query-forge 0.5.0

use std::io::Write as _;

use serde_json::json;

use crate::cli::MetadataFormat;

/// Metadata about a single input table loaded during query execution.
pub(crate) struct InputTableMeta {
    pub(crate) table_name: String,
    pub(crate) source_path: String,
    pub(crate) source_selector: Option<String>,
}

/// Metadata collected after running a query.
pub(crate) struct QueryMetadata {
    pub(crate) row_count: usize,
    pub(crate) columns: Vec<String>,
    pub(crate) input_tables: Vec<InputTableMeta>,
    pub(crate) execution_time_ms: u128,
}

/// Write query metadata to stderr in the requested format.
pub(crate) fn write_query_metadata(meta: &QueryMetadata, format: Option<&MetadataFormat>) {
    let rendered = match format {
        Some(MetadataFormat::Json) => render_meta_json(meta),
        _ => render_meta_text(meta),
    };
    let stderr = std::io::stderr();
    let mut handle = stderr.lock();
    let _ = writeln!(handle, "{rendered}");
}

fn render_meta_text(meta: &QueryMetadata) -> String {
    let mut out = String::new();

    out.push_str(&format!("rows:     {}\n", meta.row_count));
    out.push_str(&format!(
        "columns:  {}\n",
        if meta.columns.is_empty() {
            "-".to_owned()
        } else {
            meta.columns.join(", ")
        }
    ));

    let w_table = meta
        .input_tables
        .iter()
        .map(|t| t.table_name.len())
        .max()
        .unwrap_or(0)
        .max("table".len());
    let w_source = meta
        .input_tables
        .iter()
        .map(|t| t.source_path.len())
        .max()
        .unwrap_or(0)
        .max("source".len());

    for (i, t) in meta.input_tables.iter().enumerate() {
        let label = if i == 0 { "tables:   " } else { "          " };
        out.push_str(&format!(
            "{}{:<w_table$}  {:<w_source$}  {}\n",
            label,
            t.table_name,
            t.source_path,
            t.source_selector.as_deref().unwrap_or("-"),
        ));
    }
    if meta.input_tables.is_empty() {
        out.push_str("tables:   -\n");
    }

    out.push_str(&format!("time:     {}ms", meta.execution_time_ms));

    out
}

fn render_meta_json(meta: &QueryMetadata) -> String {
    let value = json!({
        "row_count": meta.row_count,
        "columns": meta.columns,
        "input_tables": meta.input_tables.iter().map(|t| json!({
            "table_name": t.table_name,
            "source_path": t.source_path,
            "source_selector": t.source_selector,
        })).collect::<Vec<_>>(),
        "execution_time_ms": meta.execution_time_ms,
    });
    serde_json::to_string_pretty(&value).unwrap_or_else(|_| "{}".to_owned())
}

#[cfg(test)]
mod tests {
    fn make_meta() -> super::QueryMetadata {
        super::QueryMetadata {
            row_count: 3,
            columns: vec!["id".to_owned(), "name".to_owned()],
            input_tables: vec![
                super::InputTableMeta {
                    table_name: "table".to_owned(),
                    source_path: "./data.csv".to_owned(),
                    source_selector: None,
                },
                super::InputTableMeta {
                    table_name: "sales".to_owned(),
                    source_path: "./sales.xlsx".to_owned(),
                    source_selector: Some("Q1".to_owned()),
                },
            ],
            execution_time_ms: 42,
        }
    }

    #[test]
    fn meta_text_contains_row_count_and_columns() {
        let meta = make_meta();
        let rendered = super::render_meta_text(&meta);
        assert!(rendered.contains("rows:     3"), "missing row count: {rendered}");
        assert!(rendered.contains("id, name"), "missing columns: {rendered}");
        assert!(rendered.contains("42ms"), "missing timing: {rendered}");
    }

    #[test]
    fn meta_text_contains_input_tables() {
        let meta = make_meta();
        let rendered = super::render_meta_text(&meta);
        assert!(rendered.contains("table"), "missing table name: {rendered}");
        assert!(rendered.contains("./data.csv"), "missing source path: {rendered}");
        assert!(rendered.contains("sales"), "missing table name: {rendered}");
        assert!(rendered.contains("./sales.xlsx"), "missing source path: {rendered}");
        assert!(rendered.contains("Q1"), "missing selector: {rendered}");
    }

    #[test]
    fn meta_text_shows_dash_for_missing_selector() {
        let meta = make_meta();
        let rendered = super::render_meta_text(&meta);
        // The first table has no selector so a dash should appear.
        assert!(
            rendered.contains("  -\n") || rendered.contains("  -"),
            "missing dash for no selector: {rendered}"
        );
    }

    #[test]
    fn meta_json_is_valid_structure() {
        let meta = make_meta();
        let rendered = super::render_meta_json(&meta);

        // Ensure it parses as valid JSON.
        let parsed: serde_json::Value =
            serde_json::from_str(&rendered).expect("metadata JSON should be valid");

        assert_eq!(parsed["row_count"], 3);
        assert_eq!(parsed["execution_time_ms"], 42);
        assert_eq!(parsed["columns"][0], "id");
        assert_eq!(parsed["columns"][1], "name");
        assert_eq!(parsed["input_tables"][0]["table_name"], "table");
        assert_eq!(parsed["input_tables"][0]["source_selector"], serde_json::Value::Null);
        assert_eq!(parsed["input_tables"][1]["table_name"], "sales");
        assert_eq!(parsed["input_tables"][1]["source_selector"], "Q1");
    }
}