Veo 3 APIで動画生成アプリを Antigravity で作る — 実装から公開まで

import Foundation
 
struct Veo3APIClient {
    private let apiKey = "YOUR_API_KEY"
    private let baseURL = "https://generativelanguage.googleapis.com/v1beta"
    
    // 動画生成ジョブを開始する
    func startVideoGeneration(prompt: String) async throws -> String {
        let url = URL(string: "\(baseURL)/models/veo-003:generateVideo?key=\(apiKey)")!
        
        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        
        let body: [String: Any] = [
            "contents": [["parts": [["text": prompt]]]],
            "generationConfig": [
                "durationSeconds": 8,
                "aspectRatio": "16:9",
                "resolution": "720p"
            ]
        ]
        
        request.httpBody = try JSONSerialization.data(withJSONObject: body)
        
        let (data, _) = try await URLSession.shared.data(for: request)
        let json = try JSONSerialization.jsonObject(with: data) as! [String: Any]
        
        // ジョブIDを返す（完了まで数十秒かかる）
        return json["name"] as! String
    }
    
    // ジョブのステータスを確認する
    func checkJobStatus(jobName: String) async throws -> VideoJobStatus {
        let url = URL(string: "\(baseURL)/\(jobName)?key=\(apiKey)")!
        let (data, _) = try await URLSession.shared.data(from: url)
        let json = try JSONSerialization.jsonObject(with: data) as! [String: Any]
        
        let done = json["done"] as? Bool ?? false
        if done {
            let response = json["response"] as? [String: Any]
            let candidates = response?["candidates"] as? [[String: Any]]
            let videoUri = candidates?.first?["video"] as? [String: Any]
            let uri = videoUri?["uri"] as? String
            return .completed(videoURL: uri)
        }
        
        return .processing
    }
}
 
enum VideoJobStatus {
    case processing
    case completed(videoURL: String?)
    case failed
}

@MainActor
class VideoGenerationViewModel: ObservableObject {
    @Published var status: GenerationStatus = .idle
    @Published var videoURL: URL?
    @Published var errorMessage: String?
    
    private let client = Veo3APIClient()
    
    func generateVideo(prompt: String) async {
        status = .starting
        
        do {
            let jobName = try await client.startVideoGeneration(prompt: prompt)
            status = .processing(progress: 0)
            
            // ポーリング（最大60秒、5秒間隔）
            for attempt in 1...12 {
                try await Task.sleep(nanoseconds: 5_000_000_000)
                
                let result = try await client.checkJobStatus(jobName: jobName)
                
                switch result {
                case .processing:
                    let progress = Double(attempt) / 12.0
                    status = .processing(progress: progress)
                    
                case .completed(let urlString):
                    if let urlString, let url = URL(string: urlString) {
                        videoURL = url
                        status = .completed
                    } else {
                        status = .failed
                        errorMessage = "動画URLの取得に失敗しました"
                    }
                    return
                    
                case .failed:
                    status = .failed
                    errorMessage = "動画の生成に失敗しました"
                    return
                }
            }
            
            // タイムアウト
            status = .failed
            errorMessage = "生成がタイムアウトしました。もう一度お試しください"
            
        } catch {
            status = .failed
            errorMessage = error.localizedDescription
        }
    }
}
 
enum GenerationStatus: Equatable {
    case idle
    case starting
    case processing(progress: Double)
    case completed
    case failed
}