1 files changed, 148 insertions, 0 deletions
diff --git a/blockd.go b/blockd.go
new file mode 100644
index 0000000..398bb96
--- /dev/null
+++ b/blockd.go
@@ -0,0 +1,148 @@
+// SPDX-FileCopyrightText: 2020 M. Shulhan <ms@kilabit.info>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package rescached
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+const (
+	lastUpdatedFormat = "2006-01-02 15:04:05 MST"
+)
+
+type Blockd struct {
+	lastUpdated time.Time
+
+	Name string `ini:"::name"` // Derived from hostname in URL.
+	URL  string `ini:"::url"`
+
+	file         string
+	fileDisabled string
+	LastUpdated  string
+
+	IsEnabled   bool // True if the hosts file un-hidden in block.d directory.
+	isFileExist bool // True if the file exist and enabled or disabled.
+}
+
+// disable the hosts block by prefixing the file name with single dot.
+func (hb *Blockd) disable() (err error) {
+	err = os.Rename(hb.file, hb.fileDisabled)
+	if err != nil {
+		return fmt.Errorf("disable: %w", err)
+	}
+	hb.IsEnabled = false
+	return nil
+}
+
+// enable the hosts block file by removing the dot prefix from file name.
+func (hb *Blockd) enable() (err error) {
+	if hb.isFileExist {
+		err = os.Rename(hb.fileDisabled, hb.file)
+	} else {
+		err = os.WriteFile(hb.file, []byte(""), 0600)
+	}
+	if err != nil {
+		return fmt.Errorf("enable: %w", err)
+	}
+	hb.IsEnabled = true
+	hb.isFileExist = true
+	return nil
+}
+
+func (hb *Blockd) init(pathDirBlock string) {
+	var (
+		fi  os.FileInfo
+		err error
+	)
+
+	hb.file = filepath.Join(pathDirBlock, hb.Name)
+	hb.fileDisabled = filepath.Join(pathDirBlock, "."+hb.Name)
+
+	fi, err = os.Stat(hb.file)
+	if err != nil {
+		hb.IsEnabled = false
+
+		fi, err = os.Stat(hb.fileDisabled)
+		if err != nil {
+			return
+		}
+
+		hb.isFileExist = true
+	} else {
+		hb.IsEnabled = true
+		hb.isFileExist = true
+	}
+
+	hb.lastUpdated = fi.ModTime()
+	hb.LastUpdated = hb.lastUpdated.Format(lastUpdatedFormat)
+}
+
+// isOld will return true if the host file has not been updated since seven
+// days.
+func (hb *Blockd) isOld() bool {
+	oneWeek := 7 * 24 * time.Hour
+	lastWeek := time.Now().Add(-1 * oneWeek)
+
+	return hb.lastUpdated.Before(lastWeek)
+}
+
+func (hb *Blockd) update() (err error) {
+	if !hb.isOld() {
+		return nil
+	}
+
+	var (
+		logp = "Blockd.update"
+
+		res      *http.Response
+		body     []byte
+		errClose error
+	)
+
+	fmt.Printf("%s %s: updating ...\n", logp, hb.Name)
+
+	err = os.MkdirAll(filepath.Dir(hb.file), 0700)
+	if err != nil {
+		return fmt.Errorf("%s %s: %w", logp, hb.Name, err)
+	}
+
+	res, err = http.Get(hb.URL)
+	if err != nil {
+		return fmt.Errorf("%s %s: %w", logp, hb.Name, err)
+	}
+	defer func() {
+		errClose = res.Body.Close()
+		if errClose != nil {
+			log.Printf("%s %q: %s", logp, hb.Name, err)
+		}
+	}()
+
+	body, err = io.ReadAll(res.Body)
+	if err != nil {
+		return fmt.Errorf("%s %q: %w", logp, hb.Name, err)
+	}
+
+	body = bytes.ReplaceAll(body, []byte("\r\n"), []byte("\n"))
+
+	if hb.IsEnabled {
+		err = os.WriteFile(hb.file, body, 0644)
+	} else {
+		err = os.WriteFile(hb.fileDisabled, body, 0644)
+	}
+	if err != nil {
+		return fmt.Errorf("%s %q: %w", logp, hb.Name, err)
+	}
+
+	hb.lastUpdated = time.Now()
+	hb.LastUpdated = hb.lastUpdated.Format(lastUpdatedFormat)
+
+	return nil
+}