Add help system with `#[help]` macro and `HelpRequest` trait

6 files changed, 67 insertions, 0 deletions

diff --git a/mingling_core/src/asset.rs b/mingling_core/src/asset.rs
index a4254ef..234fec1 100644
--- a/mingling_core/src/asset.rs
+++ b/mingling_core/src/asset.rs
@@ -16,3 +16,6 @@ pub mod node;
 
 #[doc(hidden)]
 pub mod renderer;
+
+#[doc(hidden)]
+pub mod help;
diff --git a/mingling_core/src/asset/help.rs b/mingling_core/src/asset/help.rs
new file mode 100644
index 0000000..ff2b3d4
--- /dev/null
+++ b/mingling_core/src/asset/help.rs
@@ -0,0 +1,10 @@
+use crate::RenderResult;
+
+/// Handles help rendering for command-line arguments
+pub trait HelpRequest {
+    /// The entry type
+    type Entry;
+
+    /// Process the previous value and write the result into the provided [`RenderResult`](./struct.RenderResult.html)
+    fn render_help(p: Self::Entry, r: &mut RenderResult);
+}
diff --git a/mingling_core/src/lib.rs b/mingling_core/src/lib.rs
index 87be806..aee0df6 100644
--- a/mingling_core/src/lib.rs
+++ b/mingling_core/src/lib.rs
@@ -25,6 +25,7 @@ pub use crate::asset::chain::*;
 pub use crate::asset::comp::*;
 pub use crate::asset::dispatcher::*;
 pub use crate::asset::enum_tag::*;
+pub use crate::asset::help::*;
 pub use crate::asset::node::*;
 pub use crate::asset::renderer::*;
 
diff --git a/mingling_core/src/program.rs b/mingling_core/src/program.rs
index c9cffbe..949dd45 100644
--- a/mingling_core/src/program.rs
+++ b/mingling_core/src/program.rs
@@ -289,6 +289,9 @@ pub trait ProgramCollect {
     /// Render the input [AnyOutput](./struct.AnyOutput.html)
     fn render(any: AnyOutput<Self::Enum>, r: &mut RenderResult);
 
+    /// Render help for Entry
+    fn render_help(any: AnyOutput<Self::Enum>, r: &mut RenderResult);
+
     /// Find a matching chain to continue execution based on the input [AnyOutput](./struct.AnyOutput.html), returning a new [AnyOutput](./struct.AnyOutput.html)
     #[cfg(feature = "async")]
     fn do_chain(
diff --git a/mingling_core/src/program/exec.rs b/mingling_core/src/program/exec.rs
index c1eada5..469f6d2 100644
--- a/mingling_core/src/program/exec.rs
+++ b/mingling_core/src/program/exec.rs
@@ -16,6 +16,11 @@ where
     let mut current = dispatch_args_dynamic(program, program.args.clone())?;
     let mut stop_next = false;
 
+    // If the program has Help enabled, skip actual logic and jump to Help
+    if program.user_context.help {
+        return Ok(render_help::<C>(program, current));
+    }
+
     loop {
         let final_exec = stop_next;
 
@@ -56,6 +61,11 @@ where
     let mut current = dispatch_args_dynamic(program, program.args.clone())?;
     let mut stop_next = false;
 
+    // If the program has Help enabled, skip actual logic and jump to Help
+    if program.user_context.help {
+        return Ok(render_help::<C>(program, current));
+    }
+
     loop {
         let final_exec = stop_next;
 
@@ -179,3 +189,28 @@ fn render<C: ProgramCollect<Enum = C>>(program: &Program<C>, any: AnyOutput<C>)
         }
     }
 }
+
+#[inline(always)]
+#[allow(unused_variables)]
+fn render_help<C: ProgramCollect<Enum = C>>(
+    program: &Program<C>,
+    entry: AnyOutput<C>,
+) -> RenderResult {
+    #[cfg(not(feature = "general_renderer"))]
+    {
+        let mut render_result = RenderResult::default();
+        C::render_help(entry, &mut render_result);
+        render_result
+    }
+    #[cfg(feature = "general_renderer")]
+    {
+        match program.general_renderer_name {
+            super::GeneralRendererSetting::Disable => {
+                let mut render_result = RenderResult::default();
+                C::render_help(entry, &mut render_result);
+                render_result
+            }
+            _ => RenderResult::default(),
+        }
+    }
+}
diff --git a/mingling_core/src/renderer/render_result.rs b/mingling_core/src/renderer/render_result.rs
index d9da7b7..3bde1ab 100644
--- a/mingling_core/src/renderer/render_result.rs
+++ b/mingling_core/src/renderer/render_result.rs
@@ -1,5 +1,6 @@
 use std::{
     fmt::{Display, Formatter},
+    io::Write,
     ops::Deref,
 };
 
@@ -9,6 +10,20 @@ pub struct RenderResult {
     render_text: String,
 }
 
+impl Write for RenderResult {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        let s = std::str::from_utf8(buf).map_err(|_| {
+            std::io::Error::new(std::io::ErrorKind::InvalidInput, "not valid UTF-8")
+        })?;
+        self.render_text.push_str(s);
+        Ok(buf.len())
+    }
+
+    fn flush(&mut self) -> std::io::Result<()> {
+        Ok(())
+    }
+}
+
 impl Display for RenderResult {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         writeln!(f, "{}", self.render_text.trim())