split into individual modules

Cargo.lock

@@ -168,6 +168,12 @@ dependencies = [
  "litrs",
 ]
 
+[[package]]
+name = "equivalent"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "877a4ace8713b0bcf2a4e7eec82529c029f1d0619886d18145fea96c3ffe5c0f"
+
 [[package]]
 name = "errno"
 version = "0.3.14"
@@ -178,12 +184,28 @@ dependencies = [
  "windows-sys 0.60.2",
 ]
 
+[[package]]
+name = "hashbrown"
+version = "0.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5419bdc4f6a9207fbeba6d11b604d481addf78ecd10c11ad51e76c2f6482748d"
+
 [[package]]
 name = "heck"
 version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2304e00983f87ffb38b55b444b5e3b60a884b5d30c0fca7d82fe33449bbe55ea"
 
+[[package]]
+name = "indexmap"
+version = "2.11.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4b0f83760fb341a774ed326568e19f5a863af4a952def8c39f9ab92fd95b88e5"
+dependencies = [
+ "equivalent",
+ "hashbrown",
+]
+
 [[package]]
 name = "is_terminal_polyfill"
 version = "1.70.1"
@@ -495,6 +517,7 @@ dependencies = [
 name = "wfassoc"
 version = "0.1.0"
 dependencies = [
+ "indexmap",
  "regex",
  "thiserror",
  "uuid",

README.md

@@ -6,6 +6,23 @@
 
 ## Introduction
 
-* wfassoc: Core Rust library. Rust programmer can directly utilize it.
+* `wfassoc`: Core Rust library. Rust programmer can directly utilize it.
-* wfassoc_dylib: A dynamic library exposed for C/C++ and other languages users.
+* `wfassoc_dylib`: A dynamic library exposed for C/C++ and other languages users.
-* wfassoc_exec: A executable configuring file assocation according to user given profile and request.
+* `wfassoc_exec`: A executable configuring file assocation according to user given profile and request.
+
+If you are a programmer who just want to silently set your file association for user, 
+`wfassoc_exec` would be your best choice.
+The only things you need to do is that write a TOML description file,
+and provide it and `wfassoc_exec` with your executable.
+By executing `wfassoc_exec` with this TOML file in your executable,
+you can simply achieve this goal and analyze its return value to check whether it success.
+
+However, if you are prefering taht let user decide which file associations should be created,
+even have an UI displaying all current file association related with this program (like 7-Zip File Manager does),
+you can choose `wfassoc_dylib` for your solution.
+`wfassoc_dylib` expose all essential functions for this task.
+And you can build it with your own program.
+
+At last, if all scenarios above can not cover your requirements,
+you can utilize `wfassoc` directly in Rust, change all essential code in your favor,
+and finally produce the application which onlt suit for yourself.

example/ppic.toml

@@ -0,0 +1,25 @@
+identifier = "PineapplePicture"
+path = 'C:\path\to\ppic.exe'
+clsid = "{B5291320-FE7C-4069-BF87-A0AC327FCD20}"
+
+[manners]
+common = '"C:\path\to\ppic.exe" "%1"'
+
+[exts]
+".jpg" = "common"
+".jfif" = "common"
+".gif" = "common"
+".bmp" = "common"
+".png" = "common"
+".ico" = "common"
+".jpeg" = "common"
+".tif" = "common"
+".tiff" = "common"
+".webp" = "common"
+".svg" = "common"
+".kra" = "common"
+".xcf" = "common"
+".avif" = "common"
+".qoi" = "common"
+".apng" = "common"
+".exr" = "common"

wfassoc/Cargo.toml

@@ -8,7 +8,8 @@ license = "SPDX:MIT"
 
 [dependencies]
 thiserror = { workspace = true }
-windows-sys = { version = "0.60.2", features = ["Win32_Security", "Win32_System_SystemServices"] }
+windows-sys = { version = "0.60.2", features = ["Win32_Security", "Win32_System_SystemServices", "Win32_UI_Shell"] }
 winreg = { version = "0.55.0", features = ["transactions"] }
+indexmap = "2.11.4"
 regex = "1.11.3"
 uuid = "1.18.1"

wfassoc/src/assoc.rs

@@ -0,0 +1,283 @@
+//! The module including all struct representing Windows file association concept,
+//! like file extension, ProgId, CLSID and etc.
+
+use regex::Regex;
+use std::fmt::Display;
+use std::str::FromStr;
+use std::sync::LazyLock;
+use thiserror::Error as TeError;
+use uuid::Uuid;
+
+// region: File Extension
+
+/// The struct representing an file extension which must start with dot (`.`)
+/// and followed by at least one arbitrary characters.
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Ext {
+    /// The body of file extension (excluding dot).
+    body: String,
+}
+
+impl Ext {
+    /// Create an new file extension.
+    pub fn new(raw: &str) -> Result<Self, ParseExtError> {
+        Self::from_str(raw)
+    }
+
+    /// Get the body part of file extension (excluding dot)
+    pub fn inner(&self) -> &str {
+        &self.body
+    }
+}
+
+/// The error occurs when try parsing string into FileExt.
+#[derive(Debug, TeError)]
+#[error("given file extension name \"{inner}\" is invalid")]
+pub struct ParseExtError {
+    inner: String,
+}
+
+impl ParseExtError {
+    fn new(inner: &str) -> Self {
+        Self {
+            inner: inner.to_string(),
+        }
+    }
+}
+
+impl Display for Ext {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, ".{}", self.body)
+    }
+}
+
+impl FromStr for Ext {
+    type Err = ParseExtError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        static RE: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"^\.([^\.]+)$").unwrap());
+        match RE.captures(s) {
+            Some(v) => Ok(Self {
+                body: v[1].to_string(),
+            }),
+            None => Err(ParseExtError::new(s)),
+        }
+    }
+}
+
+// endregion
+
+// region: Programmatic Identifiers (ProgId)
+
+/// The struct representing Programmatic Identifiers (ProgId).
+///
+/// Because there is optional part in standard ProgId, and not all software developers
+/// are willing to following Microsoft suggestions, there is no strict constaint for ProgId.
+/// So this struct is actually an enum which holding any possible ProgId format.
+///
+/// Reference:
+/// - https://learn.microsoft.com/en-us/windows/win32/shell/fa-progids
+/// - https://learn.microsoft.com/en-us/windows/win32/com/-progid--key
+pub enum ProgId {
+    Plain(String),
+    Loose(LosseProgId),
+    Strict(StrictProgId),
+}
+
+impl From<&str> for ProgId {
+    fn from(s: &str) -> Self {
+        // match it for strict ProgId first
+        if let Ok(v) = StrictProgId::from_str(s) {
+            return Self::Strict(v);
+        }
+        // then match for loose ProgId
+        if let Ok(v) = LosseProgId::from_str(s) {
+            return Self::Loose(v);
+        }
+        // fallback with plain
+        Self::Plain(s.to_string())
+    }
+}
+
+impl Display for ProgId {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ProgId::Plain(v) => v.fmt(f),
+            ProgId::Loose(v) => v.fmt(f),
+            ProgId::Strict(v) => v.fmt(f),
+        }
+    }
+}
+
+/// The error occurs when parsing ProgId.
+#[derive(Debug, TeError)]
+#[error("given ProgId \"{inner}\" is invalid")]
+pub struct ParseProgIdError {
+    inner: String,
+}
+
+impl ParseProgIdError {
+    fn new(s: &str) -> Self {
+        Self {
+            inner: s.to_string(),
+        }
+    }
+}
+
+/// The ProgId similar with strict ProgId, but no version part.
+pub struct LosseProgId {
+    vendor: String,
+    component: String,
+}
+
+impl LosseProgId {
+    pub fn new(vendor: &str, component: &str) -> Self {
+        Self {
+            vendor: vendor.to_string(),
+            component: component.to_string(),
+        }
+    }
+
+    pub fn get_vendor(&self) -> &str {
+        &self.vendor
+    }
+
+    pub fn get_component(&self) -> &str {
+        &self.component
+    }
+}
+
+impl FromStr for LosseProgId {
+    type Err = ParseProgIdError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        static RE: LazyLock<Regex> =
+            LazyLock::new(|| Regex::new(r"^([a-zA-Z0-9]+)\.([a-zA-Z0-9]+)$").unwrap());
+        let caps = RE.captures(s);
+        if let Some(caps) = caps {
+            let vendor = &caps[1];
+            let component = &caps[2];
+            Ok(Self::new(vendor, component))
+        } else {
+            Err(ParseProgIdError::new(s))
+        }
+    }
+}
+
+impl Display for LosseProgId {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}.{}", self.vendor, self.component)
+    }
+}
+
+/// The ProgId exactly follows `[Vendor or Application].[Component].[Version]` format.
+pub struct StrictProgId {
+    vendor: String,
+    component: String,
+    version: u32,
+}
+
+impl StrictProgId {
+    pub fn new(vendor: &str, component: &str, version: u32) -> Self {
+        Self {
+            vendor: vendor.to_string(),
+            component: component.to_string(),
+            version,
+        }
+    }
+
+    pub fn get_vendor(&self) -> &str {
+        &self.vendor
+    }
+
+    pub fn get_component(&self) -> &str {
+        &self.component
+    }
+
+    pub fn get_version(&self) -> u32 {
+        self.version
+    }
+}
+
+impl FromStr for StrictProgId {
+    type Err = ParseProgIdError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        static RE: LazyLock<Regex> =
+            LazyLock::new(|| Regex::new(r"^([a-zA-Z0-9]+)\.([a-zA-Z0-9]+)\.([0-9]+)$").unwrap());
+        let caps = RE.captures(s);
+        if let Some(caps) = caps {
+            let vendor = &caps[1];
+            let component = &caps[2];
+            let version = caps[3]
+                .parse::<u32>()
+                .map_err(|_| ParseProgIdError::new(s))?;
+            Ok(Self::new(vendor, component, version))
+        } else {
+            Err(ParseProgIdError::new(s))
+        }
+    }
+}
+
+impl Display for StrictProgId {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}.{}.{}", self.vendor, self.component, self.version)
+    }
+}
+
+// endregion
+
+// region: CLSID
+
+pub struct Clsid {
+    inner: Uuid,
+}
+
+impl Clsid {
+    pub fn new(uuid: &str) -> Result<Self, ParseClsidError> {
+        Self::from_str(uuid)
+    }
+
+    // TODO: May add CLSID generator in there.
+}
+
+/// The error occurs when parsing CLSID
+#[derive(Debug, TeError)]
+#[error("given string \"{inner}\" is invalid for uuid")]
+pub struct ParseClsidError {
+    inner: String,
+}
+
+impl ParseClsidError {
+    fn new(s: &str) -> Self {
+        Self {
+            inner: s.to_string(),
+        }
+    }
+}
+
+impl FromStr for Clsid {
+    type Err = ParseClsidError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(Self {
+            inner: Uuid::parse_str(s).map_err(|_| ParseClsidError::new(s))?,
+        })
+    }
+}
+
+impl Display for Clsid {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.inner.braced().to_string())
+    }
+}
+
+// endregion
+
+// region: Icon Resource
+
+// endregion
+
+// region: String Resource
+
+// endregion

wfassoc/src/lib.rs

@@ -4,36 +4,51 @@
 #[cfg(not(target_os = "windows"))]
 compile_error!("Crate wfassoc is only supported on Windows.");
 
+pub(crate) mod assoc;
+pub(crate) mod utilities;
+
+use indexmap::{IndexMap, IndexSet};
 use std::ffi::OsStr;
+use std::fmt::Display;
 use std::path::{Path, PathBuf};
 use thiserror::Error as TeError;
 use winreg::RegKey;
 use winreg::enums::{
     HKEY_CLASSES_ROOT, HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE, KEY_READ, KEY_WRITE,
 };
-use winreg::transaction::Transaction;
 
 // region: Error Types
 
 /// All possible error occurs in this crate.
 #[derive(Debug, TeError)]
-pub enum WfError {
+pub enum Error {
-    #[error("no administrative privilege")]
-    NoPrivilege,
     #[error("error occurs when manipulating with Registry: {0}")]
     BadRegOper(#[from] std::io::Error),
+    #[error("{0}")]
+    CastOsStr(#[from] utilities::CastOsStrError),
+
+    #[error("no administrative privilege")]
+    NoPrivilege,
     #[error("given full path to application is invalid")]
     BadFullAppPath,
-    #[error("failed when casting path or OS string into string")]
+    #[error("manner \"{0}\" is already registered")]
-    BadOsStrCast,
+    DupManner(String),
+    #[error("file extension \"{0}\" is already registered")]
+    DupExt(String),
+    #[error("the token of associated manner for file extension is invalid")]
+    InvalidAssocManner,
 }
 
 /// The result type used in this crate.
-pub type WfResult<T> = Result<T, WfError>;
+pub type Result<T> = std::result::Result<T, Error>;
 
 // endregion
 
-// region: Scope and View
+// region: Types
+
+/// The token for access registered items in Program.
+/// This is usually returned when you registering them.
+pub type Token = usize;
 
 /// The scope where wfassoc will register and unregister application.
 #[derive(Debug, Copy, Clone)]
@@ -46,7 +61,7 @@ pub enum Scope {
 
 /// The error occurs when cast View into Scope.
 #[derive(Debug, TeError)]
-#[error("hybrid view can not be cast into any scope")]
+#[error("hybrid View can not be cast into Scope")]
 pub struct TryFromViewError {}
 
 impl TryFromViewError {
@@ -58,7 +73,7 @@ impl TryFromViewError {
 impl TryFrom<View> for Scope {
     type Error = TryFromViewError;
 
-    fn try_from(value: View) -> Result<Self, Self::Error> {
+    fn try_from(value: View) -> std::result::Result<Self, Self::Error> {
         match value {
             View::User => Ok(Self::User),
             View::System => Ok(Self::System),
@@ -74,7 +89,7 @@ impl Scope {
         // If we operate on System, and we do not has privilege,
         // we think we do not have privilege, otherwise,
         // there is no privilege required.
-        !matches!(self, Self::System if !has_privilege())
+        !matches!(self, Self::System if !utilities::has_privilege())
     }
 }
 
@@ -101,113 +116,124 @@ impl From<Scope> for View {
 
 // endregion
 
-// region: Utilities
+// region: Manner
 
-/// The println macro only works on Debug mode
+/// The struct representing a program manner.
-/// for tracing the execution of some important functions.
+/// Manner usually mean the way to open files,
-macro_rules! debug_println {
+/// or more preciously, the consititution of command arguments passed to program.
-    // For no argument.
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
-    () => {
+pub struct Manner {
-        if cfg!(debug_assertions) {
+    argv: String,
-            println!();
+}
+
+impl Manner {
+    pub fn new(argv: &str) -> Self {
+        Self {
+            argv: argv.to_string(),
         }
-    };
+    }
-    // For one or more arguments like println!.
-    ($($arg:tt)*) => {
-        if cfg!(debug_assertions) {
-            println!($($arg)*);
-        }
-    };
 }
 
-/// Check whether current process has administrative privilege.
+impl Display for Manner {
-///
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-/// It usually means that checking whether current process is running as Administrator.
+        write!(f, "{}", self.argv)
-/// Return true if it is, otherwise false.
-///
-/// Reference: https://learn.microsoft.com/en-us/windows/win32/api/securitybaseapi/nf-securitybaseapi-checktokenmembership
-fn has_privilege() -> bool {
-    use windows_sys::Win32::Foundation::HANDLE;
-    use windows_sys::Win32::Security::{
-        AllocateAndInitializeSid, CheckTokenMembership, FreeSid, PSID, SECURITY_NT_AUTHORITY,
-    };
-    use windows_sys::Win32::System::SystemServices::{
-        DOMAIN_ALIAS_RID_ADMINS, SECURITY_BUILTIN_DOMAIN_RID,
-    };
-    use windows_sys::core::BOOL;
-
-    let nt_authority = SECURITY_NT_AUTHORITY.clone();
-    let mut administrators_group: PSID = PSID::default();
-    let success: BOOL = unsafe {
-        AllocateAndInitializeSid(
-            &nt_authority,
-            2,
-            SECURITY_BUILTIN_DOMAIN_RID as u32,
-            DOMAIN_ALIAS_RID_ADMINS as u32,
-            0,
-            0,
-            0,
-            0,
-            0,
-            0,
-            &mut administrators_group,
-        )
-    };
-
-    if success == 0 {
-        panic!("Win32 AllocateAndInitializeSid() failed");
     }
-
-    let mut is_member: BOOL = BOOL::default();
-    let success: BOOL =
-        unsafe { CheckTokenMembership(HANDLE::default(), administrators_group, &mut is_member) };
-
-    unsafe {
-        FreeSid(administrators_group);
-    }
-
-    if success == 0 {
-        panic!("Win32 CheckTokenMembership() failed");
-    }
-
-    is_member != 0
-}
-
-/// Try casting given &Path into &str.
-fn path_to_str(path: &Path) -> WfResult<&str> {
-    path.to_str().ok_or(WfError::BadOsStrCast)
-}
-
-/// Try casting given &OsStr into &str.
-fn osstr_to_str(osstr: &OsStr) -> WfResult<&str> {
-    osstr.to_str().ok_or(WfError::BadOsStrCast)
 }
 
 // endregion
 
-// region: Registrar
+// region: Program
 
-/// The core registrar for register and unregister application.
+/// The struct representing a complete program for registration and unregistration.
-pub struct Registrar {
+pub struct Program {
+    /// The identifier of this program.
+    identifier: String,
     /// The fully qualified path to the application.
     full_path: PathBuf,
+    /// The collection holding all manners of this program.
+    manners: IndexSet<Manner>,
+    /// The collection holding all file extensions supported by this program.
+    /// The key is file estension and value is its associated manner for opening it.
+    exts: IndexMap<assoc::Ext, Token>,
 }
 
-impl Registrar {
+impl Program {
     /// Create a new registrar for following operations.
-    pub fn new(full_path: &Path) -> Self {
+    ///
+    /// `identifier` is the unique name of this program.
+    /// If should only contain digits and alphabet chars,
+    /// and should not start with any digits.
+    /// For example, "MyApp" is okey but following names are not okey:
+    /// 
+    /// - `My App`
+    /// - `3DViewer`
+    /// - `我的Qt最时尚`
+    /// 
+    /// More preciously, `identifier` will be used as the vendor part of ProgId.
+    /// 
+    /// `full_path` is the fully qualified path to the application.
+    pub fn new(identifier: &str, full_path: &Path) -> Self {
+        // TODO: Add checker for identifier
         Self {
+            identifier: identifier.to_string(),
             full_path: full_path.to_path_buf(),
+            manners: IndexSet::new(),
+            exts: IndexMap::new(),
         }
     }
+
+    /// Add manner provided by this program.
+    pub fn add_manner(&mut self, manner: Manner) -> Result<Token> {
+        // Backup a stringfied manner for error output.
+        let manner_str = manner.to_string();
+        // Insert manner.
+        let idx = self.manners.len();
+        if self.manners.insert(manner) {
+            Ok(idx)
+        } else {
+            Err(Error::DupExt(manner_str))
+        }
+    }
+
+    /// Get the reference to manner with given token.
+    pub fn get_manner(&self, token: Token) -> Option<&Manner> {
+        self.manners.get_index(token)
+    }
+
+    /// Add file extension supported by this program and its associated manner.
+    pub fn add_ext(&mut self, ext: assoc::Ext, token: Token) -> Result<Token> {
+        // Check manner token
+        if let None = self.get_manner(token) {
+            return Err(Error::InvalidAssocManner);
+        }
+        // Backup a stringfied extension for error output.
+        let ext_str = ext.to_string();
+        // Insert file extension
+        let idx = self.exts.len();
+        if let None = self.exts.insert(ext, token) {
+            Ok(idx)
+        } else {
+            Err(Error::DupExt(ext_str))
+        }
+    }
+
+    /// Get the reference to file extension with given token.
+    pub fn get_ext(&self, token: Token) -> Option<&assoc::Ext> {
+        self.exts.get_index(token).map(|p| p.0)
+    }
 }
 
-impl Registrar {
+impl Program {
     const APP_PATHS: &str = "Software\\Microsoft\\Windows\\CurrentVersion\\App Paths";
     const APPLICATIONS: &str = "Software\\Classes\\Applications";
 
     /// Register this application.
-    pub fn register(&self, scope: Scope) -> WfResult<()> {
+    pub fn register(&self, scope: Scope) -> Result<()> {
+        // Check privilege
+        if !scope.has_privilege() {
+            return Err(Error::NoPrivilege);
+        }
+
         // Fetch root key.
         let hk = RegKey::predef(match scope {
             Scope::User => HKEY_CURRENT_USER,
@@ -222,21 +248,34 @@ impl Registrar {
         let subkey_parent = hk.open_subkey_with_flags(Self::APP_PATHS, KEY_READ)?;
         let (subkey, _) = subkey_parent.create_subkey_with_flags(file_name, KEY_WRITE)?;
         // Write App Paths values
-        subkey.set_value("", &path_to_str(&self.full_path)?)?;
+        subkey.set_value("", &utilities::path_to_str(&self.full_path)?)?;
-        subkey.set_value("Path", &osstr_to_str(&start_in)?)?;
+        subkey.set_value("Path", &utilities::osstr_to_str(&start_in)?)?;
 
         // Create Applications subkey
         debug_println!("Adding Applications subkey...");
         let subkey_parent = hk.open_subkey_with_flags(Self::APPLICATIONS, KEY_READ)?;
         let (subkey, _) = subkey_parent.create_subkey_with_flags(file_name, KEY_WRITE)?;
         // Write Applications values
-        subkey.set_value("FriendlyAppName", &"WoW!")?;
+        if !self.exts.is_empty() {
+            let (supported_types, _) =
+                subkey.create_subkey_with_flags("SupportedTypes", KEY_WRITE)?;
+            for ext in self.exts.keys() {
+                supported_types.set_value(ext.to_string(), &"")?;
+            }
+        }
 
+        // Okey
+        utilities::notify_assoc_changed();
         Ok(())
     }
 
     /// Unregister this application.
-    pub fn unregister(&self, scope: Scope) -> WfResult<()> {
+    pub fn unregister(&self, scope: Scope) -> Result<()> {
+        // Check privilege
+        if !scope.has_privilege() {
+            return Err(Error::NoPrivilege);
+        }
+
         // Fetch root key and file name.
         let hk = RegKey::predef(match scope {
             Scope::User => HKEY_CURRENT_USER,
@@ -255,13 +294,14 @@ impl Registrar {
         subkey_parent.delete_subkey_all(file_name)?;
 
         // Okey
+        utilities::notify_assoc_changed();
         Ok(())
     }
 
     /// Check whether this application has been registered.
     ///
     /// Please note that this is a rough check and do not validate any data.
-    pub fn is_registered(&self, scope: Scope) -> WfResult<bool> {
+    pub fn is_registered(&self, scope: Scope) -> Result<bool> {
         // Fetch root key and file name.
         let hk = RegKey::predef(match scope {
             Scope::User => HKEY_CURRENT_USER,
@@ -288,26 +328,28 @@ impl Registrar {
     }
 }
 
-impl Registrar {
+impl Program {
     /// Extract the file name part from full path to application,
     /// which was used in Registry path component.
-    fn extract_file_name(&self) -> WfResult<&OsStr> {
+    fn extract_file_name(&self) -> Result<&OsStr> {
-        // Get the file name part and make sure it is not empty
+        // Get the file name part and make sure it is not empty.
+        // Empty checker is CRUCIAL!
         self.full_path
             .file_name()
             .and_then(|p| if p.is_empty() { None } else { Some(p) })
-            .ok_or(WfError::BadFullAppPath)
+            .ok_or(Error::BadFullAppPath)
     }
 
     /// Extract the start in path from full path to application,
     /// which basically is the stem of full path.
-    fn extract_start_in(&self) -> WfResult<&OsStr> {
+    fn extract_start_in(&self) -> Result<&OsStr> {
         // Get parent part and make sure it is not empty
+        // Empty checker is CRUCIAL!
         self.full_path
             .parent()
             .map(|p| p.as_os_str())
             .and_then(|p| if p.is_empty() { None } else { Some(p) })
-            .ok_or(WfError::BadFullAppPath)
+            .ok_or(Error::BadFullAppPath)
     }
 }
 

wfassoc/src/utilities.rs

@@ -0,0 +1,119 @@
+//! The module containing useful stuff used in this crate.
+
+use std::ffi::OsStr;
+use std::path::Path;
+use thiserror::Error as TeError;
+
+/// The println macro only works on Debug mode
+/// for tracing the execution of some important functions.
+#[macro_export]
+macro_rules! debug_println {
+    // For no argument.
+    () => {
+        if cfg!(debug_assertions) {
+            println!();
+        }
+    };
+    // For one or more arguments like println!.
+    ($($arg:tt)*) => {
+        if cfg!(debug_assertions) {
+            println!($($arg)*);
+        }
+    };
+}
+
+// region: Windows Related
+
+/// Check whether current process has administrative privilege.
+///
+/// It usually means that checking whether current process is running as Administrator.
+/// Return true if it is, otherwise false.
+///
+/// Reference: https://learn.microsoft.com/en-us/windows/win32/api/securitybaseapi/nf-securitybaseapi-checktokenmembership
+pub fn has_privilege() -> bool {
+    use windows_sys::Win32::Foundation::HANDLE;
+    use windows_sys::Win32::Security::{
+        AllocateAndInitializeSid, CheckTokenMembership, FreeSid, PSID, SECURITY_NT_AUTHORITY,
+    };
+    use windows_sys::Win32::System::SystemServices::{
+        DOMAIN_ALIAS_RID_ADMINS, SECURITY_BUILTIN_DOMAIN_RID,
+    };
+    use windows_sys::core::BOOL;
+
+    let nt_authority = SECURITY_NT_AUTHORITY.clone();
+    let mut administrators_group: PSID = PSID::default();
+    let success: BOOL = unsafe {
+        AllocateAndInitializeSid(
+            &nt_authority,
+            2,
+            SECURITY_BUILTIN_DOMAIN_RID as u32,
+            DOMAIN_ALIAS_RID_ADMINS as u32,
+            0,
+            0,
+            0,
+            0,
+            0,
+            0,
+            &mut administrators_group,
+        )
+    };
+
+    if success == 0 {
+        panic!("Win32 AllocateAndInitializeSid() failed");
+    }
+
+    let mut is_member: BOOL = BOOL::default();
+    let success: BOOL =
+        unsafe { CheckTokenMembership(HANDLE::default(), administrators_group, &mut is_member) };
+
+    unsafe {
+        FreeSid(administrators_group);
+    }
+
+    if success == 0 {
+        panic!("Win32 CheckTokenMembership() failed");
+    }
+
+    is_member != 0
+}
+
+/// Notify Windows that some file associations are changed, and should refresh them.
+/// This function must be called once you change any file associations.
+pub fn notify_assoc_changed() -> () {
+    use windows_sys::Win32::UI::Shell::{SHCNE_ASSOCCHANGED, SHCNF_IDLIST, SHChangeNotify};
+    unsafe {
+        SHChangeNotify(
+            SHCNE_ASSOCCHANGED as i32,
+            SHCNF_IDLIST,
+            Default::default(),
+            Default::default(),
+        )
+    }
+}
+
+// endregion
+
+// region OS String Related
+
+/// The error occurs when casting `OsStr` into `str`.
+#[derive(Debug, TeError)]
+#[error("failed when casting OS string into string")]
+pub struct CastOsStrError {}
+
+impl CastOsStrError {
+    fn new() -> Self {
+        Self {}
+    }
+}
+
+/// Try casting given &Path into &str.
+pub fn path_to_str(path: &Path) -> Result<&str, CastOsStrError> {
+    path.to_str().ok_or(CastOsStrError::new())
+}
+
+/// Try casting given &OsStr into &str.
+pub fn osstr_to_str(osstr: &OsStr) -> Result<&str, CastOsStrError> {
+    osstr.to_str().ok_or(CastOsStrError::new())
+}
+
+// endregion

wfassoc_exec/src/main.rs

@@ -2,7 +2,7 @@ use clap::{Parser, Subcommand};
 use comfy_table::Table;
 use std::process;
 use thiserror::Error as TeError;
-use wfassoc::{Error as WfError, FileExt, Scope, View};
+use wfassoc::{Error as WfError, Ext, Scope, View};
 
 // region: Basic Types
 
@@ -95,7 +95,7 @@ fn run_query(cli: Cli) -> Result<()> {
         ".kra", ".xcf", ".avif", ".qoi", ".apng", ".exr",
     ];
 
-    for ext in exts.iter().map(|e| FileExt::new(e).unwrap()) {
+    for ext in exts.iter().map(|e| Ext::new(e).unwrap()) {
         if let Some(ext_assoc) = ext.query(View::Hybrid) {
             println!("{:?}", ext_assoc)
         }