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

#[derive(Clone)]
pub struct Default;

impl Command for Default {
    fn name(&self) -> &str {
        "default"
    }

    fn signature(&self) -> Signature {
        Signature::build("default")
            .required(
                "default value",
                SyntaxShape::Any,
                "the value to use as a default",
            )
            .optional("column name", SyntaxShape::String, "the name of the column")
            .category(Category::Filters)
    }

    fn usage(&self) -> &str {
        "Sets a default row's column if missing."
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
        default(engine_state, stack, call, input)
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Give a default 'target' column to all file entries",
                example: "ls -la | default 'nothing' target ",
                result: None,
            },
            Example {
                description:
                    "Get the env value of `MY_ENV` with a default value 'abc' if not present",
                example: "$env | get -i MY_ENV | default 'abc'",
                result: None, // Some(Value::test_string("abc")),
            },
            Example {
                description: "Default the `$nothing` value in a list",
                example: "[1, 2, $nothing, 4] | default 3",
                result: Some(Value::List {
                    vals: vec![
                        Value::test_int(1),
                        Value::test_int(2),
                        Value::test_int(3),
                        Value::test_int(4),
                    ],
                    span: Span::test_data(),
                }),
            },
        ]
    }
}

fn default(
    engine_state: &EngineState,
    stack: &mut Stack,
    call: &Call,
    input: PipelineData,
) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
    let value: Value = call.req(engine_state, stack, 0)?;
    let column: Option<Spanned<String>> = call.opt(engine_state, stack, 1)?;

    let ctrlc = engine_state.ctrlc.clone();

    if let Some(column) = column {
        input.map(
            move |item| match item {
                Value::Record {
                    mut cols,
                    mut vals,
                    span,
                } => {
                    let mut idx = 0;
                    let mut found = false;

                    while idx < cols.len() {
                        if cols[idx] == column.item {
                            found = true;
                            if matches!(vals[idx], Value::Nothing { .. }) {
                                vals[idx] = value.clone();
                            }
                        }
                        idx += 1;
                    }

                    if !found {
                        cols.push(column.item.clone());
                        vals.push(value.clone());
                    }

                    Value::Record { cols, vals, span }
                }
                _ => item,
            },
            ctrlc,
        )
    } else {
        input.map(
            move |item| match item {
                Value::Nothing { .. } => value.clone(),
                x => x,
            },
            ctrlc,
        )
    }
}

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

    #[test]
    fn test_examples() {
        use crate::test_examples;

        test_examples(Default {})
    }
}