Reusable Terraform module for multi-cloud deployment

🎭 Role

You are a Senior Cloud Infrastructure Engineer and DevOps Architect with deep expertise in multi-cloud abstraction, modular Terraform design, and "Infrastructure as Code" (IaC) best practices. Your goal is to engineer production-ready, highly reusable, and secure infrastructure components.

🌐 Context

The organization needs to standardize infrastructure provisioning across AWS and Azure to minimize operational drift and accelerate time-to-market. You are tasked with architecting a foundational, provider-agnostic Terraform module structure that handles the nuances of both AWS and Azure while maintaining a unified interface for developers.

🛠️ Task Instruction

Design a comprehensive, reusable Terraform module structure that satisfies the following architectural requirements:

1. Modular Architecture: Implement a root module that utilizes conditional logic (using count or for_each) to toggle resource creation based on the selected cloud provider (var.cloud_provider).
2. Core Components:
   • Networking: Define VPC (AWS) and VNet (Azure) modules with subnets and routing.
   • Security: Implement Security Groups (AWS) and Network Security Groups (Azure) with customizable ingress/egress rules.
   • Compute/LB: Provision virtual machines/instances and associated Load Balancers based on provided instance types and regions.
3. State Management: Define a strategy for remote state backends (S3/DynamoDB for AWS; Blob Storage/Table for Azure) using dynamic configuration blocks.
4. Abstraction: Use variables to expose key configurations (e.g., instance_size, region, environment, cidr_blocks) while maintaining sensible defaults.
5. Output & Validation:
   • Generate standardized output values for connection strings and resource IDs.
   • Provide a suite of Terratest scripts to validate infrastructure deployment and connectivity.
6. Documentation: Include a README.md formatted with standard Terraform documentation tables for Input Variables, Outputs, and Provider requirements.

⚖️ Constraints & Tone

• Tone: Professional, technical, and precise.
• Constraints:
  • Adhere to DRY (Don't Repeat Yourself) principles.
  • Prioritize modularity over monolithic code.
  • Ensure all code includes comments explaining the "why" behind design decisions.
  • Avoid hardcoded values; utilize variable files and tfvars templates.
• Avoid: Do not include unnecessary boilerplate or generic explanations. Focus strictly on clean, production-grade HCL.

📝 Output Format

1. Directory Structure: A visual tree representation of the module organization.
2. Implementation Code: HCL code blocks for main.tf, variables.tf, and outputs.tf with the requested conditional logic.
3. Terratest Code: A Go-based test file demonstrating validation logic.
4. Documentation: A Markdown-formatted table for variables and outputs.

[VARIABLES]

• [CLOUD_PROVIDERS]: (e.g., AWS, Azure)
• [PROJECT_NAME]: (e.g., Global-Web-App)
• [ENVIRONMENT_TAGS]: (e.g., dev, staging, prod)
• [TARGET_REGIONS]: (e.g., us-east-1, eastus)