# DOS Command Implementation Plan

## Overview
This document outlines the plan to implement the most commonly used DOS commands that are currently missing from the dosage shell implementation.

## Implementation Priority

### Phase 1: Core File/Directory Operations (High Priority)

#### 1. CD/CHDIR - Change Directory
- **Status**: Not implemented
- **Priority**: High (Essential for navigation)
- **Implementation**:
  - Update parser to recognize `CD` and `CHDIR` commands
  - Add `Chdir` variant handling in eval.zig
  - Use `std.fs.cwd().setDir()` or equivalent
  - Handle relative and absolute paths
  - Support `CD..` (parent directory)
  - Support `CD\` (root directory)
  - Update current working directory tracking in main loop

#### 2. COPY - Copy Files
- **Status**: Not implemented  
- **Priority**: High (Most common file operation)
- **Implementation**:
  - Add parsing for `COPY source dest` syntax
  - Handle FileSpec sources and destinations (files, CON, devices)
  - Implement file-to-file copying with `std.fs.copyFile()`
  - Support wildcard copying (*.txt, etc.)
  - Handle overwrite prompts and `/Y` switch
  - Support copying to/from devices like CON

#### 3. DEL/ERASE - Delete Files
- **Status**: Not implemented
- **Priority**: High (Essential file operation)
- **Implementation**:
  - Add parsing for `DEL` and `ERASE` commands
  - Support wildcard deletion (*.bak, etc.)
  - Implement confirmation prompts
  - Use `std.fs.deleteFile()` for single files
  - Use directory iteration for wildcards
  - Handle access denied and file not found errors

#### 4. MD/MKDIR - Create Directory
- **Status**: Not implemented
- **Priority**: High (Essential for file organization)
- **Implementation**:
  - Add parsing for `MD` and `MKDIR` commands
  - Use `std.fs.cwd().makeDir()` 
  - Handle nested directory creation
  - Provide appropriate error messages for existing directories

#### 5. SET - Environment Variables
- **Status**: Not implemented
- **Priority**: Medium (Important for shell functionality)
- **Implementation**:
  - Add global environment variable storage (HashMap)
  - Support `SET` (display all variables)
  - Support `SET VAR=value` (set variable)
  - Support `SET VAR` (display single variable)
  - Integrate with external command execution
  - Handle special variables like PATH, PROMPT

### Phase 2: Extended File Operations (Medium Priority)

#### 6. RD/RMDIR - Remove Directory
- **Status**: Not implemented
- **Priority**: Medium
- **Implementation**:
  - Add parsing for `RD` and `RMDIR` commands
  - Use `std.fs.cwd().deleteDir()`
  - Handle non-empty directory errors
  - Support `/S` switch for recursive deletion

#### 7. REN/RENAME - Rename Files/Directories  
- **Status**: Not implemented
- **Priority**: Medium
- **Implementation**:
  - Add parsing for `REN oldname newname` syntax
  - Use `std.fs.cwd().rename()`
  - Support wildcard renaming
  - Handle cross-drive moves (convert to copy+delete)

#### 8. MOVE - Move Files/Directories
- **Status**: Not implemented  
- **Priority**: Medium
- **Implementation**:
  - Add parsing for `MOVE source dest` syntax
  - Try rename first, fallback to copy+delete for cross-filesystem moves
  - Support directory moving
  - Handle overwrite confirmation

#### 9. PATH - Command Search Path
- **Status**: Not implemented
- **Priority**: Medium
- **Implementation**:
  - Support `PATH` (display current path)
  - Support `PATH=directory;directory2` (set path)
  - Integrate with external command resolution
  - Store in environment variables

### Phase 3: Utility Commands (Low Priority)

#### 10. PROMPT - Command Prompt Customization
- **Status**: Not implemented
- **Priority**: Low
- **Implementation**:
  - Support `PROMPT` (display current prompt)
  - Support `PROMPT text$G` (set prompt format)
  - Implement prompt codes ($P=path, $G=>, $N=drive, etc.)
  - Integrate with main shell loop

#### 11. MORE - Paged Output Display
- **Status**: Not implemented
- **Priority**: Low  
- **Implementation**:
  - Implement paging with screen height detection
  - Support "Press any key to continue" prompts
  - Handle pipe input for `command | MORE`
  - Add /S switch for squashing blank lines

#### 12. FIND - Text Search in Files
- **Status**: Not implemented
- **Priority**: Low
- **Implementation**:
  - Add parsing for `FIND "text" filename` syntax
  - Support /I switch for case-insensitive search
  - Support /V switch for non-matching lines
  - Support /N switch for line numbers
  - Handle multiple files and wildcards

#### 13. TREE - Directory Tree Display
- **Status**: Not implemented
- **Priority**: Low
- **Implementation**:
  - Implement recursive directory traversal
  - Create tree-like ASCII art display
  - Support /F switch for showing files
  - Support /A switch for ASCII characters only

#### 14. ATTRIB - File Attributes
- **Status**: Not implemented
- **Priority**: Low
- **Implementation**:
  - Display file attributes (R/H/S/A)
  - Support setting/clearing attributes
  - Use platform-specific attribute APIs
  - Handle wildcards for multiple files

#### 15. VOL - Volume Information
- **Status**: Not implemented  
- **Priority**: Low
- **Implementation**:
  - Display volume label and serial number
  - Use filesystem stat APIs
  - Handle different drive specifications

## Implementation Guidelines

### Code Organization
- Add command parsing to `src/syntax.zig` in the `parseBuiltinCommand()` function
- Add command execution to `src/eval.zig` in the builtin command switch
- Update `BuiltinCommand` enum variants as needed
- Maintain DOS-authentic error messages and behavior

### Error Handling
- Use DOS-style error messages ("File not found", "Access denied", etc.)
- Return appropriate exit codes (0 for success, 1+ for errors)
- Handle edge cases gracefully (missing arguments, invalid paths, etc.)

### Testing Strategy
- Test each command with valid and invalid arguments
- Test with various file types and permissions
- Test error conditions and edge cases
- Verify DOS-authentic behavior and output format

### Cross-Platform Considerations
- Use Zig standard library APIs for maximum portability
- Handle path separators correctly (DOS uses backslash)
- Consider case sensitivity differences between platforms
- Test on both Unix-like and Windows systems

## Dependencies and Prerequisites
- Current codebase with working parser and evaluator
- Zig standard library filesystem APIs
- Basic I/O redirection support (already implemented)
- Error handling infrastructure (already in place)

## Estimated Implementation Effort
- Phase 1 (High Priority): ~3-4 days of development
- Phase 2 (Medium Priority): ~2-3 days of development  
- Phase 3 (Low Priority): ~3-4 days of development
- **Total**: ~8-11 days for complete implementation

This plan provides a roadmap for transforming the dosage shell from a basic command interpreter into a fully functional DOS-style environment with comprehensive file and directory management capabilities.