package blocklist

import (
	"bufio"
	"os"
	"strings"
)

type Blocklist struct {
	domains map[string]struct{}
}

func Load(path string) (*Blocklist, error) {
	bl := &Blocklist{domains: make(map[string]struct{})}
	f, err := os.Open(path)
	if err != nil {
		if os.IsNotExist(err) {
			return bl, nil
		}
		return nil, err
	}
	defer f.Close()

	sc := bufio.NewScanner(f)
	for sc.Scan() {
		line := strings.TrimSpace(sc.Text())
		if line == "" || line[0] == '#' {
			continue
		}
		line = strings.ToLower(line)
		line = strings.TrimSuffix(line, ".")
		bl.domains[line] = struct{}{}
	}
	return bl, sc.Err()
}

func (bl *Blocklist) Blocked(qname string) bool {
	qname = strings.ToLower(qname)
	qname = strings.TrimSuffix(qname, ".")

	if _, ok := bl.domains[qname]; ok {
		return true
	}

	for i := 0; i < len(qname); i++ {
		if qname[i] == '.' {
			if _, ok := bl.domains[qname[i+1:]]; ok {
				return true
			}
		}
	}
	return false
}