import Foundation
import GRPCCore
import GRPCProtobuf
import GRPCNIOTransportHTTP2

/// gRPC service provider for Apple Intelligence
public struct AppleIntelligenceProvider: Appleintelligence_AppleIntelligenceService.ServiceProtocol {
    /// The underlying AI service
    private let service: AppleIntelligenceService

    /// Optional API key for authentication
    private let apiKey: String?

    public init(service: AppleIntelligenceService, apiKey: String? = nil) {
        self.service = service
        self.apiKey = apiKey
    }

    // MARK: - ServiceProtocol Implementation

    public func complete(
        request: GRPCCore.ServerRequest<Appleintelligence_CompletionRequest>,
        context: GRPCCore.ServerContext
    ) async throws -> GRPCCore.ServerResponse<Appleintelligence_CompletionResponse> {
        try validateApiKey(metadata: request.metadata)

        let message = request.message

        // Convert protobuf images to service format
        let images = message.images.map { img in
            (data: img.data, filename: img.filename.isEmpty ? nil : img.filename)
        }

        let (text, analyses) = try await service.complete(
            prompt: message.prompt,
            temperature: message.hasTemperature ? message.temperature : nil,
            maxTokens: message.hasMaxTokens ? Int(message.maxTokens) : nil,
            images: images
        )

        var response = Appleintelligence_CompletionResponse()
        response.id = UUID().uuidString
        response.text = text
        response.finishReason = "stop"

        // Include analysis results if requested
        if message.includeAnalysis {
            response.imageAnalyses = analyses.map { analysis in
                var protoAnalysis = Appleintelligence_ImageAnalysis()
                protoAnalysis.textContent = analysis.textContent
                protoAnalysis.labels = analysis.labels
                protoAnalysis.description_p = analysis.description
                return protoAnalysis
            }
        }

        return ServerResponse(message: response)
    }

    public func streamComplete(
        request: GRPCCore.ServerRequest<Appleintelligence_CompletionRequest>,
        context: GRPCCore.ServerContext
    ) async throws -> GRPCCore.StreamingServerResponse<Appleintelligence_CompletionChunk> {
        try validateApiKey(metadata: request.metadata)

        let message = request.message
        let completionId = UUID().uuidString

        // Convert protobuf images to service format
        let images = message.images.map { img in
            (data: img.data, filename: img.filename.isEmpty ? nil : img.filename)
        }

        return StreamingServerResponse { writer in
            let stream = await self.service.streamComplete(
                prompt: message.prompt,
                temperature: message.hasTemperature ? message.temperature : nil,
                maxTokens: message.hasMaxTokens ? Int(message.maxTokens) : nil,
                images: images
            )

            var lastContent = ""
            var isFirstChunk = true
            for try await (partialResponse, analyses) in stream {
                // Calculate the delta (new text since last response)
                let delta: String
                if partialResponse.hasPrefix(lastContent) {
                    delta = String(partialResponse.dropFirst(lastContent.count))
                } else {
                    delta = partialResponse
                }
                lastContent = partialResponse

                if !delta.isEmpty || isFirstChunk {
                    var chunk = Appleintelligence_CompletionChunk()
                    chunk.id = completionId
                    chunk.delta = delta
                    chunk.isFinal = false

                    // Include analyses in first chunk if requested
                    if isFirstChunk && message.includeAnalysis, let analyses = analyses {
                        chunk.imageAnalyses = analyses.map { analysis in
                            var protoAnalysis = Appleintelligence_ImageAnalysis()
                            protoAnalysis.textContent = analysis.textContent
                            protoAnalysis.labels = analysis.labels
                            protoAnalysis.description_p = analysis.description
                            return protoAnalysis
                        }
                    }

                    try await writer.write(chunk)
                    isFirstChunk = false
                }
            }

            // Send final chunk
            var finalChunk = Appleintelligence_CompletionChunk()
            finalChunk.id = completionId
            finalChunk.delta = ""
            finalChunk.isFinal = true
            finalChunk.finishReason = "stop"
            try await writer.write(finalChunk)

            return [:]
        }
    }

    public func health(
        request: GRPCCore.ServerRequest<Appleintelligence_HealthRequest>,
        context: GRPCCore.ServerContext
    ) async throws -> GRPCCore.ServerResponse<Appleintelligence_HealthResponse> {
        let isHealthy = await service.isAvailable
        let modelStatus = await service.getModelStatus()

        var response = Appleintelligence_HealthResponse()
        response.healthy = isHealthy
        response.modelStatus = modelStatus

        return ServerResponse(message: response)
    }

    // MARK: - Private Helpers

    /// Validate API key if configured
    private func validateApiKey(metadata: Metadata) throws {
        guard let expectedKey = apiKey else {
            return // No API key required
        }

        // Look for Authorization header in metadata
        let authValues = metadata["authorization"]
        guard let authHeader = authValues.first(where: { _ in true }),
              case .string(let authString) = authHeader,
              authString.hasPrefix("Bearer ") else {
            throw RPCError(code: .unauthenticated, message: "Missing or invalid Authorization header")
        }

        let providedKey = String(authString.dropFirst("Bearer ".count))
        guard providedKey == expectedKey else {
            throw RPCError(code: .unauthenticated, message: "Invalid API key")
        }
    }
}