# Task ID: 70
# Title: Implement 'diagram' command for Mermaid diagram generation
# Status: pending
# Dependencies: None
# Priority: medium
# Description: Develop a CLI command named 'diagram' that generates Mermaid diagrams to visualize task dependencies and workflows, with options to target specific tasks or generate comprehensive diagrams for all tasks.
# Details:
The task involves implementing a new command that accepts an optional '--id' parameter: if provided, the command generates a diagram illustrating the chosen task and its dependencies; if omitted, it produces a diagram that includes all tasks. The diagrams should use color coding to reflect task status and arrows to denote dependencies. In addition to CLI rendering, the command should offer an option to save the output as a Markdown (.md) file. Consider integrating with the existing task management system to pull task details and status. Pay attention to formatting consistency and error handling for invalid or missing task IDs. Comments should be added to the code to improve maintainability, and unit tests should cover edge cases such as cyclic dependencies, missing tasks, and invalid input formats.

# Test Strategy:
Verify the command functionality by testing with both specific task IDs and general invocation: 1) Run the command with a valid '--id' and ensure the resulting diagram accurately depicts the specified task's dependencies with correct color codings for statuses. 2) Execute the command without '--id' to ensure a complete workflow diagram is generated for all tasks. 3) Check that arrows correctly represent dependency relationships. 4) Validate the Markdown (.md) file export option by confirming the file format and content after saving. 5) Test error responses for non-existent task IDs and malformed inputs.

# Subtasks:
## 1. Design the 'diagram' command interface [pending]
### Dependencies: None
### Description: Define the command structure, arguments, and options for the Mermaid diagram generation feature
### Details:
Create a command specification that includes: input parameters for diagram source (file, stdin, or string), output options (file, stdout, clipboard), format options (SVG, PNG, PDF), styling parameters, and help documentation. Consider compatibility with existing command patterns in the application.

## 2. Implement Mermaid diagram generation core functionality [pending]
### Dependencies: 70.1
### Description: Create the core logic to parse Mermaid syntax and generate diagram output
### Details:
Integrate with the Mermaid library to parse diagram syntax. Implement error handling for invalid syntax. Create the rendering pipeline to generate the diagram in memory before output. Support all standard Mermaid diagram types (flowchart, sequence, class, etc.). Include proper logging for the generation process.

## 3. Develop output handling mechanisms [pending]
### Dependencies: 70.2
### Description: Implement different output options for the generated diagrams
### Details:
Create handlers for different output formats (SVG, PNG, PDF). Implement file output with appropriate naming conventions and directory handling. Add clipboard support for direct pasting. Implement stdout output for piping to other commands. Include progress indicators for longer rendering operations.

## 4. Create documentation and examples [pending]
### Dependencies: 70.3
### Description: Provide comprehensive documentation and examples for the 'diagram' command
### Details:
Write detailed command documentation with all options explained. Create example diagrams covering different diagram types. Include troubleshooting section for common errors. Add documentation on extending the command with custom themes or templates. Create integration examples showing how to use the command in workflows with other tools.

