# Root

## Overview

The `com` package is the top-level Java namespace root for this codebase. It serves as the organizational boundary for all Fujitsu-specific enterprise code, anchoring the **Futurity** product family -- a billing and pricing platform built for enterprise rate-engineering, financial calculations, and multi-client deployment scenarios.

This namespace does not contain source files directly. Instead, it functions as an organizational root that delegates all meaningful code to child sub-packages. The entire scope of the `com` subtree is effectively coextensive with the Fujitsu codebase, which currently contains a single product domain: Futurity.

The architectural story of this subtree is one of **layered customization** -- a design pattern where standard product behavior is kept separate from site-specific extensions, enabling a single codebase to serve multiple Fujitsu clients with divergent rate plans and billing rules.

## Sub-module Guide

### Fujitsu (`com.fujitsu`)

The `com.fujitsu` sub-package is the top-level namespace for all Fujitsu-related code. It acts as a client boundary, delineating code written specifically for the Fujitsu account or partnership. The package itself contains no source files -- all meaningful code lives in child sub-packages, primarily under `com.fujitsu.futurity`.

**Key characteristics:**

- **Purpose**: Organizational root for Fujitsu-related modules, following the common enterprise pattern where each client or partner gets their own top-level namespace.
- **Content**: Delegates entirely to the `futurity` product family.
- **Domain focus**: Rate-engineering, pricing calculations, billing cycle management, and financial rule evaluation.
- **Customization model**: Uses a `custom` qualifier pattern to separate standard behavior from site-specific extensions.

If new Fujitsu-related products are added to the codebase, they would nest as siblings under `com.fujitsu`, following the same organizational pattern.

## Key Patterns and Architecture

### Client-Specific Namespace Pattern

The `com.fujitsu` namespace establishes a single level of hierarchy before delegating to its children. This pattern cleanly separates partner code from any internal core logic, making it straightforward to identify, audit, and maintain client-specific customization.

### Layered Customization Model (Futurity)

The single most important architectural decision in this package subtree is the layered customization model. Standard and bespoke logic are kept separate:

- **Standard layer**: Base product behavior shared across all Fujitsu deployments.
- **Custom layer**: Site-specific extensions qualified by a `custom` qualifier, enabling deployment-specific behavior without modifying core code.

Code in `custom` sub-packages is likely gated by feature flags or deployment-specific configuration and should not be assumed to always be active. Any developer working in this subtree must understand how this qualification pattern gates feature flags, deployment-specific configuration, and variant rate plans.

### Constants Discipline

The innermost `constant` sub-module (at `com.fujitsu.futurity.bp.custom.constant`) provides a centralized location for configuration keys, rate-plan codes, and feature flags. When looking up magic strings, rate-plan identifiers, or configuration constants in this subtree, developers should reference this constants module rather than scattering raw values throughout the codebase.

### Module Hierarchy Diagram

```mermaid
flowchart TD
    Root["com root package
    (Java namespace root)"] --> Com["com package
    (Fujitsu client boundary)"]
    Com --> Fujitsu["com.fujitsu
    (Fujitsu codebase root)"]
    Fujitsu --> Futurity["com.fujitsu.futurity
    (Futurity product family)"]
    Futurity --> BP["com.fujitsu.futurity.bp
    (billing/pricing domain)"]
    Futurity --> Custom["com.fujitsu.futurity.custom
    (customization layer)"]
    BP --> Constants["com.fujitsu.futurity.bp.custom.constant
    (configuration constants)"]
    style Root fill:#f5f5f5
    style Com fill:#e3f2fd
    style Fujitsu fill:#e3f2fd
    style Futurity fill:#fff3e0
    style BP fill:#e8f5e9
    style Custom fill:#fff9c4
    style Constants fill:#f3e5f5
```

The hierarchy goes four levels deep, with each level refining scope from product family down to configuration constants.

## Dependencies and Integration

### Internal Dependencies

- **No indexed source files**: Neither this module nor its children have indexed source files in the current code index. This means no package-level dependency graph is available at the `com` level. Dependencies are documented at the `futurity` sub-module level.
- **No cross-module relationships detected**: This package does not appear to export public APIs consumed by sibling modules, nor does it import from siblings. It operates as an internal namespace boundary.

### Integration Points

- The `futurity` package is the sole functional child. Its `bp` (billing/pricing) domain, `custom` customization layer, and `constant` configuration module form the backbone of this subtree.
- The customization model (`custom` qualifiers) is the integration mechanism by which different Fujitsu client deployments customize behavior while sharing a common codebase.

## Notes for Developers

- **Indexing gap**: No source files have been indexed under this module or its children. If source code exists for these packages, the build configuration or source roots may need to be checked to ensure they are included in indexing.
- **Single child scope**: Currently, `futurity` is the only child module. The `com` module's scope is effectively coextensive with Fujitsu's code.
- **Customization awareness**: Any developer working in this subtree should understand the `custom` qualification pattern -- code in `custom` sub-packages is likely gated by feature flags or deployment-specific configuration, and should not be assumed to always be active.
- **Constants discipline**: The `constant` sub-module pattern (used by `futurity`) should be referenced when looking up configuration keys, rate-plan codes, or feature flags anywhere in this subtree.
- **Extensibility**: If new Fujitsu-related products are added, they would nest as siblings under `com.fujitsu`, following the existing organizational pattern.