watt-tf

README

wtf - Generic Terraform JSON Builder

Watt TF is a powerful CLI tool that transforms JSON and YAML configurations into Terraform JSON files - Because writing complex nested loops in HCL shouldn't make you question your career choices

Generate Terraform configuration from structured application data.

Ideal for:

• Internal Developer Platforms
• SaaS platforms
• Multi-tenant deployments
• CI/CD pipelines
• Self-service infrastructure portals

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Installation

Via Go

go install github.com/devsebastianops/watt-tf/cmd/wtf@latest

From Source

git clone https://github.com/devsebastianops/watt-tf.git
cd watt-tf
go build -o wtf ./cmd/wtf/main.go
./wtf --help

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Quick Start

Basic Usage

wtf build --input config.json --config .wtf.yaml --output terraform.tf.json

Example 1: Simple JSON to Terraform

input.json

{
  "cloudrun": {
    "image": "gcr.io/cloudrun/hello",
    "port": 8080
  }
}

.wtf.yaml

transform:
  - target: resource.google_cloud_run_service.default
    value:
      image: "${input.cloudrun.image}"
      port: "${input.cloudrun.port}"

Output (terraform.tf.json)

{
  "resource": {
    "google_cloud_run_service": {
      "default": {
        "image": "gcr.io/cloudrun/hello",
        "port": 8080
      }
    }
  }
}

Please refer to the examples directory for more detailed use cases and configurations.

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Configuration Guide

Basic Transform

The .wtf.yaml file defines how to transform your input into Terraform configuration.

transform:
  - target: resource.aws_s3_bucket.my_bucket
    value:
      bucket: "my-bucket-name"
      acl: "private"

String Interpolation

Use ${input.path.to.value} to interpolate values from your input:

transform:
  - target: resource.aws_s3_bucket.${input.bucket_name}
    value:
      bucket: "${input.bucket_name}-${input.environment}"
      tags:
        Environment: "${input.environment}"
        Owner: "${input.owner}"

Conditional Transforms

Use CEL expressions in the if field to conditionally apply transformations:

transform:
  - target: resource.aws_rds.production
    if: input.environment == 'prod'
    value:
      instance_class: "db.r5.2xlarge"
      multi_az: true
  
  - target: resource.aws_rds.development
    if: input.environment == 'dev'
    value:
      instance_class: "db.t3.micro"
      multi_az: false

Complex Conditions

CEL supports complex boolean logic:

transform:
  - target: resource.cache.redis
    if: input.enable_cache && (input.env == 'production' || input.env == 'staging')
    value:
      size: "large"

String Methods

Use string methods for pattern matching:

transform:
  - target: resource.iam_role.admin
    if: input.email.startsWith('admin@')
    value:
      permissions: ["admin"]
  
  - target: resource.cert.wildcard
    if: input.domain.contains('*.example.com')
    value:
      wildcard: true

Deep Merge

Multiple transformations to the same target are automatically merged:

transform:
  - target: resource.aws_instance.server
    value:
      instance_type: "${input.instance_type}"
  
  - target: resource.aws_instance.server  # Same target!
    value:
      tags:
        Name: "${input.server_name}"
        Environment: "${input.environment}"

Result: Both instance_type and tags exist in the final output.

Nested Paths

Deeply nested structures are automatically unflattened:

transform:
  - target: resource.aws_vpc.main.subnets.primary.tags
    value:
      Name: "${input.vpc_name}-primary"
      Tier: "public"

---

Command Reference

wtf build

Transforms your input configuration into Terraform JSON.

wtf build [OPTIONS]

Options:
  --input <FILE>      Input file (JSON or YAML) [required]
  --config <FILE>     Transformation config (.wtf.yaml) [default: .wtf.yaml]
  --output <FILE>     Output file [default: watt.tf.json]

Examples:

# Simple build
wtf build --input config.json

# Custom output
wtf build --input input.yaml --output main.tf.json

# Different config
wtf build --input config.json --config transformations.yaml --output output.tf.json

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Testing

Watt TF includes comprehensive E2E tests covering all features:

# Run all tests
go test ./tests/e2e -v

# Run specific example
go test ./tests/e2e -v -run "TestE2EExamples/01-simple-json"

# View test examples
ls -la example/

---

Use Cases

Multi-Environment Deployments

Generate environment-specific Terraform configurations from a single input:

transform:
  - target: resource.aws_instance.app
    if: input.environment == 'prod'
    value:
      instance_type: "t3.large"
      monitoring: true
  
  - target: resource.aws_instance.app
    if: input.environment == 'dev'
    value:
      instance_type: "t3.micro"
      monitoring: false

Infrastructure Templating

Reuse configuration templates across projects:

transform:
  - target: resource.aws_s3_bucket.${input.project}
    value:
      bucket: "${input.project}-${input.environment}-data"
      versioning:
        enabled: "${input.enable_versioning}"
      tags:
        Project: "${input.project}"
        Environment: "${input.environment}"
        CostCenter: "${input.cost_center}"

CI/CD Integration

Generate Terraform configurations dynamically in your pipeline:

#!/bin/bash
# Extract environment from Git branch
ENV=$(git rev-parse --abbrev-ref HEAD)

# Generate configuration
wtf build \
  --input environment.json \
  --config transforms.yaml \
  --output terraform-${ENV}.tf.json

# Apply Terraform
terraform init
terraform plan -out=plan.tfplan
terraform apply plan.tfplan

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Feedback & Contribution

We ❤️ contributions! Whether it's bug reports, feature requests, or pull requests:

Report Issues

Found a bug? Open an Issue

Contribute Code

1. Fork the repository
2. Create a feature branch: git checkout -b feature/amazing-feature
3. Commit changes: git commit -m 'Add amazing feature'
4. Push to branch: git push origin feature/amazing-feature
5. Open a Pull Request

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Roadmap

• Plugin system for custom transformers
• Jinja2 template engine for complex scenarios
• Interactive CLI mode
• VS Code extension

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License

This project is licensed under the MIT License - see the LICENSE file for details.

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Contact & Support

• GitHub: devsebastianops/watt-tf
• Issues: GitHub Issues
• Discussions: GitHub Discussions

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Made with ❤️, Happy Terraforming! 🚀