[Subissue 7/7] Template Generation Support (Optional)

[josecelano]

Parent Epic: #34 - Implement Create Environment Command
Depends On: #40 - Template System Integration
Status: OPTIONAL ENHANCEMENT
Estimated Time: 1-2 hours

⚠️ Note: This is an optional enhancement that can be deferred. It requires #40 (Template System Integration) to be completed first.

Overview

Implement the template subcommand for the create command, allowing users to generate configuration file templates. This enhances user experience by providing a starting point for configuration creation.

Goals

• Implement template subcommand in the create command structure
• Generate JSON configuration template files
• Support custom output paths for template generation
• Provide helpful placeholder content with clear replacement instructions
• Integrate with existing CLI subcommand architecture

Architecture Requirements

DDD Layer: Presentation (CLI interface) + Infrastructure (template generation)
Module Path: src/presentation/console/subcommands/create/ + src/infrastructure/templates/
Pattern: CLI Subcommand + Template Generation

Dependencies: Requires #40 (Template System Integration) to be completed first.

CLI Interface

# Generate template configuration file (JSON format)
torrust-tracker-deployer create template
# Creates: ./environment-template.json in current working directory

# Generate template in specific directory
torrust-tracker-deployer create template ./config/environment.json

# Generate template with custom filename
torrust-tracker-deployer create template ./my-environment.json

# Show help for template subcommand
torrust-tracker-deployer create template --help

Template Example

{
  "environment": {
    "name": "my-environment"
  },
  "ssh_credentials": {
    "private_key_path": "~/.ssh/id_rsa",
    "public_key_path": "~/.ssh/id_rsa.pub",
    "username": "torrust",
    "port": 22
  }
}

Acceptance Criteria

• create template subcommand generates valid JSON template
• Template includes helpful placeholder values
• Template includes comments explaining each field (if JSON supports it, or in separate docs)
• Custom output paths are supported
• Default filename is environment-template.json
• Error handling follows tiered help system pattern
• Help text provides clear usage examples

Implementation Notes

• Extend existing CLI subcommand structure from Subissue 3
• Use TemplateManager from Subissue 6 for template generation
• Follow existing patterns for CLI subcommands
• Ensure template content matches environment configuration schema

For detailed specification, see: docs/issues/epic-create-environment-command-subissue-7-template-generation-support.md

[josecelano]

✅ Issue Documentation Updated

The issue specification has been updated to reflect the implementation completed in PR #48.

Key Changes

Previous specification was outdated - it was written before PR #48 implemented struct-based template generation in the domain layer.

New v2 specification: docs/issues/41-subissue-7-template-generation-support-v2.md

What Changed

1. Architecture: Domain layer (not infrastructure) - template generation already implemented
2. Implementation scope: Thin CLI wrapper only (1-2 hours of work)
3. API: Use existing EnvironmentCreationConfig::generate_template_file() method
4. Error handling: Use existing CreateConfigError enum
5. Testing: Focus on CLI integration tests (domain logic already tested)

What's Already Done ✅

• Template generation logic in src/domain/config/environment_config.rs
• Error handling with .help() methods
• Comprehensive test coverage in domain layer
• JSON template format with placeholders

What Needs to Be Done

• Add template subcommand to CLI argument parser
• Implement handler to call existing domain method
• Add user-friendly success messages
• Write CLI integration tests

Why This Makes Implementation Easier

The hard work (template generation, error handling, validation) is already complete. This issue is now just about exposing that functionality through a CLI subcommand - a straightforward CLI integration task.

For Implementation

@copilot When implementing this:

• DO call EnvironmentCreationConfig::generate_template_file(&path).await
• DON'T create new template generation logic
• DON'T create src/infrastructure/templates/ module
• DO keep it simple - this is just a thin CLI wrapper

See the v2 specification for complete implementation details with code examples.