package campaign

import (
	"encoding/json"
	"io"
	"net/http"
	"net/http/httptest"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"testing"

	"gitea.reground.org/will/eec-campaigns/internal/listmonk"
)

// ---- fake listmonk server ----
//
// Following eec's/drip's existing pattern (httptest.NewServer fakes, no
// mocking library), but stateful enough to exercise sync.go's real
// idempotency/diff/segmentation logic rather than just counting hits.

type fakeList struct {
	ID   int
	Name string
}

type fakeCampaign struct {
	ID         int
	Name       string
	Status     string
	Subject    string
	Body       string
	AltBody    string
	FromEmail  string
	TemplateID int
	Type       string
	Tags       []string
	ListIDs    []int
	MediaIDs   []int
}

type fakeMedia struct {
	ID       int
	Filename string
}

type fakeTemplate struct {
	ID        int
	Name      string
	Body      string
	IsDefault bool
}

type testCall struct {
	CampaignID int
	Emails     []string
}

type segmentQueryCall struct {
	Query  string
	ListID int
}

type fakeListmonk struct {
	mu                sync.Mutex
	t                 *testing.T
	nextID            int
	lists             []fakeList
	campaigns         []fakeCampaign
	media             []fakeMedia
	templates         []fakeTemplate
	testCalls         []testCall
	segmentQueryCalls []segmentQueryCall
	failSegmentQuery  bool
}

func newFakeListmonk(t *testing.T) *fakeListmonk {
	return &fakeListmonk{t: t, nextID: 1}
}

func (f *fakeListmonk) id() int {
	id := f.nextID
	f.nextID++
	return id
}

func (f *fakeListmonk) client() *listmonk.Client {
	srv := httptest.NewServer(http.HandlerFunc(f.handle))
	f.t.Cleanup(srv.Close)
	return listmonk.New(srv.URL, "u", "t")
}

func (f *fakeListmonk) handle(w http.ResponseWriter, r *http.Request) {
	f.mu.Lock()
	defer f.mu.Unlock()

	switch {
	case r.Method == http.MethodGet && r.URL.Path == "/api/lists":
		f.writeLists(w)
	case r.Method == http.MethodPost && r.URL.Path == "/api/lists":
		f.createList(w, r)
	case r.Method == http.MethodGet && r.URL.Path == "/api/campaigns":
		f.writeCampaigns(w)
	case r.Method == http.MethodPost && r.URL.Path == "/api/campaigns":
		f.createCampaign(w, r)
	case r.Method == http.MethodPut && strings.HasSuffix(r.URL.Path, "/status"):
		f.setStatus(w, r)
	case r.Method == http.MethodPost && strings.HasSuffix(r.URL.Path, "/test"):
		f.recordTest(w, r)
	case r.Method == http.MethodPut && strings.HasPrefix(r.URL.Path, "/api/campaigns/"):
		f.updateCampaign(w, r)
	case r.Method == http.MethodGet && r.URL.Path == "/api/media":
		f.writeMedia(w)
	case r.Method == http.MethodPost && r.URL.Path == "/api/media":
		f.uploadMedia(w, r)
	case r.Method == http.MethodPut && r.URL.Path == "/api/subscribers/query/lists":
		f.queryAddToList(w, r)
	case r.Method == http.MethodGet && r.URL.Path == "/api/templates":
		f.writeTemplates(w)
	case r.Method == http.MethodPost && r.URL.Path == "/api/templates":
		f.createTemplate(w, r)
	case r.Method == http.MethodPut && strings.HasPrefix(r.URL.Path, "/api/templates/"):
		f.updateTemplate(w, r)
	default:
		f.t.Errorf("fakeListmonk: unhandled request %s %s", r.Method, r.URL.Path)
		w.WriteHeader(http.StatusNotFound)
	}
}

func (c fakeCampaign) toJSON() map[string]any {
	lists := make([]map[string]any, 0, len(c.ListIDs))
	for _, id := range c.ListIDs {
		lists = append(lists, map[string]any{"id": id})
	}
	media := make([]map[string]any, 0, len(c.MediaIDs))
	for _, id := range c.MediaIDs {
		media = append(media, map[string]any{"id": id})
	}
	return map[string]any{
		"id": c.ID, "name": c.Name, "status": c.Status, "subject": c.Subject,
		"body": c.Body, "altbody": c.AltBody, "from_email": c.FromEmail, "template_id": c.TemplateID,
		"type": c.Type, "tags": c.Tags, "lists": lists, "media": media,
	}
}

func (f *fakeListmonk) writeCampaigns(w http.ResponseWriter) {
	results := make([]map[string]any, 0, len(f.campaigns))
	for _, c := range f.campaigns {
		results = append(results, c.toJSON())
	}
	json.NewEncoder(w).Encode(map[string]any{"data": map[string]any{"results": results}})
}

// fakeDefaultTemplateID is the nonzero template_id real listmonk assigns
// server-side to a campaign whose create/update request omitted template_id
// entirely -- never 0, which is what makes the zero value ambiguous between
// "unspecified" and "really is 0" in campaignUnchanged.
const fakeDefaultTemplateID = 1

func (f *fakeListmonk) resolveTemplateID(body map[string]any) int {
	if v, ok := body["template_id"]; ok {
		return toInt(v)
	}
	return fakeDefaultTemplateID
}

func (f *fakeListmonk) createCampaign(w http.ResponseWriter, r *http.Request) {
	body := decodeBody(r)
	c := fakeCampaign{
		ID: f.id(), Name: str(body["name"]), Status: "draft",
		Subject: str(body["subject"]), Body: str(body["body"]), AltBody: str(body["altbody"]),
		FromEmail: str(body["from_email"]), TemplateID: f.resolveTemplateID(body),
		Type: str(body["type"]), Tags: toStrings(body["tags"]),
		ListIDs: toInts(body["lists"]), MediaIDs: toInts(body["media"]),
	}
	f.campaigns = append(f.campaigns, c)
	json.NewEncoder(w).Encode(map[string]any{"data": c.toJSON()})
}

func (f *fakeListmonk) updateCampaign(w http.ResponseWriter, r *http.Request) {
	id := pathID(r.URL.Path, "/api/campaigns/")
	body := decodeBody(r)
	for i := range f.campaigns {
		if f.campaigns[i].ID == id {
			f.campaigns[i].Subject = str(body["subject"])
			f.campaigns[i].Body = str(body["body"])
			f.campaigns[i].AltBody = str(body["altbody"])
			f.campaigns[i].FromEmail = str(body["from_email"])
			f.campaigns[i].TemplateID = f.resolveTemplateID(body)
			f.campaigns[i].Type = str(body["type"])
			f.campaigns[i].Tags = toStrings(body["tags"])
			f.campaigns[i].ListIDs = toInts(body["lists"])
			f.campaigns[i].MediaIDs = toInts(body["media"])
			json.NewEncoder(w).Encode(map[string]any{"data": f.campaigns[i].toJSON()})
			return
		}
	}
	w.WriteHeader(http.StatusNotFound)
}

func (f *fakeListmonk) setStatus(w http.ResponseWriter, r *http.Request) {
	id := pathID(strings.TrimSuffix(r.URL.Path, "/status"), "/api/campaigns/")
	body := decodeBody(r)
	for i := range f.campaigns {
		if f.campaigns[i].ID == id {
			f.campaigns[i].Status = str(body["status"])
			w.Write([]byte(`{}`))
			return
		}
	}
	w.WriteHeader(http.StatusNotFound)
}

func (f *fakeListmonk) recordTest(w http.ResponseWriter, r *http.Request) {
	id := pathID(strings.TrimSuffix(r.URL.Path, "/test"), "/api/campaigns/")
	body := decodeBody(r)
	f.testCalls = append(f.testCalls, testCall{CampaignID: id, Emails: toStrings(body["subscribers"])})
	w.Write([]byte(`{}`))
}

func (f *fakeListmonk) writeLists(w http.ResponseWriter) {
	results := make([]map[string]any, 0, len(f.lists))
	for _, l := range f.lists {
		results = append(results, map[string]any{"id": l.ID, "name": l.Name})
	}
	json.NewEncoder(w).Encode(map[string]any{"data": map[string]any{"results": results}})
}

func (f *fakeListmonk) createList(w http.ResponseWriter, r *http.Request) {
	body := decodeBody(r)
	l := fakeList{ID: f.id(), Name: str(body["name"])}
	f.lists = append(f.lists, l)
	json.NewEncoder(w).Encode(map[string]any{"data": map[string]any{"id": l.ID}})
}

func (f *fakeListmonk) writeMedia(w http.ResponseWriter) {
	results := make([]map[string]any, 0, len(f.media))
	for _, m := range f.media {
		results = append(results, map[string]any{"id": m.ID, "filename": m.Filename})
	}
	json.NewEncoder(w).Encode(map[string]any{"data": results})
}

func (f *fakeListmonk) uploadMedia(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseMultipartForm(10 << 20); err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	_, header, err := r.FormFile("file")
	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	m := fakeMedia{ID: f.id(), Filename: header.Filename}
	f.media = append(f.media, m)
	json.NewEncoder(w).Encode(map[string]any{"data": map[string]any{"id": m.ID}})
}

func (f *fakeListmonk) queryAddToList(w http.ResponseWriter, r *http.Request) {
	if f.failSegmentQuery {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(`{"message":"invalid SQL expression"}`))
		return
	}
	body := decodeBody(r)
	targetIDs := toInts(body["target_list_ids"])
	var listID int
	if len(targetIDs) > 0 {
		listID = targetIDs[0]
	}
	f.segmentQueryCalls = append(f.segmentQueryCalls, segmentQueryCall{Query: str(body["query"]), ListID: listID})
	w.Write([]byte(`{}`))
}

func (f *fakeListmonk) writeTemplates(w http.ResponseWriter) {
	results := make([]map[string]any, 0, len(f.templates))
	for _, t := range f.templates {
		results = append(results, map[string]any{"id": t.ID, "name": t.Name, "type": "campaign", "is_default": t.IsDefault})
	}
	json.NewEncoder(w).Encode(map[string]any{"data": results})
}

func (f *fakeListmonk) createTemplate(w http.ResponseWriter, r *http.Request) {
	body := decodeBody(r)
	isDefault, _ := body["is_default"].(bool)
	tpl := fakeTemplate{ID: f.id(), Name: str(body["name"]), Body: str(body["body"]), IsDefault: isDefault}
	f.templates = append(f.templates, tpl)
	json.NewEncoder(w).Encode(map[string]any{"data": map[string]any{"id": tpl.ID}})
}

func (f *fakeListmonk) updateTemplate(w http.ResponseWriter, r *http.Request) {
	id := pathID(r.URL.Path, "/api/templates/")
	body := decodeBody(r)
	for i := range f.templates {
		if f.templates[i].ID == id {
			f.templates[i].Name = str(body["name"])
			f.templates[i].Body = str(body["body"])
			f.templates[i].IsDefault, _ = body["is_default"].(bool)
			w.Write([]byte(`{}`))
			return
		}
	}
	w.WriteHeader(http.StatusNotFound)
}

func decodeBody(r *http.Request) map[string]any {
	var body map[string]any
	b, _ := io.ReadAll(r.Body)
	json.Unmarshal(b, &body)
	return body
}

func str(v any) string {
	s, _ := v.(string)
	return s
}

func toInt(v any) int {
	f, _ := v.(float64)
	return int(f)
}

func toStrings(v any) []string {
	arr, ok := v.([]any)
	if !ok {
		return nil
	}
	out := make([]string, 0, len(arr))
	for _, x := range arr {
		if s, ok := x.(string); ok {
			out = append(out, s)
		}
	}
	return out
}

func toInts(v any) []int {
	arr, ok := v.([]any)
	if !ok {
		return nil
	}
	out := make([]int, 0, len(arr))
	for _, x := range arr {
		if n, ok := x.(float64); ok {
			out = append(out, int(n))
		}
	}
	return out
}

func pathID(path, prefix string) int {
	id, _ := strconv.Atoi(strings.TrimPrefix(path, prefix))
	return id
}

// ---- test fixtures ----

func writeCampaignDir(t *testing.T, root, slug, frontmatterExtra, body string) {
	t.Helper()
	path := filepath.Join(root, "campaigns", slug, "campaign.md")
	writeFile(t, path, "---\n"+frontmatterExtra+"---\n"+body+"\n")
}

const baseFrontmatter = "subject: \"Big Announcement\"\nlists: [\"Newsletter\"]\nfrom_email: hello@example.com\n"

// ---- tests ----

func TestSyncDir_CreatesNewDraftCampaign(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	lm := f.client()

	root := t.TempDir()
	writeCampaignDir(t, root, "launch", baseFrontmatter, "Hello world.")

	result, err := SyncDir(lm, root, nil)
	if err != nil {
		t.Fatalf("SyncDir: %v", err)
	}
	if len(result.Rejected) != 0 {
		t.Fatalf("expected no rejections, got %v", result.Rejected)
	}
	if len(result.Synced) != 1 || result.Synced[0] != "launch" {
		t.Fatalf("expected launch in Synced, got %v", result.Synced)
	}
	if len(f.campaigns) != 1 {
		t.Fatalf("expected 1 campaign created, got %d", len(f.campaigns))
	}
	c := f.campaigns[0]
	if c.Status != "draft" {
		t.Errorf("expected status draft, got %q", c.Status)
	}
	if len(c.ListIDs) != 1 || c.ListIDs[0] != 3 {
		t.Errorf("expected list ID resolved to [3], got %v", c.ListIDs)
	}
}

func TestSyncDir_SecondSyncWithUnchangedContentIsNoop(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	lm := f.client()

	root := t.TempDir()
	writeCampaignDir(t, root, "launch", baseFrontmatter, "Hello world.")

	if _, err := SyncDir(lm, root, nil); err != nil {
		t.Fatalf("first SyncDir: %v", err)
	}
	result, err := SyncDir(lm, root, nil)
	if err != nil {
		t.Fatalf("second SyncDir: %v", err)
	}
	if len(result.Synced) != 0 {
		t.Errorf("expected no re-sync of unchanged content, got Synced=%v", result.Synced)
	}
	if len(result.Unchanged) != 1 || result.Unchanged[0] != "launch" {
		t.Errorf("expected launch in Unchanged, got %v", result.Unchanged)
	}
	if len(f.campaigns) != 1 {
		t.Errorf("expected still exactly 1 campaign, got %d", len(f.campaigns))
	}
}

func TestSyncDir_UnspecifiedTemplateIDDoesNotTriggerSpuriousResync(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	lm := f.client()

	root := t.TempDir()
	// baseFrontmatter never sets template_id, matching real campaign.md files
	// like reground-campaigns' welcome/campaign.md.
	writeCampaignDir(t, root, "launch", baseFrontmatter, "Hello world.")

	if _, err := SyncDir(lm, root, nil); err != nil {
		t.Fatalf("first SyncDir: %v", err)
	}
	if f.campaigns[0].TemplateID != fakeDefaultTemplateID {
		t.Fatalf("expected the fake to assign its default template_id like real listmonk does, got %d", f.campaigns[0].TemplateID)
	}

	// Re-sync with the exact same, still-unspecified template_id: this must
	// not be flagged as changed just because listmonk's stored, server-
	// assigned template_id (nonzero) doesn't literally equal the frontmatter's
	// unset value (0).
	result, err := SyncDir(lm, root, nil)
	if err != nil {
		t.Fatalf("second SyncDir: %v", err)
	}
	if len(result.Synced) != 0 {
		t.Errorf("expected no spurious re-sync from an unspecified template_id, got Synced=%v", result.Synced)
	}
	if len(result.Unchanged) != 1 || result.Unchanged[0] != "launch" {
		t.Errorf("expected launch in Unchanged, got %v", result.Unchanged)
	}
}

func TestSyncDir_UpdatesWhenContentChanges(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	lm := f.client()

	root := t.TempDir()
	writeCampaignDir(t, root, "launch", baseFrontmatter, "Hello world.")
	if _, err := SyncDir(lm, root, nil); err != nil {
		t.Fatalf("first SyncDir: %v", err)
	}

	writeCampaignDir(t, root, "launch", baseFrontmatter, "Hello, updated world.")
	result, err := SyncDir(lm, root, nil)
	if err != nil {
		t.Fatalf("second SyncDir: %v", err)
	}
	if len(result.Synced) != 1 || result.Synced[0] != "launch" {
		t.Fatalf("expected launch re-synced, got Synced=%v Unchanged=%v", result.Synced, result.Unchanged)
	}
	if len(f.campaigns) != 1 || !strings.Contains(f.campaigns[0].Body, "updated") {
		t.Errorf("expected the existing campaign's body to be updated, got %+v", f.campaigns[0])
	}
}

func TestSyncDir_SkipsNonDraftCampaignWithoutFailing(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	f.campaigns = []fakeCampaign{{ID: 1, Name: "launch", Status: "running", Subject: "Original"}}
	lm := f.client()

	root := t.TempDir()
	writeCampaignDir(t, root, "launch", baseFrontmatter, "Hello world.")

	result, err := SyncDir(lm, root, nil)
	if err != nil {
		t.Fatalf("SyncDir: %v", err)
	}
	// A sent/running campaign is a historical record, not an error -- it
	// must never land in Rejected (which fails the whole CI job) just
	// because its campaign.md is still around.
	if len(result.Rejected) != 0 {
		t.Fatalf("expected no rejection for an already-sent campaign, got %v", result.Rejected)
	}
	if len(result.Skipped) != 1 || !strings.Contains(result.Skipped[0], "running") {
		t.Fatalf("expected launch in Skipped mentioning 'running', got %v", result.Skipped)
	}
	if f.campaigns[0].Subject != "Original" {
		t.Errorf("expected the live campaign's content to be untouched, got %+v", f.campaigns[0])
	}
}

func TestSyncDir_NonDraftCampaignSkipsEvenWithAStaleListReference(t *testing.T) {
	// A finished campaign's campaign.md might reference a list that's since
	// been renamed or removed -- that must never break the build, since an
	// archived campaign has nothing left to resolve.
	f := newFakeListmonk(t)
	f.campaigns = []fakeCampaign{{ID: 1, Name: "launch", Status: "finished", Subject: "Original"}}
	lm := f.client()

	root := t.TempDir()
	fm := "subject: \"Big Announcement\"\nlists: [\"No Longer Exists\"]\nfrom_email: hello@example.com\n"
	writeCampaignDir(t, root, "launch", fm, "Hello world.")

	result, err := SyncDir(lm, root, nil)
	if err != nil {
		t.Fatalf("SyncDir: %v", err)
	}
	if len(result.Rejected) != 0 {
		t.Fatalf("expected no rejection despite the stale list reference, got %v", result.Rejected)
	}
	if len(result.Skipped) != 1 {
		t.Fatalf("expected launch in Skipped, got %v", result.Skipped)
	}
}

func TestSyncDir_AmbiguousListNameRejects(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}, {ID: 4, Name: "Newsletter"}}
	lm := f.client()

	root := t.TempDir()
	writeCampaignDir(t, root, "launch", baseFrontmatter, "Hello world.")

	result, err := SyncDir(lm, root, nil)
	if err != nil {
		t.Fatalf("SyncDir: %v", err)
	}
	if len(result.Rejected) != 1 {
		t.Fatalf("expected 1 rejection for an ambiguous list name, got %v", result.Rejected)
	}
	if len(f.campaigns) != 0 {
		t.Errorf("expected no campaign created for a rejected sync, got %d", len(f.campaigns))
	}
}

func TestSyncDir_SegmentQueryMaterializesIntoManagedList(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	query := "subscribers.attribs->>'source' = 'workshop'"
	lm := f.client()

	root := t.TempDir()
	fm := baseFrontmatter + "segment_query: \"" + query + "\"\n"
	writeCampaignDir(t, root, "launch", fm, "Hello world.")

	result, err := SyncDir(lm, root, nil)
	if err != nil {
		t.Fatalf("SyncDir: %v", err)
	}
	if len(result.Rejected) != 0 {
		t.Fatalf("expected no rejections, got %v", result.Rejected)
	}
	if len(f.segmentQueryCalls) != 1 {
		t.Fatalf("expected 1 segment query call, got %d", len(f.segmentQueryCalls))
	}
	if f.segmentQueryCalls[0].Query != query {
		t.Errorf("expected the query sent verbatim, got %q", f.segmentQueryCalls[0].Query)
	}

	var segList *fakeList
	for i := range f.lists {
		if f.lists[i].Name == "segment:launch" {
			segList = &f.lists[i]
		}
	}
	if segList == nil {
		t.Fatal("expected a managed 'segment:launch' list to be created")
	}
	if f.segmentQueryCalls[0].ListID != segList.ID {
		t.Errorf("expected the segment query call to target list %d, got %d", segList.ID, f.segmentQueryCalls[0].ListID)
	}
	if len(f.campaigns) != 1 {
		t.Fatalf("expected 1 campaign, got %d", len(f.campaigns))
	}
	found := false
	for _, id := range f.campaigns[0].ListIDs {
		if id == segList.ID {
			found = true
		}
	}
	if !found {
		t.Errorf("expected campaign to target the segment list %d, got %v", segList.ID, f.campaigns[0].ListIDs)
	}
}

func TestSyncDir_InvalidSegmentQueryRejectsWithoutCreatingCampaign(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	f.failSegmentQuery = true
	lm := f.client()

	root := t.TempDir()
	fm := baseFrontmatter + "segment_query: \"not valid sql\"\n"
	writeCampaignDir(t, root, "launch", fm, "Hello world.")

	result, err := SyncDir(lm, root, nil)
	if err != nil {
		t.Fatalf("SyncDir: %v", err)
	}
	if len(result.Rejected) != 1 || !strings.Contains(result.Rejected[0], "segment_query") {
		t.Fatalf("expected a segment_query rejection, got %v", result.Rejected)
	}
	if len(f.campaigns) != 0 {
		t.Errorf("expected no campaign created when segment_query fails, got %d", len(f.campaigns))
	}
}

func TestSyncDir_AttachmentUploadAndDedup(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	lm := f.client()

	root := t.TempDir()
	writeFile(t, filepath.Join(root, "campaigns", "launch", "assets", "flyer.pdf"), "pdf-v1")
	fm := baseFrontmatter + "attachments:\n  - assets/flyer.pdf\n"
	writeCampaignDir(t, root, "launch", fm, "Hello world.")

	if _, err := SyncDir(lm, root, nil); err != nil {
		t.Fatalf("first SyncDir: %v", err)
	}
	if len(f.media) != 1 {
		t.Fatalf("expected 1 media upload, got %d", len(f.media))
	}

	// Re-sync unchanged: no new upload.
	if _, err := SyncDir(lm, root, nil); err != nil {
		t.Fatalf("second SyncDir: %v", err)
	}
	if len(f.media) != 1 {
		t.Errorf("expected dedup to avoid a second upload, got %d media items", len(f.media))
	}

	// Change the attachment's content: a fresh upload.
	writeFile(t, filepath.Join(root, "campaigns", "launch", "assets", "flyer.pdf"), "pdf-v2")
	if _, err := SyncDir(lm, root, nil); err != nil {
		t.Fatalf("third SyncDir: %v", err)
	}
	if len(f.media) != 2 {
		t.Errorf("expected a fresh upload when attachment content changes, got %d media items", len(f.media))
	}
}

func TestSyncDir_AutomaticPreviewFiresOnlyOnChange(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	lm := f.client()

	root := t.TempDir()
	writeCampaignDir(t, root, "launch", baseFrontmatter, "Hello world.")

	if _, err := SyncDir(lm, root, []string{"me@example.com"}); err != nil {
		t.Fatalf("first SyncDir: %v", err)
	}
	if len(f.testCalls) != 1 {
		t.Fatalf("expected exactly 1 preview send after create, got %d", len(f.testCalls))
	}
	if f.testCalls[0].Emails[0] != "me@example.com" {
		t.Errorf("expected preview sent to default address, got %v", f.testCalls[0].Emails)
	}

	// Unchanged re-sync: no additional preview.
	if _, err := SyncDir(lm, root, []string{"me@example.com"}); err != nil {
		t.Fatalf("second SyncDir: %v", err)
	}
	if len(f.testCalls) != 1 {
		t.Errorf("expected no additional preview for an unchanged campaign, got %d total", len(f.testCalls))
	}

	// Change content: exactly one more preview.
	writeCampaignDir(t, root, "launch", baseFrontmatter, "Hello, updated world.")
	if _, err := SyncDir(lm, root, []string{"me@example.com"}); err != nil {
		t.Fatalf("third SyncDir: %v", err)
	}
	if len(f.testCalls) != 2 {
		t.Errorf("expected exactly 2 total previews after one content change, got %d", len(f.testCalls))
	}
}

func TestSyncDir_PreviewEmailsOverridesDefault(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	lm := f.client()

	root := t.TempDir()
	fm := baseFrontmatter + "preview_emails:\n  - cofounder@example.com\n"
	writeCampaignDir(t, root, "launch", fm, "Hello world.")

	if _, err := SyncDir(lm, root, []string{"default@example.com"}); err != nil {
		t.Fatalf("SyncDir: %v", err)
	}
	if len(f.testCalls) != 1 {
		t.Fatalf("expected 1 preview send, got %d", len(f.testCalls))
	}
	if f.testCalls[0].Emails[0] != "cofounder@example.com" {
		t.Errorf("expected campaign-level preview_emails to override the default, got %v", f.testCalls[0].Emails)
	}
}

func TestSyncDir_OneBadCampaignDoesNotAbortOthers(t *testing.T) {
	f := newFakeListmonk(t)
	f.lists = []fakeList{{ID: 3, Name: "Newsletter"}}
	lm := f.client()

	root := t.TempDir()
	writeCampaignDir(t, root, "good", baseFrontmatter, "Hello world.")
	writeCampaignDir(t, root, "bad", "lists: [\"Newsletter\"]\nfrom_email: hello@example.com\n", "Missing a subject.")

	result, err := SyncDir(lm, root, nil)
	if err != nil {
		t.Fatalf("SyncDir: %v", err)
	}
	if len(result.Synced) != 1 || result.Synced[0] != "good" {
		t.Errorf("expected good to sync despite bad's failure, got Synced=%v", result.Synced)
	}
	if len(result.Rejected) != 1 || !strings.Contains(result.Rejected[0], "bad:") {
		t.Errorf("expected bad to be rejected with a slug-prefixed message, got %v", result.Rejected)
	}
}