use crate::{
PolarsPlugin,
values::{
CustomValueSupport, NuExpression, PolarsPluginObject, PolarsPluginType, cant_convert_err,
},
};
use super::super::super::values::{Column, NuDataFrame};
use nu_plugin::{EngineInterface, EvaluatedCall, PluginCommand};
use nu_protocol::shell_error::generic::GenericError;
use nu_protocol::{
Category, Example, LabeledError, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
};
use polars::{
prelude::{Expr, IntoSeries, NamedFrom, Null, StringNameSpaceImpl, lit},
series::Series,
};
#[derive(Clone)]
pub struct StrSlice;
impl PluginCommand for StrSlice {
type Plugin = PolarsPlugin;
fn name(&self) -> &str {
"polars str-slice"
}
fn description(&self) -> &str {
"Slices the string from the start position until the selected length."
}
fn signature(&self) -> Signature {
Signature::build(self.name())
.required("start", SyntaxShape::Int, "Start of slice.")
.named("length", SyntaxShape::Int, "Optional length.", Some('l'))
.input_output_types(vec![
(
PolarsPluginType::NuExpression.into(),
PolarsPluginType::NuExpression.into(),
),
(
PolarsPluginType::NuDataFrame.into(),
PolarsPluginType::NuDataFrame.into(),
),
(
PolarsPluginType::NuLazyFrame.into(),
PolarsPluginType::NuLazyFrame.into(),
),
])
.category(Category::Custom("dataframe".into()))
}
fn examples(&self) -> Vec<Example<'_>> {
vec![
Example {
description: "Creates slices from the strings in a specified column",
example: "[[a]; [abcded] [abc321] [abc123]] | polars into-df | polars select (polars col a | polars str-slice 1 --length 2) | polars collect",
result: Some(
NuDataFrame::try_from_columns(
vec![Column::new(
"a".to_string(),
vec![
Value::test_string("bc"),
Value::test_string("bc"),
Value::test_string("bc"),
],
)],
None,
Span::test_data(),
)
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
},
Example {
description: "Creates slices from the strings",
example: "[abcded abc321 abc123] | polars into-df | polars str-slice 1 --length 2",
result: Some(
NuDataFrame::try_from_columns(
vec![Column::new(
"0".to_string(),
vec![
Value::test_string("bc"),
Value::test_string("bc"),
Value::test_string("bc"),
],
)],
None,
Span::test_data(),
)
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
},
Example {
description: "Creates slices from the strings without length",
example: "[abcded abc321 abc123] | polars into-df | polars str-slice 1",
result: Some(
NuDataFrame::try_from_columns(
vec![Column::new(
"0".to_string(),
vec![
Value::test_string("bcded"),
Value::test_string("bc321"),
Value::test_string("bc123"),
],
)],
None,
Span::test_data(),
)
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
},
]
}
fn run(
&self,
plugin: &Self::Plugin,
engine: &EngineInterface,
call: &EvaluatedCall,
mut input: PipelineData,
) -> Result<PipelineData, LabeledError> {
let metadata = input.take_metadata();
let value = input.into_value(call.head)?;
match PolarsPluginObject::try_from_value(plugin, &value)? {
PolarsPluginObject::NuDataFrame(df) => command_df(plugin, engine, call, df),
PolarsPluginObject::NuLazyFrame(lazy) => {
command_df(plugin, engine, call, lazy.collect(call.head)?)
}
PolarsPluginObject::NuExpression(expr) => command_expr(plugin, engine, call, expr),
_ => Err(cant_convert_err(
&value,
&[
PolarsPluginType::NuDataFrame,
PolarsPluginType::NuLazyFrame,
PolarsPluginType::NuExpression,
],
)),
}
.map_err(LabeledError::from)
.map(|pd| pd.set_metadata(metadata))
}
}
fn command_expr(
plugin: &PolarsPlugin,
engine: &EngineInterface,
call: &EvaluatedCall,
expr: NuExpression,
) -> Result<PipelineData, ShellError> {
let start = lit(call.req::<i64>(0)?);
let length: Expr = call
.get_flag::<i64>("length")?
.map(lit)
.unwrap_or(lit(Null {}));
let res: NuExpression = expr.into_polars().str().slice(start, length).into();
res.to_pipeline_data(plugin, engine, call.head)
}
fn command_df(
plugin: &PolarsPlugin,
engine: &EngineInterface,
call: &EvaluatedCall,
df: NuDataFrame,
) -> Result<PipelineData, ShellError> {
let start: i64 = call.req(0)?;
let start = Series::new("".into(), &[start]).into();
let length: Option<i64> = call.get_flag("length")?;
let length = match length {
Some(v) => Series::new("".into(), &[v as u64]),
None => Series::new_null("".into(), 1),
}
.into();
let series = df.as_series(call.head)?;
let chunked = series.str().map_err(|e| {
ShellError::Generic(
GenericError::new("Error casting to string", e.to_string(), call.head)
.with_help("The str-slice command can only be used with string columns"),
)
})?;
let res = chunked
.str_slice(&start, &length)
.map_err(|e| {
ShellError::Generic(GenericError::new(
"Dataframe Error",
e.to_string(),
call.head,
))
})?
.with_name(series.name().to_owned());
let df = NuDataFrame::try_from_series_vec(vec![res.into_series()], call.head)?;
df.to_pipeline_data(plugin, engine, call.head)
}
#[cfg(test)]
mod test {
use super::*;
use crate::test::test_polars_plugin_command;
#[test]
fn test_examples() -> Result<(), ShellError> {
test_polars_plugin_command(&StrSlice)
}
}