package usersession

import (
	"errors"
	"net/http"
	"net/http/httptest"
	"strings"
	"testing"
)

// testKey 是測試用的 32 byte HMAC key。
var testKey = []byte("test-key-test-key-test-key-1234!") // 32 bytes

// ─────────────────────────────────────────────────────────
// Encode / Decode roundtrip
// ─────────────────────────────────────────────────────────

func TestEncodeDecode_Roundtrip(t *testing.T) {
	sid := "abc123XYZ_-test"
	encoded := EncodeCookieValue(sid, testKey)
	if !strings.Contains(encoded, ".") {
		t.Fatalf("encoded should contain separator '.', got %q", encoded)
	}
	got, err := DecodeCookieValue(encoded, testKey)
	if err != nil {
		t.Fatalf("Decode: %v", err)
	}
	if got != sid {
		t.Fatalf("roundtrip mismatch: got %q want %q", got, sid)
	}
}

func TestDecode_TamperedSessionID(t *testing.T) {
	encoded := EncodeCookieValue("realsid", testKey)
	parts := strings.SplitN(encoded, ".", 2)
	tampered := "fakesid." + parts[1]
	_, err := DecodeCookieValue(tampered, testKey)
	if !errors.Is(err, ErrSignatureMismatch) {
		t.Fatalf("expected ErrSignatureMismatch when sessionID tampered, got %v", err)
	}
}

func TestDecode_TamperedSignature(t *testing.T) {
	encoded := EncodeCookieValue("realsid", testKey)
	parts := strings.SplitN(encoded, ".", 2)
	// 換個簽章（不同長度的 base64url 也會失敗）
	tampered := parts[0] + ".AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
	_, err := DecodeCookieValue(tampered, testKey)
	if !errors.Is(err, ErrSignatureMismatch) {
		t.Fatalf("expected ErrSignatureMismatch, got %v", err)
	}
}

func TestDecode_DifferentKeyFails(t *testing.T) {
	encoded := EncodeCookieValue("sid", testKey)
	other := []byte("other-key-other-key-other-key-1!")
	_, err := DecodeCookieValue(encoded, other)
	if !errors.Is(err, ErrSignatureMismatch) {
		t.Fatalf("expected ErrSignatureMismatch with different key, got %v", err)
	}
}

func TestDecode_MalformedValues(t *testing.T) {
	cases := map[string]string{
		"empty":        "",
		"no separator": "noseparator",
		"only sep":     ".",
		"empty sid":    ".sigonly",
		"empty sig":    "sidonly.",
	}
	for name, val := range cases {
		t.Run(name, func(t *testing.T) {
			_, err := DecodeCookieValue(val, testKey)
			if !errors.Is(err, ErrInvalidCookie) {
				t.Fatalf("%s: expected ErrInvalidCookie, got %v", name, err)
			}
		})
	}
}

// ─────────────────────────────────────────────────────────
// WriteCookie / ReadCookie / ClearCookie via httptest
// ─────────────────────────────────────────────────────────

func newCookieCfg() CookieConfig {
	return CookieConfig{
		Name:       DefaultCookieName,
		Path:       "/",
		HTTPOnly:   true,
		Secure:     false,
		SameSite:   http.SameSiteLaxMode,
		MaxAge:     86400,
		SigningKey: testKey,
	}
}

func TestWriteAndReadCookie_Roundtrip(t *testing.T) {
	cfg := newCookieCfg()
	sid := "session-abc-123"

	w := httptest.NewRecorder()
	if err := WriteCookie(w, cfg, sid); err != nil {
		t.Fatalf("WriteCookie: %v", err)
	}

	// 從 response 取出 Set-Cookie，做成 request cookie 模擬 browser 回傳
	resp := w.Result()
	cookies := resp.Cookies()
	if len(cookies) != 1 {
		t.Fatalf("expected 1 Set-Cookie, got %d", len(cookies))
	}
	c := cookies[0]
	if c.Name != DefaultCookieName {
		t.Fatalf("cookie name: got %q want %q", c.Name, DefaultCookieName)
	}
	if !c.HttpOnly {
		t.Fatalf("HttpOnly should be true")
	}
	if c.SameSite != http.SameSiteLaxMode {
		t.Fatalf("SameSite should be Lax")
	}
	if c.MaxAge != 86400 {
		t.Fatalf("MaxAge: got %d want 86400", c.MaxAge)
	}

	r := httptest.NewRequest(http.MethodGet, "/", nil)
	r.AddCookie(c)
	got, ok := ReadCookie(r, cfg)
	if !ok {
		t.Fatalf("ReadCookie: ok=false")
	}
	if got != sid {
		t.Fatalf("ReadCookie: got %q want %q", got, sid)
	}
}

func TestReadCookie_NoCookie(t *testing.T) {
	cfg := newCookieCfg()
	r := httptest.NewRequest(http.MethodGet, "/", nil)
	if _, ok := ReadCookie(r, cfg); ok {
		t.Fatalf("ReadCookie should return ok=false when no cookie present")
	}
}

func TestReadCookie_TamperedValue(t *testing.T) {
	cfg := newCookieCfg()
	r := httptest.NewRequest(http.MethodGet, "/", nil)
	// 故意放一個簽章錯的 cookie
	r.AddCookie(&http.Cookie{Name: cfg.Name, Value: "tampered.sig"})
	if _, ok := ReadCookie(r, cfg); ok {
		t.Fatalf("ReadCookie should return ok=false for tampered cookie")
	}
}

func TestClearCookie_SetsExpiration(t *testing.T) {
	cfg := newCookieCfg()
	w := httptest.NewRecorder()

	ClearCookie(w, cfg)
	cookies := w.Result().Cookies()
	if len(cookies) != 1 {
		t.Fatalf("expected 1 Set-Cookie, got %d", len(cookies))
	}
	c := cookies[0]
	if c.MaxAge >= 0 {
		t.Fatalf("ClearCookie MaxAge should be < 0, got %d", c.MaxAge)
	}
	if c.Value != "" {
		t.Fatalf("ClearCookie value should be empty, got %q", c.Value)
	}
	if c.Name != cfg.Name || c.Path != cfg.Path {
		t.Fatalf("ClearCookie must use same Name/Path; got name=%q path=%q", c.Name, c.Path)
	}
}

func TestClearCookie_BrowserCannotRead(t *testing.T) {
	cfg := newCookieCfg()

	// 1. WriteCookie → 得到一個 cookie
	w1 := httptest.NewRecorder()
	if err := WriteCookie(w1, cfg, "sid-X"); err != nil {
		t.Fatalf("WriteCookie: %v", err)
	}
	original := w1.Result().Cookies()[0]

	// 2. ClearCookie → 得到一個 expiration cookie
	w2 := httptest.NewRecorder()
	ClearCookie(w2, cfg)
	expirationCookie := w2.Result().Cookies()[0]

	// 3. 模擬 browser 在收到 expiration cookie 後立刻發 request — 此時應該沒有 cookie
	//    （這裡無法直接模擬 browser 的 cookie jar 邏輯，但能驗證 expiration cookie 內容是空的、
	//     若 browser 真的把它存下來，後續 ReadCookie 會失敗）。
	r := httptest.NewRequest(http.MethodGet, "/", nil)
	r.AddCookie(&http.Cookie{Name: expirationCookie.Name, Value: expirationCookie.Value})
	if _, ok := ReadCookie(r, cfg); ok {
		t.Fatalf("after ClearCookie, ReadCookie of cleared value must fail")
	}
	// sanity check：原本的 cookie 仍然能讀（驗證 ReadCookie 本身沒壞）
	r2 := httptest.NewRequest(http.MethodGet, "/", nil)
	r2.AddCookie(original)
	if _, ok := ReadCookie(r2, cfg); !ok {
		t.Fatalf("baseline: original cookie should still read OK")
	}
}

// ─────────────────────────────────────────────────────────
// CookieConfig validation
// ─────────────────────────────────────────────────────────

func TestWriteCookie_MissingSigningKey(t *testing.T) {
	cfg := CookieConfig{} // SigningKey 為 nil
	w := httptest.NewRecorder()
	err := WriteCookie(w, cfg, "sid")
	if !errors.Is(err, ErrInvalidConfig) {
		t.Fatalf("expected ErrInvalidConfig, got %v", err)
	}
}

func TestWriteCookie_EmptySessionID(t *testing.T) {
	cfg := newCookieCfg()
	w := httptest.NewRecorder()
	err := WriteCookie(w, cfg, "")
	if !errors.Is(err, ErrInvalidCookie) {
		t.Fatalf("expected ErrInvalidCookie, got %v", err)
	}
}

func TestReadCookie_MissingSigningKey(t *testing.T) {
	cfg := CookieConfig{} // SigningKey 為 nil
	r := httptest.NewRequest(http.MethodGet, "/", nil)
	r.AddCookie(&http.Cookie{Name: DefaultCookieName, Value: "anything.thing"})
	if _, ok := ReadCookie(r, cfg); ok {
		t.Fatalf("ReadCookie should fail when SigningKey missing")
	}
}

func TestCookieConfig_Defaults(t *testing.T) {
	cfg := CookieConfig{SigningKey: testKey} // 其他欄位都用預設

	if cfg.resolvedName() != DefaultCookieName {
		t.Fatalf("resolvedName default mismatch")
	}
	if cfg.resolvedPath() != "/" {
		t.Fatalf("resolvedPath default should be '/'")
	}
	if cfg.resolvedSameSite() != http.SameSiteLaxMode {
		t.Fatalf("resolvedSameSite default should be Lax")
	}
}