feat: add exponential backoff, some UI elements to see the resut of a scrape

scraper/internal/writer/writer.go

@@ -19,6 +19,8 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"sort"
+	"strconv"
 	"strings"
 
 	"github.com/libnovel/scraper/internal/scraper"
@@ -113,7 +115,101 @@ func (w *Writer) WriteChapter(slug string, chapter scraper.Chapter) error {
 	return nil
 }
 
-// ─── Path helpers ─────────────────────────────────────────────────────────────
+// ─── Catalogue helpers ────────────────────────────────────────────────────────
+
+// ListBooks returns metadata for every book that has a metadata.yaml under root.
+// Books with unreadable metadata files are silently skipped.
+func (w *Writer) ListBooks() ([]scraper.BookMeta, error) {
+	entries, err := os.ReadDir(w.root)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("writer: list books: %w", err)
+	}
+	var books []scraper.BookMeta
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		meta, ok, _ := w.ReadMetadata(e.Name())
+		if !ok {
+			continue
+		}
+		books = append(books, meta)
+	}
+	sort.Slice(books, func(i, j int) bool {
+		return books[i].Title < books[j].Title
+	})
+	return books, nil
+}
+
+// ChapterInfo is a lightweight chapter descriptor derived from on-disk files.
+type ChapterInfo struct {
+	Number int
+	Title  string // first line of the markdown file (without the leading "# ")
+}
+
+// ListChapters returns all chapters on disk for slug, sorted by number.
+func (w *Writer) ListChapters(slug string) ([]ChapterInfo, error) {
+	bookDir := w.bookDir(slug)
+	var chapters []ChapterInfo
+
+	// Walk vol-*/range-*/ directories.
+	volDirs, err := filepath.Glob(filepath.Join(bookDir, "vol-*"))
+	if err != nil {
+		return nil, fmt.Errorf("writer: list chapters glob: %w", err)
+	}
+	for _, vd := range volDirs {
+		rangeDirs, _ := filepath.Glob(filepath.Join(vd, "*-*"))
+		for _, rd := range rangeDirs {
+			files, _ := filepath.Glob(filepath.Join(rd, "chapter-*.md"))
+			for _, f := range files {
+				base := filepath.Base(f) // chapter-N.md
+				numStr := strings.TrimSuffix(strings.TrimPrefix(base, "chapter-"), ".md")
+				n, err := strconv.Atoi(numStr)
+				if err != nil {
+					continue
+				}
+				title := chapterTitle(f, n)
+				chapters = append(chapters, ChapterInfo{Number: n, Title: title})
+			}
+		}
+	}
+	sort.Slice(chapters, func(i, j int) bool {
+		return chapters[i].Number < chapters[j].Number
+	})
+	return chapters, nil
+}
+
+// chapterTitle reads the first non-empty line of a markdown file and strips
+// the leading "# " heading marker. Falls back to "Chapter N".
+func chapterTitle(path string, n int) string {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return fmt.Sprintf("Chapter %d", n)
+	}
+	for _, line := range strings.SplitN(string(data), "\n", 10) {
+		line = strings.TrimSpace(line)
+		if line == "" {
+			continue
+		}
+		return strings.TrimPrefix(line, "# ")
+	}
+	return fmt.Sprintf("Chapter %d", n)
+}
+
+// ReadChapter returns the raw markdown content for chapter number n of slug.
+func (w *Writer) ReadChapter(slug string, n int) (string, error) {
+	// Reconstruct path using the same bucketing formula as chapterPath.
+	ref := scraper.ChapterRef{Number: n, Volume: 0}
+	path := w.chapterPath(slug, ref)
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return "", fmt.Errorf("writer: read chapter %d: %w", n, err)
+	}
+	return string(data), nil
+}
 
 // bookDir returns the root directory for a book slug.
 func (w *Writer) bookDir(slug string) string {