// Package logx 提供服务边界日志能力。
// 它只记录 transport 层可见的请求、响应、错误语义和耗时，不承载业务判断。
package logx

import (
	"bytes"
	"context"
	"encoding/json"
	"io"
	"log/slog"
	"mime"
	"net/http"
	"strings"
	"time"

	"hyapp/pkg/xerr"

	"google.golang.org/grpc"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
	"google.golang.org/protobuf/encoding/protojson"
	"google.golang.org/protobuf/proto"
)

const (
	// maxLoggedBytes 限制单个 request/response 字段的日志体积，避免大响应污染 stdout。
	maxLoggedBytes = 8192
	// redactedValue 是敏感字段统一替换值，保证日志可读但不可用于重放凭证。
	redactedValue = "***REDACTED***"
)

// HTTPMiddleware 在 gateway HTTP 边界记录请求体、响应体、状态码和耗时。
// requestIDFromContext 由 gateway 注入，logx 不直接依赖具体 transport 包，避免反向耦合。
func HTTPMiddleware(service string, requestIDFromContext func(context.Context) string, next http.Handler) http.Handler {
	return http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
		startedAt := time.Now()
		requestBody := readAndRestoreBody(request)
		capture := newHTTPResponseCapture(writer)

		next.ServeHTTP(capture, request)

		requestID := strings.TrimSpace(requestIDFromContext(request.Context()))
		args := []any{
			"service", service,
			"request_id", requestID,
			"method", request.Method,
			"path", request.URL.Path,
			"query", request.URL.RawQuery,
			"status", capture.statusCode,
			"duration_ms", time.Since(startedAt).Milliseconds(),
			"request", safePayload(requestBody),
			"response", safePayload(capture.body.Bytes()),
		}
		if capture.statusCode >= http.StatusInternalServerError {
			slog.Error("http_access", args...)
			return
		}
		slog.Info("http_access", args...)
	})
}

// UnaryServerInterceptor 在内部 gRPC 服务边界记录 protobuf request/response。
// 内部链路统一 gRPC + protobuf，因此这里是排查跨服务参数和返回值的主入口。
func UnaryServerInterceptor(service string) grpc.UnaryServerInterceptor {
	return func(ctx context.Context, request any, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (any, error) {
		if strings.Contains(info.FullMethod, "/grpc.health.v1.Health/") {
			// 健康检查高频且无业务参数，跳过可避免日志噪音淹没真实业务请求。
			return handler(ctx, request)
		}

		startedAt := time.Now()
		response, err := handler(ctx, request)
		code := codes.OK
		if err != nil {
			code = status.Code(err)
		}

		args := []any{
			"service", service,
			"request_id", requestIDFromPayload(request),
			"method", info.FullMethod,
			"grpc_code", code.String(),
			"reason", string(xerr.ReasonFromGRPC(err)),
			"duration_ms", time.Since(startedAt).Milliseconds(),
			"request", safePayloadFromValue(request),
			"response", safePayloadFromValue(response),
		}
		if err != nil {
			slog.Error("grpc_access", args...)
			return response, err
		}
		slog.Info("grpc_access", args...)
		return response, nil
	}
}

type httpResponseCapture struct {
	http.ResponseWriter
	statusCode int
	body       bytes.Buffer
}

func newHTTPResponseCapture(writer http.ResponseWriter) *httpResponseCapture {
	return &httpResponseCapture{
		ResponseWriter: writer,
		statusCode:     http.StatusOK,
	}
}

func (c *httpResponseCapture) WriteHeader(statusCode int) {
	c.statusCode = statusCode
	c.ResponseWriter.WriteHeader(statusCode)
}

func (c *httpResponseCapture) Write(data []byte) (int, error) {
	if c.body.Len() < maxLoggedBytes {
		remaining := maxLoggedBytes - c.body.Len()
		if len(data) > remaining {
			c.body.Write(data[:remaining])
		} else {
			c.body.Write(data)
		}
	}

	return c.ResponseWriter.Write(data)
}

func readAndRestoreBody(request *http.Request) []byte {
	if request.Body == nil {
		return nil
	}
	mediaType, _, _ := mime.ParseMediaType(request.Header.Get("Content-Type"))
	if strings.HasPrefix(mediaType, "multipart/") {
		// 文件上传请求体可能很大，且包含二进制内容；日志只记录占位符并保留原始流给 handler。
		return []byte("<multipart body omitted>")
	}

	body, err := io.ReadAll(request.Body)
	if err != nil {
		// 读取失败时把空 body 交还给后续 handler，让真实解码错误仍由 handler 返回。
		request.Body = io.NopCloser(bytes.NewReader(nil))
		return nil
	}
	request.Body.Close()
	request.Body = io.NopCloser(bytes.NewReader(body))
	return body
}

func safePayloadFromValue(value any) any {
	if value == nil {
		return nil
	}
	if message, ok := value.(proto.Message); ok {
		raw, err := protojson.MarshalOptions{UseProtoNames: true}.Marshal(message)
		if err != nil {
			return "<proto_marshal_failed>"
		}
		return safePayload(raw)
	}

	raw, err := json.Marshal(value)
	if err != nil {
		return "<json_marshal_failed>"
	}
	return safePayload(raw)
}

func requestIDFromPayload(value any) string {
	payload, ok := safePayloadFromValue(value).(map[string]any)
	if !ok {
		return ""
	}
	meta, ok := payload["meta"].(map[string]any)
	if !ok {
		return ""
	}
	if requestID, ok := meta["request_id"].(string); ok {
		return requestID
	}
	return ""
}

func safePayload(raw []byte) any {
	raw = bytes.TrimSpace(raw)
	if len(raw) == 0 {
		return nil
	}
	if len(raw) > maxLoggedBytes {
		raw = raw[:maxLoggedBytes]
	}

	var payload any
	if err := json.Unmarshal(raw, &payload); err != nil {
		return string(raw)
	}
	return redactValue(payload)
}

func redactValue(value any) any {
	switch typed := value.(type) {
	case map[string]any:
		redacted := make(map[string]any, len(typed))
		for key, field := range typed {
			if isSensitiveKey(key) {
				redacted[key] = redactedValue
				continue
			}
			redacted[key] = redactValue(field)
		}
		return redacted
	case []any:
		for index, item := range typed {
			typed[index] = redactValue(item)
		}
		return typed
	default:
		return value
	}
}

func isSensitiveKey(key string) bool {
	normalized := strings.ToLower(strings.ReplaceAll(key, "-", "_"))
	sensitiveParts := []string{
		"password",
		"credential",
		"secret",
		"token",
		"access_token",
		"refresh_token",
		"id_token",
		"user_sig",
		"usersig",
		"authorization",
		"signature",
		"private_key",
		"callback_auth",
	}
	for _, part := range sensitiveParts {
		if strings.Contains(normalized, part) {
			return true
		}
	}
	return false
}