// Package audit records administrative write actions to the admin_action_log
// table so security/compliance can trace who did what across lottery admin
// endpoints. Every admin CRUD in PR C calls WriteAdminAction inside its own
// transaction; the caller is expected to have already validated permissions.
package audit

import (
	"context"
	"crypto/sha1"
	"encoding/hex"
	"fmt"
	"strings"
	"time"

	"gorm.io/gorm"
)

// Action code convention: dot-separated, prefix by domain (e.g.
// "lottery.activity.create", "lottery.prize.delete"). Keep them short and
// stable so downstream analytics can pivot without maintaining a translation
// table.
const (
	ActionLotteryActivityCreate  = "lottery.activity.create"
	ActionLotteryActivityUpdate  = "lottery.activity.update"
	ActionLotteryActivityDelete  = "lottery.activity.delete"
	ActionLotteryActivityPublish = "lottery.activity.publish"
	ActionLotteryActivityPause   = "lottery.activity.pause"
	ActionLotteryPrizeCreate     = "lottery.prize.create"
	ActionLotteryPrizeUpdate     = "lottery.prize.update"
	ActionLotteryPrizeDelete     = "lottery.prize.delete"
	ActionLotteryRulesPut        = "lottery.activity.rules.put"
	ActionLotteryChancesGrant    = "lottery.chances.grant"
)

// AdminActionLog is the GORM entity for admin_action_log.
type AdminActionLog struct {
	Id           int64     `gorm:"primaryKey"`
	ActorUserId  int64     `gorm:"type:bigint unsigned;not null;comment:操作者 user.id"`
	Action       string    `gorm:"type:varchar(64);not null;comment:动作 code"`
	TargetIds    string    `gorm:"type:varchar(255);not null;default:'';comment:被操作对象 ID"`
	RequestHash  string    `gorm:"type:varchar(64);not null;default:'';comment:请求摘要"`
	IP           string    `gorm:"type:varchar(45);not null;default:'';comment:操作者 IP"`
	UserAgent    string    `gorm:"type:varchar(255);not null;default:'';comment:操作者 UA"`
	CreatedAt    time.Time `gorm:"<-:create;default:CURRENT_TIMESTAMP;comment:操作时间"`
}

// TableName pins the entity to the migration table name.
func (AdminActionLog) TableName() string { return "admin_action_log" }

// Entry is the pre-hashed convenience input to WriteAdminAction. Callers
// build one with actor + action + payload fields; the writer computes the
// request hash and inserts inside tx.
type Entry struct {
	ActorUserId int64
	Action      string
	// TargetIds is stringified list of primary keys touched by this action.
	// Free-form: comma-separated ints, JSON array, etc.
	TargetIds string
	// RequestBody is hashed to produce request_hash. Pass nil if not applicable.
	RequestBody []byte
	IP          string
	UserAgent   string
}

// WriteAdminAction inserts an admin_action_log row inside the caller's tx.
// The row lives-or-dies with the caller's transaction: a rollback drops the
// audit trail, which is the intended coupling — we don't want to record
// actions that never happened.
func WriteAdminAction(ctx context.Context, tx *gorm.DB, e Entry) error {
	if tx == nil {
		return fmt.Errorf("audit: WriteAdminAction requires a transaction handle")
	}
	if e.ActorUserId == 0 || e.Action == "" {
		return fmt.Errorf("audit: WriteAdminAction requires ActorUserId and Action")
	}
	row := AdminActionLog{
		ActorUserId: e.ActorUserId,
		Action:      strings.TrimSpace(e.Action),
		TargetIds:   e.TargetIds,
		RequestHash: hashBody(e.RequestBody),
		IP:          e.IP,
		UserAgent:   truncate(e.UserAgent, 255),
	}
	return tx.WithContext(ctx).Create(&row).Error
}

func hashBody(body []byte) string {
	if len(body) == 0 {
		return ""
	}
	sum := sha1.Sum(body)
	return hex.EncodeToString(sum[:])
}

func truncate(s string, max int) string {
	if len(s) <= max {
		return s
	}
	return s[:max]
}