add hosts editor doc

doc/devdocs/modules/hostsfileeditor.md

@@ -0,0 +1,102 @@
+# Hosts File Editor
+
+[Learn](https://learn.microsoft.com/en-us/windows/powertoys/hosts-file-editor)
+
+## Overview
+
+The Hosts File Editor module provides a convenient way to edit the system's hosts file. The hosts file is a plain text file used by the operating system to map hostnames to IP addresses, allowing users to override DNS for specific domain names.
+
+## Code Structure
+
+![Code structure](../images/hostsfileeditor/code%20structure.png)
+
+The Hosts File Editor module is structured into three primary components:
+
+1. **Hosts** - Entry point for the Hosts File Editor. Manages core services and settings through helper utilities.
+2. **HostsModuleInterface** - Interface for integrating the Hosts module with the PowerToys system.
+3. **HostsUILib** - Implements the UI layer using WinUI 3.
+
+This structure is similar to the Environment Variables for Windows module.
+
+## Key Components
+
+### Main Entry Points
+
+- **Module Entry**: [Program.cs](/src/modules/Hosts/Program.cs) → [App.xaml.cs](/src/modules/Hosts/HostsXAML/App.xaml.cs)
+- **Settings UI**: 
+  - Main Window: [MainWindow.xaml.cs](/src/modules/Hosts/Hosts/HostsXAML/MainWindow.xaml.cs)
+  - View: [HostsMainPage.xaml.cs](/src/modules/Hosts/HostsUILib/HostsMainPage.xaml.cs)
+  - ViewModel: [HostsMainPage.xaml.cs](/src/modules/Hosts/HostsUILib/HostsMainPage.xaml.cs)
+- **Runner Integration**: [HostsModuleInterface](/src/modules/Hosts/HostsModuleInterface)
+
+### Runner Integration
+
+The module is loaded by the PowerToys runner from:
+- [main.cpp](/src/runner/main.cpp) (Lines 183-184): Loads Hosts Module using `L"WinUI3Apps/PowerToys.HostsModuleInterface.dll"`
+
+### Settings Management
+
+- [HostsViewModel.cs](/src/settings-ui/Settings.UI/ViewModels/HostsViewModel.cs): Hosts UI in PowerToys settings
+- [HostsProperties.cs](/src/settings-ui/Settings.UI.Library/HostsProperties.cs): In settings UI
+- [HostsSettings.cs](/src/settings-ui/Settings.UI.Library/HostsSettings.cs): Wrapper with HostsProperties
+
+### Module Components
+
+#### HostsModuleInterface
+
+- Defines the interface for integrating the Hosts module with the PowerToys system.
+
+#### Hosts (Main Project)
+
+- [Program.cs](/src/modules/Hosts/Hosts/Program.cs): Launch app
+- [HostsXAML](/src/modules/Hosts/Hosts/HostsXAML): Initialize service and loads the main window
+- [Host.cs](/src/modules/Hosts/Hosts/Helpers/Host.cs): Access to services register
+- [NativeEventWaiter.cs](/src/modules/Hosts/Hosts/Helpers/NativeEventWaiter.cs): Gets the dispatcher queue for posting UI updates from a background thread
+- [UserSettings.cs](/src/modules/Hosts/Hosts/Settings/UserSettings.cs): Manages reading, tracking, and updating user settings from settings.json
+
+#### HostsUILib
+
+- [HostsMainPage.xaml.cs](/src/modules/Hosts/HostsUILib/HostsMainPage.xaml.cs): Main page
+- [ViewModels](/src/modules/Hosts/HostsUILib/ViewModels): Contains view models that manage state and logic
+- [Models](/src/modules/Hosts/HostsUILib/Models): Models for managing host entries
+  - [AddressType.cs](/src/modules/Hosts/HostsUILib/Models/AddressType.cs): Specifies whether an address is IPv4, IPv6, or Invalid
+  - [Entry.cs](/src/modules/Hosts/HostsUILib/Models/Entry.cs): Represents a single hosts file entry (IP address, hostnames, comment, flags)
+  - [HostsData.cs](/src/modules/Hosts/HostsUILib/Models/HostsData.cs): Converts the list of entries into a read-only collection
+- [Settings](/src/modules/Hosts/HostsUILib/Settings): Settings configuration
+- [Consts.cs](/src/modules/Hosts/HostsUILib/Consts.cs): Defines constants like max hosts IP length
+- [Helpers](/src/modules/Hosts/HostsUILib/Helpers): Utilities for dealing with hosts IP, filter features, and file loading
+
+## Call Flow
+
+1. **Enable app**: runner/main.cpp → settings.ui/settings.ui.library
+2. **Start app**: Program.cs → HostsXAML → HostsMainPage
+3. **Load hosts data**: ViewModel → HostsData → Helpers (load and parse file)
+4. **User edits**: UI bound to ViewModel updates entries
+5. **Save changes**: ViewModel triggers file write through Helpers
+6. **Settings management**: UserSettings.cs persists user preferences
+
+## Key Features
+
+| Feature | Key Function |
+|---------|--------------|
+| Adding a new entry | `Add(Entry entry)` |
+| Filtering host file entries | `ApplyFilters()` |
+| Open Hosts File | `ReadHosts()` |
+| Additional Lines | `UpdateAdditionalLines(string lines)` |
+
+## Settings
+
+| Setting | Implementation |
+|---------|---------------|
+| Open as administrator | `UserSettings()` |
+| Additional lines position | `UserSettings()->AdditionalLinesPosition` |
+| Consider loopback addresses as duplicates | `UserSettings()->LoopbackDuplicates` |
+| Encoding Setting | `UserSettings()->Encoding` |
+
+## How to Build and Debug
+
+1. Build PowerToys Project in debug mode
+2. Set Hosts as the startup project
+3. Launch Hosts File Editor in debug mode
+4. Attach the debugger to PowerToys.Hosts.dll
+5. Add breakpoints in the Hosts code

doc/devdocs/modules/readme.md

@@ -8,6 +8,7 @@ This section contains documentation for individual PowerToys modules, including
 |--------|-------------|---------------|
 | Environment Variables | Tool for managing user and system environment variables | [Architecture & Implementation](environmentvariables.md) |
 | FancyZones | Window manager utility for custom window layouts | [Architecture & Implementation](fancyzones.md), [Debugging Tools](fancyzones-tools.md) |
+| Hosts File Editor | Tool for managing the system hosts file | [Architecture & Implementation](hostsfileeditor.md) |
 | Keyboard Manager | Tool for remapping keys and keyboard shortcuts | [Documentation](keyboardmanager/README.md) |
 | NewPlus | Context menu extension for creating new files in File Explorer | [Architecture & Implementation](newplus.md) |
 | Quick Accent | Tool for quickly inserting accented characters and special symbols | [Architecture & Implementation](quickaccent.md) |