package handlers

import (
	"image/color"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"strconv"
	"strings"
	"testing"
	"testing/fstest"
	"time"

	"github.com/go-chi/chi/v5"

	"sneak.berlin/go/pixa/internal/encurl"
	"sneak.berlin/go/pixa/internal/imgcache"
)

// photoPath is the path of the JPEG that newSignedHostServer serves.
const photoPath = "/images/photo.jpg"

// newSignedHostServer returns a router for both image routes, and the Handlers
// behind it, whose fetcher serves a JPEG at photoPath on signedHost. signedHost
// is not on the allowlist, so a /v1/image/ URL for it is served only with a
// valid signature.
func newSignedHostServer(t *testing.T) (*Handlers, http.Handler) {
	t.Helper()

	cache, err := imgcache.NewCache(setupTestDB(t), imgcache.CacheConfig{
		StateDir:    t.TempDir(),
		CacheTTL:    time.Hour,
		NegativeTTL: 5 * time.Minute,
	})
	if err != nil {
		t.Fatalf("imgcache.NewCache() error = %v", err)
	}

	jpegData := generateTestJPEG(t, 100, 100, color.RGBA{255, 0, 0, 255})

	svc, err := imgcache.NewService(&imgcache.ServiceConfig{
		Cache: cache,
		Fetcher: newMockFetcher(fstest.MapFS{
			signedHost + photoPath: &fstest.MapFile{Data: jpegData},
		}),
		SigningKey: testSigningKey,
	})
	if err != nil {
		t.Fatalf("imgcache.NewService() error = %v", err)
	}

	encGen, err := encurl.NewGenerator(testSigningKey)
	if err != nil {
		t.Fatalf("encurl.NewGenerator() error = %v", err)
	}

	h := &Handlers{
		log:    slog.New(slog.DiscardHandler),
		imgSvc: svc,
		encGen: encGen,
	}

	r := chi.NewRouter()
	r.Get("/v1/image/*", h.HandleImage())
	r.Get("/v1/e/{token}/*", h.HandleImageEnc())

	return h, r
}

// getMaxAge sends a GET for target to srv, requires a 200, and returns the
// max-age of the response's Cache-Control header, which must read
// "public, max-age=<seconds>, immutable".
func getMaxAge(t *testing.T, srv http.Handler, target string) int {
	t.Helper()

	req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, target, nil)
	rec := httptest.NewRecorder()

	srv.ServeHTTP(rec, req)

	header := rec.Header().Get("Cache-Control")
	t.Logf("GET %s: %d, Cache-Control: %s", target, rec.Code, header)

	if rec.Code != http.StatusOK {
		t.Fatalf("status = %d, want %d", rec.Code, http.StatusOK)
	}

	value, hasPrefix := strings.CutPrefix(header, "public, max-age=")
	value, hasSuffix := strings.CutSuffix(value, ", immutable")

	maxAge, err := strconv.Atoi(value)
	if !hasPrefix || !hasSuffix || err != nil {
		t.Fatalf("Cache-Control = %q, want public, max-age=<seconds>, immutable",
			header)
	}

	return maxAge
}

// TestHandleImage_SignedURL_MaxAgeEndsAtExp verifies that an image served
// through a signed URL expiring in 60 seconds may be cached for at most those
// 60 seconds. The lower bound of 50 shows the max-age is the time left, not 0.
func TestHandleImage_SignedURL_MaxAgeEndsAtExp(t *testing.T) {
	t.Parallel()

	h, srv := newSignedHostServer(t)

	signedURL, err := h.imgSvc.GenerateSignedURL("", &imgcache.ImageRequest{
		SourceHost: signedHost,
		SourcePath: photoPath,
		Size:       imgcache.Size{Width: 50, Height: 50},
		Format:     imgcache.FormatJPEG,
	}, time.Minute)
	if err != nil {
		t.Fatalf("GenerateSignedURL() error = %v", err)
	}

	maxAge := getMaxAge(t, srv, signedURL)
	if maxAge < 50 || maxAge > 60 {
		t.Errorf("max-age = %d, want 50 to 60", maxAge)
	}
}

// TestHandleImage_AllowlistedHost_MaxAge verifies the max-age of an image from
// an allowlisted host, which is served without checking sig or exp. A URL with
// no exp may be cached for a year. A URL whose exp has passed is the one request
// that reaches the header after its expiry, and must get 0, never less.
func TestHandleImage_AllowlistedHost_MaxAge(t *testing.T) {
	t.Parallel()

	pastExp := strconv.FormatInt(time.Now().Add(-time.Hour).Unix(), 10)

	tests := []struct {
		name       string
		query      string
		wantMaxAge int
	}{
		{"no exp", "", 31536000},
		{"exp already past", "?exp=" + pastExp, 0},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			fix := setupTestHandler(t)

			r := chi.NewRouter()
			r.Get("/v1/image/*", fix.handler.HandleImage())

			maxAge := getMaxAge(t, r,
				"/v1/image/"+fix.goodHost+"/images/photo.jpg/50x50.jpeg"+tt.query)
			if maxAge != tt.wantMaxAge {
				t.Errorf("max-age = %d, want %d", maxAge, tt.wantMaxAge)
			}
		})
	}
}

// TestHandleImageEnc_MaxAge verifies that an image served through an encrypted
// URL with a 60 second TTL may be cached for at most those 60 seconds, that one
// with a two-year TTL may be cached for a year, and that one made without a
// TTL, which never expires, may be cached for a year.
func TestHandleImageEnc_MaxAge(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name        string
		expiresAt   int64
		wantAtLeast int
		wantAtMost  int
	}{
		{"60 second TTL", time.Now().Add(time.Minute).Unix(), 50, 60},
		{"two-year TTL", time.Now().Add(2 * 365 * 24 * time.Hour).Unix(), 31536000, 31536000},
		{"no TTL", 0, 31536000, 31536000},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			h, srv := newSignedHostServer(t)

			token, err := h.encGen.Generate(&encurl.Payload{
				SourceHost: signedHost,
				SourcePath: photoPath,
				Width:      50,
				Height:     50,
				Format:     imgcache.FormatJPEG,
				ExpiresAt:  tt.expiresAt,
			})
			if err != nil {
				t.Fatalf("Generate() error = %v", err)
			}

			maxAge := getMaxAge(t, srv, "/v1/e/"+token+"/img.jpg")
			if maxAge < tt.wantAtLeast || maxAge > tt.wantAtMost {
				t.Errorf("max-age = %d, want %d to %d",
					maxAge, tt.wantAtLeast, tt.wantAtMost)
			}
		})
	}
}