package cache

import (
	"io"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"codeberg.org/VARASYS/ZDDC/zddc/internal/config"
)

// newTestCache spins up an httptest server as the upstream and
// returns the cache + the upstream's URL. The upstream's behavior is
// the caller's to define.
func newTestCache(t *testing.T, mode string, upstreamHandler http.HandlerFunc) (*Cache, *httptest.Server) {
	t.Helper()
	upstream := httptest.NewServer(upstreamHandler)
	t.Cleanup(upstream.Close)
	root := t.TempDir()
	c, err := New(config.Config{
		Root:     root,
		Upstream: upstream.URL,
		Mode:     mode,
	})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	return c, upstream
}

func TestNew_RequiresUpstream(t *testing.T) {
	if _, err := New(config.Config{Root: t.TempDir()}); err == nil {
		t.Error("expected error for empty upstream")
	}
}

func TestNew_StripsTrailingSlash(t *testing.T) {
	c, err := New(config.Config{
		Root:     t.TempDir(),
		Upstream: "http://example.com/",
	})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	if got := c.Upstream(); got != "http://example.com" {
		t.Errorf("Upstream() = %q, want trailing slash stripped", got)
	}
}

func TestNew_BearerFile(t *testing.T) {
	dir := t.TempDir()
	tokenPath := filepath.Join(dir, "token")
	if err := os.WriteFile(tokenPath, []byte("  abc123\n"), 0o600); err != nil {
		t.Fatalf("write token: %v", err)
	}
	c, err := New(config.Config{
		Root:       t.TempDir(),
		Upstream:   "http://example.com",
		BearerFile: tokenPath,
	})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	if c.bearer != "abc123" {
		t.Errorf("bearer = %q, want abc123 (whitespace trimmed)", c.bearer)
	}
}

func TestNew_BearerFileEmptyRejected(t *testing.T) {
	dir := t.TempDir()
	empty := filepath.Join(dir, "empty")
	_ = os.WriteFile(empty, []byte("\n\n"), 0o600)
	if _, err := New(config.Config{
		Root:       t.TempDir(),
		Upstream:   "http://example.com",
		BearerFile: empty,
	}); err == nil {
		t.Error("expected error for empty bearer file")
	}
}

func TestServeHTTP_RejectsWriteMethods(t *testing.T) {
	c, _ := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {
		t.Errorf("upstream should not be called for write methods")
	})
	for _, method := range []string{http.MethodPut, http.MethodPost, http.MethodDelete} {
		rec := httptest.NewRecorder()
		r := httptest.NewRequest(method, "/foo", nil)
		c.ServeHTTP(rec, r)
		if rec.Code != http.StatusMethodNotAllowed {
			t.Errorf("%s = %d, want 405", method, rec.Code)
		}
		if got := rec.Header().Get("Allow"); got != "GET, HEAD" {
			t.Errorf("%s Allow = %q", method, got)
		}
	}
}

func TestServeHTTP_MissThenHit(t *testing.T) {
	var hits int32
	c, upstream := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {
		atomic.AddInt32(&hits, 1)
		if r.URL.Path != "/foo.txt" {
			t.Errorf("upstream got %q, want /foo.txt", r.URL.Path)
		}
		w.Header().Set("Content-Type", "text/plain")
		w.Header().Set("Last-Modified", "Mon, 02 Jan 2006 15:04:05 GMT")
		_, _ = w.Write([]byte("hello"))
	})
	_ = upstream

	// First request: miss.
	rec := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodGet, "/foo.txt", nil)
	c.ServeHTTP(rec, r)
	if rec.Code != http.StatusOK {
		t.Fatalf("first GET = %d", rec.Code)
	}
	if got := rec.Header().Get(HeaderName); got != "miss" {
		t.Errorf("first cache header = %q, want miss", got)
	}
	if got := rec.Body.String(); got != "hello" {
		t.Errorf("body = %q", got)
	}

	// Cache file should exist.
	cached := filepath.Join(c.root, "foo.txt")
	if _, err := os.Stat(cached); err != nil {
		t.Fatalf("expected cached file: %v", err)
	}

	// Second request: hit. Wait briefly to let the marker write race finish.
	rec2 := httptest.NewRecorder()
	r2 := httptest.NewRequest(http.MethodGet, "/foo.txt", nil)
	c.ServeHTTP(rec2, r2)
	if rec2.Code != http.StatusOK {
		t.Fatalf("second GET = %d", rec2.Code)
	}
	if got := rec2.Header().Get(HeaderName); got != "hit" {
		t.Errorf("second cache header = %q, want hit", got)
	}
	if got := rec2.Body.String(); got != "hello" {
		t.Errorf("second body = %q", got)
	}

	// Marker file should be present.
	marker := filepath.Join(c.root, MarkerFile)
	mb, err := os.ReadFile(marker)
	if err != nil {
		t.Fatalf("marker missing: %v", err)
	}
	if !strings.Contains(string(mb), "upstream:") {
		t.Errorf("marker contents unexpected: %s", string(mb))
	}
}

func TestServeHTTP_ProxyModeDoesNotPersist(t *testing.T) {
	c, _ := newTestCache(t, "proxy", func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte("payload"))
	})
	rec := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodGet, "/foo.txt", nil)
	c.ServeHTTP(rec, r)
	if rec.Code != http.StatusOK {
		t.Fatalf("status = %d", rec.Code)
	}
	if got := rec.Header().Get(HeaderName); got != "proxy" {
		t.Errorf("cache header = %q, want proxy", got)
	}
	cached := filepath.Join(c.root, "foo.txt")
	if _, err := os.Stat(cached); !os.IsNotExist(err) {
		t.Errorf("proxy mode wrote to cache: %v", err)
	}
	// Marker also shouldn't exist (no caching happened).
	if _, err := os.Stat(filepath.Join(c.root, MarkerFile)); !os.IsNotExist(err) {
		t.Errorf("marker file written in proxy mode")
	}
}

func TestServeHTTP_DirectoriesAreNeverCached(t *testing.T) {
	c, _ := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/html")
		_, _ = w.Write([]byte("<html>listing</html>"))
	})
	rec := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodGet, "/Project/", nil)
	c.ServeHTTP(rec, r)
	if rec.Code != http.StatusOK {
		t.Fatalf("status = %d", rec.Code)
	}
	if got := rec.Header().Get(HeaderName); got != "proxy" {
		t.Errorf("cache header = %q, want proxy (directories don't cache)", got)
	}
	// No file or directory should have been created at the URL location.
	if entries, _ := os.ReadDir(c.root); len(entries) > 0 {
		t.Errorf("directory request created cache entries: %v", entries)
	}
}

func TestServeHTTP_HEAD_HitDoesNotReturnBody(t *testing.T) {
	c, _ := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte("hello"))
	})
	// Seed the cache via GET.
	rec := httptest.NewRecorder()
	c.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/foo.txt", nil))
	if rec.Code != http.StatusOK {
		t.Fatalf("seed: %d", rec.Code)
	}

	// HEAD: should be a hit, no body.
	rec2 := httptest.NewRecorder()
	c.ServeHTTP(rec2, httptest.NewRequest(http.MethodHead, "/foo.txt", nil))
	if rec2.Code != http.StatusOK {
		t.Fatalf("HEAD: %d", rec2.Code)
	}
	if rec2.Body.Len() != 0 {
		t.Errorf("HEAD body length = %d, want 0", rec2.Body.Len())
	}
}

func TestServeHTTP_OfflineServesStale(t *testing.T) {
	root := t.TempDir()
	// Pre-seed a cached file.
	if err := os.WriteFile(filepath.Join(root, "stale.txt"), []byte("stale-content"), 0o644); err != nil {
		t.Fatalf("seed: %v", err)
	}
	c, err := New(config.Config{
		Root:     root,
		Upstream: "http://127.0.0.1:1", // unreachable port
		Mode:     "cache",
	})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	// Speed up the timeout so the test doesn't hang.
	c.client.Timeout = 200 * time.Millisecond

	rec := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodGet, "/stale.txt", nil)
	c.ServeHTTP(rec, r)
	if rec.Code != http.StatusOK {
		t.Fatalf("offline-with-cache = %d, want 200", rec.Code)
	}
	if got := rec.Header().Get(HeaderName); got != "hit" {
		// On hit we don't even hit the network. That's expected.
		t.Logf("first attempt was %q (likely cache hit before any network)", got)
	}
	if got := rec.Body.String(); got != "stale-content" {
		t.Errorf("body = %q", got)
	}
}

func TestServeHTTP_OfflineMissReturns503(t *testing.T) {
	root := t.TempDir()
	c, err := New(config.Config{
		Root:     root,
		Upstream: "http://127.0.0.1:1",
		Mode:     "cache",
	})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	c.client.Timeout = 200 * time.Millisecond

	rec := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodGet, "/never-cached.txt", nil)
	c.ServeHTTP(rec, r)
	if rec.Code != http.StatusServiceUnavailable {
		t.Errorf("offline-no-cache = %d, want 503", rec.Code)
	}
	if got := rec.Header().Get(HeaderName); got != "offline" {
		t.Errorf("cache header = %q, want offline", got)
	}
}

func TestServeHTTP_BearerForwarded(t *testing.T) {
	dir := t.TempDir()
	tokenPath := filepath.Join(dir, "token")
	_ = os.WriteFile(tokenPath, []byte("secrettoken"), 0o600)
	var seenAuth string
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		seenAuth = r.Header.Get("Authorization")
		_, _ = w.Write([]byte("ok"))
	}))
	defer upstream.Close()

	c, err := New(config.Config{
		Root:       t.TempDir(),
		Upstream:   upstream.URL,
		Mode:       "cache",
		BearerFile: tokenPath,
	})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	rec := httptest.NewRecorder()
	c.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/foo.txt", nil))
	if seenAuth != "Bearer secrettoken" {
		t.Errorf("Authorization = %q, want Bearer secrettoken", seenAuth)
	}
}

func TestServeHTTP_PreservesQuery(t *testing.T) {
	var seenURL string
	c, _ := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {
		seenURL = r.URL.RequestURI()
		w.Header().Set("Cache-Control", "no-store") // no-cache the JSON response
		_, _ = w.Write([]byte(`{}`))
	})
	rec := httptest.NewRecorder()
	c.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/foo.txt?q=bar", nil))
	if seenURL != "/foo.txt?q=bar" {
		t.Errorf("upstream saw %q, want /foo.txt?q=bar", seenURL)
	}
}

func TestServeHTTP_HonorsNoStore(t *testing.T) {
	c, _ := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Cache-Control", "no-store")
		_, _ = w.Write([]byte("ephemeral"))
	})
	rec := httptest.NewRecorder()
	c.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/dynamic.json", nil))
	if rec.Code != http.StatusOK {
		t.Fatalf("status: %d", rec.Code)
	}
	if got := rec.Header().Get(HeaderName); got != "proxy" {
		t.Errorf("cache header = %q, want proxy (no-store should bypass cache)", got)
	}
	cached := filepath.Join(c.root, "dynamic.json")
	if _, err := os.Stat(cached); !os.IsNotExist(err) {
		t.Errorf("no-store response was cached")
	}
}

func TestServeHTTP_PathTraversalRejected(t *testing.T) {
	called := false
	c, _ := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {
		called = true
		_, _ = w.Write([]byte("data"))
	})
	rec := httptest.NewRecorder()
	c.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/../etc/passwd", nil))
	// The upstream may still be called (the proxy doesn't gatekeep), but
	// we MUST NOT cache to a path that escapes the root.
	_ = called
	root := c.root
	parent := filepath.Dir(root)
	if _, err := os.Stat(filepath.Join(parent, "etc", "passwd")); !os.IsNotExist(err) {
		t.Error("path traversal wrote outside cache root")
	}
}

func TestServeHTTP_ForwardsErrorStatus(t *testing.T) {
	c, _ := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {
		http.Error(w, "Forbidden", http.StatusForbidden)
	})
	rec := httptest.NewRecorder()
	c.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/secret.txt", nil))
	if rec.Code != http.StatusForbidden {
		t.Errorf("status = %d, want 403", rec.Code)
	}
	cached := filepath.Join(c.root, "secret.txt")
	if _, err := os.Stat(cached); !os.IsNotExist(err) {
		t.Error("403 response was cached")
	}
}

func TestRevalidate_PurgesOn403(t *testing.T) {
	root := t.TempDir()
	if err := os.WriteFile(filepath.Join(root, "victim.txt"), []byte("cached"), 0o644); err != nil {
		t.Fatalf("seed: %v", err)
	}
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		http.Error(w, "Forbidden", http.StatusForbidden)
	}))
	defer upstream.Close()
	c, err := New(config.Config{Root: root, Upstream: upstream.URL, Mode: "cache"})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	c.revalidate("/victim.txt", time.Now())
	if _, err := os.Stat(filepath.Join(root, "victim.txt")); !os.IsNotExist(err) {
		t.Error("revalidate did not purge after 403")
	}
}

func TestRevalidate_PurgesOn404(t *testing.T) {
	root := t.TempDir()
	if err := os.WriteFile(filepath.Join(root, "gone.txt"), []byte("cached"), 0o644); err != nil {
		t.Fatalf("seed: %v", err)
	}
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		http.NotFound(w, r)
	}))
	defer upstream.Close()
	c, err := New(config.Config{Root: root, Upstream: upstream.URL, Mode: "cache"})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	c.revalidate("/gone.txt", time.Now())
	if _, err := os.Stat(filepath.Join(root, "gone.txt")); !os.IsNotExist(err) {
		t.Error("revalidate did not purge after 404")
	}
}

func TestRevalidate_NoPurgeOn200ButRefreshes(t *testing.T) {
	root := t.TempDir()
	old := []byte("old-content")
	if err := os.WriteFile(filepath.Join(root, "fresh.txt"), old, 0o644); err != nil {
		t.Fatalf("seed: %v", err)
	}
	// Set the file's mtime to an hour ago.
	hourAgo := time.Now().Add(-time.Hour)
	_ = os.Chtimes(filepath.Join(root, "fresh.txt"), hourAgo, hourAgo)

	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write([]byte("new-content"))
	}))
	defer upstream.Close()
	c, err := New(config.Config{Root: root, Upstream: upstream.URL, Mode: "cache"})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	c.revalidate("/fresh.txt", hourAgo)
	got, _ := os.ReadFile(filepath.Join(root, "fresh.txt"))
	if string(got) != "new-content" {
		t.Errorf("revalidate did not refresh: got %q", string(got))
	}
}

func TestRevalidate_NoOpOn304(t *testing.T) {
	root := t.TempDir()
	original := []byte("original")
	if err := os.WriteFile(filepath.Join(root, "still.txt"), original, 0o644); err != nil {
		t.Fatalf("seed: %v", err)
	}
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Always return 304; assume client sent If-Modified-Since.
		if r.Header.Get("If-Modified-Since") == "" {
			t.Errorf("revalidate did not send If-Modified-Since")
		}
		w.WriteHeader(http.StatusNotModified)
	}))
	defer upstream.Close()
	c, err := New(config.Config{Root: root, Upstream: upstream.URL, Mode: "cache"})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	c.revalidate("/still.txt", time.Now())
	got, _ := os.ReadFile(filepath.Join(root, "still.txt"))
	if string(got) != "original" {
		t.Errorf("304 caused content change: got %q", string(got))
	}
}

func TestRangeRequest_Hit(t *testing.T) {
	c, _ := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/plain")
		_, _ = w.Write([]byte("0123456789"))
	})
	// Seed cache.
	rec := httptest.NewRecorder()
	c.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/data.txt", nil))
	if rec.Code != http.StatusOK {
		t.Fatalf("seed: %d", rec.Code)
	}

	// Range request.
	rec2 := httptest.NewRecorder()
	r2 := httptest.NewRequest(http.MethodGet, "/data.txt", nil)
	r2.Header.Set("Range", "bytes=2-5")
	c.ServeHTTP(rec2, r2)
	if rec2.Code != http.StatusPartialContent {
		t.Fatalf("range = %d, want 206", rec2.Code)
	}
	if rec2.Body.String() != "2345" {
		t.Errorf("range body = %q", rec2.Body.String())
	}
	if got := rec2.Header().Get("Content-Range"); !strings.HasPrefix(got, "bytes 2-5/") {
		t.Errorf("Content-Range = %q", got)
	}
}

func TestServeHTTP_ConcurrentRequestsForSameURL(t *testing.T) {
	// Stress the marker-once and tmpfile path with parallel misses.
	var hits int32
	c, _ := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {
		atomic.AddInt32(&hits, 1)
		_, _ = io.WriteString(w, "concurrent")
	})
	var wg sync.WaitGroup
	for i := 0; i < 8; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			rec := httptest.NewRecorder()
			c.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/c.txt", nil))
			if rec.Code != http.StatusOK {
				t.Errorf("status = %d", rec.Code)
			}
			if rec.Body.String() != "concurrent" {
				t.Errorf("body = %q", rec.Body.String())
			}
		}()
	}
	wg.Wait()

	// File should exist with the right content.
	got, err := os.ReadFile(filepath.Join(c.root, "c.txt"))
	if err != nil {
		t.Fatalf("read: %v", err)
	}
	if string(got) != "concurrent" {
		t.Errorf("cached body = %q", string(got))
	}
}

func TestCachePathFor_Boundaries(t *testing.T) {
	c, _ := newTestCache(t, "cache", func(w http.ResponseWriter, r *http.Request) {})
	cases := []struct {
		urlPath string
		ok      bool
	}{
		{"", false},
		{"/", false},
		{"/../etc/passwd", false},
		{"/foo/../bar", false},
		{"/foo/bar.txt", true},
		{"/" + MarkerFile, false},
		{"/Project/foo.txt", true},
	}
	for _, tc := range cases {
		_, ok := c.cachePathFor(tc.urlPath)
		if ok != tc.ok {
			t.Errorf("cachePathFor(%q) ok=%v, want %v", tc.urlPath, ok, tc.ok)
		}
	}
}