package common

import (
	"context"
	"fmt"
	"runtime"
	"strconv"
	"strings"
	"sync"
)

type contextKey string

const (
	// ContextTenantIDKey 用于在 Context 中存储租户ID
	ContextTenantIDKey contextKey = "tenantId"
	// DBSettingTenantID 用于在 GORM DB 上临时覆盖租户ID
	DBSettingTenantID = "tenant_id"
	// DBSettingTenantSkip 用于临时跳过租户过滤
	DBSettingTenantSkip = "tenant_skip"
)

var requestContextStore sync.Map

// BindRequestContext 绑定当前请求上下文到当前协程，返回清理函数
func BindRequestContext(ctx context.Context) func() {
	gid := goroutineID()
	if gid == 0 {
		return func() {}
	}
	requestContextStore.Store(gid, ctx)
	return func() {
		requestContextStore.Delete(gid)
	}
}

// GetRequestContext 获取当前协程绑定的请求上下文
func GetRequestContext() context.Context {
	gid := goroutineID()
	if gid == 0 {
		return nil
	}
	if v, ok := requestContextStore.Load(gid); ok {
		if ctx, ok := v.(context.Context); ok {
			return ctx
		}
	}
	return nil
}

// TenantIDFromContext 从 Context 中获取租户ID
func TenantIDFromContext(ctx context.Context) string {
	if ctx == nil {
		return ""
	}
	value := ctx.Value(ContextTenantIDKey)
	if value == nil {
		return ""
	}
	return strings.TrimSpace(toString(value))
}

// CurrentTenantID 获取当前协程绑定的租户ID
func CurrentTenantID() string {
	return TenantIDFromContext(GetRequestContext())
}

func goroutineID() uint64 {
	var buf [64]byte
	n := runtime.Stack(buf[:], false)
	if n <= 0 {
		return 0
	}
	fields := strings.Fields(string(buf[:n]))
	if len(fields) < 2 {
		return 0
	}
	id, err := strconv.ParseUint(fields[1], 10, 64)
	if err != nil {
		return 0
	}
	return id
}

func toString(value interface{}) string {
	switch v := value.(type) {
	case string:
		return v
	case []byte:
		return string(v)
	default:
		return fmt.Sprint(value)
	}
}