inspect: Print factory details of an element

Example:

 $ gst-inspect-rs videotestsrc

examples/Cargo.toml

@@ -35,6 +35,7 @@ derive_more = "0.99.5"
 futures = "0.3"
 byte-slice-cast = "1"
 cairo-rs = { git = "https://github.com/gtk-rs/gtk-rs-core", features=["use_glib"], optional = true }
+clap = { version = "4.3.0", features = ["derive"] }
 pango = { git = "https://github.com/gtk-rs/gtk-rs-core", optional = true }
 pangocairo = { git = "https://github.com/gtk-rs/gtk-rs-core", optional = true }
 glutin = { version = "0.29", optional = true }

examples/src/bin/gst-inspect.rs

@@ -19,11 +19,14 @@
 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 use ansi_term::Color;
+use clap::{Arg, Command};
 use gst::prelude::*;
 
 const BRBLUE: Color = Color::RGB(97, 127, 166);
 const PLUGIN_NAME_COLOR: Color = BRBLUE;
 const ELEMENT_NAME_COLOR: Color = Color::Green;
+const PROP_NAME_COLOR: Color = BRBLUE;
+const HEADING_COLOR: Color = Color::Yellow;
 
 fn print_element_list() {
     let registry = gst::Registry::get();
@@ -47,8 +50,64 @@ fn print_element_list() {
     }
 }
 
-fn main() {
-    gst::init().unwrap();
-
-    print_element_list();
+fn print_property(name: &str, value: &str) {
+    let formatted_name = format!("{:<25}", name);
+    println!(" {}{}", PROP_NAME_COLOR.paint(formatted_name), value);
+}
+
+fn print_factory_details_info(factory: &gst::ElementFactory) {
+    let rank = factory.rank();
+    println!("{}", HEADING_COLOR.paint("Factory details:"));
+    print_property("Rank", &format!("{} ({})", rank, i32::from(rank)));
+    print_property("Long name", factory.longname());
+    print_property("Klass", factory.klass());
+    print_property("Description", factory.description());
+    print_property("Author", factory.author());
+}
+
+fn print_element_info(feature: &gst::PluginFeature) -> Result<(), String> {
+    let Ok(factory) = feature.load() else {
+        return Err(format!("element factory '{}' couldn't be loaded", feature.name()));
+    };
+    let element_factory = factory.downcast_ref::<gst::ElementFactory>().unwrap();
+    let Ok(element) = element_factory.create_with_name(None) else {
+        return Err(format!(
+            "couldn't construct element '{}' for some reason",
+            feature.name()
+        ));
+    };
+
+    print_factory_details_info(element_factory);
+
+    Ok(())
+}
+
+fn print_feature_info(feature_name: &str) -> Result<(), String> {
+    let registry = gst::Registry::get();
+
+    let feature = registry.find_feature(feature_name, gst::ElementFactory::static_type());
+    let Some(feature) = feature else {
+        return Err(format!("No such element or plugin '{}'", feature_name));
+    };
+
+    print_element_info(&feature)
+}
+
+fn main() {
+    let matches = Command::new("prog")
+        .arg(Arg::new("ELEMENT-NAME | PLUGIN-NAME"))
+        .get_matches();
+    let mut st: i32 = 0;
+
+    gst::init().unwrap();
+    if let Some(fname) = matches.get_one::<String>("ELEMENT-NAME | PLUGIN-NAME") {
+        if let Err(e) = print_feature_info(fname) {
+            println!("{}", e);
+            st = -1;
+        }
+    } else {
+        print_element_list();
+    }
+
+    std::process::exit(st);
 }