# Extension Development API

This document provides comprehensive guidance for developing extensions for provisioning, including providers, task services, and cluster configurations.

## Overview

Provisioning supports three types of extensions:

1. **Providers**: Cloud infrastructure providers (AWS, UpCloud, Local, etc.)
2. **Task Services**: Infrastructure components (Kubernetes, Cilium, Containerd, etc.)
3. **Clusters**: Complete deployment configurations (BuildKit, CI/CD, etc.)

All extensions follow a standardized structure and API for seamless integration.

## Extension Structure

### Standard Directory Layout

```bash
extension-name/
├── manifest.toml              # Extension metadata
├── schemas/                   # Nickel configuration files
│   ├── main.ncl               # Main schema
│   ├── settings.ncl           # Settings schema
│   ├── version.ncl            # Version configuration
│   └── contracts.ncl          # Contract definitions
├── nulib/                     # Nushell library modules
│   ├── mod.nu                 # Main module
│   ├── create.nu              # Creation operations
│   ├── delete.nu              # Deletion operations
│   └── utils.nu               # Utility functions
├── templates/                 # Jinja2 templates
│   ├── config.j2              # Configuration templates
│   └── scripts/               # Script templates
├── generate/                  # Code generation scripts
│   └── generate.nu            # Generation commands
├── README.md                  # Extension documentation
└── metadata.toml              # Extension metadata
```

## Provider Extension API

### Provider Interface

All providers must implement the following interface:

#### Core Operations

- `create-server(config: record) -> record`
- `delete-server(server_id: string) -> null`
- `list-servers() -> list<record>`
- `get-server-info(server_id: string) -> record`
- `start-server(server_id: string) -> null`
- `stop-server(server_id: string) -> null`
- `reboot-server(server_id: string) -> null`

#### Pricing and Plans

- `get-pricing() -> list<record>`
- `get-plans() -> list<record>`
- `get-zones() -> list<record>`

#### SSH and Access

- `get-ssh-access(server_id: string) -> record`
- `configure-firewall(server_id: string, rules: list<record>) -> null`

### Provider Development Template

#### Nickel Configuration Schema

Create `schemas/settings.ncl`:

```nickel
# Provider settings schema
{
  ProviderSettings = {
    # Authentication configuration
    auth | {
      method | "api_key" | "certificate" | "oauth" | "basic",
      api_key | String = null,
      api_secret | String = null,
      username | String = null,
      password | String = null,
      certificate_path | String = null,
      private_key_path | String = null,
    },

    # API configuration
    api | {
      base_url | String,
      version | String = "v1",
      timeout | Number = 30,
      retries | Number = 3,
    },

    # Default server configuration
    defaults: {
        plan?: str
        zone?: str
        os?: str
        ssh_keys?: [str]
        firewall_rules?: [FirewallRule]
    }

    # Provider-specific settings
    features: {
        load_balancer?: bool = false
        storage_encryption?: bool = true
        backup?: bool = true
        monitoring?: bool = false
    }
}

schema FirewallRule {
    direction: "ingress" | "egress"
    protocol: "tcp" | "udp" | "icmp"
    port?: str
    source?: str
    destination?: str
    action: "allow" | "deny"
}

schema ServerConfig {
    hostname: str
    plan: str
    zone: str
    os: str = "ubuntu-22.04"
    ssh_keys: [str] = []
    tags?: {str: str} = {}
    firewall_rules?: [FirewallRule] = []
    storage?: {
        size?: int
        type?: str
        encrypted?: bool = true
    }
    network?: {
        public_ip?: bool = true
        private_network?: str
        bandwidth?: int
    }
}
```

#### Nushell Implementation

Create `nulib/mod.nu`:

```nushell
use std log

# Provider name and version
export const PROVIDER_NAME = "my-provider"
export const PROVIDER_VERSION = "1.0.0"

# Import sub-modules
use create.nu *
use delete.nu *
use utils.nu *

# Provider interface implementation
export def "provider-info" [] -> record {
    {
        name: $PROVIDER_NAME,
        version: $PROVIDER_VERSION,
        type: "provider",
        interface: "API",
        supported_operations: [
            "create-server", "delete-server", "list-servers",
            "get-server-info", "start-server", "stop-server"
        ],
        required_auth: ["api_key", "api_secret"],
        supported_os: ["ubuntu-22.04", "debian-11", "centos-8"],
        regions: (get-zones).name
    }
}

export def "validate-config" [config: record] -> record {
    mut errors = []
    mut warnings = []

    # Validate authentication
    if ($config | get -o "auth.api_key" | is-empty) {
        $errors = ($errors | append "Missing API key")
    }

    if ($config | get -o "auth.api_secret" | is-empty) {
        $errors = ($errors | append "Missing API secret")
    }

    # Validate API configuration
    let api_url = ($config | get -o "api.base_url")
    if ($api_url | is-empty) {
        $errors = ($errors | append "Missing API base URL")
    } else {
        try {
            http get $"($api_url)/health" | ignore
        } catch {
            $warnings = ($warnings | append "API endpoint not reachable")
        }
    }

    {
        valid: ($errors | is-empty),
        errors: $errors,
        warnings: $warnings
    }
}

export def "test-connection" [config: record] -> record {
    try {
        let api_url = ($config | get "api.base_url")
        let response = (http get $"($api_url)/account" --headers {
            Authorization: $"Bearer ($config | get 'auth.api_key')"
        })

        {
            success: true,
            account_info: $response,
            message: "Connection successful"
        }
    } catch {|e|
        {
            success: false,
            error: ($e | get msg),
            message: "Connection failed"
        }
    }
}
```

Create `nulib/create.nu`:

```nushell
use std log
use utils.nu *

export def "create-server" [
    config: record       # Server configuration
    --check              # Check mode only
    --wait               # Wait for completion
] -> record {
    log info $"Creating server: ($config.hostname)"

    if $check {
        return {
            action: "create-server",
            hostname: $config.hostname,
            check_mode: true,
            would_create: true,
            estimated_time: "2-5 minutes"
        }
    }

    # Validate configuration
    let validation = (validate-server-config $config)
    if not $validation.valid {
        error make {
            msg: $"Invalid server configuration: ($validation.errors | str join ', ')"
        }
    }

    # Prepare API request
    let api_config = (get-api-config)
    let request_body = {
        hostname: $config.hostname,
        plan: $config.plan,
        zone: $config.zone,
        os: $config.os,
        ssh_keys: $config.ssh_keys,
        tags: $config.tags,
        firewall_rules: $config.firewall_rules
    }

    try {
        let response = (http post $"($api_config.base_url)/servers" --headers {
            Authorization: $"Bearer ($api_config.auth.api_key)"
            Content-Type: "application/json"
        } $request_body)

        let server_id = ($response | get id)
        log info $"Server creation initiated: ($server_id)"

        if $wait {
            let final_status = (wait-for-server-ready $server_id)
            {
                success: true,
                server_id: $server_id,
                hostname: $config.hostname,
                status: $final_status,
                ip_addresses: (get-server-ips $server_id),
                ssh_access: (get-ssh-access $server_id)
            }
        } else {
            {
                success: true,
                server_id: $server_id,
                hostname: $config.hostname,
                status: "creating",
                message: "Server creation in progress"
            }
        }
    } catch {|e|
        error make {
            msg: $"Server creation failed: ($e | get msg)"
        }
    }
}

def validate-server-config [config: record] -> record {
    mut errors = []

    # Required fields
    if ($config | get -o hostname | is-empty) {
        $errors = ($errors | append "Hostname is required")
    }

    if ($config | get -o plan | is-empty) {
        $errors = ($errors | append "Plan is required")
    }

    if ($config | get -o zone | is-empty) {
        $errors = ($errors | append "Zone is required")
    }

    # Validate plan exists
    let available_plans = (get-plans)
    if not ($config.plan in ($available_plans | get name)) {
        $errors = ($errors | append $"Invalid plan: ($config.plan)")
    }

    # Validate zone exists
    let available_zones = (get-zones)
    if not ($config.zone in ($available_zones | get name)) {
        $errors = ($errors | append $"Invalid zone: ($config.zone)")
    }

    {
        valid: ($errors | is-empty),
        errors: $errors
    }
}

def wait-for-server-ready [server_id: string] -> string {
    mut attempts = 0
    let max_attempts = 60  # 10 minutes

    while $attempts < $max_attempts {
        let server_info = (get-server-info $server_id)
        let status = ($server_info | get status)

        match $status {
            "running" => { return "running" },
            "error" => { error make { msg: "Server creation failed" } },
            _ => {
                log info $"Server status: ($status), waiting..."
                sleep 10sec
                $attempts = $attempts + 1
            }
        }
    }

    error make { msg: "Server creation timeout" }
}
```

### Provider Registration

Add provider metadata in `metadata.toml`:

```toml
[extension]
name = "my-provider"
type = "provider"
version = "1.0.0"
description = "Custom cloud provider integration"
author = "Your Name <your.email@example.com>"
license = "MIT"

[compatibility]
provisioning_version = ">=2.0.0"
nushell_version = ">=0.107.0"
nickel_version = ">=1.15.0"

[capabilities]
server_management = true
load_balancer = false
storage_encryption = true
backup = true
monitoring = false

[authentication]
methods = ["api_key", "certificate"]
required_fields = ["api_key", "api_secret"]

[regions]
default = "us-east-1"
available = ["us-east-1", "us-west-2", "eu-west-1"]

[support]
documentation = "https://docs.example.com/provider"
issues = "https://github.com/example/provider/issues"
```

## Task Service Extension API

### Task Service Interface

Task services must implement:

#### Core Operations

- `install(config: record) -> record`
- `uninstall(config: record) -> null`
- `configure(config: record) -> null`
- `status() -> record`
- `restart() -> null`
- `upgrade(version: string) -> record`

#### Version Management

- `get-current-version() -> string`
- `get-available-versions() -> list<string>`
- `check-updates() -> record`

### Task Service Development Template

#### Nickel Schema

Create `schemas/version.ncl`:

```nickel
# Task service version configuration
{
  taskserv_version = {
    name | String = "my-service",
    version | String = "1.0.0",

    # Version source configuration
    source | {
      type | String = "github",
      repository | String,
      release_pattern | String = "v{version}",
    },

    # Installation configuration
    install | {
      method | String = "binary",
      binary_name | String,
      binary_path | String = "/usr/local/bin",
      config_path | String = "/etc/my-service",
      data_path | String = "/var/lib/my-service",
    },

    # Dependencies
    dependencies | [
      {
        name | String,
        version | String = ">=1.0.0",
      }
    ],

    # Service configuration
    service | {
      type | String = "systemd",
      user | String = "my-service",
      group | String = "my-service",
      ports | [Number] = [8080, 9090],
    },

    # Health check configuration
    health_check | {
      endpoint | String,
      interval | Number = 30,
      timeout | Number = 5,
      retries | Number = 3,
    },
  }
}
```

#### Nushell Implementation

Create `nulib/mod.nu`:

```nushell
use std log
use ../../../lib_provisioning *

export const SERVICE_NAME = "my-service"
export const SERVICE_VERSION = "1.0.0"

export def "taskserv-info" [] -> record {
    {
        name: $SERVICE_NAME,
        version: $SERVICE_VERSION,
        type: "taskserv",
        category: "application",
        description: "Custom application service",
        dependencies: ["containerd"],
        ports: [8080, 9090],
        config_files: ["/etc/my-service/config.yaml"],
        data_directories: ["/var/lib/my-service"]
    }
}

export def "install" [
    config: record = {}
    --check              # Check mode only
    --version: string    # Specific version to install
] -> record {
    let install_version = if ($version | is-not-empty) {
        $version
    } else {
        (get-latest-version)
    }

    log info $"Installing ($SERVICE_NAME) version ($install_version)"

    if $check {
        return {
            action: "install",
            service: $SERVICE_NAME,
            version: $install_version,
            check_mode: true,
            would_install: true,
            requirements_met: (check-requirements)
        }
    }

    # Check system requirements
    let req_check = (check-requirements)
    if not $req_check.met {
        error make {
            msg: $"Requirements not met: ($req_check.missing | str join ', ')"
        }
    }

    # Download and install
    let binary_path = (download-binary $install_version)
    install-binary $binary_path
    create-user-and-directories
    generate-config $config
    install-systemd-service

    # Start service
    systemctl start $SERVICE_NAME
    systemctl enable $SERVICE_NAME

    # Verify installation
    let health = (check-health)
    if not $health.healthy {
        error make { msg: "Service failed health check after installation" }
    }

    {
        success: true,
        service: $SERVICE_NAME,
        version: $install_version,
        status: "running",
        health: $health
    }
}

export def "uninstall" [
    --force              # Force removal even if running
    --keep-data         # Keep data directories
] -> null {
    log info $"Uninstalling ($SERVICE_NAME)"

    # Stop and disable service
    try {
        systemctl stop $SERVICE_NAME
        systemctl disable $SERVICE_NAME
    } catch {
        log warning "Failed to stop systemd service"
    }

    # Remove binary
    try {
        rm -f $"/usr/local/bin/($SERVICE_NAME)"
    } catch {
        log warning "Failed to remove binary"
    }

    # Remove configuration
    try {
        rm -rf $"/etc/($SERVICE_NAME)"
    } catch {
        log warning "Failed to remove configuration"
    }

    # Remove data directories (unless keeping)
    if not $keep_data {
        try {
            rm -rf $"/var/lib/($SERVICE_NAME)"
        } catch {
            log warning "Failed to remove data directories"
        }
    }

    # Remove systemd service file
    try {
        rm -f $"/etc/systemd/system/($SERVICE_NAME).service"
        systemctl daemon-reload
    } catch {
        log warning "Failed to remove systemd service"
    }

    log info $"($SERVICE_NAME) uninstalled successfully"
}

export def "status" [] -> record {
    let systemd_status = try {
        systemctl is-active $SERVICE_NAME | str trim
    } catch {
        "unknown"
    }

    let health = (check-health)
    let version = (get-current-version)

    {
        service: $SERVICE_NAME,
        version: $version,
        systemd_status: $systemd_status,
        health: $health,
        uptime: (get-service-uptime),
        memory_usage: (get-memory-usage),
        cpu_usage: (get-cpu-usage)
    }
}

def check-requirements [] -> record {
    mut missing = []
    mut met = true

    # Check for containerd
    if not (which containerd | is-not-empty) {
        $missing = ($missing | append "containerd")
        $met = false
    }

    # Check for systemctl
    if not (which systemctl | is-not-empty) {
        $missing = ($missing | append "systemctl")
        $met = false
    }

    {
        met: $met,
        missing: $missing
    }
}

def check-health [] -> record {
    try {
        let response = (http get "http://localhost:9090/health")
        {
            healthy: true,
            status: ($response | get status),
            last_check: (date now)
        }
    } catch {
        {
            healthy: false,
            error: "Health endpoint not responding",
            last_check: (date now)
        }
    }
}
```

## Cluster Extension API

### Cluster Interface

Clusters orchestrate multiple components:

#### Core Operations

- `create(config: record) -> record`
- `delete(config: record) -> null`
- `status() -> record`
- `scale(replicas: int) -> record`
- `upgrade(version: string) -> record`

#### Component Management

- `list-components() -> list<record>`
- `component-status(name: string) -> record`
- `restart-component(name: string) -> null`

### Cluster Development Template

#### Nickel Configuration

Create `schemas/cluster.ncl`:

```nickel
# Cluster configuration schema
{
  ClusterConfig = {
    # Cluster metadata
    name | String,
    version | String = "1.0.0",
    description | String = "",

    # Components to deploy
    components | [Component],

    # Resource requirements
    resources | {
      min_nodes | Number = 1,
      cpu_per_node | String = "2",
      memory_per_node | String = "4Gi",
      storage_per_node | String = "20Gi",
    },

    # Network configuration
    network | {
      cluster_cidr | String = "10.244.0.0/16",
      service_cidr | String = "10.96.0.0/12",
      dns_domain | String = "cluster.local",
    },

    # Feature flags
    features | {
      monitoring | Bool = true,
      logging | Bool = true,
      ingress | Bool = false,
      storage | Bool = true,
    },
  },

  Component = {
    name | String,
    type | String | "taskserv" | "application" | "infrastructure",
    version | String = "",
    enabled | Bool = true,
    dependencies | [String] = [],
    config | {} = {},
    resources | {
      cpu | String = "",
      memory | String = "",
      storage | String = "",
      replicas | Number = 1,
    } = {},
  },

  # Example cluster configuration
  buildkit_cluster = {
    name = "buildkit",
    version = "1.0.0",
    description = "Container build cluster with BuildKit and registry",
    components = [
      {
        name = "containerd",
        type = "taskserv",
        version = "1.7.0",
        enabled = true,
        dependencies = [],
      },
      {
        name = "buildkit",
        type = "taskserv",
        version = "0.12.0",
        enabled = true,
        dependencies = ["containerd"],
        config = {
          worker_count = 4,
          cache_size = "10Gi",
          registry_mirrors = ["registry:5000"],
        },
      },
      {
        name = "registry",
        type = "application",
        version = "2.8.0",
        enabled = true,
        dependencies = [],
        config = {
          storage_driver = "filesystem",
          storage_path = "/var/lib/registry",
          auth_enabled = false,
        },
        resources = {
          cpu = "500m",
          memory = "1Gi",
          storage = "50Gi",
          replicas = 1,
        },
      },
    ],
    resources = {
      min_nodes = 1,
      cpu_per_node = "4",
      memory_per_node = "8Gi",
      storage_per_node = "100Gi",
    },
    features = {
      monitoring = true,
      logging = true,
      ingress = false,
      storage = true,
    },
  },
}
```

#### Nushell Implementation

Create `nulib/mod.nu`:

```nushell
use std log
use ../../../lib_provisioning *

export const CLUSTER_NAME = "my-cluster"
export const CLUSTER_VERSION = "1.0.0"

export def "cluster-info" [] -> record {
    {
        name: $CLUSTER_NAME,
        version: $CLUSTER_VERSION,
        type: "cluster",
        category: "build",
        description: "Custom application cluster",
        components: (get-cluster-components),
        required_resources: {
            min_nodes: 1,
            cpu_per_node: "2",
            memory_per_node: "4Gi",
            storage_per_node: "20Gi"
        }
    }
}

export def "create" [
    config: record = {}
    --check              # Check mode only
    --wait               # Wait for completion
] -> record {
    log info $"Creating cluster: ($CLUSTER_NAME)"

    if $check {
        return {
            action: "create-cluster",
            cluster: $CLUSTER_NAME,
            check_mode: true,
            would_create: true,
            components: (get-cluster-components),
            requirements_check: (check-cluster-requirements)
        }
    }

    # Validate cluster requirements
    let req_check = (check-cluster-requirements)
    if not $req_check.met {
        error make {
            msg: $"Cluster requirements not met: ($req_check.issues | str join ', ')"
        }
    }

    # Get component deployment order
    let components = (get-cluster-components)
    let deployment_order = (resolve-component-dependencies $components)

    mut deployment_status = []

    # Deploy components in dependency order
    for component in $deployment_order {
        log info $"Deploying component: ($component.name)"

        try {
            let result = match $component.type {
                "taskserv" => {
                    taskserv create $component.name --config $component.config --wait
                },
                "application" => {
                    deploy-application $component
                },
                _ => {
                    error make { msg: $"Unknown component type: ($component.type)" }
                }
            }

            $deployment_status = ($deployment_status | append {
                component: $component.name,
                status: "deployed",
                result: $result
            })

        } catch {|e|
            log error $"Failed to deploy ($component.name): ($e.msg)"
            $deployment_status = ($deployment_status | append {
                component: $component.name,
                status: "failed",
                error: $e.msg
            })

            # Rollback on failure
            rollback-cluster-deployment $deployment_status
            error make { msg: $"Cluster deployment failed at component: ($component.name)" }
        }
    }

    # Configure cluster networking and integrations
    configure-cluster-networking $config
    setup-cluster-monitoring $config

    # Wait for all components to be ready
    if $wait {
        wait-for-cluster-ready
    }

    {
        success: true,
        cluster: $CLUSTER_NAME,
        components: $deployment_status,
        endpoints: (get-cluster-endpoints),
        status: "running"
    }
}

export def "delete" [
    config: record = {}
    --force              # Force deletion
] -> null {
    log info $"Deleting cluster: ($CLUSTER_NAME)"

    let components = (get-cluster-components)
    let deletion_order = ($components | reverse)  # Delete in reverse order

    for component in $deletion_order {
        log info $"Removing component: ($component.name)"

        try {
            match $component.type {
                "taskserv" => {
                    taskserv delete $component.name --force=$force
                },
                "application" => {
                    remove-application $component --force=$force
                },
                _ => {
                    log warning $"Unknown component type: ($component.type)"
                }
            }
        } catch {|e|
            log error $"Failed to remove ($component.name): ($e.msg)"
            if not $force {
                error make { msg: $"Component removal failed: ($component.name)" }
            }
        }
    }

    # Clean up cluster-level resources
    cleanup-cluster-networking
    cleanup-cluster-monitoring
    cleanup-cluster-storage

    log info $"Cluster ($CLUSTER_NAME) deleted successfully"
}

def get-cluster-components [] -> list<record> {
    [
        {
            name: "containerd",
            type: "taskserv",
            version: "1.7.0",
            dependencies: []
        },
        {
            name: "my-service",
            type: "taskserv",
            version: "1.0.0",
            dependencies: ["containerd"]
        },
        {
            name: "registry",
            type: "application",
            version: "2.8.0",
            dependencies: []
        }
    ]
}

def resolve-component-dependencies [components: list<record>] -> list<record> {
    # Topological sort of components based on dependencies
    mut sorted = []
    mut remaining = $components

    while ($remaining | length) > 0 {
        let no_deps = ($remaining | where {|comp|
            ($comp.dependencies | all {|dep|
                $dep in ($sorted | get name)
            })
        })

        if ($no_deps | length) == 0 {
            error make { msg: "Circular dependency detected in cluster components" }
        }

        $sorted = ($sorted | append $no_deps)
        $remaining = ($remaining | where {|comp|
            not ($comp.name in ($no_deps | get name))
        })
    }

    $sorted
}
```

## Extension Registration and Discovery

### Extension Registry

Extensions are registered in the system through:

1. **Directory Structure**: Placed in appropriate directories (providers/, taskservs/, cluster/)
2. **Metadata Files**: `metadata.toml` with extension information
3. **Schema Files**: `schemas/` directory with Nickel schema files

### Registration API

#### `register-extension(path: string, type: string) -> record`

Registers a new extension with the system.

**Parameters:**

- `path`: Path to extension directory
- `type`: Extension type (provider, taskserv, cluster)

#### `unregister-extension(name: string, type: string) -> null`

Removes extension from the registry.

#### `list-registered-extensions(type?: string) -> list<record>`

Lists all registered extensions, optionally filtered by type.

### Extension Validation

#### Validation Rules

1. **Structure Validation**: Required files and directories exist
2. **Schema Validation**: Nickel schemas are valid
3. **Interface Validation**: Required functions are implemented
4. **Dependency Validation**: Dependencies are available
5. **Version Validation**: Version constraints are met

#### `validate-extension(path: string, type: string) -> record`

Validates extension structure and implementation.

## Testing Extensions

### Test Framework

Extensions should include comprehensive tests:

#### Unit Tests

Create `tests/unit_tests.nu`:

```nushell
use std testing

export def test_provider_config_validation [] {
    let config = {
        auth: { api_key: "test-key", api_secret: "test-secret" },
        api: { base_url: "https://api.test.com" }
    }

    let result = (validate-config $config)
    assert ($result.valid == true)
    assert ($result.errors | is-empty)
}

export def test_server_creation_check_mode [] {
    let config = {
        hostname: "test-server",
        plan: "1xCPU-1 GB",
        zone: "test-zone"
    }

    let result = (create-server $config --check)
    assert ($result.check_mode == true)
    assert ($result.would_create == true)
}
```

#### Integration Tests

Create `tests/integration_tests.nu`:

```nushell
use std testing

export def test_full_server_lifecycle [] {
    # Test server creation
    let create_config = {
        hostname: "integration-test",
        plan: "1xCPU-1 GB",
        zone: "test-zone"
    }

    let server = (create-server $create_config --wait)
    assert ($server.success == true)
    let server_id = $server.server_id

    # Test server info retrieval
    let info = (get-server-info $server_id)
    assert ($info.hostname == "integration-test")
    assert ($info.status == "running")

    # Test server deletion
    delete-server $server_id

    # Verify deletion
    let final_info = try { get-server-info $server_id } catch { null }
    assert ($final_info == null)
}
```

### Running Tests

```bash
# Run unit tests
nu tests/unit_tests.nu

# Run integration tests
nu tests/integration_tests.nu

# Run all tests
nu tests/run_all_tests.nu
```

## Documentation Requirements

### Extension Documentation

Each extension must include:

1. **README.md**: Overview, installation, and usage
2. **API.md**: Detailed API documentation
3. **EXAMPLES.md**: Usage examples and tutorials
4. **CHANGELOG.md**: Version history and changes

### API Documentation Template

```bash
# Extension Name API

## Overview
Brief description of the extension and its purpose.

## Installation
Steps to install and configure the extension.

## Configuration
Configuration schema and options.

## API Reference
Detailed API documentation with examples.

## Examples
Common usage patterns and examples.

## Troubleshooting
Common issues and solutions.
```

## Best Practices

### Development Guidelines

1. **Follow Naming Conventions**: Use consistent naming for functions and variables
2. **Error Handling**: Implement comprehensive error handling and recovery
3. **Logging**: Use structured logging for debugging and monitoring
4. **Configuration Validation**: Validate all inputs and configurations
5. **Documentation**: Document all public APIs and configurations
6. **Testing**: Include comprehensive unit and integration tests
7. **Versioning**: Follow semantic versioning principles
8. **Security**: Implement secure credential handling and API calls

### Performance Considerations

1. **Caching**: Cache expensive operations and API calls
2. **Parallel Processing**: Use parallel execution where possible
3. **Resource Management**: Clean up resources properly
4. **Batch Operations**: Batch API calls when possible
5. **Health Monitoring**: Implement health checks and monitoring

### Security Best Practices

1. **Credential Management**: Store credentials securely
2. **Input Validation**: Validate and sanitize all inputs
3. **Access Control**: Implement proper access controls
4. **Audit Logging**: Log all security-relevant operations
5. **Encryption**: Encrypt sensitive data in transit and at rest

This extension development API provides a comprehensive framework for building robust, scalable, and maintainable extensions for provisioning.