pub enum ShellError {
    /// An operator received two arguments of incompatible types.
    ///
    /// ## Resolution
    ///
    /// Check each argument's type and convert one or both as needed.
    #[error("Type mismatch during operation.")]
    #[diagnostic(code(nu::shell::type_mismatch))]
    OperatorMismatch {
        #[label = "type mismatch for operator"]
        op_span: Span,
        lhs_ty: String,
        #[label("{lhs_ty}")]
        lhs_span: Span,
        rhs_ty: String,
        #[label("{rhs_ty}")]
        rhs_span: Span,
    },

    /// The pipelined input into a command was not of the expected type. For example, it might
    /// expect a string input, but received a table instead.
    ///
    /// ## Resolution
    ///
    /// Check the relevant pipeline and extract or convert values as needed.
    #[error("Pipeline mismatch.")]
    #[diagnostic(code(nu::shell::pipeline_mismatch))]
    PipelineMismatch {
        exp_input_type: String,
        #[label("expected: {exp_input_type}")]
        dst_span: Span,
        #[label("value originates from here")]
        src_span: Span,
    },

    // TODO: properly unify
    /// The pipelined input into a command was not of the expected type. For example, it might
    /// expect a string input, but received a table instead.
    ///
    /// (duplicate of [`ShellError::PipelineMismatch`] that reports the observed type)
    ///
    /// ## Resolution
    ///
    /// Check the relevant pipeline and extract or convert values as needed.
    #[error("Input type not supported.")]
    #[diagnostic(code(nu::shell::only_supports_this_input_type))]
    OnlySupportsThisInputType {
        exp_input_type: String,
        wrong_type: String,
        #[label("only {exp_input_type} input data is supported")]
        dst_span: Span,
        #[label("input type: {wrong_type}")]
        src_span: Span,
    },

    /// No input value was piped into the command.
    ///
    /// ## Resolution
    ///
    /// Only use this command to process values from a previous expression.
    #[error("Pipeline empty.")]
    #[diagnostic(code(nu::shell::pipeline_mismatch))]
    PipelineEmpty {
        #[label("no input value was piped in")]
        dst_span: Span,
    },

    // TODO: remove non type error usages
    /// A command received an argument of the wrong type.
    ///
    /// ## Resolution
    ///
    /// Convert the argument type before passing it in, or change the command to accept the type.
    #[error("Type mismatch.")]
    #[diagnostic(code(nu::shell::type_mismatch))]
    TypeMismatch {
        err_message: String,
        #[label = "{err_message}"]
        span: Span,
    },
    /// An operation received parameters with some sort of incompatibility
    /// (for example, different number of rows in a table, incompatible column names, etc).
    ///
    /// ## Resolution
    ///
    /// Refer to the specific error message for details on what's incompatible and then fix your
    /// inputs to make sure they match that way.
    #[error("Incompatible parameters.")]
    #[diagnostic(code(nu::shell::incompatible_parameters))]
    IncompatibleParametersSingle {
        msg: String,
        #[label = "{msg}"]
        span: Span,
    },

    /// Failed to convert a value of one type into a different type.
    ///
    /// ## Resolution
    ///
    /// Not all values can be coerced this way. Check the supported type(s) and try again.
    #[error("Can't convert to {to_type}.")]
    #[diagnostic(code(nu::shell::cant_convert))]
    CantConvert {
        to_type: String,
        from_type: String,
        #[label("can't convert {from_type} to {to_type}")]
        span: Span,
        #[help]
        help: Option<String>,
    },

    /// An error happened while tryin to create a range.
    ///
    /// This can happen in various unexpected situations, for example if the range would loop forever (as would be the case with a 0-increment).
    ///
    /// ## Resolution
    ///
    /// Check your range values to make sure they're countable and would not loop forever.
    #[error("Can't convert range to countable values")]
    #[diagnostic(code(nu::shell::range_to_countable))]
    CannotCreateRange {
        #[label = "can't convert to countable values"]
        span: Span,
    },

    /// The given operation can only be performed on lists.
    ///
    /// ## Resolution
    ///
    /// Check the input type to this command. Are you sure it's a list?
    #[error("Not a list value")]
    #[diagnostic(code(nu::shell::not_a_list))]
    NotAList {
        #[label = "value not a list"]
        dst_span: Span,
        #[label = "value originates here"]
        src_span: Span,
    },

    /// An operation was attempted with an input unsupported for some reason.
    ///
    /// ## Resolution
    ///
    /// This error is fairly generic. Refer to the specific error message for further details.
    #[error("Unsupported input")]
    #[diagnostic(code(nu::shell::unsupported_input))]
    UnsupportedInput(
        String,
        String,
        #[label("{0}")] Span, // call head (the name of the command itself)
        #[label("input type: {1}")] Span,
    ),

    /// A custom value could not be converted to a Dataframe.
    ///
    /// ## Resolution
    ///
    /// Make sure conversion to a Dataframe is possible for this value or convert it to a type that does, first.
    #[error("Casting error")]
    #[diagnostic(code(nu::shell::downcast_not_possible))]
    DowncastNotPossible(String, #[label("{0}")] Span),
}