backend/internal/model/material.go

package model

import (
	"database/sql/driver"
	"encoding/json"
	"time"

	"github.com/google/uuid"
	"gorm.io/gorm"
)

// MaterialFileType 文件类型
type MaterialFileType string

const (
	MaterialFileTypePDF  MaterialFileType = "pdf"
	MaterialFileTypeWord MaterialFileType = "word"
	MaterialFileTypePPT  MaterialFileType = "ppt"
)

// MaterialStatus 资料状态
type MaterialStatus string

const (
	MaterialStatusActive   MaterialStatus = "active"
	MaterialStatusInactive MaterialStatus = "inactive"
)

// MaterialSubject 学科分类
type MaterialSubject struct {
	ID          string    `json:"id" gorm:"type:varchar(36);primaryKey"`
	Name        string    `json:"name" gorm:"type:varchar(100);not null"`
	Icon        string    `json:"icon" gorm:"type:varchar(50)"`         // MaterialCommunityIcons name
	Color       string    `json:"color" gorm:"type:varchar(20)"`        // 主题色
	Description string    `json:"description" gorm:"type:varchar(255)"` // 描述
	SortOrder   int       `json:"sort_order" gorm:"default:0;index"`    // 排序权重
	IsActive    bool      `json:"is_active" gorm:"default:true;index"`  // 是否启用
	CreatedAt   time.Time `json:"created_at" gorm:"autoCreateTime"`
	UpdatedAt   time.Time `json:"updated_at" gorm:"autoUpdateTime"`

	// 关联
	Materials []MaterialFile `json:"materials,omitempty" gorm:"foreignKey:SubjectID"`
}

// BeforeCreate 创建前生成UUID
func (s *MaterialSubject) BeforeCreate(tx *gorm.DB) error {
	if s.ID == "" {
		s.ID = uuid.New().String()
	}
	return nil
}

func (MaterialSubject) TableName() string {
	return "material_subjects"
}

// StringArray 字符串数组类型（用于tags）
type StringArray []string

// Value 实现 driver.Valuer 接口
func (a StringArray) Value() (driver.Value, error) {
	if a == nil {
		return nil, nil
	}
	return json.Marshal(a)
}

// Scan 实现 sql.Scanner 接口
func (a *StringArray) Scan(value any) error {
	if value == nil {
		*a = nil
		return nil
	}
	var data []byte
	switch v := value.(type) {
	case []byte:
		data = v
	case string:
		data = []byte(v)
	default:
		return nil
	}
	return json.Unmarshal(data, a)
}

// MaterialFile 文件资料
type MaterialFile struct {
	ID            string           `json:"id" gorm:"type:varchar(36);primaryKey"`
	SubjectID     string           `json:"subject_id" gorm:"type:varchar(36);index;not null"`
	Title         string           `json:"title" gorm:"type:varchar(200);not null"`
	Description   string           `json:"description" gorm:"type:text"`
	FileType      MaterialFileType `json:"file_type" gorm:"type:varchar(20);not null;index"`
	FileSize      int64            `json:"file_size" gorm:"default:0"`                          // 文件大小(字节)
	FileURL       string           `json:"file_url" gorm:"type:text;not null"`                  // 文件URL
	FileName      string           `json:"file_name" gorm:"type:varchar(255)"`                  // 原始文件名
	DownloadCount int              `json:"download_count" gorm:"default:0"`                     // 下载次数
	AuthorID      string           `json:"author_id" gorm:"type:varchar(36);index"`             // 上传者ID
	Tags          StringArray      `json:"tags" gorm:"type:json"`                               // 标签
	Status        MaterialStatus   `json:"status" gorm:"type:varchar(20);default:active;index"` // 状态
	CreatedAt     time.Time        `json:"created_at" gorm:"autoCreateTime;index"`
	UpdatedAt     time.Time        `json:"updated_at" gorm:"autoUpdateTime"`

	// 关联
	Subject *MaterialSubject `json:"subject,omitempty" gorm:"foreignKey:SubjectID"`
	Author  *User            `json:"author,omitempty" gorm:"foreignKey:AuthorID"`
}

// BeforeCreate 创建前生成UUID
func (f *MaterialFile) BeforeCreate(tx *gorm.DB) error {
	if f.ID == "" {
		f.ID = uuid.New().String()
	}
	return nil
}

func (MaterialFile) TableName() string {
	return "material_files"
}