package handlers

import (
	"image/jpeg"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"testing"
	"time"

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

// requireServedPhoto requires that rec answers 200 with the JPEG at photoPath
// on signedHost at the 50x50 that encPhotoURL and the generator tests ask for.
func requireServedPhoto(t *testing.T, rec *httptest.ResponseRecorder) {
	t.Helper()

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

	contentType := rec.Header().Get("Content-Type")
	if contentType != "image/jpeg" {
		t.Errorf("Content-Type = %q, want image/jpeg", contentType)
	}

	img, err := jpeg.DecodeConfig(rec.Body)
	if err != nil {
		t.Fatalf("body is not a JPEG: %v", err)
	}

	if img.Width != 50 || img.Height != 50 {
		t.Errorf("image is %dx%d, want 50x50", img.Width, img.Height)
	}
}

// TestHandleImageEnc_ValidToken_ServesImage verifies that a token made with
// the signing key serves the image it asks for.
func TestHandleImageEnc_ValidToken_ServesImage(t *testing.T) {
	t.Parallel()

	h, srv := newSignedHostServer(t, slog.New(slog.DiscardHandler))

	rec := httptest.NewRecorder()
	srv.ServeHTTP(rec, httptest.NewRequestWithContext(
		t.Context(), http.MethodGet, encPhotoURL(t, h), nil))

	requireServedPhoto(t, rec)
}

// TestHandleImageEnc_RejectedToken verifies that a token that has expired
// answers 410, and that a token with one character changed, a token cut
// short, and a token made with another signing key answer 400. The server
// would serve the photo for a token it accepted.
func TestHandleImageEnc_RejectedToken(t *testing.T) {
	t.Parallel()

	h, srv := newSignedHostServer(t, slog.New(slog.DiscardHandler))

	photo := encurl.Payload{
		SourceHost: signedHost,
		SourcePath: photoPath,
		Width:      50,
		Height:     50,
	}

	valid, err := h.encGen.Generate(&photo)
	if err != nil {
		t.Fatalf("Generate() error = %v", err)
	}

	expiredPhoto := photo
	expiredPhoto.ExpiresAt = time.Now().Add(-time.Minute).Unix()

	expired, err := h.encGen.Generate(&expiredPhoto)
	if err != nil {
		t.Fatalf("Generate() error = %v", err)
	}

	otherGen, err := encurl.NewGenerator("another-signing-key-fedcba9876543210")
	if err != nil {
		t.Fatalf("encurl.NewGenerator() error = %v", err)
	}

	otherKey, err := otherGen.Generate(&photo)
	if err != nil {
		t.Fatalf("Generate() error = %v", err)
	}

	// Changing a character in the middle always changes the decoded bytes;
	// the last character of unpadded base64 can carry unused bits.
	middle := len(valid) / 2

	replacement := "A"
	if valid[middle] == 'A' {
		replacement = "B"
	}

	changed := valid[:middle] + replacement + valid[middle+1:]

	tests := []struct {
		name       string
		token      string
		wantStatus int
	}{
		{"expired", expired, http.StatusGone},
		{"one character changed", changed, http.StatusBadRequest},
		{"cut short", valid[:middle], http.StatusBadRequest},
		{"another signing key", otherKey, http.StatusBadRequest},
	}

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

			rec := getEncToken(srv, tt.token)
			t.Logf("GET /v1/e/%s/img.jpg: %d %s", tt.token, rec.Code, rec.Body)

			if rec.Code != tt.wantStatus {
				t.Errorf("status = %d, want %d", rec.Code, tt.wantStatus)
			}
		})
	}
}