catalyst/caql/wildcard.go

// Adapted from https://github.com/golang/go
// Original License:
//
// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the https://go.dev/LICENSE file.

package caql

import (
	"errors"
	"strings"
	"unicode/utf8"
)

// ErrBadPattern indicates a pattern was malformed.
var ErrBadPattern = errors.New("syntax error in pattern")

// match reports whether name matches the shell pattern.
// The pattern syntax is:
//
//	pattern:
//		{ term }
//	term:
//		'%'         matches any sequence of non-/ characters
//		'_'         matches any single non-/ character
//		c           matches character c (c != '%', '_', '\\')
//		'\\' c      matches character c
//
// match requires pattern to match all of name, not just a substring.
// The only possible returned error is ErrBadPattern, when pattern
// is malformed.
//
func match(pattern, name string) (matched bool, err error) {
Pattern:
	for len(pattern) > 0 {
		var star bool
		var chunk string
		star, chunk, pattern = scanChunk(pattern)
		if star && chunk == "" {
			// Trailing * matches rest of string unless it has a /.
			return !strings.ContainsRune(name, '/'), nil
		}
		// Look for match at current position.
		t, ok, err := matchChunk(chunk, name)
		// if we're the last chunk, make sure we've exhausted the name
		// otherwise we'll give a false result even if we could still match
		// using the star
		if ok && (len(t) == 0 || len(pattern) > 0) {
			name = t

			continue
		}
		if err != nil {
			return false, err
		}
		if star {
			// Look for match skipping i+1 bytes.
			// Cannot skip /.
			for i := 0; i < len(name) && name[i] != '/'; i++ {
				t, ok, err := matchChunk(chunk, name[i+1:])
				if ok {
					// if we're the last chunk, make sure we exhausted the name
					if len(pattern) == 0 && len(t) > 0 {
						continue
					}
					name = t

					continue Pattern
				}
				if err != nil {
					return false, err
				}
			}
		}
		// Before returning false with no error,
		// check that the remainder of the pattern is syntactically valid.
		for len(pattern) > 0 {
			_, chunk, pattern = scanChunk(pattern)
			if _, _, err := matchChunk(chunk, ""); err != nil {
				return false, err
			}
		}

		return false, nil
	}

	return len(name) == 0, nil
}

// scanChunk gets the next segment of pattern, which is a non-star string
// possibly preceded by a star.
func scanChunk(pattern string) (star bool, chunk, rest string) {
	for len(pattern) > 0 && pattern[0] == '%' {
		pattern = pattern[1:]
		star = true
	}
	var i int
Scan:
	for i = 0; i < len(pattern); i++ {
		switch pattern[i] {
		case '\\':
			// error check handled in matchChunk: bad pattern.
			if i+1 < len(pattern) {
				i++
			}
		case '%':
			break Scan
		}
	}

	return star, pattern[0:i], pattern[i:]
}

// matchChunk checks whether chunk matches the beginning of s.
// If so, it returns the remainder of s (after the match).
// Chunk is all single-character operators: literals, char classes, and ?.
func matchChunk(chunk, s string) (rest string, ok bool, err error) {
	// failed records whether the match has failed.
	// After the match fails, the loop continues on processing chunk,
	// checking that the pattern is well-formed but no longer reading s.
	failed := false
	for len(chunk) > 0 {
		if !failed && len(s) == 0 {
			failed = true
		}
		switch chunk[0] {
		case '_':
			if !failed {
				if s[0] == '/' {
					failed = true
				}
				_, n := utf8.DecodeRuneInString(s)
				s = s[n:]
			}
			chunk = chunk[1:]
		case '\\':
			chunk = chunk[1:]
			if len(chunk) == 0 {
				return "", false, ErrBadPattern
			}

			fallthrough
		default:
			if !failed {
				if chunk[0] != s[0] {
					failed = true
				}
				s = s[1:]
			}
			chunk = chunk[1:]
		}
	}
	if failed {
		return "", false, nil
	}

	return s, true, nil
}