package bus

import (
	"fmt"
	"strings"
)

// match reports whether subject matches pattern using the wildcard rules
// described in the package comment: "*" matches exactly one non-empty token,
// ">" matches one or more trailing tokens and must be the last token, and any
// other token matches an identical subject token. Callers must have validated
// both inputs, so an empty token or a misplaced ">" never reaches here.
func match(pattern, subject string) bool {
	p := strings.Split(pattern, ".")
	s := strings.Split(subject, ".")
	i, j := 0, 0
	for i < len(p) {
		if p[i] == ">" {
			// ">" is guaranteed to be the last token; it needs at least one
			// remaining subject token.
			return j < len(s)
		}
		if j >= len(s) {
			return false
		}
		if p[i] != "*" && p[i] != s[j] {
			return false
		}
		i++
		j++
	}
	return j == len(s)
}

// validateSubject rejects an empty subject or one containing an empty token
// (leading/trailing/repeated dots).
func validateSubject(subject string) error {
	if subject == "" {
		return fmt.Errorf("bus: subject must not be empty: %w", ErrInvalidArgument)
	}
	if strings.HasPrefix(subject, ".") || strings.HasSuffix(subject, ".") || strings.Contains(subject, "..") {
		return fmt.Errorf("bus: subject %q contains an empty token: %w", subject, ErrInvalidArgument)
	}
	return nil
}

// validatePattern rejects an empty pattern, one with an empty token, or one
// where the ">" wildcard is not the final token.
func validatePattern(pattern string) error {
	if pattern == "" {
		return fmt.Errorf("bus: pattern must not be empty: %w", ErrInvalidArgument)
	}
	if strings.HasPrefix(pattern, ".") || strings.HasSuffix(pattern, ".") || strings.Contains(pattern, "..") {
		return fmt.Errorf("bus: pattern %q contains an empty token: %w", pattern, ErrInvalidArgument)
	}
	tokens := strings.Split(pattern, ".")
	for i, tok := range tokens {
		if tok == ">" && i != len(tokens)-1 {
			return fmt.Errorf("bus: pattern %q: '>' wildcard must be the last token: %w", pattern, ErrInvalidArgument)
		}
	}
	return nil
}