use nu_engine::CallExt;

use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{IntoPipelineData, PipelineData, ShellError, Signature, SyntaxShape, Value};
use std::convert::TryInto;

#[derive(Clone)]
pub struct Last;

impl Command for Last {
    fn name(&self) -> &str {
        "last"
    }

    fn signature(&self) -> Signature {
        Signature::build("last").optional(
            "rows",
            SyntaxShape::Int,
            "starting from the back, the number of rows to return",
        )
    }

    fn usage(&self) -> &str {
        "Show only the last number of rows."
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        let rows: Option<i64> = call.opt(engine_state, stack, 0)?;
        let iter_count: i64 = input.into_iter().count() as i64;
        let beginning_rows_to_skip = rows_to_skip(iter_count, rows);
        dbg!(beginning_rows_to_skip);

        // let beginning_rows_to_skip = 3;

        match input {
            PipelineData::Stream(stream) => {
                dbg!("Stream");
                Ok(stream
                    .skip(beginning_rows_to_skip.try_into().unwrap())
                    .into_pipeline_data())
            }
            PipelineData::Value(Value::List { vals, .. }) => {
                dbg!("Value");
                Ok(vals
                    .into_iter()
                    .skip(beginning_rows_to_skip.try_into().unwrap())
                    .into_pipeline_data())
            }
            _ => {
                dbg!("Fall to the bottom");
                Ok(PipelineData::Value(Value::Nothing { span: call.head }))
            }
        }

        // Ok(PipelineData::Value(Value::Nothing { span: call.head }))
    }
}

fn rows_to_skip(count: i64, rows: Option<i64>) -> i64 {
    let end_rows_desired = if let Some(quantity) = rows {
        quantity
    } else {
        1
    };

    if end_rows_desired < count {
        return count - end_rows_desired;
    } else {
        return 0;
    };
}