package storage

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"testing"
	"time"
)

func newTestEngine(t *testing.T) *Engine {
	t.Helper()
	engine, err := New(t.TempDir())
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	return engine
}

func TestSlugify(t *testing.T) {
	t.Parallel()

	cases := []struct {
		input string
		want  string
	}{
		{"Core Service API", "core-service-api"},
		{"core-service-api", "core-service-api"},
		{"  Spaced   Out  Title  ", "spaced-out-title"},
		{"Deploy & Rollback", "deploy-rollback"},
		{"API_v2 (Internal)", "api-v2-internal"},
		{"Release 2024/Q1 -- Notes", "release-2024-q1-notes"},
		{"Überwachen der Dienste", "uberwachen-der-dienste"},
		{"Straße", "strase"},
		{"C++ & Rust: side by side", "c-rust-side-by-side"},
		{"emoji 🚀 launch", "emoji-launch"},
		{"multiple---hyphens", "multiple-hyphens"},
		{"trailing hyphen-", "trailing-hyphen"},
		{"---leading", "leading"},
		{"!!!", ""},
		{"", ""},
		{"日本語 title", "title"},
		{"snake_case_and__doubles", "snake-case-and-doubles"},
	}

	for _, tc := range cases {
		if got := Slugify(tc.input); got != tc.want {
			t.Errorf("Slugify(%q) = %q, want %q", tc.input, got, tc.want)
		}
	}
}

func TestSlugifyCapsLength(t *testing.T) {
	t.Parallel()

	long := strings.Repeat("word ", 100)
	got := Slugify(long)
	if len(got) > maxSlugLen {
		t.Fatalf("slug length %d exceeds the %d cap", len(got), maxSlugLen)
	}
	if strings.HasSuffix(got, "-") {
		t.Fatalf("capped slug must not end in a hyphen: %q", got)
	}
}

func TestNormalizeSlug(t *testing.T) {
	t.Parallel()

	valid := map[string]string{
		"Core Service API": "core-service-api",
		"core-service-api": "core-service-api",
		"  Spaced  ":       "spaced",
		"Ünïcödé Slug":     "unicode-slug",
	}
	for input, want := range valid {
		got, err := NormalizeSlug(input)
		if err != nil {
			t.Errorf("NormalizeSlug(%q) returned %v", input, err)
			continue
		}
		if got != want {
			t.Errorf("NormalizeSlug(%q) = %q, want %q", input, got, want)
		}
	}

	invalid := []string{
		"",
		"   ",
		"../etc/passwd",
		"..",
		"nested/path",
		"back\\slash",
		"null\x00byte",
		"!!!",
		strings.Repeat("x", 2*maxSlugLen+1),
	}
	for _, input := range invalid {
		if _, err := NormalizeSlug(input); !errors.Is(err, ErrInvalidSlug) {
			t.Errorf("NormalizeSlug(%q) should be rejected, got %v", input, err)
		}
	}
}

func TestSaveReadDeleteDoc(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	slug, err := engine.SaveDoc("Core Service API", "# Core Service API\n\nBody.\n")
	if err != nil {
		t.Fatalf("SaveDoc: %v", err)
	}
	if slug != "core-service-api" {
		t.Fatalf("expected core-service-api, got %q", slug)
	}

	if _, err := os.Stat(filepath.Join(engine.DocsDir(), "core-service-api.md")); err != nil {
		t.Fatalf("Markdown file missing: %v", err)
	}

	content, err := engine.ReadDoc("Core Service API")
	if err != nil {
		t.Fatalf("ReadDoc: %v", err)
	}
	if !strings.Contains(content, "Body.") {
		t.Fatalf("unexpected content: %q", content)
	}

	if _, err := engine.ReadDoc("never-saved"); !errors.Is(err, ErrNotFound) {
		t.Fatalf("expected ErrNotFound, got %v", err)
	}

	if err := engine.DeleteDoc("Core Service API"); err != nil {
		t.Fatalf("DeleteDoc: %v", err)
	}
	if _, err := engine.ReadDoc("core-service-api"); !errors.Is(err, ErrNotFound) {
		t.Fatalf("expected ErrNotFound after delete, got %v", err)
	}
	if err := engine.DeleteDoc("core-service-api"); !errors.Is(err, ErrNotFound) {
		t.Fatalf("expected ErrNotFound on a second delete, got %v", err)
	}
}

func TestDeleteDocCascadesComments(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	if _, err := engine.SaveDoc("doomed", "# Doomed\n"); err != nil {
		t.Fatal(err)
	}
	if _, err := engine.AppendComment("doomed", CommentInput{Author: "a", Role: "user", Content: "hi"}); err != nil {
		t.Fatal(err)
	}

	commentPath := filepath.Join(engine.CommentsDir(), "doomed-comments.json")
	if _, err := os.Stat(commentPath); err != nil {
		t.Fatalf("expected the comment file to exist: %v", err)
	}

	if err := engine.DeleteDoc("doomed"); err != nil {
		t.Fatal(err)
	}
	if _, err := os.Stat(commentPath); !os.IsNotExist(err) {
		t.Fatalf("expected the comment file to be removed, stat returned %v", err)
	}
}

func TestSaveDocNormalizesLineEndings(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	if _, err := engine.SaveDoc("crlf", "line one\r\nline two\r\n\r\n"); err != nil {
		t.Fatal(err)
	}
	content, err := engine.ReadDoc("crlf")
	if err != nil {
		t.Fatal(err)
	}
	if strings.Contains(content, "\r") {
		t.Fatalf("carriage returns survived: %q", content)
	}
	if content != "line one\nline two\n" {
		t.Fatalf("unexpected normalization: %q", content)
	}
}

func TestCommentBadges(t *testing.T) {
	t.Parallel()

	cases := map[Role]string{
		RoleUser:      "🟢",
		RoleOperator:  "🔵",
		RoleDeveloper: "🔴",
	}
	for role, badge := range cases {
		if role.Badge() != badge {
			t.Errorf("role %s badge = %q, want %q", role, role.Badge(), badge)
		}
		if !role.Valid() {
			t.Errorf("role %s should be valid", role)
		}
	}
	if Role("admin").Badge() != "" || Role("admin").Valid() {
		t.Error("an unknown role must have no badge and be invalid")
	}

	for _, raw := range []string{"user", "USER", " User "} {
		if role, err := ParseRole(raw); err != nil || role != RoleUser {
			t.Errorf("ParseRole(%q) = %v, %v", raw, role, err)
		}
	}
	if _, err := ParseRole("root"); !errors.Is(err, ErrInvalidRole) {
		t.Errorf("expected ErrInvalidRole, got %v", err)
	}
}

func TestAppendCommentValidation(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	if _, err := engine.AppendComment("valid", CommentInput{Role: "developer", Content: "  "}); !errors.Is(err, ErrInvalidComment) {
		t.Errorf("blank content should be rejected, got %v", err)
	}
	if _, err := engine.AppendComment("valid", CommentInput{Role: "wizard", Content: "hello"}); !errors.Is(err, ErrInvalidRole) {
		t.Errorf("unknown role should be rejected, got %v", err)
	}
	if _, err := engine.AppendComment("../escape", CommentInput{Role: "user", Content: "hi"}); !errors.Is(err, ErrInvalidSlug) {
		t.Errorf("traversal slug should be rejected, got %v", err)
	}

	comment, err := engine.AppendComment("valid", CommentInput{Role: "user", Content: "hello"})
	if err != nil {
		t.Fatalf("AppendComment: %v", err)
	}
	if comment.Author != "User" {
		t.Errorf("an omitted author should default to the role label, got %q", comment.Author)
	}
	if comment.Badge != "🟢" {
		t.Errorf("expected the user badge, got %q", comment.Badge)
	}
	if comment.ID == "" || comment.Timestamp.IsZero() {
		t.Error("expected an ID and a timestamp")
	}
}

func TestCommentsAreSortedAndDeduplicatedByID(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	base := time.Date(2026, 1, 1, 12, 0, 0, 0, time.UTC)
	for i, offset := range []int{30, 10, 20} {
		if _, err := engine.AppendComment("ordered", CommentInput{
			Author:    fmt.Sprintf("user-%d", i),
			Role:      "user",
			Content:   fmt.Sprintf("comment %d", i),
			Timestamp: base.Add(time.Duration(offset) * time.Minute),
		}); err != nil {
			t.Fatal(err)
		}
	}

	comments, err := engine.ListComments("ordered")
	if err != nil {
		t.Fatal(err)
	}
	if len(comments) != 3 {
		t.Fatalf("expected 3 comments, got %d", len(comments))
	}
	for i := 1; i < len(comments); i++ {
		if comments[i].Timestamp.Before(comments[i-1].Timestamp) {
			t.Fatalf("comments are not in chronological order: %+v", comments)
		}
	}
	if strings.TrimSpace(comments[0].Content) != "comment 1" {
		t.Fatalf("expected the earliest comment first, got %q", comments[0].Content)
	}
}

func TestDeleteComment(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	first, err := engine.AppendComment("prune", CommentInput{Role: "user", Content: "first"})
	if err != nil {
		t.Fatal(err)
	}
	if _, err := engine.AppendComment("prune", CommentInput{Role: "user", Content: "second"}); err != nil {
		t.Fatal(err)
	}

	removed, err := engine.DeleteComment("prune", first.ID)
	if err != nil || !removed {
		t.Fatalf("expected the comment to be removed, got %v / %v", removed, err)
	}
	removed, err = engine.DeleteComment("prune", "does-not-exist")
	if err != nil || removed {
		t.Fatalf("deleting an unknown ID must be a no-op, got %v / %v", removed, err)
	}

	remaining, err := engine.ListComments("prune")
	if err != nil {
		t.Fatal(err)
	}
	if len(remaining) != 1 || strings.TrimSpace(remaining[0].Content) != "second" {
		t.Fatalf("unexpected remaining comments: %+v", remaining)
	}
}

func TestListAndSearchDocs(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	for _, title := range []string{"Alpha Service", "Beta Service", "Gamma Gateway"} {
		if _, err := engine.SaveDoc(title, "# "+title+"\n"); err != nil {
			t.Fatal(err)
		}
	}
	if _, err := engine.AppendComment("alpha-service", CommentInput{Role: "user", Content: "hi"}); err != nil {
		t.Fatal(err)
	}

	all, err := engine.ListDocs()
	if err != nil {
		t.Fatal(err)
	}
	if len(all) != 3 {
		t.Fatalf("expected 3 documents, got %d", len(all))
	}
	// Titles come from the document's H1, not from a slug-derived guess.
	for _, doc := range all {
		if doc.Title != "Alpha Service" && doc.Title != "Beta Service" && doc.Title != "Gamma Gateway" {
			t.Fatalf("document %s has title %q; expected the H1 heading", doc.Slug, doc.Title)
		}
	}

	detailed, err := engine.ListDocsDetailed()
	if err != nil {
		t.Fatal(err)
	}
	for _, doc := range detailed {
		if doc.Slug == "alpha-service" && doc.Comments != 1 {
			t.Fatalf("expected 1 comment on alpha-service, got %d", doc.Comments)
		}
	}

	hits, err := engine.Search("gateway")
	if err != nil {
		t.Fatal(err)
	}
	if len(hits) != 1 || hits[0].Slug != "gamma-gateway" {
		t.Fatalf("unexpected search hits: %+v", hits)
	}

	// Temp files left by an interrupted write must never surface in the index.
	if err := os.WriteFile(filepath.Join(engine.DocsDir(), ".godoc-tmp-123"), []byte("x"), 0o644); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(filepath.Join(engine.DocsDir(), "not-markdown.txt"), []byte("x"), 0o644); err != nil {
		t.Fatal(err)
	}
	all, err = engine.ListDocs()
	if err != nil {
		t.Fatal(err)
	}
	if len(all) != 3 {
		t.Fatalf("index must ignore temp and non-Markdown files, got %d entries", len(all))
	}
}

func TestExtractTitleAndTitleize(t *testing.T) {
	t.Parallel()

	cases := []struct {
		content string
		slug    string
		want    string
	}{
		{"# Core Service API\n\nbody", "core-service-api", "Core Service API"},
		{"## Only an H2\n\nbody", "only-an-h2", "Only an H2"},
		{"no heading here", "plain-slug", "Plain Slug"},
		{"", "empty-slug", "Empty Slug"},
	}
	for _, tc := range cases {
		if got := ExtractTitle(tc.content, tc.slug); got != tc.want {
			t.Errorf("ExtractTitle(%q, %q) = %q, want %q", tc.content, tc.slug, got, tc.want)
		}
	}
}

func TestConcurrentAppendsLoseNothing(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	const (
		writers = 50
		perDoc  = 40
	)

	var wg sync.WaitGroup
	errs := make(chan error, writers)

	for w := 0; w < writers; w++ {
		wg.Add(1)
		go func(worker int) {
			defer wg.Done()
			role := Roles()[worker%3]
			for n := 0; n < perDoc; n++ {
				if _, err := engine.AppendComment("hot", CommentInput{
					Author:  fmt.Sprintf("worker-%02d", worker),
					Role:    string(role),
					Content: fmt.Sprintf("note %d from %d", n, worker),
				}); err != nil {
					errs <- err
					return
				}
			}
		}(w)
	}
	wg.Wait()
	close(errs)

	for err := range errs {
		t.Fatalf("concurrent append failed: %v", err)
	}

	comments, err := engine.ListComments("hot")
	if err != nil {
		t.Fatal(err)
	}
	if len(comments) != writers*perDoc {
		t.Fatalf("expected %d comments, got %d", writers*perDoc, len(comments))
	}

	seen := make(map[string]struct{}, len(comments))
	for _, comment := range comments {
		key := comment.Author + "|" + comment.Content
		if _, dup := seen[key]; dup {
			t.Fatalf("duplicate entry after concurrent writes: %s", key)
		}
		seen[key] = struct{}{}
	}
}

func TestConcurrentReadsNeverSeeTornWrites(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	const marker = "SENTINEL-HEADER\n"
	body := strings.Repeat("payload line\n", 500)

	var wg sync.WaitGroup
	errs := make(chan error, 32)

	for w := 0; w < 16; w++ {
		wg.Add(1)
		go func(worker int) {
			defer wg.Done()
			for n := 0; n < 25; n++ {
				if _, err := engine.SaveDoc("live", marker+body); err != nil {
					errs <- err
					return
				}
			}
		}(w)
	}
	for r := 0; r < 16; r++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for n := 0; n < 100; n++ {
				content, err := engine.ReadDoc("live")
				if err != nil {
					if !errors.Is(err, ErrNotFound) {
						errs <- err
					}
					return
				}
				if !strings.HasPrefix(content, marker) {
					errs <- fmt.Errorf("torn read: %q", content[:min(len(content), 40)])
					return
				}
			}
		}()
	}
	wg.Wait()
	close(errs)

	for err := range errs {
		t.Fatalf("concurrent access failed: %v", err)
	}

	entries, err := os.ReadDir(engine.DocsDir())
	if err != nil {
		t.Fatal(err)
	}
	for _, entry := range entries {
		if strings.HasPrefix(entry.Name(), ".godoc-tmp-") {
			t.Fatalf("atomic write leaked a temp file: %s", entry.Name())
		}
	}
}

func TestStats(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	if _, err := engine.SaveDoc("counted", "# Counted\n"); err != nil {
		t.Fatal(err)
	}
	for i, role := range []Role{RoleUser, RoleUser, RoleOperator, RoleDeveloper, RoleDeveloper, RoleDeveloper} {
		if _, err := engine.AppendComment("counted", CommentInput{
			Author:  fmt.Sprintf("author-%d", i),
			Role:    string(role),
			Content: fmt.Sprintf("comment %d", i),
		}); err != nil {
			t.Fatal(err)
		}
	}

	stats, err := engine.Stats("counted")
	if err != nil {
		t.Fatal(err)
	}
	if stats.Total != 6 {
		t.Fatalf("expected 6 comments, got %d", stats.Total)
	}
	if stats.ByRole["developer"] != 3 || stats.ByRole["user"] != 2 || stats.ByRole["operator"] != 1 {
		t.Fatalf("unexpected tally: %+v", stats.ByRole)
	}
	if stats.MostActive != "developer" {
		t.Fatalf("expected developer as the most active role, got %q", stats.MostActive)
	}
	if stats.OldestAt == nil || stats.LatestAt == nil {
		t.Fatal("expected the time bounds to be populated")
	}
}

func TestEngineSatisfiesDocumentedInterface(t *testing.T) {
	t.Parallel()
	engine := newTestEngine(t)

	exists, err := engine.DocExists("Core Service API")
	if err != nil || exists {
		t.Fatalf("DocExists before save = %v / %v", exists, err)
	}
	if _, err := engine.SaveDoc("Core Service API", "# Core Service API\n"); err != nil {
		t.Fatal(err)
	}
	exists, err = engine.DocExists("core-service-api")
	if err != nil || !exists {
		t.Fatalf("DocExists after save = %v / %v", exists, err)
	}

	meta, err := engine.Stat("core-service-api")
	if err != nil {
		t.Fatal(err)
	}
	if meta.Title != "Core Service API" {
		t.Fatalf("Stat title = %q", meta.Title)
	}
	if meta.Size <= 0 || meta.Modified.IsZero() {
		t.Fatalf("Stat returned incomplete metadata: %+v", meta)
	}
}

func TestResolveRootHonoursEnvironment(t *testing.T) {
	dir := t.TempDir()
	t.Setenv("GO_DOC_DATA_DIR", dir)
	if got := ResolveRoot(); got != dir {
		t.Fatalf("ResolveRoot() = %q, want %q", got, dir)
	}

	if _, err := New("  "); err == nil {
		t.Fatal("New must reject an empty root")
	}
}