nushell/crates/nu-command/src/strings/encode_decode/encode.rs

use nu_engine::CallExt;
use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span, Spanned,
    SyntaxShape, Type, Value,
};

#[derive(Clone)]
pub struct Encode;

impl Command for Encode {
    fn name(&self) -> &str {
        "encode"
    }

    fn usage(&self) -> &str {
        // Note: "Encode a UTF-8 string into other forms" is semantically incorrect because
        // Nushell strings, as abstract values, have no user-facing encoding.
        // (Remember that "encoding" exclusively means "how the characters are
        // observably represented by bytes").
        "Encode a string into bytes."
    }

    fn search_terms(&self) -> Vec<&str> {
        vec!["text", "encoding", "decoding"]
    }

    fn signature(&self) -> nu_protocol::Signature {
        Signature::build("encode")
            .input_output_types(vec![(Type::String, Type::Binary)])
            .required("encoding", SyntaxShape::String, "the text encoding to use")
            .switch(
                "ignore-errors",
                "when a character isn't in the given encoding, replace with a HTML entity (like `&#127880;`)",
                Some('i'),
            )
            .category(Category::Strings)
    }

    fn extra_usage(&self) -> &str {
        r#"Multiple encodings are supported; here are a few:
big5, euc-jp, euc-kr, gbk, iso-8859-1, cp1252, latin5

Note that since the Encoding Standard doesn't specify encoders for utf-16le and utf-16be, these are not yet supported.

For a more complete list of encodings, please refer to the encoding_rs
documentation link at https://docs.rs/encoding_rs/latest/encoding_rs/#statics"#
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Encode an UTF-8 string into Shift-JIS",
                example: r#""負けると知って戦うのが、遥かに美しいのだ" | encode shift-jis"#,
                result: Some(Value::binary(
                    vec![
                        0x95, 0x89, 0x82, 0xaf, 0x82, 0xe9, 0x82, 0xc6, 0x92, 0x6d, 0x82, 0xc1,
                        0x82, 0xc4, 0x90, 0xed, 0x82, 0xa4, 0x82, 0xcc, 0x82, 0xaa, 0x81, 0x41,
                        0x97, 0x79, 0x82, 0xa9, 0x82, 0xc9, 0x94, 0xfc, 0x82, 0xb5, 0x82, 0xa2,
                        0x82, 0xcc, 0x82, 0xbe,
                    ],
                    Span::test_data(),
                )),
            },
            Example {
                description: "Replace characters with HTML entities if they can't be encoded",
                example: r#""🎈" | encode -i shift-jis"#,
                result: Some(Value::binary(
                    vec![0x26, 0x23, 0x31, 0x32, 0x37, 0x38, 0x38, 0x30, 0x3b],
                    Span::test_data(),
                )),
            },
        ]
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        let head = call.head;
        let encoding: Spanned<String> = call.req(engine_state, stack, 0)?;
        let ignore_errors = call.has_flag("ignore-errors");

        match input {
            PipelineData::ExternalStream { stdout: None, .. } => Ok(PipelineData::empty()),
            PipelineData::ExternalStream {
                stdout: Some(stream),
                ..
            } => {
                let s = stream.into_string()?;
                super::encoding::encode(head, encoding, &s.item, s.span, ignore_errors)
                    .map(|val| val.into_pipeline_data())
            }
            PipelineData::Value(v, ..) => {
                let span = v.span();
                match v {
                    Value::String { val: s, .. } => {
                        super::encoding::encode(head, encoding, &s, span, ignore_errors)
                            .map(|val| val.into_pipeline_data())
                    }
                    Value::Error { error, .. } => Err(*error),
                    _ => Err(ShellError::OnlySupportsThisInputType {
                        exp_input_type: "string".into(),
                        wrong_type: v.get_type().to_string(),
                        dst_span: head,
                        src_span: v.span(),
                    }),
                }
            }
            // This should be more precise, but due to difficulties in getting spans
            // from PipelineData::ListStream, this is as it is.
            _ => Err(ShellError::UnsupportedInput(
                "non-string input".into(),
                "value originates from here".into(),
                head,
                input.span().unwrap_or(head),
            )),
        }
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn test_examples() {
        crate::test_examples(Encode)
    }
}