vrl 0.32.0

use crate::{compiler::prelude::*, stdlib::csv_utils::parse_single_byte_delimiter};
use csv::ReaderBuilder;
use std::sync::LazyLock;

static DEFAULT_DELIMITER: LazyLock<Value> = LazyLock::new(|| Value::Bytes(Bytes::from(",")));

static PARAMETERS: LazyLock<Vec<Parameter>> = LazyLock::new(|| {
    vec![
        Parameter::required("value", kind::BYTES, "The string to parse."),
        Parameter::optional(
            "delimiter",
            kind::BYTES,
            "The field delimiter to use when parsing. Must be a single-byte UTF-8 character.",
        )
        .default(&DEFAULT_DELIMITER),
    ]
});

fn parse_csv(csv_string: Value, delimiter: Value) -> Resolved {
    let csv_string = csv_string.try_bytes()?;
    let delimiter = parse_single_byte_delimiter(delimiter)?;

    let reader = ReaderBuilder::new()
        .has_headers(false)
        .delimiter(delimiter)
        .from_reader(&*csv_string);
    reader
        .into_byte_records()
        .next()
        .transpose()
        .map_err(|err| format!("invalid csv record: {err}").into()) // shouldn't really happen
        .map(|record| {
            record
                .map(|record| {
                    record
                        .iter()
                        .map(|x| Bytes::copy_from_slice(x).into())
                        .collect::<Vec<Value>>()
                })
                .unwrap_or_default()
                .into()
        })
}

#[derive(Clone, Copy, Debug)]
pub struct ParseCsv;

impl Function for ParseCsv {
    fn identifier(&self) -> &'static str {
        "parse_csv"
    }

    fn usage(&self) -> &'static str {
        "Parses a single CSV formatted row. Only the first row is parsed in case of multiline input value."
    }

    fn category(&self) -> &'static str {
        Category::Parse.as_ref()
    }

    fn internal_failure_reasons(&self) -> &'static [&'static str] {
        &[
            "The delimiter must be a single-byte UTF-8 character.",
            "`value` is not a valid CSV string.",
        ]
    }

    fn return_kind(&self) -> u16 {
        kind::ARRAY
    }

    fn notices(&self) -> &'static [&'static str] {
        &[indoc! {"
            All values are returned as strings. We recommend manually coercing values to desired
            types as you see fit.
        "}]
    }

    fn examples(&self) -> &'static [Example] {
        &[
            example! {
                title: "Parse a single CSV formatted row",
                source: r#"parse_csv!(s'foo,bar,"foo "", bar"')"#,
                result: Ok(r#"["foo", "bar", "foo \", bar"]"#),
            },
            example! {
                title: "Parse a single CSV formatted row with custom delimiter",
                source: r#"parse_csv!("foo bar", delimiter: " ")"#,
                result: Ok(r#"["foo", "bar"]"#),
            },
        ]
    }

    fn compile(
        &self,
        _state: &state::TypeState,
        _ctx: &mut FunctionCompileContext,
        arguments: ArgumentList,
    ) -> Compiled {
        let value = arguments.required("value");
        let delimiter = arguments.optional("delimiter");
        Ok(ParseCsvFn { value, delimiter }.as_expr())
    }

    fn parameters(&self) -> &'static [Parameter] {
        PARAMETERS.as_slice()
    }
}

#[derive(Debug, Clone)]
struct ParseCsvFn {
    value: Box<dyn Expression>,
    delimiter: Option<Box<dyn Expression>>,
}

impl FunctionExpression for ParseCsvFn {
    fn resolve(&self, ctx: &mut Context) -> Resolved {
        let csv_string = self.value.resolve(ctx)?;
        let delimiter = self
            .delimiter
            .map_resolve_with_default(ctx, || DEFAULT_DELIMITER.clone())?;

        parse_csv(csv_string, delimiter)
    }

    fn type_def(&self, _: &state::TypeState) -> TypeDef {
        TypeDef::array(inner_kind()).fallible()
    }
}

#[inline]
fn inner_kind() -> Collection<Index> {
    let mut v = Collection::any();
    v.set_unknown(Kind::bytes());
    v
}

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

    test_function![
        parse_csv => ParseCsv;

        valid {
            args: func_args![value: value!("foo,bar,\"foo \"\", bar\"")],
            want: Ok(value!(["foo", "bar", "foo \", bar"])),
            tdef: TypeDef::array(inner_kind()).fallible(),
        }

        invalid_utf8 {
            args: func_args![value: value!(Bytes::copy_from_slice(&b"foo,b\xFFar"[..]))],
            want: Ok(value!(vec!["foo".into(), value!(Bytes::copy_from_slice(&b"b\xFFar"[..]))])),
            tdef: TypeDef::array(inner_kind()).fallible(),
        }

        custom_delimiter {
            args: func_args![value: value!("foo bar"), delimiter: value!(" ")],
            want: Ok(value!(["foo", "bar"])),
            tdef: TypeDef::array(inner_kind()).fallible(),
        }

        invalid_delimiter {
            args: func_args![value: value!("foo bar"), delimiter: value!(",,")],
            want: Err("delimiter must be a single character"),
            tdef: TypeDef::array(inner_kind()).fallible(),
        }

        single_value {
            args: func_args![value: value!("foo")],
            want: Ok(value!(["foo"])),
            tdef: TypeDef::array(inner_kind()).fallible(),
        }

        empty_string {
            args: func_args![value: value!("")],
            want: Ok(value!([])),
            tdef: TypeDef::array(inner_kind()).fallible(),
        }

        multiple_lines {
            args: func_args![value: value!("first,line\nsecond,line,with,more,fields")],
            want: Ok(value!(["first", "line"])),
            tdef: TypeDef::array(inner_kind()).fallible(),
        }
    ];
}