xs/nu/commands/
last_command.rs

1use nu_engine::CallExt;
2use nu_protocol::engine::{Call, Command, EngineState, Stack};
3use nu_protocol::{Category, PipelineData, ShellError, Signature, SyntaxShape, Type, Value};
4
5use crate::nu::util;
6use crate::store::{ReadOptions, Store};
7
8#[derive(Clone)]
9pub struct LastCommand {
10    store: Store,
11}
12
13impl LastCommand {
14    pub fn new(store: Store) -> Self {
15        Self { store }
16    }
17}
18
19impl Command for LastCommand {
20    fn name(&self) -> &str {
21        ".last"
22    }
23
24    fn signature(&self) -> Signature {
25        Signature::build(".last")
26            .input_output_types(vec![(Type::Nothing, Type::Any)])
27            .optional(
28                "topic",
29                SyntaxShape::String,
30                "topic to get most recent frame from (default: all topics)",
31            )
32            .optional(
33                "count",
34                SyntaxShape::Int,
35                "number of frames to return (default: 1)",
36            )
37            .switch(
38                "with-timestamp",
39                "include timestamp extracted from frame ID",
40                None,
41            )
42            .category(Category::Experimental)
43    }
44
45    fn description(&self) -> &str {
46        "get the most recent frame(s) for a topic"
47    }
48
49    fn run(
50        &self,
51        engine_state: &EngineState,
52        stack: &mut Stack,
53        call: &Call,
54        _input: PipelineData,
55    ) -> Result<PipelineData, ShellError> {
56        let raw_topic: Option<String> = call.opt(engine_state, stack, 0)?;
57        let raw_count: Option<i64> = call.opt(engine_state, stack, 1)?;
58        let with_timestamp = call.has_flag(engine_state, stack, "with-timestamp")?;
59        let span = call.head;
60
61        // Disambiguate: if topic parses as a positive integer and count is absent,
62        // treat it as the count (topics cannot start with digits per ADR 0002)
63        let (topic, n) = match (&raw_topic, raw_count) {
64            (Some(t), None) if t.parse::<usize>().is_ok() => (None, t.parse::<usize>().unwrap()),
65            _ => (raw_topic, raw_count.map(|v| v as usize).unwrap_or(1)),
66        };
67
68        let options = ReadOptions::builder().last(n).maybe_topic(topic).build();
69
70        let frames: Vec<Value> = self
71            .store
72            .read_sync(options)
73            .map(|frame| util::frame_to_value(&frame, span, with_timestamp))
74            .collect();
75
76        if frames.is_empty() {
77            Ok(PipelineData::Empty)
78        } else if frames.len() == 1 {
79            Ok(PipelineData::Value(
80                frames.into_iter().next().unwrap(),
81                None,
82            ))
83        } else {
84            Ok(PipelineData::Value(Value::list(frames, span), None))
85        }
86    }
87}
xs/nu/commands/last_command.rs

xs/nu/commands/
last_command.rs
