cli/show: add possibility to choose a task by idx

Closes #26

src/cli/show.rs

@@ -25,10 +25,10 @@ pub struct Args {
     #[clap(short, long)]
     clip: bool,
 
-    part: Option<PrintPart>,
+    rest: Vec<String>,
 }
 
-#[derive(clap::ValueEnum, Clone)]
+#[derive(Clone, clap::ValueEnum)]
 enum PrintPart {
     Project,
     DirPath,
@@ -49,17 +49,61 @@ impl std::str::FromStr for PrintPart {
 }
 
 pub fn execute(repo: impl Repository, args: Args) {
-    let task = match repo.get_current_task_opt() {
-        Ok(None) => {
-            return eprintln!("You don't have an active task.");
+    let (idx, part) = match args.rest.len() {
+        0 => (None, None),
+        1 => {
+            let first = args.rest.first().unwrap();
+            match first.parse::<usize>() {
+                Ok(idx) => (Some(idx), None),
+                Err(idx_err) => match first.parse::<PrintPart>() {
+                    Ok(part) => (None, Some(part)),
+                    Err(part_err) => {
+                        return eprint!(
+                            r#"error: Invalid value "{}": {}; {}"#,
+                            first, idx_err, part_err
+                        )
+                    }
+                },
+            }
         }
-        Ok(Some(CurrentTaskInfo { task, .. })) => task,
-        Err(err) => {
-            return eprintln!("Cannot read current task: {}", err);
+        2 => {
+            let mut rest = args.rest.iter();
+            let first = rest.next().unwrap();
+            let second = rest.next().unwrap();
+
+            let idx = match first.parse::<usize>() {
+                Ok(idx) => Some(idx),
+                Err(err) => return eprint!(r#"error: Invalid value "{}": {}"#, first, err),
+            };
+            let part = match second.parse::<PrintPart>() {
+                Ok(part) => Some(part),
+                Err(err) => return eprint!(r#"error: Invalid value "{}": {}"#, second, err),
+            };
+
+            (idx, part)
+        }
+        _ => return eprintln!("error: To much arguments: {}", args.rest.join(",")),
+    };
+
+    let task = if let Some(idx) = idx {
+        match repo.get_task_opt(idx) {
+            Ok(Some(task)) => task,
+            Ok(None) => return eprintln!("The task not found"),
+            Err(err) => return eprintln!("Cannot get the task: {}", err),
+        }
+    } else {
+        match repo.get_current_task_opt() {
+            Ok(None) => {
+                return eprintln!("You don't have an active task.");
+            }
+            Ok(Some(CurrentTaskInfo { task, .. })) => task,
+            Err(err) => {
+                return eprintln!("Cannot read current task: {}", err);
+            }
         }
     };
 
-    match args.part {
+    match part {
         None => {
             if args.clip {
                 eprintln!("[WARNING]: You don't provide part. --clip option will ignore.");