// An error type for FFI errors. These errors occur at the UniFFI level, not
// the library level.
fileprivate enum UniffiInternalError: LocalizedError {
    case bufferOverflow
    case incompleteData
    case unexpectedOptionalTag
    case unexpectedEnumCase
    case unexpectedNullPointer
    case unexpectedRustCallStatusCode
    case unexpectedRustCallError
    case unexpectedStaleHandle
    case rustPanic(_ message: String)

    public var errorDescription: String? {
        switch self {
        case .bufferOverflow: return "Reading the requested value would read past the end of the buffer"
        case .incompleteData: return "The buffer still has data after lifting its containing value"
        case .unexpectedOptionalTag: return "Unexpected optional tag; should be 0 or 1"
        case .unexpectedEnumCase: return "Raw enum value doesn't match any cases"
        case .unexpectedNullPointer: return "Raw pointer value was null"
        case .unexpectedRustCallStatusCode: return "Unexpected RustCallStatus code"
        case .unexpectedRustCallError: return "CALL_ERROR but no errorClass specified"
        case .unexpectedStaleHandle: return "The object in the handle map has been dropped already"
        case let .rustPanic(message): return message
        }
    }
}

fileprivate let CALL_SUCCESS: Int8 = 0
fileprivate let CALL_ERROR: Int8 = 1
fileprivate let CALL_PANIC: Int8 = 2
fileprivate let CALL_CANCELLED: Int8 = 3

fileprivate extension RustCallStatus {
    init() {
        self.init(
            code: CALL_SUCCESS,
            errorBuf: RustBuffer.init(
                capacity: 0,
                len: 0,
                data: nil
            )
        )
    }
}

private func rustCall<T>(_ callback: (UnsafeMutablePointer<RustCallStatus>) -> T) throws -> T {
    try makeRustCall(callback, errorHandler: nil)
}

private func rustCallWithError<T>(
    _ errorHandler: @escaping (RustBuffer) throws -> Error,
    _ callback: (UnsafeMutablePointer<RustCallStatus>) -> T) throws -> T {
    try makeRustCall(callback, errorHandler: errorHandler)
}

private func makeRustCall<T>(
    _ callback: (UnsafeMutablePointer<RustCallStatus>) -> T,
    errorHandler: ((RustBuffer) throws -> Error)?
) throws -> T {
    uniffiEnsureInitialized()
    var callStatus = RustCallStatus.init()
    let returnedVal = callback(&callStatus)
    try uniffiCheckCallStatus(callStatus: callStatus, errorHandler: errorHandler)
    return returnedVal
}

private func uniffiCheckCallStatus(
    callStatus: RustCallStatus,
    errorHandler: ((RustBuffer) throws -> Error)?
) throws {
    switch callStatus.code {
        case CALL_SUCCESS:
            return

        case CALL_ERROR:
            if let errorHandler = errorHandler {
                throw try errorHandler(callStatus.errorBuf)
            } else {
                callStatus.errorBuf.deallocate()
                throw UniffiInternalError.unexpectedRustCallError
            }

        case CALL_PANIC:
            // When the rust code sees a panic, it tries to construct a RustBuffer
            // with the message.  But if that code panics, then it just sends back
            // an empty buffer.
            if callStatus.errorBuf.len > 0 {
                throw UniffiInternalError.rustPanic(try {{ Type::String.borrow()|lift_fn }}(callStatus.errorBuf))
            } else {
                callStatus.errorBuf.deallocate()
                throw UniffiInternalError.rustPanic("Rust panic")
            }

        case CALL_CANCELLED:
                throw CancellationError()

        default:
            throw UniffiInternalError.unexpectedRustCallStatusCode
    }
}