refactor: make crawler importable and add export pipeline

Move monkeyd and pdfout out of internal/ so other modules can import them,
and add export.Export, which holds the crawl-to-PDF sequence the CLI used to
inline. The CLI now parses flags and delegates, so an embedding program gets
the same defaults and validation.

monkeyd-crawler/monkeyd/novel_test.go

@@ -0,0 +1,119 @@
+package monkeyd
+
+import (
+	"net/url"
+	"testing"
+)
+
+// novelFixture reproduces the two traits that break naive crawlers: the list is
+// newest-first, and chapter numbering has a gap (no chapter 4).
+const novelFixture = `<html><head><title>TEN TRUYEN</title></head><body>
+<h1>TEN TRUYEN</h1>
+<div class="list-chapters">
+  <div class="item"><div class="episode-title"><a href="https://monkeydd.com/n/5.html">5</a></div></div>
+  <div class="item"><div class="episode-title"><a href="https://monkeydd.com/n/3.html">3</a></div></div>
+  <div class="item"><div class="episode-title"><a href="/n/2.html">2</a></div></div>
+  <div class="item"><div class="episode-title"><a href="https://monkeydd.com/n/1.html">1</a></div></div>
+</div></body></html>`
+
+func TestParseNovelPageOrdersChaptersForReading(t *testing.T) {
+	novel, err := ParseNovelPage([]byte(novelFixture), "https://monkeydd.com/n.html")
+	if err != nil {
+		t.Fatalf("ParseNovelPage: %v", err)
+	}
+
+	if novel.Title != "TEN TRUYEN" {
+		t.Errorf("Title = %q", novel.Title)
+	}
+	if novel.Slug != "n" {
+		t.Errorf("Slug = %q, want %q", novel.Slug, "n")
+	}
+
+	wantLabels := []string{"1", "2", "3", "5"}
+	if len(novel.Chapters) != len(wantLabels) {
+		t.Fatalf("got %d chapters, want %d", len(novel.Chapters), len(wantLabels))
+	}
+	for i, want := range wantLabels {
+		if novel.Chapters[i].Label != want {
+			t.Errorf("chapter %d label = %q, want %q", i, novel.Chapters[i].Label, want)
+		}
+	}
+	// Relative hrefs must resolve against the novel URL.
+	if got, want := novel.Chapters[1].URL, "https://monkeydd.com/n/2.html"; got != want {
+		t.Errorf("chapter 2 URL = %q, want %q", got, want)
+	}
+}
+
+func TestParseNovelPageNoChapters(t *testing.T) {
+	if _, err := ParseNovelPage([]byte(`<html><title>x</title><body></body></html>`),
+		"https://monkeydd.com/n.html"); err == nil {
+		t.Fatal("want an error when no chapters are listed")
+	}
+}
+
+const selectFixture = `<html><body>
+<select name="selected_chapter" id="selected_chapter">
+  <option value="n,5">5</option>
+  <option value="n,chuong-3">Chương 3</option>
+  <option value="n,1">1</option>
+  <option value="14">malformed</option>
+</select></body></html>`
+
+func TestChapterRefsFromSelect(t *testing.T) {
+	base, err := url.Parse("https://monkeydd.com/n.html")
+	if err != nil {
+		t.Fatal(err)
+	}
+	refs, err := ChapterRefsFromSelect([]byte(selectFixture), base)
+	if err != nil {
+		t.Fatalf("ChapterRefsFromSelect: %v", err)
+	}
+
+	if len(refs) != 3 {
+		t.Fatalf("got %d refs %+v, want 3 (malformed option skipped)", len(refs), refs)
+	}
+	if got, want := refs[0].URL, "https://monkeydd.com/n/1.html"; got != want {
+		t.Errorf("first ref URL = %q, want %q", got, want)
+	}
+	if got, want := refs[1].URL, "https://monkeydd.com/n/chuong-3.html"; got != want {
+		t.Errorf("second ref URL = %q, want %q", got, want)
+	}
+}
+
+func TestReconcileChapterRefs(t *testing.T) {
+	ref := func(u string) ChapterRef { return ChapterRef{Label: u, URL: u} }
+
+	t.Run("dropdown superset wins", func(t *testing.T) {
+		list := []ChapterRef{ref("a"), ref("b")}
+		sel := []ChapterRef{ref("a"), ref("b"), ref("c")}
+
+		final, extra := ReconcileChapterRefs(list, sel)
+		if len(final) != 3 {
+			t.Errorf("got %d chapters, want the 3 from the dropdown", len(final))
+		}
+		if len(extra) != 0 {
+			t.Errorf("got %d extra, want 0", len(extra))
+		}
+	})
+
+	t.Run("disagreement is reported not silently merged", func(t *testing.T) {
+		list := []ChapterRef{ref("a"), ref("z")}
+		sel := []ChapterRef{ref("a"), ref("b")}
+
+		final, extra := ReconcileChapterRefs(list, sel)
+		if len(final) != 2 || final[1].URL != "z" {
+			t.Errorf("final = %+v, want the landing page list", final)
+		}
+		if len(extra) != 1 || extra[0].URL != "b" {
+			t.Errorf("extra = %+v, want [b] so the caller can warn", extra)
+		}
+	})
+
+	t.Run("empty dropdown falls back to the list", func(t *testing.T) {
+		list := []ChapterRef{ref("a")}
+		final, extra := ReconcileChapterRefs(list, nil)
+		if len(final) != 1 || len(extra) != 0 {
+			t.Errorf("final = %+v, extra = %+v", final, extra)
+		}
+	})
+}