forked from extern/nushell
108 lines
3.1 KiB
Rust
108 lines
3.1 KiB
Rust
use nu_engine::CallExt;
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use nu_protocol::ast::Call;
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use nu_protocol::engine::{Command, EngineState, Stack};
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use nu_protocol::{IntoPipelineData, PipelineData, ShellError, Signature, SyntaxShape};
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use std::convert::TryInto;
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#[derive(Clone)]
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pub struct Last;
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impl Command for Last {
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fn name(&self) -> &str {
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"last"
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}
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fn signature(&self) -> Signature {
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Signature::build("last").optional(
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"rows",
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SyntaxShape::Int,
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"starting from the back, the number of rows to return",
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)
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}
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fn usage(&self) -> &str {
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"Show only the last number of rows."
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}
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fn run(
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&self,
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engine_state: &EngineState,
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stack: &mut Stack,
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call: &Call,
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input: PipelineData,
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) -> Result<PipelineData, ShellError> {
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let rows: Option<i64> = call.opt(engine_state, stack, 0)?;
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let v: Vec<_> = input.into_iter().collect();
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let vlen: i64 = v.len() as i64;
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let beginning_rows_to_skip = rows_to_skip(vlen, rows);
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/*
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let end_rows_desired = if let Some(quantity) = rows {
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quantity
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} else {
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1
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};
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let beginning_rows_to_skip = if end_rows_desired < v.len() {
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v.len() - end_rows_desired
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} else {
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0
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};
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*/
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let iter = v
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.into_iter()
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.skip(beginning_rows_to_skip.try_into().unwrap());
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//let iter = v.into_iter().skip(beginning_rows_to_skip);
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/*
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let iter_count: i64 = input.into_iter().count() as i64;
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let beginning_rows_to_skip = rows_to_skip(iter_count, rows);
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dbg!(beginning_rows_to_skip);
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*/
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// let beginning_rows_to_skip = 3;
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/*
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match input {
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PipelineData::Stream(stream) => {
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dbg!("Stream");
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Ok(stream
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.skip(beginning_rows_to_skip.try_into().unwrap())
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.into_pipeline_data())
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}
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PipelineData::Value(Value::List { vals, .. }) => {
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dbg!("Value");
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Ok(vals
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.into_iter()
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.skip(beginning_rows_to_skip.try_into().unwrap())
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.into_pipeline_data())
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}
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_ => {
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dbg!("Fall to the bottom");
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Ok(PipelineData::Value(Value::Nothing { span: call.head }))
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}
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}
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*/
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Ok(iter.into_pipeline_data())
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// Ok(PipelineData::Value(Value::Nothing { span: call.head }))
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}
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}
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fn rows_to_skip(count: i64, rows: Option<i64>) -> i64 {
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let end_rows_desired = if let Some(quantity) = rows {
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quantity
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} else {
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1
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};
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if end_rows_desired < count {
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return count - end_rows_desired;
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} else {
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return 0;
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};
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}
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