use crate::prelude::*;
use nu_engine::WholeStreamCommand;
use nu_errors::ShellError;
use nu_protocol::{dataframe::NuDataFrame, Signature, SyntaxShape, Value};

use super::utils::{convert_columns, parse_polars_error};

pub struct DataFrame;

impl WholeStreamCommand for DataFrame {
    fn name(&self) -> &str {
        "pls drop"
    }

    fn usage(&self) -> &str {
        "Creates a new dataframe by dropping the selected columns"
    }

    fn signature(&self) -> Signature {
        Signature::build("pls drop").required(
            "columns",
            SyntaxShape::Table,
            "column names to be dropped",
        )
    }

    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
        command(args)
    }

    fn examples(&self) -> Vec<Example> {
        vec![Example {
            description: "drop column a",
            example: "[[a b]; [1 2] [3 4]] | pls to-df | pls drop [a]",
            result: None,
        }]
    }
}

fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
    let tag = args.call_info.name_tag.clone();
    let mut args = args.evaluate_once()?;

    let columns: Vec<Value> = args.req(0)?;
    let (col_string, col_span) = convert_columns(&columns, &tag)?;

    let df = NuDataFrame::try_from_stream(&mut args.input, &tag.span)?;

    let new_df = match col_string.iter().next() {
        Some(col) => df
            .as_ref()
            .drop(col)
            .map_err(|e| parse_polars_error::<&str>(&e, &col_span, None)),
        None => Err(ShellError::labeled_error(
            "Empty names list",
            "No column names where found",
            &col_span,
        )),
    }?;

    // If there are more columns in the drop selection list, these
    // are added from the resulting dataframe
    let res = col_string.iter().skip(1).try_fold(new_df, |new_df, col| {
        new_df
            .drop(col)
            .map_err(|e| parse_polars_error::<&str>(&e, &col_span, None))
    })?;

    Ok(OutputStream::one(NuDataFrame::dataframe_to_value(res, tag)))
}