flowstdlib 1.0.0

The standard library of functions and flows for 'flow' programs
Documentation 
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use serde_json::{json, Value};

use flowcore::errors::Result;
use flowcore::{RunAgain, RUN_AGAIN};
use flowmacro::flow_function;

#[flow_function]
fn inner_index(
    value: &Value,
    previous_value: &Value,
    previous_index: &Value,
    select_index: &Value,
) -> Result<(Option<Value>, RunAgain)> {
    let mut output_map = serde_json::Map::new();

    if let Some(prev_idx) = previous_index.as_i64() {
        let index = prev_idx + 1;

        // Always output the 'value" and its index
        output_map.insert("index".into(), json!(index));

        if let Some(sel_idx) = select_index.as_i64() {
            match sel_idx {
                // A 'select_index' value of -1 indicates to output the last value before the null
                -1 if value.is_null() => {
                    output_map.insert("selected_value".into(), previous_value.clone());
                }
                // If 'select_value' is not -1 then see if it matches the current index
                _ if sel_idx == index => {
                    output_map.insert("selected_value".into(), value.clone());
                }
                _ => {}
            }
        }
    }

    Ok((Some(Value::Object(output_map)), RUN_AGAIN))
}

#[cfg(test)]
#[allow(clippy::unwrap_used, clippy::expect_used)]
mod test {
    use serde_json::{json, Value};

    use super::inner_index;

    #[test]
    fn select_index_0() {
        let value = json!(42);
        let previous_value = Value::Null;
        let previous_index = json!(-1);
        let select_index = json!(0);

        let (result, _) = inner_index(&value, &previous_value, &previous_index, &select_index)
            .expect("_index() failed");

        let output_map = result.expect("No output map");

        assert_eq!(
            output_map
                .pointer("/selected_value")
                .expect("Could not select route"),
            &json!(42)
        );
    }

    #[test]
    fn not_select_index_0() {
        let value = json!(42);
        let previous_value = Value::Null;
        let previous_index = json!(1);
        let select_index = json!(1);

        let (result, _) = inner_index(&value, &previous_value, &previous_index, &select_index)
            .expect("_index() failed");

        let output_map = result.expect("No output map");

        assert_eq!(output_map.pointer("/selected_value"), None);
    }

    #[test]
    fn select_index_1() {
        let value = json!(42);
        let previous_value = Value::Null;
        let previous_index = json!(0);
        let select_index = json!(1);

        let (result, _) = inner_index(&value, &previous_value, &previous_index, &select_index)
            .expect("_index() failed");

        let output_map = result.expect("No output map");

        assert_eq!(
            output_map
                .pointer("/selected_value")
                .expect("Could not select route"),
            &json!(42)
        );
    }

    #[test]
    fn not_select_index_1() {
        let value = json!(42);
        let previous_value = Value::Null;
        let previous_index = json!(1);
        let select_index = json!(0);

        let (result, _) = inner_index(&value, &previous_value, &previous_index, &select_index)
            .expect("_index() failed");

        let output_map = result.expect("No output map");

        assert_eq!(output_map.pointer("/selected_value"), None);
    }

    #[test]
    fn select_last() {
        let value = Value::Null;
        let previous_value = json!(42);
        let previous_index = json!(7);
        let select_index = json!(-1);

        let (result, _) = inner_index(&value, &previous_value, &previous_index, &select_index)
            .expect("_index() failed");

        let output_map = result.expect("No output map");

        assert_eq!(
            output_map
                .pointer("/selected_value")
                .expect("Could not select route"),
            &json!(42)
        );
    }

    #[test]
    fn not_select_last() {
        let value = json!(43);
        let previous_value = json!(42);
        let previous_index = json!(7);
        let select_index = json!(-1);

        let (result, _) = inner_index(&value, &previous_value, &previous_index, &select_index)
            .expect("_index() failed");

        let output_map = result.expect("No output map");

        assert_eq!(output_map.pointer("/selected_value"), None);
    }
}