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package goparsify
import (
"bytes"
"fmt"
"strings"
"unicode/utf8"
)
type Node struct {
Token string
Children []*Node
Result interface{}
}
type Parser func(*State) *Node
// Parserish types are any type that can be turned into a Parser by Parsify
// These currently include *Parser and string literals.
//
// This makes recursive grammars cleaner and allows string literals to be used directly in most contexts.
// eg, matching balanced paren:
// ```go
// var group Parser
// group = And("(", Maybe(&group), ")")
// ```
// vs
// ```go
// var group ParserPtr{}
// group.P = And(Exact("("), Maybe(group.Parse), Exact(")"))
// ```
type Parserish interface{}
func Parsify(p Parserish) Parser {
switch p := p.(type) {
//case func(*State) *Node:
// return NewParser("anonymous func", p)
case Parser:
return p
case *Parser:
// Todo: Maybe capture this stack and on nil show it? Is there a good error library to do this?
return func(ptr *State) *Node {
return (*p)(ptr)
}
case string:
return Exact(p)
default:
panic(fmt.Errorf("cant turn a `%T` into a parser", p))
}
}
func ParsifyAll(parsers ...Parserish) []Parser {
ret := make([]Parser, len(parsers))
for i, parser := range parsers {
ret[i] = Parsify(parser)
}
return ret
}
func ParseString(parser Parserish, input string) (result interface{}, remaining string, err error) {
p := Parsify(parser)
ps := &State{input, 0, Error{}}
ret := p(ps)
if ps.Error.Expected != "" {
return nil, ps.Get(), ps.Error
}
return ret.Result, ps.Get(), nil
}
func Exact(match string) Parser {
return NewParser(match, func(ps *State) *Node {
if !strings.HasPrefix(ps.Get(), match) {
ps.ErrorHere(match)
return nil
}
ps.Advance(len(match))
return &Node{Token: match}
})
}
func parseRepetition(defaultMin, defaultMax int, repetition ...int) (min int, max int) {
min = defaultMin
max = defaultMax
switch len(repetition) {
case 0:
case 1:
min = repetition[0]
case 2:
min = repetition[0]
max = repetition[1]
default:
panic(fmt.Errorf("Dont know what %d repetion args mean", len(repetition)))
}
return min, max
}
// parseMatcher turns a string in the format a-f01234A-F into:
// - a set string of matches string(01234)
// - a set of ranges [][]rune{{'a', 'f'}, {'A', 'F'}}
func parseMatcher(matcher string) (matches string, ranges [][]rune) {
runes := []rune(matcher)
for i := 0; i < len(runes); i++ {
if i+2 < len(runes) && runes[i+1] == '-' {
start := runes[i]
end := runes[i+2]
if start <= end {
ranges = append(ranges, []rune{start, end})
} else {
ranges = append(ranges, []rune{end, start})
}
} else if i+1 < len(runes) && runes[i] == '\\' {
matches += string(runes[i+1])
} else {
matches += string(runes[i])
}
}
return matches, ranges
}
func Chars(matcher string, repetition ...int) Parser {
return NewParser("["+matcher+"]", charsImpl(matcher, false, repetition...))
}
func NotChars(matcher string, repetition ...int) Parser {
return NewParser("!["+matcher+"]", charsImpl(matcher, true, repetition...))
}
func charsImpl(matcher string, stopOn bool, repetition ...int) Parser {
min, max := parseRepetition(1, -1, repetition...)
matches, ranges := parseMatcher(matcher)
return func(ps *State) *Node {
matched := 0
for ps.Pos+matched < len(ps.Input) {
if max != -1 && matched >= max {
break
}
r, w := utf8.DecodeRuneInString(ps.Input[ps.Pos+matched:])
anyMatched := strings.ContainsRune(matches, r)
if !anyMatched {
for _, rng := range ranges {
if r >= rng[0] && r <= rng[1] {
anyMatched = true
}
}
}
if anyMatched == stopOn {
break
}
matched += w
}
if matched < min {
ps.ErrorHere(matcher)
return nil
}
result := ps.Input[ps.Pos : ps.Pos+matched]
ps.Advance(matched)
return &Node{Token: result}
}
}
var ws = NewParser("WS", Chars("\t\n\v\f\r \x85\xA0", 0))
func WS(ps *State) *Node {
ws(ps)
return nil
}
func String(quote rune) Parser {
return NewParser("string", func(ps *State) *Node {
var r rune
var w int
var matched int
r, matched = utf8.DecodeRuneInString(ps.Input[ps.Pos:])
if r != quote {
ps.ErrorHere("\"")
return nil
}
result := &bytes.Buffer{}
for ps.Pos+matched < len(ps.Input) {
r, w = utf8.DecodeRuneInString(ps.Input[ps.Pos+matched:])
matched += w
if r == '\\' {
r, w = utf8.DecodeRuneInString(ps.Input[ps.Pos+matched:])
result.WriteRune(r)
matched += w
continue
}
if r == quote {
ps.Advance(matched)
return &Node{Token: result.String()}
}
result.WriteRune(r)
}
ps.ErrorHere("\"")
return nil
})
}
|
