Add prepend and append commands

src/commands/append.rs

@@ -0,0 +1,49 @@
+use crate::commands::WholeStreamCommand;
+use crate::errors::ShellError;
+use crate::parser::CommandRegistry;
+use crate::prelude::*;
+
+#[derive(Deserialize)]
+struct AppendArgs {
+    row: Tagged<Value>,
+}
+
+pub struct Append;
+
+impl WholeStreamCommand for Append {
+    fn name(&self) -> &str {
+        "append"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("append").required(
+            "row value",
+            SyntaxShape::Any,
+            "the value of the row to append to the table",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Append the given row to the table"
+    }
+
+    fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        args.process(registry, append)?.run()
+    }
+}
+
+fn append(
+    AppendArgs { row }: AppendArgs,
+    RunnableContext { input, .. }: RunnableContext,
+) -> Result<OutputStream, ShellError> {
+    let mut after: VecDeque<Tagged<Value>> = VecDeque::new();
+    after.push_back(row);
+
+    Ok(OutputStream::from_input(
+        input.values.chain(after),
+    ))
+}

src/commands/prepend.rs

@@ -0,0 +1,49 @@
+use crate::commands::WholeStreamCommand;
+use crate::errors::ShellError;
+use crate::parser::CommandRegistry;
+use crate::prelude::*;
+
+#[derive(Deserialize)]
+struct PrependArgs {
+    row: Tagged<Value>,
+}
+
+pub struct Prepend;
+
+impl WholeStreamCommand for Prepend {
+    fn name(&self) -> &str {
+        "prepend"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("prepend").required(
+            "row value",
+            SyntaxShape::Any,
+            "the value of the row to prepend to the table",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Prepend the given row to the front of the table"
+    }
+
+    fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        args.process(registry, prepend)?.run()
+    }
+}
+
+fn prepend(
+    PrependArgs { row }: PrependArgs,
+    RunnableContext { input, .. }: RunnableContext,
+) -> Result<OutputStream, ShellError> {
+    let mut prepend: VecDeque<Tagged<Value>> = VecDeque::new();
+    prepend.push_back(row);
+
+    Ok(OutputStream::from_input(
+        prepend.chain(input.values),
+    ))
+}