package handlers

import (
	"encoding/json"
	"fmt"
	"image/color"
	"log/slog"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
	"testing/fstest"
	"time"

	"github.com/go-chi/chi/v5"
	"sneak.berlin/go/pixa/internal/httpfetcher"
	"sneak.berlin/go/pixa/internal/imgcache"
	"sneak.berlin/go/pixa/internal/signature"
)

// allowlistedHost is the only host on the allowlist of the image route
// newImageRoute builds.
const allowlistedHost = "allowed.example.com"

// newImageRoute returns the image route of a Handlers whose service fetches
// with fetcher and checks signatures with testSigningKey.
func newImageRoute(t *testing.T, fetcher httpfetcher.Fetcher) 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("failed to create cache: %v", err)
	}

	svc, err := imgcache.NewService(&imgcache.ServiceConfig{
		Cache:      cache,
		Fetcher:    fetcher,
		SigningKey: testSigningKey,
		Allowlist:  []string{allowlistedHost},
	})
	if err != nil {
		t.Fatalf("failed to create service: %v", err)
	}

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

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

	return r
}

// newPhotoFetcher returns a mock fetcher that serves a JPEG at photoPath on
// each of hosts, and answers any other URL with an upstream error.
func newPhotoFetcher(t *testing.T, hosts ...string) *httpfetcher.MockFetcher {
	t.Helper()

	photo := &fstest.MapFile{
		Data: generateTestJPEG(t, 100, 100, color.RGBA{255, 0, 0, 255}),
	}

	files := fstest.MapFS{}
	for _, host := range hosts {
		files[host+photoPath] = photo
	}

	return httpfetcher.NewMock(files)
}

// photoURL returns the image route URL of photoPath on host, as a 50x50 JPEG.
func photoURL(host string) string {
	return "/v1/image/" + host + photoPath + "/50x50.jpeg"
}

// photoURLWithSig returns photoURL(host) with sig and expires as its sig and
// exp.
func photoURLWithSig(host, sig string, expires time.Time) string {
	return fmt.Sprintf("%s?sig=%s&exp=%d", photoURL(host), sig, expires.Unix())
}

// photoSignature returns the signature of photoURL(host) at the default
// quality and fit, made with key and expiring at expires.
func photoSignature(key, host string, expires time.Time) string {
	return signature.New(key).Sign(&signature.Request{
		SourceHost: host,
		SourcePath: photoPath,
		Width:      50,
		Height:     50,
		Format:     string(imgcache.FormatJPEG),
		Quality:    85,
		FitMode:    string(imgcache.FitCover),
		Expires:    expires,
	})
}

// sendGet sends a GET for target to route and returns the response.
func sendGet(
	t *testing.T, route http.Handler, target string,
) *httptest.ResponseRecorder {
	t.Helper()

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

	route.ServeHTTP(rec, req)
	t.Logf("GET %s: %d", target, rec.Code)

	return rec
}

// checkErrorBody checks that rec has status wantStatus and the JSON error body
// the image route sends: wantError, wantStatus and the time in RFC 3339.
func checkErrorBody(
	t *testing.T, rec *httptest.ResponseRecorder, wantStatus int, wantError string,
) {
	t.Helper()

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

	if ct := rec.Header().Get("Content-Type"); ct != "application/json" {
		t.Errorf("Content-Type = %q, want application/json", ct)
	}

	var body struct {
		Error     string `json:"error"`
		Status    int    `json:"status"`
		Timestamp string `json:"timestamp"`
	}

	err := json.NewDecoder(rec.Body).Decode(&body)
	if err != nil {
		t.Fatalf("decoding response body: %v", err)
	}

	if body.Error != wantError || body.Status != wantStatus {
		t.Errorf("body error and status = %q %d, want %q %d",
			body.Error, body.Status, wantError, wantStatus)
	}

	_, err = time.Parse(time.RFC3339, body.Timestamp)
	if err != nil {
		t.Errorf("body timestamp: %v", err)
	}
}

// TestHandleImage_ErrorAnswers checks the status and the JSON error body the
// image route answers each request below with. The JPEG at photoPath exists on
// signedHost and on each host below that differs from it, so a request refused
// with 401 would otherwise be served.
func TestHandleImage_ErrorAnswers(t *testing.T) {
	t.Parallel()

	// A signature for signedHost must not verify for any of these.
	parentHost := "example.com"
	siblingHost := "other.example.com"
	subdomainHost := "img." + signedHost
	appendedHost := signedHost + ".example.net"

	photos := newPhotoFetcher(t,
		signedHost, parentHost, siblingHost, subdomainHost, appendedHost)
	// The real fetcher refuses localhost before any lookup or connection.
	realFetcher := httpfetcher.New(httpfetcher.DefaultConfig())

	exp := time.Now().Add(time.Hour)
	expired := time.Now().Add(-time.Hour)
	sig := photoSignature(testSigningKey, signedHost, exp)
	otherKeySig := photoSignature("another-signing-key", signedHost, exp)
	expiredSig := photoSignature(testSigningKey, signedHost, expired)
	localhostSig := photoSignature(testSigningKey, "localhost", exp)

	// The error every request refused for its signature gets.
	const unauthorized = "unauthorized"

	tests := []struct {
		name       string
		fetcher    httpfetcher.Fetcher
		target     string
		wantStatus int
		wantError  string
	}{
		{"no sig or exp", photos, photoURL(signedHost),
			http.StatusUnauthorized, unauthorized},
		{"exp but no sig", photos,
			fmt.Sprintf("%s?exp=%d", photoURL(signedHost), exp.Unix()),
			http.StatusUnauthorized, unauthorized},
		{"sig made with another key", photos,
			photoURLWithSig(signedHost, otherKeySig, exp),
			http.StatusUnauthorized, unauthorized},
		{"sig without its = padding", photos,
			photoURLWithSig(signedHost, strings.TrimRight(sig, "="), exp),
			http.StatusUnauthorized, unauthorized},
		{"sig in upper case", photos,
			photoURLWithSig(signedHost, strings.ToUpper(sig), exp),
			http.StatusUnauthorized, unauthorized},
		{"expired sig", photos, photoURLWithSig(signedHost, expiredSig, expired),
			http.StatusUnauthorized, unauthorized},
		{"sig sent for the parent domain", photos,
			photoURLWithSig(parentHost, sig, exp),
			http.StatusUnauthorized, unauthorized},
		{"sig sent for a sibling host", photos,
			photoURLWithSig(siblingHost, sig, exp),
			http.StatusUnauthorized, unauthorized},
		{"sig sent for a subdomain", photos,
			photoURLWithSig(subdomainHost, sig, exp),
			http.StatusUnauthorized, unauthorized},
		{"sig sent with another domain appended", photos,
			photoURLWithSig(appendedHost, sig, exp),
			http.StatusUnauthorized, unauthorized},
		{"unparseable path", photos,
			"/v1/image/" + allowlistedHost + photoPath + "/big.jpeg",
			http.StatusBadRequest, "invalid image URL: invalid size format"},
		{"blocked upstream address", realFetcher,
			photoURLWithSig("localhost", localhostSig, exp),
			http.StatusForbidden, "forbidden"},
		{"upstream error", photos,
			"/v1/image/" + allowlistedHost + "/images/missing.jpg/50x50.jpeg",
			http.StatusBadGateway, "upstream error"},
	}

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

			rec := sendGet(t, newImageRoute(t, tt.fetcher), tt.target)
			checkErrorBody(t, rec, tt.wantStatus, tt.wantError)
		})
	}
}

// TestHandleImage_AllowlistOrSignature checks that the image route serves an
// image without a signature for a host on the allowlist only, and for another
// host only with a valid signature.
func TestHandleImage_AllowlistOrSignature(t *testing.T) {
	t.Parallel()

	photos := newPhotoFetcher(t, allowlistedHost, signedHost)
	exp := time.Now().Add(time.Hour)
	sig := photoSignature(testSigningKey, signedHost, exp)

	tests := []struct {
		name       string
		target     string
		wantStatus int
	}{
		{"allowlisted host, no sig", photoURL(allowlistedHost), http.StatusOK},
		{"other host, no sig", photoURL(signedHost), http.StatusUnauthorized},
		{"other host, valid sig", photoURLWithSig(signedHost, sig, exp),
			http.StatusOK},
	}

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

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