Add ability to extract headers from first row

crates/nu-cli/src/commands/headers.rs

@@ -1,9 +1,12 @@
 use crate::commands::WholeStreamCommand;
+use indexmap::IndexMap;
 use crate::context::CommandRegistry;
 use crate::prelude::*;
 use futures::stream::StreamExt;
 use nu_errors::ShellError;
 use nu_protocol::{ReturnSuccess, Signature, UntaggedValue, Value};
+use std::fs::File;
+use std::io::Write;
 
 pub struct Headers;
 #[derive(Deserialize)]
@@ -27,13 +30,37 @@ impl WholeStreamCommand for Headers {
         args.process(registry, count)?.run()
     }
 }
+
+//Rows is an array of dictionaries. Each dictionary maps header to content for that row.
+//Take the first row and extract all content and save them as headers.
+//Take the rest of the rows and replace the old column names with the new headers.
+
 pub fn count(
     HeadersArgs {}: HeadersArgs,
     RunnableContext { input, name, .. }: RunnableContext,
 ) -> Result<OutputStream, ShellError> {
+
+
     let stream = async_stream! {
         let rows: Vec<Value> = input.values.collect().await;
 
+        let mut entries = IndexMap::new();
+        let headers: Value = rows[0].clone();
+        match &headers.value {
+            UntaggedValue::Row(d) => {
+                entries = d.entries.clone();
+                ()
+            }
+            _ => ()
+        }
+        let mut heads = vec![];
+        for (k, v) in entries.iter() {
+            heads.push(v.as_string().unwrap());
+        }
+
+        let mut file =  File::create("headout").unwrap();
+        write!(file, "args: {:#?}", heads);
+
         yield ReturnSuccess::value(UntaggedValue::int(rows.len()).into_value(name))
     };