// Copyright 2022 E99p1ant. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package db

import (
	"context"

	"github.com/pkg/errors"
	"github.com/sirupsen/logrus"
	"github.com/thanhpk/randstr"
	"gorm.io/gorm"

	"github.com/tamakyi/TamaBox/internal/dbutil"
)

var Conversations ConversationStore

type ConversationStore interface {
	Create(ctx context.Context, opts CreateConversationOptions) (*Conversation, error)
	GetByID(ctx context.Context, id uint) (*Conversation, error)
	GetByToken(ctx context.Context, token string) (*Conversation, error)
	GetByIDAndOwner(ctx context.Context, id, ownerID uint) (*Conversation, error)
	GetByIDAndAsker(ctx context.Context, id, askerID uint) (*Conversation, error)
	IncrementMessageCount(ctx context.Context, id uint) error
	IncrementMessageCountIfBelow(ctx context.Context, id uint, max int) (bool, error)
	DecrementMessageCount(ctx context.Context, id uint) error
	MaybeClose(ctx context.Context, id uint, max int) error
	Close(ctx context.Context, id uint) error
	// ListByOwner 返回某箱主拥有的会话。limit>0 时启用分页（取 limit 条、跳过 offset 条），
	// 用于私聊列表分页；导出场景传 limit=0 取全量，行为与改造前一致。
	ListByOwner(ctx context.Context, ownerID uint, limit, offset int) ([]*Conversation, error)
	// CountByOwner 统计某箱主拥有的会话总数（分页看板与"加载更多"判定用）。
	CountByOwner(ctx context.Context, ownerID uint) (int64, error)
	// ListByAsker 返回某提问者发起的会话；分页语义同 ListByOwner。
	ListByAsker(ctx context.Context, askerID uint, limit, offset int) ([]*Conversation, error)
	// CountByAsker 统计某提问者发起的会话总数。
	CountByAsker(ctx context.Context, askerID uint) (int64, error)
	MarkDeletedByOwner(ctx context.Context, id uint) error
}

func NewConversationStore(db *gorm.DB) ConversationStore {
	return &conversations{db}
}

type conversations struct {
	*gorm.DB
}

type Conversation struct {
	dbutil.Model
	OwnerID          uint   `gorm:"index:idx_conversation_owner" json:"owner_id"`
	AskerID          uint   `gorm:"index:idx_conversation_asker" json:"asker_id"`
	Token            string `gorm:"size:6;uniqueIndex" json:"token"`
	MaxMessages      int    `gorm:"default:20" json:"max_messages"`
	MessageCount     int    `gorm:"default:0" json:"message_count"`
	IsClosed         bool   `gorm:"default:false" json:"is_closed"`
	IsDeletedByOwner bool   `gorm:"default:false" json:"is_deleted_by_owner"` // 新增
}

func (c *Conversation) BeforeCreate(tx *gorm.DB) error {
	c.MessageCount = 0
	c.Token = randstr.String(6)
	return nil
}

type CreateConversationOptions struct {
	OwnerID     uint
	AskerID     uint
	MaxMessages int
}

func (db *conversations) Create(ctx context.Context, opts CreateConversationOptions) (*Conversation, error) {
	conversation := &Conversation{
		OwnerID:     opts.OwnerID,
		AskerID:     opts.AskerID,
		MaxMessages: opts.MaxMessages,
	}
	if err := db.WithContext(ctx).Create(conversation).Error; err != nil {
		return nil, errors.Wrap(err, "create conversation")
	}
	return conversation, nil
}

func (db *conversations) GetByID(ctx context.Context, id uint) (*Conversation, error) {
	var conv Conversation
	if err := db.WithContext(ctx).First(&conv, id).Error; err != nil {
		return nil, errors.Wrap(err, "get conversation")
	}
	return &conv, nil
}

func (db *conversations) GetByToken(ctx context.Context, token string) (*Conversation, error) {
	var conv Conversation
	if err := db.WithContext(ctx).Where("token = ?", token).First(&conv).Error; err != nil {
		return nil, errors.Wrap(err, "get conversation by token")
	}
	return &conv, nil
}

func (db *conversations) GetByIDAndOwner(ctx context.Context, id, ownerID uint) (*Conversation, error) {
	var conv Conversation
	if err := db.WithContext(ctx).Where("id = ? AND owner_id = ?", id, ownerID).First(&conv).Error; err != nil {
		return nil, errors.Wrap(err, "get by owner")
	}
	return &conv, nil
}

func (db *conversations) GetByIDAndAsker(ctx context.Context, id, askerID uint) (*Conversation, error) {
	var conv Conversation
	if err := db.WithContext(ctx).Where("id = ? AND asker_id = ?", id, askerID).First(&conv).Error; err != nil {
		return nil, errors.Wrap(err, "get by asker")
	}
	return &conv, nil
}

func (db *conversations) IncrementMessageCount(ctx context.Context, id uint) error {
	return db.WithContext(ctx).Model(&Conversation{}).Where("id = ?", id).UpdateColumn("message_count", gorm.Expr("message_count + 1")).Error
}

// IncrementMessageCountIfBelow 原子地检查并递增消息计数：
// 仅当 message_count < max 且未关闭时才 +1，返回 true。
// 并发场景下（同一对话两端同时发送）可防止消息数超出上限。
func (db *conversations) IncrementMessageCountIfBelow(ctx context.Context, id uint, max int) (bool, error) {
	res := db.WithContext(ctx).Model(&Conversation{}).
		Where("id = ? AND message_count < ? AND is_closed = ?", id, max, false).
		UpdateColumn("message_count", gorm.Expr("message_count + 1"))
	if res.Error != nil {
		return false, errors.Wrap(res.Error, "increment message count if below")
	}
	return res.RowsAffected > 0, nil
}

// DecrementMessageCount 回滚一次消息计数（计数已递增但消息落库失败时调用）。
func (db *conversations) DecrementMessageCount(ctx context.Context, id uint) error {
	return db.WithContext(ctx).Model(&Conversation{}).
		Where("id = ? AND message_count > 0", id).
		UpdateColumn("message_count", gorm.Expr("message_count - 1")).Error
}

// MaybeClose 当消息数达到上限时关闭对话（幂等，供发送消息后调用）。
func (db *conversations) MaybeClose(ctx context.Context, id uint, max int) error {
	return db.WithContext(ctx).Model(&Conversation{}).
		Where("id = ? AND message_count >= ? AND is_closed = ?", id, max, false).
		Update("is_closed", true).Error
}

func (db *conversations) Close(ctx context.Context, id uint) error {
	return db.WithContext(ctx).Model(&Conversation{}).Where("id = ?", id).Update("is_closed", true).Error
}

func (db *conversations) ListByOwner(ctx context.Context, ownerID uint, limit, offset int) ([]*Conversation, error) {
	var convs []*Conversation
	q := db.WithContext(ctx).Where("owner_id = ? AND is_deleted_by_owner = ? AND token != ''", ownerID, false).
		Order("created_at DESC")
	if limit > 0 {
		q = q.Limit(limit)
		if offset > 0 {
			q = q.Offset(offset)
		}
	}
	if err := q.Find(&convs).Error; err != nil {
		return nil, errors.Wrap(err, "list by owner")
	}
	return convs, nil
}

func (db *conversations) CountByOwner(ctx context.Context, ownerID uint) (int64, error) {
	var count int64
	if err := db.WithContext(ctx).Model(&Conversation{}).
		Where("owner_id = ? AND is_deleted_by_owner = ? AND token != ''", ownerID, false).
		Count(&count).Error; err != nil {
		return 0, errors.Wrap(err, "count by owner")
	}
	return count, nil
}

func (db *conversations) ListByAsker(ctx context.Context, askerID uint, limit, offset int) ([]*Conversation, error) {
	var convs []*Conversation
	q := db.WithContext(ctx).Where("asker_id = ? AND is_deleted_by_owner = ? AND token != ''", askerID, false).
		Order("created_at DESC")
	if limit > 0 {
		q = q.Limit(limit)
		if offset > 0 {
			q = q.Offset(offset)
		}
	}
	if err := q.Find(&convs).Error; err != nil {
		return nil, errors.Wrap(err, "list by asker")
	}
	return convs, nil
}

func (db *conversations) CountByAsker(ctx context.Context, askerID uint) (int64, error) {
	var count int64
	if err := db.WithContext(ctx).Model(&Conversation{}).
		Where("asker_id = ? AND is_deleted_by_owner = ? AND token != ''", askerID, false).
		Count(&count).Error; err != nil {
		return 0, errors.Wrap(err, "count by asker")
	}
	return count, nil
}

func (db *conversations) MarkDeletedByOwner(ctx context.Context, id uint) error {
	var conv Conversation
	if err := db.WithContext(ctx).First(&conv, id).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			// 已删除或不存在：幂等，不影响调用方。
			return nil
		}
		return errors.Wrap(err, "get conversation for delete")
	}
	if conv.IsDeletedByOwner {
		// 已经是删除状态：幂等返回，避免重复请求多次回退配额计数。
		return nil
	}

	if err := db.WithContext(ctx).Model(&Conversation{}).Where("id = ?", id).Update("is_deleted_by_owner", true).Error; err != nil {
		return errors.Wrap(err, "mark conversation deleted by owner")
	}

	// 回退定量收集计数：删除私聊会话等价于少一条已收集内容，
	// 否则达上限后即便删掉旧会话，功能仍会显示 quota_reached 关闭，须手动重置计数。
	if conv.OwnerID != 0 {
		// 用本 store 的 *gorm.DB 构造，避免依赖包级全局单例（详见 DeleteByID 注释）。
		if err := NewFeatureControlsStore(db.DB).IncrementQuota(ctx, conv.OwnerID, FeatureChat, -1); err != nil {
			logrus.WithContext(ctx).WithError(err).Errorf("Failed to decrement chat quota for user %d", conv.OwnerID)
		}
	}
	return nil
}