package parser

import (
	"bufio"
	"io"
	"strings"
)

func init() {
	RegisterDomainsParser(adblockDomainsParser{})
}

type adblockDomainsParser struct{}

func (adblockDomainsParser) CanHandle(line string) bool {
	return strings.HasPrefix(strings.ToLower(line), `[adblock`) ||
		strings.HasPrefix(line, "@@") || // exception
		strings.HasPrefix(line, "||") || // blah
		line[0] == '*'
}

func (adblockDomainsParser) ParseDomains(r io.Reader) (domains []string, ignored int, err error) {
	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if isComment(line) {
			continue
		}

		// Common AdBlock patterns:
		// ||domain.com^
		// |http://domain.com|
		// domain.com/path
		// *domain.com*
		switch {
		case strings.HasPrefix(line, `||`): // domain anchor
			if i := strings.IndexByte(line, '^'); i != -1 {
				domains = append(domains, line[2:i])
				continue
			}
		case strings.HasPrefix(line, `|`) && strings.HasSuffix(line, `|`):
			domains = append(domains, line[1:len(line)-2])
			continue
		case strings.HasPrefix(line, `[`):
			continue
		}
		ignored++
	}
	if err = scanner.Err(); err != nil {
		return
	}
	return unique(domains), ignored, nil
}