vise/go/vm/input.go

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package vm
import (
"context"
"fmt"
"regexp"
"git.defalsify.org/festive/cache"
"git.defalsify.org/festive/state"
)
var (
inputRegexStr = "^[a-zA-Z0-9].*$"
inputRegex = regexp.MustCompile(inputRegexStr)
ctrlRegexStr = "^[><_^]$"
ctrlRegex = regexp.MustCompile(ctrlRegexStr)
symRegexStr = "^[a-zA-Z0-9][a-zA-Z0-9_]+$"
symRegex = regexp.MustCompile(symRegexStr)
)
// CheckInput validates the given byte string as client input.
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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.
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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.
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func ValidSym(input []byte) error {
if !symRegex.Match(input) {
return fmt.Errorf("Input '%s' does not match 'sym' format /%s/", input, symRegexStr)
}
return nil
}
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// false if target is not valid
func valid(target []byte) bool {
var ok bool
if len(target) == 0 {
return false
}
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err := ValidSym(target)
if err == nil {
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ok = true
}
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if !ok {
err = validControl(target)
if err == nil {
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ok = true
}
}
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return ok
}
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// 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
}
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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, ca cache.Memory, ctx context.Context) (string, uint16, error) {
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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
}
err = ca.Pop()
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
}
case '^':
notTop := true
for notTop {
notTop, err := st.Top()
if notTop {
break
}
sym, err = st.Up()
if err != nil {
return sym, idx, err
}
err = ca.Pop()
if err != nil {
return sym, idx, err
}
}
default:
sym = string(target)
err := st.Down(sym)
if err != nil {
return sym, idx, err
}
err = ca.Push()
if err != nil {
return sym, idx, err
}
idx = 0
}
return sym, idx, nil
}