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|
package bechars
import (
"fmt"
"strings"
"src.userspace.com.au/felix/lexer"
)
const (
lower = "abcdefghijklmnopqrstuvwxyz"
upper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
numeric = "0123456789"
space = " \t\n\r\f\v"
punct = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~]"
)
// Generator will generate strings of characters
// that match the provided POSIX bracket expression.
type Generator struct {
l *lexer.Lexer
tok *lexer.Token
maxRune *rune
minRune *rune
}
// Option functions allows configuration of the generator.
type Option func(*Generator) error
// New creates a new generator.
func New(opts ...Option) (*Generator, error) {
out := new(Generator)
for _, o := range opts {
if err := o(out); err != nil {
return nil, err
}
}
return out, nil
}
// MaxRune sets the maximum rune for any generated sequences.
func MaxRune(r rune) Option {
return func(g *Generator) error {
g.maxRune = &r
return nil
}
}
// MinRune sets the minimum rune for any generated sequences.
func MinRune(r rune) Option {
return func(g *Generator) error {
g.minRune = &r
return nil
}
}
func ensureRangeLimits(g *Generator) {
if g.maxRune == nil {
maxRune := '\u007F'
g.maxRune = &maxRune
}
if g.minRune == nil {
minRune := '\u0000'
g.minRune = &minRune
}
}
func (g *Generator) next() bool {
var ok bool
g.tok, ok = g.l.NextToken()
return g.tok != nil && !ok
}
// Generate will return the string from the POSIX bracket expression.
func (g *Generator) Generate(be string) (string, error) {
ensureRangeLimits(g)
g.l = lexer.New(be, startState)
g.l.Start()
g.next()
if g.tok.Type != tBREStart {
return "", fmt.Errorf("missing opening '['")
}
return g.buildSequence()
}
func (g *Generator) buildSequence() (string, error) {
var out strings.Builder
for g.next() {
//fmt.Println(g.tok.Value)
switch g.tok.Type {
case tCharacter:
out.WriteString(g.tok.Value)
case tClass:
s, err := g.getClass(g.tok.Value)
if err != nil {
return "", err
}
out.WriteString(g.filter(s, ""))
case tRangeStart:
start := g.tok.Value
if g.next(); g.tok.Type != tRangeDash {
// Impossible situ?
return "", fmt.Errorf("invalid range")
}
if g.next(); g.tok.Type != tRangeEnd {
return "", fmt.Errorf("invalid range")
}
end := g.tok.Value
s := g.getRange([]rune(start)[0], []rune(end)[0])
out.WriteString(g.filter(s, ""))
case tBREStart, tBREEnd:
// No op
case tNot:
nots, err := g.buildSequence()
if err != nil {
return "", err
}
s := g.getRange(*g.minRune, *g.maxRune)
out.WriteString(g.filter(s, nots))
case lexer.ErrorToken:
return "", fmt.Errorf("%s", g.tok.Value)
default:
panic("invalid token")
}
}
return out.String(), nil
}
func (g Generator) getClass(c string) (string, error) {
var out string
switch c {
case ":alnum:":
out = numeric + upper + lower
case ":cntrl:":
out = g.getRange('\u0000', '\u001F') + "\u007F"
case ":lower:":
out = lower
case ":space:":
out = space
case ":alpha:":
out = upper + lower
case ":digit:":
out = numeric
case ":print:":
fallthrough
case ":graph:":
c, err := g.getClass(":cntrl:")
if err != nil {
return "", err
}
out = g.filter(g.getRange(*g.minRune, *g.maxRune), c)
case ":upper:":
out = upper
case ":blank:":
out = " \t"
case ":word:":
c, err := g.getClass(":alnum:")
if err != nil {
return "", err
}
out = c + "_"
case ":punct:":
out = punct
case ":xdigit:":
out = "abcdefABCDEF" + numeric
default:
return "", fmt.Errorf("invalid class '%s'", c)
}
return out, nil
}
func (g *Generator) getRange(start, end rune) string {
// Swap?
if start > end {
tmp := start
start = end
end = tmp
}
var out strings.Builder
for i := start; i <= end; i++ {
out.WriteRune(i)
}
return out.String()
}
func (g *Generator) filter(in, exclude string) string {
var out strings.Builder
for _, r := range in {
if r < *g.minRune {
continue
}
if r > *g.maxRune {
continue
}
if strings.ContainsRune(exclude, r) {
continue
}
out.WriteRune(r)
}
return out.String()
}
|
