# Com

## Overview

The `com` package is the top-level Java namespace root for the codebase, and in this context, it primarily serves as the organizational boundary for **Fujitsu-specific enterprise code**. It represents the client-facing code subtree for Fujitsu — a large Japanese technology company — and contains 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, delegating all meaningful code to child sub-packages. Currently, the only child and therefore the sole domain under this umbrella is the `futurity` product family.

## Sub-module Guide

### Fujitsu (`fujitsu`)

The `com.fujitsu` sub-package is the top-level namespace for Fujitsu-specific code. It acts as a client boundary — meaning it delineates code written specifically for the Fujitsu account or partnership — and currently houses the Futurity product family.

**Key characteristics:**

- **Purpose**: Organizational root for all Fujitsu-related modules. This is a common pattern in enterprise codebases where each client or partner gets their own top-level namespace.
- **Content**: The package itself contains no source files. All meaningful code lives in child sub-packages, primarily under `com.fujitsu.futurity`.
- **Domain focus**: Through its `futurity` child, this namespace covers rate-engineering, pricing calculations, billing cycle management, and financial rule evaluation.
- **Customization model**: Uses a `custom` qualifier pattern to separate standard product behavior from site-specific extensions, enabling a single codebase to serve multiple Fujitsu clients with divergent rate plans and billing rules.
- **Nesting depth**: The hierarchy goes four levels deep (`futurity` → `bp` → `custom` → `constant`), with each level refining scope from product family down to configuration constants.

The Futurity product family is the only module nested under `com.fujitsu` today. If new Fujitsu-related products are added to the codebase in the future, they would naturally nest as siblings under `com.fujitsu`, keeping 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 is common in enterprise codebases where a client-specific root package contains multiple product domains. It allows the codebase to cleanly separate partner code from internal core logic.

### Layered Customization Model (Futurity)

Since the only meaningful code lives under `futurity`, the architecture of `com` is effectively the architecture of Futurity — specifically, its layered customization model where standard and bespoke logic are kept separate:

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

This is the single most important architectural decision in this package subtree. Any developer working in this codebase must understand how the `custom` 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 developers look up any magic strings, rate-plan identifiers, or configuration constants in this subtree, they should reference this constants module rather than scattering raw values throughout the codebase.

## 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.

### Module Hierarchy Diagram

```mermaid
flowchart TD
    Root["com
(java namespace root)"] --> 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 Fujitsu fill:#e3f2fd
    style Futurity fill:#e3f2fd
    style BP fill:#fff3e0
    style Custom fill:#e8f5e9
    style Constants fill:#f3e5f5
```

## 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.