package database

import (
	"context"
	"fmt"
	"log/slog"
	"time"

	"gorm.io/gorm"

	"rill/internal/model"
)

// Migration 描述一次数据库结构变更，Version 必须唯一且递增。
type Migration struct {
	Version int
	Name    string
	Up      func(*gorm.DB) error
}

// migrations 按 Version 升序登记所有迁移，新增迁移只能追加。
var migrations = []Migration{
	{
		Version: 1,
		Name:    "create_notes",
		Up: func(tx *gorm.DB) error {
			return tx.AutoMigrate(&model.Note{})
		},
	},
	{
		Version: 2,
		Name:    "create_user_groups",
		Up: func(tx *gorm.DB) error {
			if err := tx.AutoMigrate(&model.UserGroup{}); err != nil {
				return err
			}
			now := time.Now()
			seeds := []struct {
				id   uint
				name string
				desc string
			}{
				{id: model.GroupIDAdmin, name: "admin", desc: "Administrator group"},
				{id: model.GroupIDUser, name: "user", desc: "Regular user group"},
			}
			for _, seed := range seeds {
				if err := tx.Exec(
					"INSERT INTO user_groups (id, name, description, is_system, created_at, updated_at) VALUES (?, ?, ?, ?, ?, ?)",
					seed.id, seed.name, seed.desc, true, now, now,
				).Error; err != nil {
					return err
				}
			}
			return nil
		},
	},
	{
		Version: 3,
		Name:    "create_users",
		Up: func(tx *gorm.DB) error {
			return tx.AutoMigrate(&model.User{}, &model.UserGroupMember{})
		},
	},
	{
		Version: 4,
		Name:    "seed_admin_user",
		Up:      seedAdminUser,
	},
	{
		Version: 5,
		Name:    "translate_builtin_data",
		Up: func(tx *gorm.DB) error {
			statements := []string{
				"UPDATE user_groups SET description = 'Administrator group' WHERE id = 0 AND description = '管理员组'",
				"UPDATE user_groups SET description = 'Regular user group' WHERE id = 1 AND description = '普通用户组'",
				"UPDATE users SET nickname = 'Administrator' WHERE username = 'admin' AND nickname = '管理员'",
			}
			for _, statement := range statements {
				if err := tx.Exec(statement).Error; err != nil {
					return err
				}
			}
			return nil
		},
	},
	{
		Version: 6,
		Name:    "add_user_profile_fields",
		Up: func(tx *gorm.DB) error {
			return tx.AutoMigrate(&model.User{})
		},
	},
	{
		Version: 7,
		Name:    "create_site_settings",
		Up: func(tx *gorm.DB) error {
			if err := tx.AutoMigrate(&model.SiteSetting{}); err != nil {
				return err
			}
			now := time.Now()
			return tx.Exec(
				"INSERT INTO site_settings (id, site_name, logo, footer, created_at, updated_at) VALUES (?, ?, '', '', ?, ?)",
				model.SiteSettingID, "Rill", now, now,
			).Error
		},
	},
	{
		Version: 8,
		Name:    "create_files",
		Up: func(tx *gorm.DB) error {
			return tx.AutoMigrate(&model.File{})
		},
	},
	{
		Version: 9,
		Name:    "create_file_operations",
		Up: func(tx *gorm.DB) error {
			return tx.AutoMigrate(&model.FileOperation{})
		},
	},
	{
		Version: 10,
		Name:    "create_nav_links",
		Up: func(tx *gorm.DB) error {
			return tx.AutoMigrate(&model.NavLink{}, &model.NavLinkTranslation{})
		},
	},
}

// schemaMigration 记录已应用的迁移版本。
type schemaMigration struct {
	Version   int `gorm:"primaryKey"`
	Name      string
	AppliedAt time.Time
}

func (schemaMigration) TableName() string { return "schema_migrations" }

// Migrate 依次执行未应用的迁移，每个迁移在独立事务中完成并记录版本，可重复调用。
func Migrate(ctx context.Context, db *gorm.DB) error {
	tx := db.WithContext(ctx)
	if err := tx.AutoMigrate(&schemaMigration{}); err != nil {
		return fmt.Errorf("初始化迁移记录表失败: %w", err)
	}

	var applied []int
	if err := tx.Model(&schemaMigration{}).Pluck("version", &applied).Error; err != nil {
		return fmt.Errorf("读取迁移记录失败: %w", err)
	}
	done := make(map[int]bool, len(applied))
	for _, version := range applied {
		done[version] = true
	}

	for _, m := range migrations {
		if done[m.Version] {
			continue
		}
		err := tx.Transaction(func(tx *gorm.DB) error {
			if err := m.Up(tx); err != nil {
				return err
			}
			return tx.Create(&schemaMigration{Version: m.Version, Name: m.Name, AppliedAt: time.Now()}).Error
		})
		if err != nil {
			return fmt.Errorf("执行迁移 %d_%s 失败: %w", m.Version, m.Name, err)
		}
		slog.Info("数据库迁移已应用", "version", m.Version, "name", m.Name)
	}
	return nil
}