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

use nu_engine::command_prelude::*;

#[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.
More information can be found here: https://docs.rs/encoding_rs/latest/encoding_rs/#utf-16le-utf-16be-and-unicode-encoding-schemes

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 --ignore-errors shift-jis"#,
                result: Some(Value::binary(
                    vec![0x26, 0x23, 0x31, 0x32, 0x37, 0x38, 0x38, 0x30, 0x3b],
                    Span::test_data(),
                )),
            },
        ]
    }

    fn is_const(&self) -> bool {
        true
    }

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

    fn run_const(
        &self,
        working_set: &StateWorkingSet,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        let encoding: Spanned<String> = call.req_const(working_set, 0)?;
        let ignore_errors = call.has_flag_const(working_set, "ignore-errors")?;
        run(call, input, encoding, ignore_errors)
    }
}

fn run(
    call: &Call,
    input: PipelineData,
    encoding: Spanned<String>,
    ignore_errors: bool,
) -> Result<PipelineData, ShellError> {
    let head = call.head;

    match input {
        PipelineData::ByteStream(stream, ..) => {
            let span = stream.span();
            let s = stream.into_string()?;
            super::encoding::encode(head, encoding, &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 {
            msg: "non-string input".into(),
            input: "value originates from here".into(),
            msg_span: head,
            input_span: input.span().unwrap_or(head),
        }),
    }
}

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

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