8. Schema Versioning & Migration

import SwiftData

// Setiap versi schema didefinisikan dalam enum terpisah
// Model di dalam enum menggunakan nama yang sama tapi tipe berbeda

// Versi 1: User hanya punya name
enum SchemaV1: VersionedSchema {
    static var versionIdentifier = Schema.Version(1, 0, 0)
    static var models: [any PersistentModel.Type] { [User.self, Task.self] }
    
    @Model final class User {
        var name: String
        var email: String
        
        init(name: String, email: String) {
            self.name = name
            self.email = email
        }
    }
    
    @Model final class Task {
        var title: String
        var isCompleted: Bool = false
        
        init(title: String) { self.title = title }
    }
}

// Versi 2: User punya firstName + lastName (split dari name)
//          Task punya dueDate yang baru
enum SchemaV2: VersionedSchema {
    static var versionIdentifier = Schema.Version(2, 0, 0)
    static var models: [any PersistentModel.Type] { [User.self, Task.self] }
    
    @Model final class User {
        var firstName: String
        var lastName: String
        var email: String
        
        init(firstName: String, lastName: String, email: String) {
            self.firstName = firstName
            self.lastName = lastName
            self.email = email
        }
        
        var fullName: String { "\(firstName) \(lastName)" }
    }
    
    @Model final class Task {
        var title: String
        var isCompleted: Bool = false
        var dueDate: Date?
        var priority: String = "medium"
        
        init(title: String) { self.title = title }
    }
}

// Versi 3: User punya profileImageData (external storage)
enum SchemaV3: VersionedSchema {
    static var versionIdentifier = Schema.Version(3, 0, 0)
    static var models: [any PersistentModel.Type] { [User.self, Task.self] }
    
    @Model final class User {
        var firstName: String
        var lastName: String
        var email: String
        
        @Attribute(.externalStorage)
        var profileImageData: Data?
        
        init(firstName: String, lastName: String, email: String) {
            self.firstName = firstName
            self.lastName = lastName
            self.email = email
        }
    }
    
    @Model final class Task {
        var title: String
        var isCompleted: Bool = false
        var dueDate: Date?
        var priority: String = "medium"
        
        init(title: String) { self.title = title }
    }
}

// Definisikan migration path dari satu versi ke versi berikutnya
enum AppMigrationPlan: SchemaMigrationPlan {
    // Daftar semua versi schema yang pernah ada (urutan kronologis)
    static var schemas: [any VersionedSchema.Type] {
        [SchemaV1.self, SchemaV2.self, SchemaV3.self]
    }
    
    // Stage migration yang perlu logika khusus
    static var stages: [MigrationStage] {
        [migrateV1toV2, migrateV2toV3]
    }
    
    // V1 → V2: split "name" menjadi "firstName" dan "lastName"
    static let migrateV1toV2 = MigrationStage.custom(
        fromVersion: SchemaV1.self,
        toVersion: SchemaV2.self,
        willMigrate: nil,
        didMigrate: { context in
            // Setelah schema diupdate, isi nilai baru dari data lama
            // CATATAN: di sini kita akses SchemaV2.User (versi baru)
            let users = try context.fetch(FetchDescriptor<SchemaV2.User>())
            
            for user in users {
                // Data nama lama sudah di-migrate ke firstName oleh SwiftData
                // (karena nama kolom sama, SwiftData map otomatis)
                // Tapi lastName perlu diisi:
                if user.lastName.isEmpty {
                    // Split dari firstName jika memungkinkan
                    let parts = user.firstName.split(separator: " ", maxSplits: 1)
                    if parts.count == 2 {
                        user.firstName = String(parts[0])
                        user.lastName = String(parts[1])
                    } else {
                        user.lastName = ""  // Tidak ada last name
                    }
                }
            }
            
            try context.save()
        }
    )
    
    // V2 → V3: tambah profileImageData (nullable, default nil — tidak butuh logika khusus)
    static let migrateV2toV3 = MigrationStage.lightweight(
        fromVersion: SchemaV2.self,
        toVersion: SchemaV3.self
    )
}

// Gunakan di ModelContainer
let container = try ModelContainer(
    for: SchemaV3.User.self, SchemaV3.Task.self,
    migrationPlan: AppMigrationPlan.self
)