// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

/*
Package app provides the business logic layer for Mattermost Channels.

This package serves as the core business logic layer that sits between the API layer (api4)
and the data access layer (store). It contains the primary application logic for all
Mattermost functionality including user management, channel operations, post handling,
notifications, authentication, authorization, and integrations.

# Architecture

The app package follows a layered architecture pattern:

	┌─────────────────────────────────────────────────────────────────┐
	│                       API Layer (api4)                         │
	├─────────────────────────────────────────────────────────────────┤
	│                    Business Logic (app)                        │
	├─────────────────────────────────────────────────────────────────┤
	│                     Data Access (store)                        │
	└─────────────────────────────────────────────────────────────────┘

# Core Components

## App Structure

The App struct is the main entry point for business logic operations. It is a pure
functional component that does not hold state, constructed per request and provides
access to business logic methods through its association with the Channels struct.

## Server

The Server struct manages the HTTP server, routing, middleware, and service lifecycle.
It coordinates between platform services, manages enterprise features, handles
clustering, and provides the runtime environment for the application.

## Channels

The Channels struct contains all channels-related state and enterprise interface
implementations. It manages plugins, file storage, image processing, and coordinates
various enterprise features like compliance, LDAP, and SAML.

## Platform Service

The platform service handles non-entity related functionalities required by the
application including database access, configuration management, caching, licensing,
metrics, and search engines.

# Design Patterns

## Request Context Pattern
All business logic methods accept a request.CTX parameter for request-scoped
logging, tracing, and cancellation.

## Interface Segregation
Enterprise features are accessed through interfaces in the einterfaces package,
allowing for modular enterprise functionality.

## Dependency Injection
Services and dependencies are injected through the Server and Channels structs,
enabling testability and modularity.

## Event-Driven Architecture
The application uses WebSocket events and plugin hooks for real-time updates
and extensibility.

# Key Responsibilities

  - Business logic: Core application rules and workflows
  - Data orchestration: Coordinate between multiple stores and services
  - External integrations: Third-party service calls and API interactions
  - Cache management: Handle cache invalidation and updates
  - Event handling: Trigger notifications, webhooks, and background jobs

# Error Handling

The package uses model.AppError for consistent error handling across the
application. Errors include structured information for logging, user
messages, and HTTP status codes.

This package is central to the Mattermost server architecture and provides
the foundation for all collaboration features in the platform.
*/
package app