package handlers

import (
	"errors"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"slices"
	"strings"
	"testing"
	"time"

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

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

// The content types the tests below expect.
const (
	avifType = "image/avif"
	webpType = "image/webp"
	jpegType = "image/jpeg"
	jsonType = "application/json"
)

// TestFormatForAccept verifies the format chosen for the format auto from each
// Accept header below, and the error for one that allows none of AVIF, WebP
// and JPEG or is not valid.
func TestFormatForAccept(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name    string
		accept  string
		want    imgcache.ImageFormat
		wantErr error
	}{
		{"AVIF-capable browser",
			"image/avif,image/webp,image/apng,image/svg+xml,image/*,*/*;q=0.8",
			imgcache.FormatAVIF, nil},
		{"WebP-capable browser",
			"image/webp,image/png,image/svg+xml,image/*;q=0.8,*/*;q=0.5",
			imgcache.FormatWebP, nil},
		{"WebP only", webpType, imgcache.FormatWebP, nil},
		{"neither", "image/png,image/*;q=0.8,*/*;q=0.5", imgcache.FormatJPEG, nil},
		{"wildcard only", "*/*", imgcache.FormatJPEG, nil},
		{"image wildcard only", "image/*", imgcache.FormatJPEG, nil},
		{"absent", "", imgcache.FormatJPEG, nil},
		{"q=0 on AVIF", "image/avif;q=0,image/webp,*/*", imgcache.FormatWebP, nil},
		{"AVIF named twice, once with q=0", "image/avif,image/avif;q=0.0,*/*",
			imgcache.FormatJPEG, nil},
		{"upper case and spaces", " Image/AVIF ; Q=0.5 ", imgcache.FormatAVIF, nil},
		{"q=0 on JPEG", "image/jpeg;q=0,image/*", "", errNotAcceptable},
		{"q=0 on everything", "*/*;q=0", "", errNotAcceptable},
		{"PNG only", "image/png", "", errNotAcceptable},
		{"malformed media range", "image/", "", errInvalidAccept},
		{"q not a number", "image/avif;q=high", "", errInvalidAccept},
		{"q above 1", "image/avif;q=2", "", errInvalidAccept},
	}

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

			got, err := formatForAccept(tt.accept)
			t.Logf("Accept %q: %q, %v", tt.accept, got, err)

			if got != tt.want || !errors.Is(err, tt.wantErr) {
				t.Errorf("formatForAccept(%q) = %q, %v, want %q, %v",
					tt.accept, got, err, tt.want, tt.wantErr)
			}
		})
	}
}

// autoPhotoURLs returns a signed /v1/image/ URL and an encrypted /v1/e/ URL,
// both valid for a minute, for the JPEG at photoPath on signedHost at 50x50 in
// the format auto, made with h's image service and generator.
func autoPhotoURLs(t *testing.T, h *Handlers) (string, string) {
	t.Helper()

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

	token, err := h.encGen.Generate(&encurl.Payload{
		SourceHost: signedHost,
		SourcePath: photoPath,
		Width:      50,
		Height:     50,
		Format:     imgcache.FormatAuto,
		ExpiresAt:  time.Now().Add(time.Minute).Unix(),
	})
	if err != nil {
		t.Fatalf("Generate() error = %v", err)
	}

	return signedURL, "/v1/e/" + token + "/img.jpg"
}

// requestImage sends method for target to srv with an Accept header line for
// each of accept, and returns the response.
func requestImage(
	t *testing.T, srv http.Handler, method, target string, accept ...string,
) *httptest.ResponseRecorder {
	t.Helper()

	req := httptest.NewRequestWithContext(t.Context(), method, target, nil)

	for _, value := range accept {
		req.Header.Add("Accept", value)
	}

	rec := httptest.NewRecorder()
	srv.ServeHTTP(rec, req)
	t.Logf("%s %s with Accept %q: %d, Content-Type %s, Vary %v, X-Pixa-Cache %s",
		method, target, accept, rec.Code, rec.Header().Get("Content-Type"),
		rec.Header().Values("Vary"), rec.Header().Get("X-Pixa-Cache"))

	return rec
}

// TestFormatAuto_ChosenFromAccept requests an auto URL on each image route
// with each Accept below, and checks the answer and that it carries
// Vary: Accept. The signed URL is signed for auto, so it is valid whatever
// Accept chooses.
func TestFormatAuto_ChosenFromAccept(t *testing.T) {
	t.Parallel()

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

	tests := []struct {
		name       string
		accept     []string
		wantStatus int
		wantType   string
	}{
		{"AVIF accepted", []string{"image/avif,image/webp,*/*;q=0.8"},
			http.StatusOK, avifType},
		{"WebP accepted", []string{"image/webp,*/*;q=0.8"}, http.StatusOK, webpType},
		{"no Accept", nil, http.StatusOK, jpegType},
		{"two Accept lines", []string{"image/png", webpType}, http.StatusOK, webpType},
		{"none of the three", []string{"image/gif"},
			http.StatusNotAcceptable, jsonType},
		{"not valid", []string{"image/avif;q=high"}, http.StatusBadRequest, jsonType},
	}

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

			for _, target := range []string{signedURL, encryptedURL} {
				rec := requestImage(t, srv, http.MethodGet, target, tt.accept...)
				gotType := rec.Header().Get("Content-Type")

				if rec.Code != tt.wantStatus || gotType != tt.wantType {
					t.Errorf("%s: %d %s, want %d %s; body %s", target,
						rec.Code, gotType, tt.wantStatus, tt.wantType, rec.Body)
				}

				if !slices.Contains(rec.Header().Values("Vary"), "Accept") {
					t.Errorf("%s: Vary = %v, want Accept in it",
						target, rec.Header().Values("Vary"))
				}
			}
		})
	}
}

// TestFormatAuto_SignatureCoversAuto verifies that a /v1/image/ URL with the
// format auto is checked against a signature for auto, not for the format
// chosen: a URL signed for avif, with auto put in its path, is refused for a
// client whose Accept chooses AVIF.
func TestFormatAuto_SignatureCoversAuto(t *testing.T) {
	t.Parallel()

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

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

	target := strings.Replace(signedForAVIF, "/50x50.avif?", "/50x50.auto?", 1)
	if target == signedForAVIF {
		t.Fatalf("no /50x50.avif? in %s", signedForAVIF)
	}

	rec := requestImage(t, srv, http.MethodGet, target, avifType)
	if rec.Code != http.StatusUnauthorized {
		t.Errorf("status = %d, want %d", rec.Code, http.StatusUnauthorized)
	}
}

// TestFormatAuto_CachesEachFormatApart requests an auto URL for AVIF, then
// JPEG, then both again. Each format is processed once and then served from
// the cache, with an ETag of its own, so a client never gets the other format
// from the cache.
func TestFormatAuto_CachesEachFormatApart(t *testing.T) {
	t.Parallel()

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

	steps := []struct {
		wantType  string
		wantCache string
	}{
		{avifType, "MISS"},
		{jpegType, "MISS"},
		{avifType, "HIT"},
		{jpegType, "HIT"},
	}

	etags := make(map[string]string)

	for _, step := range steps {
		rec := requestImage(t, srv, http.MethodGet, signedURL, step.wantType)
		gotType := rec.Header().Get("Content-Type")
		gotCache := rec.Header().Get("X-Pixa-Cache")

		if rec.Code != http.StatusOK || gotType != step.wantType ||
			gotCache != step.wantCache {
			t.Fatalf("Accept %s: %d %s %s, want 200 %s %s", step.wantType,
				rec.Code, gotType, gotCache, step.wantType, step.wantCache)
		}

		etag := rec.Header().Get("ETag")
		if previous, seen := etags[gotType]; seen && previous != etag {
			t.Errorf("%s ETag changed from %s to %s", gotType, previous, etag)
		}

		etags[gotType] = etag
	}

	if etags[avifType] == etags[jpegType] {
		t.Errorf("AVIF and JPEG have the same ETag %s", etags[avifType])
	}
}

// TestFormatAuto_Vary verifies that on each image route a HEAD answer and a
// 304 for an auto URL carry Vary: Accept, and that the answer for a URL with
// a fixed format does not.
func TestFormatAuto_Vary(t *testing.T) {
	t.Parallel()

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

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

	signedURL, encryptedURL := autoPhotoURLs(t, h)

	for _, urls := range [][2]string{
		{signedURL, signedPhotoURL(t, h)},
		{encryptedURL, encPhotoURL(t, h)},
	} {
		autoURL, fixedURL := urls[0], urls[1]

		head := requestImage(t, srv, http.MethodHead, autoURL, webpType)
		checkVaryAccept(t, head, http.StatusOK, true)

		req := httptest.NewRequestWithContext(t.Context(), http.MethodGet,
			autoURL, nil)
		req.Header.Set("Accept", webpType)
		req.Header.Set("If-None-Match", head.Header().Get("ETag"))

		notModified := httptest.NewRecorder()
		srv.ServeHTTP(notModified, req)
		checkVaryAccept(t, notModified, http.StatusNotModified, true)

		fixed := requestImage(t, srv, http.MethodGet, fixedURL)
		checkVaryAccept(t, fixed, http.StatusOK, false)
	}
}

// checkVaryAccept fails the test unless rec answered wantStatus and, as
// wantVary says, has or has not Accept in its Vary header.
func checkVaryAccept(
	t *testing.T, rec *httptest.ResponseRecorder, wantStatus int, wantVary bool,
) {
	t.Helper()

	vary := rec.Header().Values("Vary")
	t.Logf("status %d, Vary %v", rec.Code, vary)

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

	if slices.Contains(vary, "Accept") != wantVary {
		t.Errorf("Vary = %v, want Accept in it: %v", vary, wantVary)
	}
}