feat: add guts for handling outputs and rendering them

src/lib.rs

@@ -0,0 +1,58 @@
+mod cli;
+mod output;
+
+use clap::{Parser, error::ErrorKind};
+use cli::Cli;
+
+use output::render_error;
+
+#[derive(Debug, PartialEq)]
+pub struct CliError {
+  pub code: i32,
+  pub message: String,
+}
+
+impl CliError {
+  pub fn info(message: impl Into<String>) -> Self {
+    Self {
+      code: 0,
+      message: message.into(),
+    }
+  }
+
+  pub fn runtime(message: impl Into<String>) -> Self {
+    Self {
+      code: 1,
+      message: message.into(),
+    }
+  }
+
+  pub fn usage(message: impl Into<String>) -> Self {
+    Self {
+      code: 2,
+      message: message.into(),
+    }
+  }
+}
+
+pub type CliResult<T> = Result<T, CliError>;
+
+pub async fn run(_cli: Cli) -> CliResult<()> {
+  Ok(())
+}
+
+pub fn parse_cli_from<I, T>(args: I) -> CliResult<Cli>
+where
+  I: IntoIterator<Item = T>,
+  T: Into<std::ffi::OsString> + Clone,
+{
+  Cli::try_parse_from(args).map_err(|e| match e.kind() {
+    ErrorKind::DisplayHelp | ErrorKind::DisplayVersion => CliError::info(e.to_string()),
+    _ => CliError::usage(e.to_string()),
+  })
+}
+
+pub fn render_cli_error(err: &CliError, pretty: bool) -> String {
+  render_error(err, pretty)
+    .unwrap_or_else(|_| "{\"error\":{\"code\":1,\"message\":\"Unexpected error.\"}}".to_string())
+}

src/output.rs

@@ -0,0 +1,33 @@
+use serde::Serialize;
+
+use crate::{CliError, CliResult};
+
+#[derive(Debug, Serialize)]
+struct ErrorBody<'a> {
+  pub code: i32,
+  pub message: &'a str,
+}
+
+#[derive(Debug, Serialize)]
+struct ErrorEnvelope<'a> {
+  pub error: ErrorBody<'a>,
+}
+
+pub fn render_json<T: Serialize>(value: &T, pretty: bool) -> CliResult<String> {
+  if pretty {
+    serde_json::to_string_pretty(value).map_err(|_| CliError::runtime("Failed to serialize output"))
+  } else {
+    serde_json::to_string(value).map_err(|_| CliError::runtime("Failed to serialize output"))
+  }
+}
+
+pub fn render_error(err: &CliError, pretty: bool) -> CliResult<String> {
+  let envelope = ErrorEnvelope {
+    error: ErrorBody {
+      code: err.code,
+      message: &err.message,
+    },
+  };
+
+  render_json(&envelope, pretty)
+}