AI Module

public protocol LLMClient: Sendable {
    func streamResponse(messages: [LLMMessage]) -> AsyncThrowingStream<String, Error>
}

public func streamResponse(
    messages: [LLMMessage],
    model: String? = nil,
    temperature: Double? = nil
) -> AsyncThrowingStream<String, Error>

public struct LLMMessage: Sendable, Equatable {
    public let role: String   // "user" | "assistant" | "system"
    public let content: String
}

@available(iOS 17.0, *)
func createLLMClient(httpClient: any HTTPClient) -> any LLMClient {
    guard let baseURL = URL(string: AppConfiguration.PROXY_BASE_URL),
          !AppConfiguration.PROXY_BASE_URL.contains("YOUR"),
          !AppConfiguration.PROXY_BASE_URL.contains("placeholder") else {
        AppLogger.info("LLM provider: EchoLLMClient (PROXY_BASE_URL not configured)", category: AppLogger.ai)
        return EchoLLMClient()
    }

    let proxyPath = AppConfiguration.PROXY_PATH

    var defaultHeaders: [String: String] = [:]
    if let headersJson = ProcessInfo.processInfo.environment["PROXY_DEFAULT_HEADERS"] {
        defaultHeaders = parseHeadersJSON(headersJson)
    }

    let proxyClient = ProxyLLMClient(
        baseURL: baseURL,
        httpClient: httpClient,  // carries the auth + retry interceptors
        path: proxyPath,
        defaultHeaders: defaultHeaders
    )

    AppLogger.info(
        "LLM provider: ProxyLLMClient (url=\(AppConfiguration.PROXY_BASE_URL), path=\(proxyPath))",
        category: AppLogger.ai
    )
    return proxyClient
}

// In ViewModel
for try await chunk in llmClient.streamResponse(messages: messages) {
    // Update UI with each token
    currentResponse += chunk
}

// supabase/functions/ai/index.ts
const ALLOWED_MODELS = ['openai/gpt-3.5-turbo', 'openai/gpt-4o-mini']
// default when the client omits `model`:
const { messages, model = 'openai/gpt-3.5-turbo', temperature = 0.7 } = await req.json()

let stream = llmClient.streamResponse(
    messages: messages,
    model: "anthropic/claude-3.7-sonnet",  // must be in ALLOWED_MODELS
    temperature: 0.7
)

// supabase/functions/ai/index.ts
serve(async (req) => {
  // 1. Verify user auth (Supabase JWT)
  // 2. Check the active AI entitlement (server-trusted, RevenueCat-backed)
  // 3. Consume the per-user rate limit (60 req / 60 min by default)
  // 4. Validate model against ALLOWED_MODELS + bounds-check messages
  // 5. Call OpenRouter with the server-side key and stream tokens back
})

supabase secrets set OPENROUTER_API_KEY=sk-or-v1-YOUR_KEY
supabase functions deploy ai

let systemMessage = LLMMessage(
    role: "system",
    content: """
    You are a professional Swift developer.
    Provide clear, concise answers with code examples.
    """
)

let messages = [systemMessage] + conversationHistory + [userMessage]

import AI

final class OpenAIClient: LLMClient {
    func streamResponse(messages: [LLMMessage]) -> AsyncThrowingStream<String, Error> {
        // Direct OpenAI API integration — no proxy
    }
}

// Then return it from createLLMClient(...) in LLMClientFactory.swift