Add CLI interface for printing plugin documentation

This patch adds a CLI interface for printing the plugin documentation
using the new infrastructure for self-describing configuration objects.

Signed-off-by: Matthias Beyer <matthias.beyer@ifm.com>

4 files changed, 64 insertions, 3 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 36e0e83b..9379c13a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3437,6 +3437,7 @@ dependencies = [
  "tedge_api",
  "tedge_core",
  "tedge_lib",
+ "term_size",
  "termcolor",
  "termimad",
  "tokio",
@@ -3667,6 +3668,16 @@ dependencies = [
 ]
 
 [[package]]
+name = "term_size"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e4129646ca0ed8f45d09b929036bafad5377103edd06e50bf574b353d2b08d9"
+dependencies = [
+ "libc",
+ "winapi",
+]
+
+[[package]]
 name = "termcolor"
 version = "1.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/tedge/Cargo.toml b/tedge/Cargo.toml
index d2585fc7..d00b13bc 100644
--- a/tedge/Cargo.toml
+++ b/tedge/Cargo.toml
@@ -19,6 +19,7 @@ nu-ansi-term = "0.45.1"
 pretty = { version = "0.11.3", features = ["termcolor"] }
 termcolor = "1.1.3"
 termimad = "0.20.1"
+term_size = "0.3.2"
 
 tedge_api = { path = "../crates/core/tedge_api" }
 tedge_core = { path = "../crates/core/tedge_core" }
diff --git a/tedge/src/cli.rs b/tedge/src/cli.rs
index a8fd7235..b61308e6 100644
--- a/tedge/src/cli.rs
+++ b/tedge/src/cli.rs
@@ -30,4 +30,11 @@ pub(crate) enum CliCommand {
     /// Print the supported plugin kinds
     #[clap(name = "get-plugin-kinds")]
     GetPluginKinds,
+
+    /// Print the documentation of the configuration of the available plugins
+    #[clap(name = "doc")]
+    Doc {
+        /// Print the doc only for this plugin
+        plugin_name: Option<String>
+    },
 }
diff --git a/tedge/src/main.rs b/tedge/src/main.rs
index 95ec66b0..5bc0a41d 100644
--- a/tedge/src/main.rs
+++ b/tedge/src/main.rs
@@ -1,9 +1,11 @@
 use std::collections::HashMap;
 use std::collections::HashSet;
+use std::io::Write;
 
 use clap::Parser;
 use miette::IntoDiagnostic;
 
+use pretty::Arena;
 use tedge_api::PluginBuilder;
 use tedge_core::TedgeApplication;
 use tedge_core::TedgeApplicationBuilder;
@@ -22,7 +24,7 @@ mod logging;
 struct Registry {
     app_builder: TedgeApplicationBuilder,
     plugin_kinds: HashSet<String>,
-    doc_printers: HashMap<String, Box<dyn FnOnce()>>,
+    doc_printers: HashMap<String, Box<dyn FnOnce() -> Result<(), miette::Error>>>,
 }
 
 macro_rules! register_plugin {
@@ -36,6 +38,29 @@ macro_rules! register_plugin {
                     miette::bail!("Plugin kind '{}' was already registered, cannot register!", kind_name)
                 }
 
+                let kind_name_str = kind_name.to_string();
+                registry.doc_printers.insert(kind_name.to_string(), Box::new(move || {
+                    let mut stdout = std::io::stdout();
+                    if let Some(config_desc) = <$pluginbuilder as PluginBuilder<tedge_core::PluginDirectory>>::kind_configuration() {
+                        let terminal_width = term_size::dimensions().map(|(w, _)| w).unwrap_or(80);
+                        let arena = Arena::new();
+
+                        let rendered_doc = crate::config::as_terminal_doc(&config_desc, &arena);
+
+                        let mut output = String::new();
+                        rendered_doc.render_fmt(terminal_width, &mut output).into_diagnostic()?;
+
+                        writeln!(stdout, " ----- Documentation for {}", kind_name_str)
+                                .into_diagnostic()?;
+
+                        writeln!(stdout, "{}", output).into_diagnostic()?;
+                    } else {
+                        writeln!(stdout, " Documentation for {} is unavailable", kind_name)
+                            .into_diagnostic()?;
+                    }
+                    Ok(())
+                }));
+
                 Registry {
                     app_builder: registry.app_builder.with_plugin_builder($pbinstance)?,
                     plugin_kinds: registry.plugin_kinds,
@@ -68,7 +93,6 @@ async fn main() -> miette::Result<()> {
     };
     info!("Building application");
 
-
     let registry = {
         cfg_table::cfg_table! {
             [not(feature = "mqtt")] => register_plugin!(
@@ -138,7 +162,8 @@ async fn main() -> miette::Result<()> {
 
     match args.command {
         cli::CliCommand::Run { config } => {
-            let (cancel_sender, application) = registry.app_builder.with_config_from_path(config).await?;
+            let (cancel_sender, application) =
+                registry.app_builder.with_config_from_path(config).await?;
             info!("Application built");
 
             debug!("Verifying the configuration");
@@ -165,6 +190,23 @@ async fn main() -> miette::Result<()> {
             }
             Ok(())
         }
+        cli::CliCommand::Doc { plugin_name } => {
+            let mut registry = registry;
+            if let Some(plugin_name) = plugin_name {
+                let printer = registry
+                    .doc_printers
+                    .remove(&plugin_name)
+                    .ok_or_else(|| miette::miette!("Plugin named '{}' not found", plugin_name))?;
+
+                (printer)()?;
+            } else {
+                for printer in registry.doc_printers.into_values() {
+                    printer()?;
+                }
+            }
+
+            Ok(())
+        }
     }
 }