subscriptions: prevent downloading already existing file

server/archive/utils.go

@@ -0,0 +1,58 @@
+package archive
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	"github.com/marcopiovanello/yt-dlp-web-ui/v3/server/config"
+)
+
+// Perform a search on the archive.txt file an determines if a download
+// has already be done.
+func DownloadExists(ctx context.Context, url string) (bool, error) {
+	cmd := exec.CommandContext(
+		ctx,
+		config.Instance().DownloaderPath,
+		"--print",
+		"%(extractor)s %(id)s",
+		url,
+	)
+	stdout, err := cmd.Output()
+	if err != nil {
+		return false, err
+	}
+
+	extractorAndURL := bytes.Trim(stdout, "\n")
+
+	fd, err := os.Open(filepath.Join(config.Instance().Dir(), "archive.txt"))
+	if err != nil {
+		return false, err
+	}
+	defer fd.Close()
+
+	scanner := bufio.NewScanner(fd)
+
+	// search linearly for lower memory usage...
+	// the a pre-sorted with hashed values version of the archive.txt file can be loaded in memory
+	// and perform a binary search on it.
+	for scanner.Scan() {
+		if bytes.Equal(scanner.Bytes(), extractorAndURL) {
+			return true, nil
+		}
+	}
+
+	// data, err := io.ReadAll(fd)
+	// if err != nil {
+	// 	return false, err
+	// }
+
+	// slices.BinarySearchFunc(data, extractorAndURL, func(a []byte, b []byte) int {
+	// 	return hash(a).Compare(hash(b))
+	// })
+
+	return false, nil
+}