package service

import (
	"net/http"
	"testing"

	"github.com/google/uuid"
)

const (
	testValidUUID    = "01970000-0000-7000-8000-000000000001"
	testValidUUIDAlt = "01970000-0000-7000-8000-000000000002"
)

func newReq(t *testing.T) *http.Request {
	t.Helper()
	req, err := http.NewRequest("POST", "https://api.anthropic.com/v1/messages", nil)
	if err != nil {
		t.Fatalf("NewRequest: %v", err)
	}
	return req
}

func TestEnsureClaudeCodeSessionID_NilRequest(t *testing.T) {
	// Should not panic.
	ensureClaudeCodeSessionID(nil, nil, "oauth", true)
}

func TestEnsureClaudeCodeSessionID_FromMetadataJSON(t *testing.T) {
	req := newReq(t)
	body := []byte(`{"metadata":{"user_id":"{\"device_id\":\"abc\",\"account_uuid\":\"\",\"session_id\":\"` + testValidUUID + `\"}"}}`)
	ensureClaudeCodeSessionID(req, body, "oauth", true)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got != testValidUUID {
		t.Fatalf("session_id = %q, want %q", got, testValidUUID)
	}
}

func TestEnsureClaudeCodeSessionID_FromMetadataLegacy(t *testing.T) {
	req := newReq(t)
	// legacy format: user_{64hex}_account_{uuid}_session_{uuid}
	dev := "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
	acc := "11111111-2222-3333-4444-555555555555"
	uid := "user_" + dev + "_account_" + acc + "_session_" + testValidUUID
	body := []byte(`{"metadata":{"user_id":"` + uid + `"}}`)
	ensureClaudeCodeSessionID(req, body, "oauth", true)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got != testValidUUID {
		t.Fatalf("session_id = %q, want %q", got, testValidUUID)
	}
}

// 安全测试：metadata.user_id 中的 session_id 不是合法 UUID 时，
// 必须 fallback 到 OAuth UUID 兜底，而不是写入恶意值。
func TestEnsureClaudeCodeSessionID_RejectsMalformedMetadataUUID(t *testing.T) {
	req := newReq(t)
	// session_id 字段是 36 字符但非 UUID 格式（凑数 hex+dash）
	bogus := "abcdefab-0000-0000-0000-not-a-real-uuid"
	body := []byte(`{"metadata":{"user_id":"{\"device_id\":\"abc\",\"account_uuid\":\"\",\"session_id\":\"` + bogus + `\"}"}}`)
	ensureClaudeCodeSessionID(req, body, "oauth", true)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got == bogus {
		t.Fatalf("malformed metadata session_id was written verbatim: %q", got)
	}
	if got == "" {
		t.Fatalf("expected OAuth mimic to fallback to UUID, got empty")
	}
	if _, err := uuid.Parse(got); err != nil {
		t.Fatalf("fallback session_id is not a valid UUID: %q (err=%v)", got, err)
	}
}

func TestEnsureClaudeCodeSessionID_PreservesExistingValidHeader(t *testing.T) {
	req := newReq(t)
	setHeaderRaw(req.Header, "X-Claude-Code-Session-Id", testValidUUID)
	ensureClaudeCodeSessionID(req, nil, "oauth", true)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got != testValidUUID {
		t.Fatalf("session_id = %q, want preserved %q", got, testValidUUID)
	}
}

func TestEnsureClaudeCodeSessionID_OverwritesInvalidHeader(t *testing.T) {
	req := newReq(t)
	setHeaderRaw(req.Header, "X-Claude-Code-Session-Id", "not-a-uuid")
	ensureClaudeCodeSessionID(req, nil, "oauth", true)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got == "not-a-uuid" {
		t.Fatalf("invalid header was not overwritten: %q", got)
	}
	if _, err := uuid.Parse(got); err != nil {
		t.Fatalf("fallback session_id is not a valid UUID: %q (err=%v)", got, err)
	}
}

func TestEnsureClaudeCodeSessionID_OAuthMimicFallback(t *testing.T) {
	req := newReq(t)
	ensureClaudeCodeSessionID(req, nil, "oauth", true)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got == "" {
		t.Fatalf("expected OAuth mimic fallback to set X-Claude-Code-Session-Id")
	}
	if _, err := uuid.Parse(got); err != nil {
		t.Fatalf("fallback session_id is not a valid UUID: %q (err=%v)", got, err)
	}
}

// API key passthrough 路径必须不被污染：缺失 session-id 时不强制生成。
func TestEnsureClaudeCodeSessionID_DoesNotPolluteAPIKey(t *testing.T) {
	req := newReq(t)
	ensureClaudeCodeSessionID(req, nil, "api_key", false)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got != "" {
		t.Fatalf("API key path should NOT auto-generate session-id, got %q", got)
	}
}

// API key 路径即使 body 中有合法 metadata.user_id，也不应该派生 session-id 头。
// 这是 fresh code review 发现的 C1 修复：保护客户端原始语义。
func TestEnsureClaudeCodeSessionID_APIKeyIgnoresMetadata(t *testing.T) {
	req := newReq(t)
	// 客户端传入合法的 metadata.user_id，但 tokenType=api_key
	body := []byte(`{"metadata":{"user_id":"{\"device_id\":\"abc\",\"account_uuid\":\"\",\"session_id\":\"` + testValidUUID + `\"}"}}`)
	ensureClaudeCodeSessionID(req, body, "api_key", false)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got != "" {
		t.Fatalf("API key path must NOT derive session-id from metadata, got %q", got)
	}
}

// OAuth 路径即使 mimic=false 也应该从 metadata 派生 header：
// OAuth 凭证本身就是 Claude Code 类型账号，metadata.user_id 可信任。
// 这与 API key 路径不同（API key 是任意第三方调用方）。
func TestEnsureClaudeCodeSessionID_OAuthNonMimicDerivesFromMetadata(t *testing.T) {
	req := newReq(t)
	body := []byte(`{"metadata":{"user_id":"{\"device_id\":\"abc\",\"account_uuid\":\"\",\"session_id\":\"` + testValidUUID + `\"}"}}`)
	ensureClaudeCodeSessionID(req, body, "oauth", false)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got != testValidUUID {
		t.Fatalf("OAuth must derive session-id from metadata regardless of mimic flag, got %q want %q", got, testValidUUID)
	}
}

// API key 路径若客户端传入了非法 UUID header，必须删除避免向上游透传。
// 这是 C2 修复：UUID 校验承诺要对所有路径生效。
func TestEnsureClaudeCodeSessionID_APIKeyDeletesInvalidHeader(t *testing.T) {
	req := newReq(t)
	setHeaderRaw(req.Header, "X-Claude-Code-Session-Id", "not-a-uuid")
	ensureClaudeCodeSessionID(req, nil, "api_key", false)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got != "" {
		t.Fatalf("API key path must delete invalid header, got %q", got)
	}
}

// API key 路径若客户端传入了合法 UUID header，规范化保留（不删除）。
func TestEnsureClaudeCodeSessionID_APIKeyPreservesValidHeader(t *testing.T) {
	req := newReq(t)
	setHeaderRaw(req.Header, "X-Claude-Code-Session-Id", testValidUUID)
	ensureClaudeCodeSessionID(req, nil, "api_key", false)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got != testValidUUID {
		t.Fatalf("API key path must preserve valid client header, got %q want %q", got, testValidUUID)
	}
}

// OAuth 但非 mimic 场景：保留客户端原始语义，不自动生成。
func TestEnsureClaudeCodeSessionID_OAuthNonMimicDoesNotForce(t *testing.T) {
	req := newReq(t)
	ensureClaudeCodeSessionID(req, nil, "oauth", false)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	if got != "" {
		t.Fatalf("non-mimic OAuth should not auto-generate, got %q", got)
	}
}

// 验证不同 UUID 输入会被规范化为 canonical 小写形式。
func TestEnsureClaudeCodeSessionID_CanonicalForm(t *testing.T) {
	req := newReq(t)
	// 大写 UUID 输入
	upper := "01970000-0000-7000-8000-ABCDEF000003"
	setHeaderRaw(req.Header, "X-Claude-Code-Session-Id", upper)
	ensureClaudeCodeSessionID(req, nil, "oauth", true)

	got := getHeaderRaw(req.Header, "X-Claude-Code-Session-Id")
	want := "01970000-0000-7000-8000-abcdef000003"
	if got != want {
		t.Fatalf("session_id = %q, want canonical %q", got, want)
	}
}