nil { return false, err } return topOk, nil case '<': _, prevOk := st.Sides() return prevOk, nil case '>': nextOk, _ := st.Sides() return nextOk, nil } return true, nil } // route parsed target symbol to navigation state change method, func applyTarget(target []byte, st *state.State, ctx context.Context) (string, uint16, error) { var err error sym, idx := st.Where() ok := valid(target) if !ok { return sym, idx, fmt.Errorf("invalid input: %x", target) } switch target[0] { case '_': sym, err = st.Up() if err != nil { return sym, idx, err } case '>': idx, err = st.Next() if err != nil { return sym, idx, err } case '<': idx, err = st.Previous() if err != nil { return sym, idx, err } default: sym = string(target) st.Down(sym) idx = 0 } return sym, idx, nil }