fetcher 0.15.3

Data automation and pipelining framework
Documentation 
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/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

//! This module contains the [`Shorten`] transform

use super::TransformField;
use crate::actions::transforms::result::{OptionUnwrapTransformResultExt, TransformResult};

use std::{convert::Infallible, iter};

/// Shorten a field to [`len`](`Shorten::len`).
///
/// Makes the field completely empty if [`len`](`Shorten::len`) is 0,
/// or trims the field to [`len`](`Shorten::len`) characters and adds "..." to the end
#[derive(Debug)]
pub struct Shorten {
	/// The maximum length of the field string in characters
	pub len: usize,
}

impl TransformField for Shorten {
	type Err = Infallible;

	async fn transform_field(
		&mut self,
		value: Option<&str>,
	) -> Result<TransformResult<String>, Self::Err> {
		// len == 0 means we should unset the field. Same effect as Set with value: None here
		let new_val = if self.len == 0 {
			None
		} else if let Some(value) = value {
			// pass-through the value if it's shorter than max len
			if value.chars().count() < self.len {
				Some(value.to_owned())
			} else {
				// take self.len chars from value and append "..."
				Some(
					value
						.chars()
						.take(self.len)
						.chain(iter::repeat_n('.', 3))
						.collect::<String>(),
				)
			}
		} else {
			None
		};

		Ok(new_val.unwrap_or_empty())
	}
}