feat(wfassoc): add query_ext method and improve CLI output

- Implement query_ext method to check default program associations
- Enhance CLI query command with tabular output showing associations
- Refactor program building into Composition struct for better organization
- Update documentation comments for clarity

wfassoc/src/assoc.rs

@@ -98,8 +98,8 @@ impl From<&str> for ProgId {
 impl Display for ProgId {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            ProgId::Other(v) => v.fmt(f),
-            ProgId::Std(v) => v.fmt(f),
+            ProgId::Other(v) => write!(f, "{}", v),
+            ProgId::Std(v) => write!(f, "{}", v),
         }
     }
 }

wfassoc/src/lib.rs

@@ -9,6 +9,7 @@ pub mod utilities;
 pub mod wincmd;
 pub mod winreg_extra;
 
+use assoc::{Ext, ProgId};
 use indexmap::{IndexMap, IndexSet};
 use regex::Regex;
 use std::ffi::OsStr;
@@ -19,7 +20,6 @@ use winreg::RegKey;
 use winreg::enums::{
     HKEY_CLASSES_ROOT, HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE, KEY_READ, KEY_WRITE,
 };
-use assoc::{Ext, ProgId};
 
 // region: Error Types
 
@@ -327,7 +327,7 @@ impl Program {
 impl Program {
     const CLASSES: &str = "Software\\Classes";
 
-    /// Set the default "open with" of given extension to this program.
+    /// Set the default "open with" of given token associated extension to this program.
     pub fn link_ext(&self, ext: Token, scope: Scope) -> Result<()> {
         // Check privilege
         if !scope.has_privilege() {
@@ -357,10 +357,10 @@ impl Program {
         Ok(())
     }
 
-    /// Remove this program from the default "open with" of given extension.
+    /// Remove this program from the default "open with" of given token associated extension.
     ///
     /// If the default "open with" of given extension is not our program,
-    /// this function do nothing.
+    /// or there is no such file extension, this function do nothing.
     pub fn unlink_ext(&self, ext: Token, scope: Scope) -> Result<()> {
         // Check privilege
         if !scope.has_privilege() {
@@ -398,6 +398,44 @@ impl Program {
         // Okey
         Ok(())
     }
+
+    /// Query the default "open with" of given token associated extension.
+    ///
+    /// This function will return its associated ProgId if it is existing.
+    pub fn query_ext(&self, ext: Token, view: View) -> Result<Option<ProgId>> {
+        // Fetch file extension
+        let (ext, _) = match self.exts.get_index(ext) {
+            Some(v) => v,
+            None => return Err(Error::InvalidExtToken),
+        };
+
+        // Fetch root key and navigate to Classes
+        let hk = match view {
+            View::User => RegKey::predef(HKEY_CURRENT_USER),
+            View::System => RegKey::predef(HKEY_LOCAL_MACHINE),
+            View::Hybrid => RegKey::predef(HKEY_CLASSES_ROOT),
+        };
+        let classes = match view {
+            View::User | View::System => hk.open_subkey_with_flags(Self::CLASSES, KEY_READ)?,
+            View::Hybrid => hk.open_subkey_with_flags("", KEY_READ)?,
+        };
+
+        // Open key for this extension if possible
+        let rv =
+            match winreg_extra::try_open_subkey_with_flags(&classes, ext.to_string(), KEY_READ)? {
+                Some(subkey) => {
+                    // Try get associated ProgId if possible
+                    match winreg_extra::try_get_value::<String, _>(&subkey, "")? {
+                        Some(value) => Some(ProgId::from(value.as_str())),
+                        None => None,
+                    }
+                }
+                None => None,
+            };
+
+        // Okey
+        Ok(rv)
+    }
 }
 
 impl Program {
@@ -429,7 +467,7 @@ impl Program {
         ProgId::Std(assoc::StdProgId::new(
             &self.identifier,
             &utilities::capitalize_first_ascii(ext.inner()),
-            None
+            None,
         ))
     }
 }