package main

import (
	"archive/zip"
	"bytes"
	"encoding/json"
	"fmt"
	"image"
	"image/color"
	"image/jpeg"
	"io"
	"mime/multipart"
	"net/http"
	"net/http/httptest"
	"net/url"
	"os"
	"path/filepath"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

func setupTestServer(t *testing.T) (*httptest.Server, *Server) {
	t.Helper()
	dir := t.TempDir()
	srv := NewServer(dir, 20<<20)

	require.NoError(t, srv.createGallery("test-gallery", "secret123"))

	ts := httptest.NewServer(srv.Handler())
	t.Cleanup(ts.Close)
	return ts, srv
}

// noRedirectClient returns an *http.Client that does NOT follow redirects,
// so we can inspect 303 responses and Set-Cookie headers.
func noRedirectClient() *http.Client {
	return &http.Client{
		CheckRedirect: func(req *http.Request, via []*http.Request) error {
			return http.ErrUseLastResponse
		},
	}
}

// login performs a POST login and returns the session cookies on success.
func login(t *testing.T, ts *httptest.Server, gallery, password string) []*http.Cookie {
	t.Helper()
	client := noRedirectClient()

	resp, err := client.PostForm(ts.URL+"/g/"+gallery, url.Values{"password": {password}})
	require.NoError(t, err)
	defer resp.Body.Close()

	require.Equal(t, http.StatusSeeOther, resp.StatusCode, "login should redirect on success")
	return resp.Cookies()
}

// authedGet performs a GET with the given cookies attached.
func authedGet(t *testing.T, rawURL string, cookies []*http.Cookie) *http.Response {
	t.Helper()
	req, err := http.NewRequest(http.MethodGet, rawURL, nil)
	require.NoError(t, err)
	for _, c := range cookies {
		req.AddCookie(c)
	}
	resp, err := http.DefaultClient.Do(req)
	require.NoError(t, err)
	return resp
}

// makeTestJPEG creates a small valid JPEG in memory.
func makeTestJPEG() []byte {
	img := image.NewRGBA(image.Rect(0, 0, 10, 10))
	for y := 0; y < 10; y++ {
		for x := 0; x < 10; x++ {
			img.Set(x, y, color.RGBA{R: 255, A: 255})
		}
	}
	var buf bytes.Buffer
	jpeg.Encode(&buf, img, nil)
	return buf.Bytes()
}

// uploadPhoto uploads a single JPEG to the gallery via multipart POST.
func uploadPhoto(t *testing.T, ts *httptest.Server, gallery string, cookies []*http.Cookie, filename string, data []byte) *http.Response {
	t.Helper()

	var body bytes.Buffer
	mw := multipart.NewWriter(&body)
	part, err := mw.CreateFormFile("photos", filename)
	require.NoError(t, err)
	_, err = part.Write(data)
	require.NoError(t, err)
	require.NoError(t, mw.Close())

	req, err := http.NewRequest(http.MethodPost, ts.URL+"/g/"+gallery+"/upload", &body)
	require.NoError(t, err)
	req.Header.Set("Content-Type", mw.FormDataContentType())
	for _, c := range cookies {
		req.AddCookie(c)
	}

	resp, err := http.DefaultClient.Do(req)
	require.NoError(t, err)
	return resp
}

// bodyString reads and returns the full response body as a string.
func bodyString(t *testing.T, resp *http.Response) string {
	t.Helper()
	defer resp.Body.Close()
	b, err := io.ReadAll(resp.Body)
	require.NoError(t, err)
	return string(b)
}

// setupWithPhoto creates a server, logs in, uploads one photo, and returns
// everything needed for subsequent assertions.
func setupWithPhoto(t *testing.T, filename string) (*httptest.Server, *Server, []*http.Cookie) {
	t.Helper()
	ts, srv := setupTestServer(t)
	cookies := login(t, ts, "test-gallery", "secret123")

	resp := uploadPhoto(t, ts, "test-gallery", cookies, filename, makeTestJPEG())
	defer resp.Body.Close()

	var result map[string]int
	require.NoError(t, json.NewDecoder(resp.Body).Decode(&result))
	require.Equal(t, 1, result["uploaded"])

	return ts, srv, cookies
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

func TestIndexListsGalleries(t *testing.T) {
	ts, _ := setupTestServer(t)

	resp, err := http.Get(ts.URL + "/")
	require.NoError(t, err)
	body := bodyString(t, resp)

	assert.Equal(t, 200, resp.StatusCode)
	assert.Contains(t, body, "test-gallery")
}

func TestLoginFlow(t *testing.T) {
	ts, _ := setupTestServer(t)
	client := noRedirectClient()

	resp, err := client.PostForm(ts.URL+"/g/test-gallery", url.Values{"password": {"secret123"}})
	require.NoError(t, err)
	defer resp.Body.Close()

	assert.Equal(t, http.StatusSeeOther, resp.StatusCode)

	var found bool
	for _, c := range resp.Cookies() {
		if c.Name == "session_test-gallery" && c.Value != "" {
			found = true
		}
	}
	assert.True(t, found, "session cookie should be set after login")
}

func TestSessionCookieHasSecureFlag(t *testing.T) {
	ts, _ := setupTestServer(t)
	client := noRedirectClient()

	resp, err := client.PostForm(ts.URL+"/g/test-gallery", url.Values{"password": {"secret123"}})
	require.NoError(t, err)
	defer resp.Body.Close()

	require.Equal(t, http.StatusSeeOther, resp.StatusCode)

	var sessionCookie *http.Cookie
	for _, c := range resp.Cookies() {
		if c.Name == "session_test-gallery" {
			sessionCookie = c
			break
		}
	}
	require.NotNil(t, sessionCookie, "session cookie must be present")
	assert.True(t, sessionCookie.Secure, "session cookie must have the Secure flag set")
}

func TestLoginWrongPassword(t *testing.T) {
	ts, _ := setupTestServer(t)

	resp, err := http.PostForm(ts.URL+"/g/test-gallery", url.Values{"password": {"wrong"}})
	require.NoError(t, err)
	body := bodyString(t, resp)

	assert.Equal(t, 200, resp.StatusCode)
	assert.Contains(t, body, "Wrong password")
}

func TestGalleryViewEmpty(t *testing.T) {
	ts, _ := setupTestServer(t)
	cookies := login(t, ts, "test-gallery", "secret123")

	resp := authedGet(t, ts.URL+"/g/test-gallery", cookies)
	body := bodyString(t, resp)

	assert.Equal(t, 200, resp.StatusCode)
	assert.Contains(t, body, "No photos yet")
}

func TestUploadAndView(t *testing.T) {
	ts, _, cookies := setupWithPhoto(t, "holiday.jpg")

	resp := authedGet(t, ts.URL+"/g/test-gallery", cookies)
	body := bodyString(t, resp)

	assert.Contains(t, body, "holiday.jpg")
}

func TestThumbServing(t *testing.T) {
	ts, _, cookies := setupWithPhoto(t, "thumb-test.jpg")

	resp := authedGet(t, ts.URL+"/g/test-gallery/thumb/thumb-test.jpg", cookies)
	defer resp.Body.Close()

	assert.Equal(t, 200, resp.StatusCode)
	assert.Contains(t, resp.Header.Get("Content-Type"), "image/jpeg")

	_, err := jpeg.Decode(resp.Body)
	assert.NoError(t, err, "thumbnail should be a decodable JPEG")
}

func TestThumbServesSourceWhenThumbNotReady(t *testing.T) {
	// When the background worker hasn't generated a thumb yet,
	// handleThumb should serve the source image as fallback.
	ts, srv := setupTestServer(t)
	cookies := login(t, ts, "test-gallery", "secret123")

	// Write a photo directly — don't start the thumb worker, so no thumb exists.
	dir := srv.galleryDir("test-gallery")
	original := makeTestJPEG()
	require.NoError(t, os.WriteFile(filepath.Join(dir, "nothumb.jpg"), original, 0644))

	resp := authedGet(t, ts.URL+"/g/test-gallery/thumb/nothumb.jpg", cookies)
	body, err := io.ReadAll(resp.Body)
	resp.Body.Close()
	require.NoError(t, err)

	assert.Equal(t, 200, resp.StatusCode)
	assert.Equal(t, original, body,
		"when thumbnail is not ready, should serve the source image as fallback")
}

func TestThumbWorkerGeneratesThumbnails(t *testing.T) {
	dir := t.TempDir()
	srv := NewServer(dir, 20<<20)
	require.NoError(t, srv.createGallery("test-gallery", "secret123"))

	// Write a photo directly.
	galleryDir := srv.galleryDir("test-gallery")
	require.NoError(t, os.WriteFile(filepath.Join(galleryDir, "worker-test.jpg"), makeTestJPEG(), 0644))

	// Start the worker and trigger a scan.
	srv.startThumbWorker()
	srv.triggerThumbScan("test-gallery")

	// Wait for the thumbnail to appear (up to 5s).
	thumbPath := filepath.Join(galleryDir, ".thumbs-v2", "worker-test.jpg")
	require.Eventually(t, func() bool {
		_, err := os.Stat(thumbPath)
		return err == nil
	}, 5*time.Second, 50*time.Millisecond, "thumbnail should be generated by the background worker")

	// Verify it's a valid JPEG.
	data, err := os.ReadFile(thumbPath)
	require.NoError(t, err)
	_, err = jpeg.Decode(bytes.NewReader(data))
	assert.NoError(t, err, "generated thumbnail should be a valid JPEG")
}

func TestUploadTriggersThumbWorker(t *testing.T) {
	dir := t.TempDir()
	srv := NewServer(dir, 20<<20)
	require.NoError(t, srv.createGallery("test-gallery", "secret123"))
	srv.startThumbWorker()

	ts := httptest.NewServer(srv.Handler())
	t.Cleanup(ts.Close)

	cookies := login(t, ts, "test-gallery", "secret123")
	resp := uploadPhoto(t, ts, "test-gallery", cookies, "upload-trigger.jpg", makeTestJPEG())
	resp.Body.Close()

	// The upload should have triggered an immediate scan. Wait for the thumb.
	thumbPath := filepath.Join(srv.galleryDir("test-gallery"), ".thumbs-v2", "upload-trigger.jpg")
	require.Eventually(t, func() bool {
		_, err := os.Stat(thumbPath)
		return err == nil
	}, 5*time.Second, 50*time.Millisecond,
		"upload should trigger background thumbnail generation")
}

func TestOldThumbsDirCleanedUp(t *testing.T) {
	dir := t.TempDir()
	srv := NewServer(dir, 20<<20)
	require.NoError(t, srv.createGallery("test-gallery", "secret123"))

	// Create the old .thumbs directory with some content.
	oldThumbsDir := filepath.Join(srv.galleryDir("test-gallery"), ".thumbs")
	require.NoError(t, os.MkdirAll(oldThumbsDir, 0755))
	require.NoError(t, os.WriteFile(filepath.Join(oldThumbsDir, "old.jpg"), []byte("old"), 0644))

	srv.cleanupOldThumbs()

	_, err := os.Stat(oldThumbsDir)
	assert.True(t, os.IsNotExist(err), "old .thumbs directory should be removed")
}

func TestPhotoServing(t *testing.T) {
	ts, _, cookies := setupWithPhoto(t, "original.jpg")

	resp := authedGet(t, ts.URL+"/g/test-gallery/photo/original.jpg", cookies)
	body, err := io.ReadAll(resp.Body)
	resp.Body.Close()
	require.NoError(t, err)

	assert.Equal(t, 200, resp.StatusCode)
	assert.Equal(t, makeTestJPEG(), body, "served photo should match uploaded content")
}

func TestZipDownload(t *testing.T) {
	ts, _, cookies := setupWithPhoto(t, "zip-pic.jpg")

	resp := authedGet(t, ts.URL+"/g/test-gallery/zip", cookies)
	zipBody, err := io.ReadAll(resp.Body)
	resp.Body.Close()
	require.NoError(t, err)

	assert.Equal(t, 200, resp.StatusCode)
	assert.Equal(t, "application/zip", resp.Header.Get("Content-Type"))

	zr, err := zip.NewReader(bytes.NewReader(zipBody), int64(len(zipBody)))
	require.NoError(t, err)

	names := make([]string, len(zr.File))
	for i, f := range zr.File {
		names[i] = f.Name
	}
	assert.Contains(t, names, "zip-pic.jpg")
}

func TestUnauthenticatedAccessBlocked(t *testing.T) {
	ts, _, _ := setupWithPhoto(t, "secret.jpg")

	paths := []string{
		"/g/test-gallery",
		"/g/test-gallery/photo/secret.jpg",
		"/g/test-gallery/thumb/secret.jpg",
		"/g/test-gallery/zip",
	}

	for _, p := range paths {
		resp, err := http.Get(ts.URL + p)
		require.NoError(t, err)
		body := bodyString(t, resp)

		assert.Contains(t, body, `name="password"`, "path %q should show login form", p)
		assert.NotContains(t, body, "secret.jpg", "path %q should not leak photo filename", p)
	}
}

func TestRateLimiting(t *testing.T) {
	ts, _ := setupTestServer(t)

	for i := 0; i < loginRateMaxAttempts; i++ {
		resp, err := http.PostForm(ts.URL+"/g/test-gallery", url.Values{"password": {"wrong"}})
		require.NoError(t, err)
		resp.Body.Close()
		assert.Equal(t, 200, resp.StatusCode, "attempt %d should be allowed", i+1)
	}

	// The next attempt should be rate-limited
	resp, err := http.PostForm(ts.URL+"/g/test-gallery", url.Values{"password": {"wrong"}})
	require.NoError(t, err)
	body := bodyString(t, resp)

	assert.Equal(t, http.StatusTooManyRequests, resp.StatusCode)
	assert.Contains(t, body, "Too many login attempts")
}

func TestUploadSizeEnforcedAtReadTime(t *testing.T) {
	ts, srv := setupTestServer(t)
	srv.maxUploadSize = 256
	cookies := login(t, ts, "test-gallery", "secret123")

	// Upload a file of exactly maxUploadSize bytes (passes the fh.Size
	// check: fh.Size <= maxUploadSize). The file must be saved to disk.
	exactData := bytes.Repeat([]byte{0xFF}, int(srv.maxUploadSize))
	resp := uploadPhoto(t, ts, "test-gallery", cookies, "exact.jpg", exactData)
	var result map[string]int
	require.NoError(t, json.NewDecoder(resp.Body).Decode(&result))
	resp.Body.Close()
	require.Equal(t, 1, result["uploaded"], "file at exactly maxUploadSize should be accepted")

	// Verify every file on disk is at most maxUploadSize bytes.
	// This is the invariant that io.LimitReader enforces as defense-in-depth:
	// even if the fh.Size check were somehow bypassed, the copy itself
	// must never write more than maxUploadSize bytes.
	dir := srv.galleryDir("test-gallery")
	entries, err := os.ReadDir(dir)
	require.NoError(t, err)

	for _, e := range entries {
		if e.IsDir() || !isAllowedExt(e.Name()) {
			continue
		}
		info, err := e.Info()
		require.NoError(t, err)
		assert.LessOrEqual(t, info.Size(), srv.maxUploadSize,
			"file %q on disk (%d bytes) must not exceed maxUploadSize (%d)",
			e.Name(), info.Size(), srv.maxUploadSize)
	}

	// Now test copyUploadFile directly: given a reader with more data than
	// maxUploadSize, the copy must be capped at maxUploadSize bytes.
	oversized := bytes.NewReader(bytes.Repeat([]byte{0xAB}, int(srv.maxUploadSize)+500))
	tmpPath := filepath.Join(t.TempDir(), "test-copy.dat")
	n, err := srv.copyUploadFile(tmpPath, oversized)
	require.NoError(t, err)
	assert.LessOrEqual(t, n, srv.maxUploadSize,
		"copyUploadFile should write at most maxUploadSize bytes, got %d", n)
}

// makeUnsupportedJPEG creates a JPEG that Go's stdlib cannot decode
// (unsupported luma/chroma subsampling ratio with H=3) but ImageMagick can.
// This simulates real-world JPEGs that use features outside Go's support.
func makeUnsupportedJPEG() []byte {
	img := image.NewRGBA(image.Rect(0, 0, 200, 200))
	for y := 0; y < 200; y++ {
		for x := 0; x < 200; x++ {
			img.Set(x, y, color.RGBA{R: uint8(x), G: uint8(y), B: 128, A: 255})
		}
	}
	var buf bytes.Buffer
	jpeg.Encode(&buf, img, &jpeg.Options{Quality: 90})
	data := buf.Bytes()

	// Find the SOF0 marker (FF C0) and change luma sampling factor to H=3, V=1.
	// Go's image/jpeg rejects h=3 or v=3 as "unsupported subsampling ratio",
	// but ImageMagick handles it gracefully.
	for i := 0; i < len(data)-1; i++ {
		if data[i] == 0xFF && data[i+1] == 0xC0 {
			// SOF0 header: marker(2) + length(2) + precision(1) + height(2) + width(2) + nf(1) + component(3*nf)
			compStart := i + 2 + 2 + 1 + 2 + 2 + 1
			data[compStart+1] = 0x31 // H=3, V=1
			break
		}
	}
	return data
}

func TestThumbFallbackToImageMagick(t *testing.T) {
	dir := t.TempDir()
	srv := NewServer(dir, 20<<20)
	require.NoError(t, srv.createGallery("test-gallery", "secret123"))

	// Create a JPEG that Go's stdlib can't decode but ImageMagick can.
	unsupportedJPEG := makeUnsupportedJPEG()

	// Write directly to the gallery dir.
	galleryDir := srv.galleryDir("test-gallery")
	require.NoError(t, os.WriteFile(filepath.Join(galleryDir, "tricky.jpg"), unsupportedJPEG, 0644))

	// Start the worker and trigger a scan.
	srv.startThumbWorker()
	srv.triggerThumbScan("test-gallery")

	// Wait for the thumbnail to appear.
	thumbPath := filepath.Join(galleryDir, ".thumbs-v2", "tricky.jpg")
	require.Eventually(t, func() bool {
		_, err := os.Stat(thumbPath)
		return err == nil
	}, 5*time.Second, 50*time.Millisecond, "thumbnail should be generated by the background worker")

	// The thumbnail should be a valid, fully decodable JPEG.
	thumbData, err := os.ReadFile(thumbPath)
	require.NoError(t, err)

	_, err = jpeg.Decode(bytes.NewReader(thumbData))
	assert.NoError(t, err, "thumbnail should be a fully decodable JPEG even when Go's stdlib can't decode the original")

	// The thumbnail must not be the raw original.
	assert.NotEqual(t, unsupportedJPEG, thumbData,
		"thumbnail must not be the broken original")
}

// makeLargeTestJPEG creates a larger JPEG that takes more time to thumbnail.
func makeLargeTestJPEG() []byte {
	img := image.NewRGBA(image.Rect(0, 0, 3000, 2000))
	for y := 0; y < 2000; y++ {
		for x := 0; x < 3000; x++ {
			img.Set(x, y, color.RGBA{R: uint8(x % 256), G: uint8(y % 256), B: 128, A: 255})
		}
	}
	var buf bytes.Buffer
	jpeg.Encode(&buf, img, &jpeg.Options{Quality: 90})
	return buf.Bytes()
}

func TestWorkerGeneratesAllThumbnails(t *testing.T) {
	dir := t.TempDir()
	srv := NewServer(dir, 20<<20)
	require.NoError(t, srv.createGallery("test-gallery", "secret123"))

	// Write 20 photos directly to the gallery dir.
	galleryDir := srv.galleryDir("test-gallery")
	numPhotos := 20
	for i := 0; i < numPhotos; i++ {
		filename := fmt.Sprintf("photo_%03d.jpg", i)
		require.NoError(t, os.WriteFile(filepath.Join(galleryDir, filename), makeTestJPEG(), 0644))
	}

	// Start the worker and trigger a scan.
	srv.startThumbWorker()
	srv.triggerThumbScan("test-gallery")

	// Wait for all thumbnails to appear.
	thumbsDir := filepath.Join(galleryDir, ".thumbs-v2")
	require.Eventually(t, func() bool {
		entries, err := os.ReadDir(thumbsDir)
		if err != nil {
			return false
		}
		return len(entries) >= numPhotos
	}, 10*time.Second, 100*time.Millisecond,
		"all %d thumbnails should be generated by the background worker", numPhotos)

	// Verify each is a valid JPEG.
	for i := 0; i < numPhotos; i++ {
		filename := fmt.Sprintf("photo_%03d.jpg", i)
		data, err := os.ReadFile(filepath.Join(thumbsDir, filename))
		require.NoError(t, err)
		_, err = jpeg.Decode(bytes.NewReader(data))
		assert.NoError(t, err, "thumbnail %s should be a valid JPEG", filename)
	}
}

func setupTestServerNoThumbs(t *testing.T) (*httptest.Server, *Server) {
	t.Helper()
	dir := t.TempDir()
	srv := NewServer(dir, 20<<20)

	require.NoError(t, srv.createGalleryOpts("test-gallery", "secret123", false))

	ts := httptest.NewServer(srv.Handler())
	t.Cleanup(ts.Close)
	return ts, srv
}

func TestNoThumbsGalleryServesSourceInGrid(t *testing.T) {
	ts, srv := setupTestServerNoThumbs(t)
	cookies := login(t, ts, "test-gallery", "secret123")

	// Upload a photo directly.
	dir := srv.galleryDir("test-gallery")
	require.NoError(t, os.WriteFile(filepath.Join(dir, "pic.jpg"), makeTestJPEG(), 0644))

	// The gallery HTML should use /photo/ URLs, not /thumb/ URLs.
	resp := authedGet(t, ts.URL+"/g/test-gallery", cookies)
	body := bodyString(t, resp)

	assert.Contains(t, body, "/g/test-gallery/photo/pic.jpg",
		"gallery grid should use photo URLs when thumbnails are disabled")
	assert.NotContains(t, body, "/g/test-gallery/thumb/pic.jpg",
		"gallery grid should NOT use thumb URLs when thumbnails are disabled")
}

func TestThumbsEnabledGalleryServesThumbsInGrid(t *testing.T) {
	ts, srv := setupTestServer(t) // default: thumbs enabled
	cookies := login(t, ts, "test-gallery", "secret123")

	dir := srv.galleryDir("test-gallery")
	require.NoError(t, os.WriteFile(filepath.Join(dir, "pic.jpg"), makeTestJPEG(), 0644))

	resp := authedGet(t, ts.URL+"/g/test-gallery", cookies)
	body := bodyString(t, resp)

	assert.Contains(t, body, "/g/test-gallery/thumb/pic.jpg",
		"gallery grid should use thumb URLs when thumbnails are enabled")
}

func TestInvalidGalleryName404(t *testing.T) {
	ts, _ := setupTestServer(t)

	cases := []struct {
		name string
		path string
	}{
		{"path traversal", "/g/../../etc"},
		{"spaces", "/g/foo bar"},
		{"dots", "/g/hello.world"},
		{"xss", "/g/<script>"},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			resp, err := http.Get(ts.URL + tc.path)
			require.NoError(t, err)
			resp.Body.Close()
			assert.Equal(t, 404, resp.StatusCode)
		})
	}
}