regexes.go

package firevault

import (
	"regexp"
	"sync"
)

// regexCache provides thread-safe lazy compilation and caching of regex patterns
type regexCache struct {
	mu       sync.RWMutex
	patterns map[string]*regexp.Regexp
}

// global regex cache instance
var rxCache = &regexCache{
	patterns: make(map[string]*regexp.Regexp),
}

// getOrCompile retrieves a cached regex or compiles it if not present
func (rc *regexCache) getOrCompile(pattern string) *regexp.Regexp {
	// fast path: check if already compiled (read lock)
	rc.mu.RLock()
	if rx, exists := rc.patterns[pattern]; exists {
		rc.mu.RUnlock()
		return rx
	}
	rc.mu.RUnlock()

	// slow path: compile and cache (write lock)
	rc.mu.Lock()
	defer rc.mu.Unlock()

	// double-check after acquiring write lock (another goroutine may have compiled it)
	if rx, exists := rc.patterns[pattern]; exists {
		return rx
	}

	rx := regexp.MustCompile(pattern)
	rc.patterns[pattern] = rx
	return rx
}

// regex pattern constants
const (
	emailPattern              = "^(?:(?:(?:(?:[a-zA-Z]|\\d|[!#\\$%&'\\*\\+\\-\\/=\\?\\^_`{\\|}~]|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])+(?:\\.([a-zA-Z]|\\d|[!#\\$%&'\\*\\+\\-\\/=\\?\\^_`{\\|}~]|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])+)*)|(?:(?:\\x22)(?:(?:(?:(?:\\x20|\\x09)*(?:\\x0d\\x0a))?(?:\\x20|\\x09)+)?(?:(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x7f]|\\x21|[\\x23-\\x5b]|[\\x5d-\\x7e]|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])|(?:(?:[\\x01-\\x09\\x0b\\x0c\\x0d-\\x7f]|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}]))))*(?:(?:(?:\\x20|\\x09)*(?:\\x0d\\x0a))?(\\x20|\\x09)+)?(?:\\x22))))@(?:(?:(?:[a-zA-Z]|\\d|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])|(?:(?:[a-zA-Z]|\\d|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])(?:[a-zA-Z]|\\d|-|\\.|~|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])*(?:[a-zA-Z]|\\d|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])))\\.)+(?:(?:[a-zA-Z]|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])|(?:(?:[a-zA-Z]|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])(?:[a-zA-Z]|\\d|-|\\.|~|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])*(?:[a-zA-Z]|[\\x{00A0}-\\x{D7FF}\\x{F900}-\\x{FDCF}\\x{FDF0}-\\x{FFEF}])))\\.?$"
	lowerUpperBoundaryPattern = `([a-z])([A-Z])`
	upperDigitBoundaryPattern = `([A-Z])([0-9])`
	lowerDigitBoundaryPattern = `([a-z])([0-9])`
	digitInstancePattern      = `\d`
)

// emailRegex returns the compiled email validation regex
func emailRegex() *regexp.Regexp {
	return rxCache.getOrCompile(emailPattern)
}

// lowerUpperBoundaryRegex returns the compiled lower-upper boundary regex
func lowerUpperBoundaryRegex() *regexp.Regexp {
	return rxCache.getOrCompile(lowerUpperBoundaryPattern)
}

// upperDigitBoundaryRegex returns the compiled upper-digit boundary regex
func upperDigitBoundaryRegex() *regexp.Regexp {
	return rxCache.getOrCompile(upperDigitBoundaryPattern)
}

// lowerDigitBoundaryRegex returns the compiled lower-digit boundary regex
func lowerDigitBoundaryRegex() *regexp.Regexp {
	return rxCache.getOrCompile(lowerDigitBoundaryPattern)
}

// digitInstanceRegex returns the compiled digit instance regex
func digitInstanceRegex() *regexp.Regexp {
	return rxCache.getOrCompile(digitInstancePattern)
}