import Foundation
import NIO
import NIOHTTP1

/// In-process HTTP server mimicking ARRI ALEXA 35 REST API shape.
/// Endpoint paths kept in one place (`ArriSimPaths`) — mirror of the driver's
/// constants file; correct both together when verified against hardware.
public enum ArriSimPaths {
    public static let systemInfo = "/api/v1/system/info"
    public static let recordingStatus = "/api/v1/recording/status"
    public static let metadata = "/api/v1/camera/metadata"
    public static let lookCurrent = "/api/v1/look/current"
}

public actor ArriSimulator {
    private var group: MultiThreadedEventLoopGroup?
    private var channel: Channel?
    public private(set) var boundPort: Int?

    // Scriptable state.
    private var recording = false
    private var clipName: String?
    private var ei = 800
    private var wb = 5600
    private var tint = 0
    private var fps = 24.0
    private var timecode = "00:00:00:00"
    /// Raw JSON bodies of accepted look uploads (Sendable; decode in consumers).
    public private(set) var uploadedLooks: [Data] = []

    public init() {}

    // MARK: Scripting hooks

    public func setRecording(_ on: Bool, clipName: String? = nil) {
        recording = on
        if let c = clipName { self.clipName = c }
        if !on { /* keep clip name for last-clip queries */ }
    }

    public func setMetadata(ei: Int, wb: Int, tint: Int, fps: Double, timecode: String) {
        self.ei = ei
        self.wb = wb
        self.tint = tint
        self.fps = fps
        self.timecode = timecode
    }

    // MARK: Request handling (called from channel handler)

    func handle(method: HTTPMethod, uri: String, body: Data?) -> (status: HTTPResponseStatus, body: Data) {
        switch (method, uri) {
        case (.GET, ArriSimPaths.systemInfo):
            return (.ok, json([
                "model": "ALEXA 35",
                "serialNumber": "SIM-35-0001",
                "firmwareVersion": "SUP 2.0-sim",
            ]))
        case (.GET, ArriSimPaths.recordingStatus):
            var obj: [String: Any] = ["recording": recording]
            if let c = clipName { obj["clipName"] = c }
            return (.ok, json(obj))
        case (.GET, ArriSimPaths.metadata):
            return (.ok, json([
                "exposureIndex": ei,
                "whiteBalance": wb,
                "tint": tint,
                "fps": fps,
                "timecode": timecode,
            ]))
        case (.GET, ArriSimPaths.lookCurrent):
            guard let last = uploadedLooks.last else {
                return (.notFound, json(["error": "no look set"]))
            }
            return (.ok, last)
        case (.PUT, ArriSimPaths.lookCurrent):
            guard let body,
                  (try? JSONSerialization.jsonObject(with: body) as? [String: Any]) != nil else {
                return (.badRequest, json(["error": "invalid JSON"]))
            }
            uploadedLooks.append(body)
            return (.ok, json(["status": "accepted"]))
        default:
            return (.notFound, json(["error": "unknown path"]))
        }
    }

    private func json(_ obj: [String: Any]) -> Data {
        (try? JSONSerialization.data(withJSONObject: obj, options: [.sortedKeys])) ?? Data()
    }

    // MARK: Lifecycle

    public func start(port: Int) async throws {
        let group = MultiThreadedEventLoopGroup(numberOfThreads: 1)
        self.group = group
        let sim = self
        let bootstrap = ServerBootstrap(group: group)
            .serverChannelOption(ChannelOptions.socketOption(.so_reuseaddr), value: 1)
            .childChannelInitializer { channel in
                channel.pipeline.configureHTTPServerPipeline().flatMap {
                    channel.pipeline.addHandler(HTTPSimHandler(sim: sim))
                }
            }
        let channel = try await bootstrap.bind(host: "127.0.0.1", port: port).get()
        self.channel = channel
        boundPort = channel.localAddress?.port
    }

    public func stop() async throws {
        try await channel?.close()
        try await group?.shutdownGracefully()
        channel = nil
        group = nil
        boundPort = nil
    }
}

/// Minimal HTTP1 request handler bridging into the actor.
final class HTTPSimHandler: ChannelInboundHandler, @unchecked Sendable {
    typealias InboundIn = HTTPServerRequestPart
    typealias OutboundOut = HTTPServerResponsePart

    private let sim: ArriSimulator
    private var method: HTTPMethod = .GET
    private var uri: String = "/"
    private var bodyBuffer: ByteBuffer?

    init(sim: ArriSimulator) {
        self.sim = sim
    }

    func channelRead(context: ChannelHandlerContext, data: NIOAny) {
        switch unwrapInboundIn(data) {
        case .head(let head):
            method = head.method
            uri = head.uri
            bodyBuffer = nil
        case .body(var buf):
            if bodyBuffer == nil {
                bodyBuffer = buf
            } else {
                bodyBuffer?.writeBuffer(&buf)
            }
        case .end:
            let body = bodyBuffer.map { Data($0.readableBytesView) }
            let m = method
            let u = uri
            let channel = context.channel
            let loop = context.eventLoop
            Task {
                let (status, respBody) = await self.sim.handle(method: m, uri: u, body: body)
                loop.execute {
                    var headers = HTTPHeaders()
                    headers.add(name: "Content-Type", value: "application/json")
                    headers.add(name: "Content-Length", value: "\(respBody.count)")
                    let head = HTTPResponseHead(version: .http1_1, status: status, headers: headers)
                    channel.write(HTTPServerResponsePart.head(head), promise: nil)
                    var buf = channel.allocator.buffer(capacity: respBody.count)
                    buf.writeBytes(respBody)
                    channel.write(HTTPServerResponsePart.body(.byteBuffer(buf)), promise: nil)
                    channel.writeAndFlush(HTTPServerResponsePart.end(nil), promise: nil)
                }
            }
        }
    }
}