# gittrends-app/core architecture

> Architecture diagram of the GitHub repository gittrends-app/core, generated by GitDiagram from its file tree, README and a sample of source files (last updated 2026-07-31). It is an AI-made overview: check details against the source.

- Interactive diagram: https://gitdiagram.com/gittrends-app/core
- Repository: https://github.com/gittrends-app/core

## Overview

#### Purpose and Public Entry Points
`@gittrends-app/core` is a Node.js 20+ TypeScript library that retrieves GitHub GraphQL data and normalizes it into runtime-validated domain entities. Consumers import its public API from `src/index.ts`, notably `GithubClient`, `GithubService`, the `Service` contract, and optional caching/buffering decorators. Runnable usage patterns are in `samples/search-repositories.ts` and `samples/get-resources.ts`.

#### Service Abstraction and Composition
`Service` defines the application-facing retrieval contract; `GithubService` implements it against GitHub. Services are deliberately composable: callers can wrap a source service with caching and buffered iteration without changing the consumer API.
- `src/services/Service.ts`
- `src/services/github/GithubService.ts`
- `src/services/CacheService.ts`
- `src/services/BufferedService.ts`

`PassThroughService` provides the base delegation pattern used by wrappers: request flow is consumer → optional decorators → GitHub-backed source.

#### GitHub Transport Boundary
`GithubClient` owns the external GitHub API boundary: API base URL, token authentication, request timeout, and shared maximum concurrency across primary queries and nested enrichment. Query execution is centralized by `QueryRunner`, isolating GraphQL request/error behavior from resource-specific lookup logic.
- `src/services/github/GithubClient.ts`
- `src/services/github/graphql/QueryRunner.ts`
- `src/helpers/throttler.ts`

GitHub GraphQL is the only identified external service; no application database or server runtime is present.

#### GraphQL Query Construction and Lookup Layer
Resource retrieval is modeled as lookups that generate/query distinct GitHub GraphQL shapes: repositories, search, users, issues, pull requests, commits, discussions, releases, tags, and connection-based related data. Lookup implementations sit between the service API and GraphQL runner, forming the main query specialization boundary.
- `src/services/github/graphql/lookups/Lookup.ts`
- `src/services/github/graphql/lookups/RepositoryLookup.ts`
- `src/services/github/graphql/lookups/ConnectionLookup.ts`

GraphQL fragments consolidate reusable selection sets and allow lookup responses to include nested domain data consistently.
- `src/services/github/graphql/fragments/Fragment.ts`
- `src/services/github/graphql/fragments/RepositoryFragment.ts`
- `src/services/github/graphql/fragments/TimelineItemFragment.ts`

#### Resource Iteration, Pagination, and Enrichment
The `resources()` API exposes async page iteration. Pagination standardizes emitted `data` plus opaque continuation cursor, `per_page`, and `has_more`; callers feed the cursor back to resume. GitHub resource handlers connect named resources to their lookups and apply resource-specific mapping/enrichment.
- `src/services/pagination.ts`
- `src/services/github/resources/repos.ts`
- `src/services/github/resources/enrichment.ts`

Nested enrichment—such as comments or review-thread/timeline-related data—remains behind this resource layer and shares client concurrency controls rather than bypassing transport governance.

#### Domain Entity Boundary
GitHub GraphQL output is transformed into entity models representing repository activity and actors. Zod-backed entity schemas are the runtime-validation boundary, preventing raw or malformed API responses from leaking through the public service API.
- `src/entities/index.ts`
- `src/entities/Repository.ts`
- `src/entities/Issue.ts`

Common GraphQL/domain concepts—node identity, actors, comments, reactions, and repository-scoped nodes—are factored into base entity schemas.
- `src/entities/base/Node.ts`
- `src/entities/base/GitActorSchema.ts`
- `src/entities/base/RepositoryNode.ts`

#### Cache and Buffer Operational Semantics
`CacheService` treats cache reads/writes as best effort: backend failure must not fail the underlying GitHub request. `BufferedService` batches/controls iteration behavior while preserving the `Service` interface. These wrappers are infrastructure-neutral: cache persistence is supplied by the consuming application through the exported cache interface.
- `src/services/CacheService.ts`
- `src/services/BufferedService.ts`
- `src/services/PassThroughService.ts

Main entry points: [`src/services/github/GithubService.ts`](https://github.com/gittrends-app/core/blob/main/src/services/github/GithubService.ts) (GitHub service), [`src/index.ts`](https://github.com/gittrends-app/core/blob/main/src/index.ts) (Package exports), [`src/services/github/graphql/lookups/Lookup.ts`](https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/lookups/Lookup.ts) (GraphQL lookups), [`src/services/github/resources/repos.ts`](https://github.com/gittrends-app/core/blob/main/src/services/github/resources/repos.ts) (Resource handlers)

## Diagram (Mermaid)

```mermaid
flowchart TD

subgraph group_public["Public API"]
  node_consumer(("Library consumer"))
  node_public_api["Package exports<br/>TypeScript entrypoint<br/>[index.ts]"]
end

subgraph group_services["Service Composition"]
  node_service_contract["Service contract<br/>interface<br/>[Service.ts]"]
  node_cache_service["Cache decorator<br/>service decorator<br/>[CacheService.ts]"]
  node_buffered_service["Buffered decorator<br/>service decorator<br/>[BufferedService.ts]"]
  node_pass_through["Delegating base<br/>service base"]
end

subgraph group_github["GitHub Integration"]
  node_github_service["GitHub service<br/>Service implementation<br/>[GithubService.ts]"]
  node_pagination["Async pagination<br/>page protocol<br/>[pagination.ts]"]
  node_resource_handlers["Resource handlers<br/>resource mapping<br/>[repos.ts]"]
  node_enrichment["Nested enrichment<br/>resource enrichment<br/>[enrichment.ts]"]
  node_lookup_layer["GraphQL lookups<br/>query specialization<br/>[Lookup.ts]"]
  node_repository_lookup["Repository lookup"]
  node_connection_lookup["Connection lookup"]
  node_fragments["GraphQL fragments<br/>selection sets<br/>[Fragment.ts]"]
  node_query_runner["Query runner<br/>GraphQL executor<br/>[QueryRunner.ts]"]
  node_github_client{{"GitHub client<br/>transport client<br/>[GithubClient.ts]"}}
  node_throttler["Shared throttler<br/>concurrency control<br/>[throttler.ts]"]
  node_github_api{{"GitHub GraphQL API<br/>external API"}}
end

subgraph group_domain["Domain Models"]
  node_entities["Validated entities<br/>Zod schemas<br/>[index.ts]"]
  node_repository_entity["Repository entity<br/>domain schema<br/>[Repository.ts]"]
  node_issue_entity["Issue entity<br/>domain schema<br/>[Issue.ts]"]
  node_node_base["Entity base schemas<br/>domain schema base<br/>[Node.ts]"]
end

node_consumer -->|"imports"| node_public_api
node_public_api -->|"exports"| node_service_contract
node_public_api -->|"exports"| node_github_service
node_public_api -->|"exports optional decorator"| node_cache_service
node_public_api -->|"exports optional decorator"| node_buffered_service
node_cache_service -->|"extends delegation"| node_pass_through
node_buffered_service -->|"extends delegation"| node_pass_through
node_pass_through -->|"preserves"| node_service_contract
node_github_service -->|"implements"| node_service_contract
node_cache_service -.->|"wraps source"| node_github_service
node_buffered_service -.->|"wraps source"| node_github_service
node_github_service -->|"exposes resources&#40;&#41;"| node_pagination
node_github_service -->|"dispatches resources"| node_resource_handlers
node_resource_handlers -->|"applies nested data"| node_enrichment
node_resource_handlers -->|"uses"| node_lookup_layer
node_lookup_layer -->|"specializes"| node_repository_lookup
node_lookup_layer -->|"specializes"| node_connection_lookup
node_lookup_layer -->|"composes"| node_fragments
node_lookup_layer -->|"executes through"| node_query_runner
node_enrichment -->|"queries through"| node_query_runner
node_query_runner -->|"uses transport"| node_github_client
node_github_client -->|"shares concurrency"| node_throttler
node_github_client -->|"GraphQL requests"| node_github_api
node_resource_handlers -->|"maps and validates"| node_entities
node_entities -->|"exports"| node_repository_entity
node_entities -->|"exports"| node_issue_entity
node_repository_entity -->|"builds on"| node_node_base
node_issue_entity -->|"builds on"| node_node_base

click node_public_api "https://github.com/gittrends-app/core/blob/main/src/index.ts"
click node_service_contract "https://github.com/gittrends-app/core/blob/main/src/services/Service.ts"
click node_cache_service "https://github.com/gittrends-app/core/blob/main/src/services/CacheService.ts"
click node_buffered_service "https://github.com/gittrends-app/core/blob/main/src/services/BufferedService.ts"
click node_pass_through "https://github.com/gittrends-app/core/blob/main/src/services/PassThroughService.ts"
click node_github_service "https://github.com/gittrends-app/core/blob/main/src/services/github/GithubService.ts"
click node_pagination "https://github.com/gittrends-app/core/blob/main/src/services/pagination.ts"
click node_resource_handlers "https://github.com/gittrends-app/core/blob/main/src/services/github/resources/repos.ts"
click node_enrichment "https://github.com/gittrends-app/core/blob/main/src/services/github/resources/enrichment.ts"
click node_lookup_layer "https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/lookups/Lookup.ts"
click node_repository_lookup "https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/lookups/RepositoryLookup.ts"
click node_connection_lookup "https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/lookups/ConnectionLookup.ts"
click node_fragments "https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/fragments/Fragment.ts"
click node_query_runner "https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/QueryRunner.ts"
click node_github_client "https://github.com/gittrends-app/core/blob/main/src/services/github/GithubClient.ts"
click node_throttler "https://github.com/gittrends-app/core/blob/main/src/helpers/throttler.ts"
click node_entities "https://github.com/gittrends-app/core/blob/main/src/entities/index.ts"
click node_repository_entity "https://github.com/gittrends-app/core/blob/main/src/entities/Repository.ts"
click node_issue_entity "https://github.com/gittrends-app/core/blob/main/src/entities/Issue.ts"
click node_node_base "https://github.com/gittrends-app/core/blob/main/src/entities/base/Node.ts"

classDef toneNeutral fill:#f8fafc,stroke:#334155,stroke-width:1.5px,color:#0f172a
classDef toneBlue fill:#dbeafe,stroke:#2563eb,stroke-width:1.5px,color:#172554
classDef toneAmber fill:#fef3c7,stroke:#d97706,stroke-width:1.5px,color:#78350f
classDef toneMint fill:#dcfce7,stroke:#16a34a,stroke-width:1.5px,color:#14532d
classDef toneRose fill:#ffe4e6,stroke:#e11d48,stroke-width:1.5px,color:#881337
classDef toneIndigo fill:#e0e7ff,stroke:#4f46e5,stroke-width:1.5px,color:#312e81
classDef toneTeal fill:#ccfbf1,stroke:#0f766e,stroke-width:1.5px,color:#134e4a
class node_consumer,node_public_api toneBlue
class node_service_contract,node_cache_service,node_buffered_service,node_pass_through toneAmber
class node_github_service,node_pagination,node_resource_handlers,node_enrichment,node_lookup_layer,node_repository_lookup,node_connection_lookup,node_fragments,node_query_runner,node_github_client,node_throttler,node_github_api toneMint
class node_entities,node_repository_entity,node_issue_entity,node_node_base toneRose
```

## Components

### Public API

- **Library consumer**: consumer · Uses the retrieval API and resumes cursored pages.
- [Package exports](https://github.com/gittrends-app/core/blob/main/src/index.ts): TypeScript entrypoint · `src/index.ts`

### Service Composition

- [Service contract](https://github.com/gittrends-app/core/blob/main/src/services/Service.ts): interface · Stable retrieval contract shared by sources and decorators. · `src/services/Service.ts`
- [Cache decorator](https://github.com/gittrends-app/core/blob/main/src/services/CacheService.ts): service decorator · Best-effort cache failures do not fail source retrieval. · `src/services/CacheService.ts`
- [Buffered decorator](https://github.com/gittrends-app/core/blob/main/src/services/BufferedService.ts): service decorator · Controls iteration while preserving the Service interface. · `src/services/BufferedService.ts`
- [Delegating base](https://github.com/gittrends-app/core/blob/main/src/services/PassThroughService.ts): service base · Delegation pattern used by wrappers. · `src/services/PassThroughService.ts`

### GitHub Integration

- [GitHub service](https://github.com/gittrends-app/core/blob/main/src/services/github/GithubService.ts): Service implementation · `src/services/github/GithubService.ts`
- [Async pagination](https://github.com/gittrends-app/core/blob/main/src/services/pagination.ts): page protocol · Emits data, opaque cursor, per_page, and has_more. · `src/services/pagination.ts`
- [Resource handlers](https://github.com/gittrends-app/core/blob/main/src/services/github/resources/repos.ts): resource mapping · Maps named resources and applies resource-specific enrichment. · `src/services/github/resources/repos.ts`
- [Nested enrichment](https://github.com/gittrends-app/core/blob/main/src/services/github/resources/enrichment.ts): resource enrichment · Fetches related comments and timeline/review data. · `src/services/github/resources/enrichment.ts`
- [GraphQL lookups](https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/lookups/Lookup.ts): query specialization · Builds resource and connection query shapes. · `src/services/github/graphql/lookups/Lookup.ts`
- [Repository lookup](https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/lookups/RepositoryLookup.ts): lookup · `src/services/github/graphql/lookups/RepositoryLookup.ts`
- [Connection lookup](https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/lookups/ConnectionLookup.ts): lookup · `src/services/github/graphql/lookups/ConnectionLookup.ts`
- [GraphQL fragments](https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/fragments/Fragment.ts): selection sets · Reusable nested selection sets for lookup responses. · `src/services/github/graphql/fragments/Fragment.ts`
- [Query runner](https://github.com/gittrends-app/core/blob/main/src/services/github/graphql/QueryRunner.ts): GraphQL executor · Centralizes GraphQL request and error behavior. · `src/services/github/graphql/QueryRunner.ts`
- [GitHub client](https://github.com/gittrends-app/core/blob/main/src/services/github/GithubClient.ts): transport client · Owns API URL, token, timeout, and shared concurrency. · `src/services/github/GithubClient.ts`
- [Shared throttler](https://github.com/gittrends-app/core/blob/main/src/helpers/throttler.ts): concurrency control · Governs primary and nested GitHub requests. · `src/helpers/throttler.ts`
- **GitHub GraphQL API**: external API

### Domain Models

- [Validated entities](https://github.com/gittrends-app/core/blob/main/src/entities/index.ts): Zod schemas · Runtime boundary preventing raw API output from reaching consumers. · `src/entities/index.ts`
- [Repository entity](https://github.com/gittrends-app/core/blob/main/src/entities/Repository.ts): domain schema · `src/entities/Repository.ts`
- [Issue entity](https://github.com/gittrends-app/core/blob/main/src/entities/Issue.ts): domain schema · `src/entities/Issue.ts`
- [Entity base schemas](https://github.com/gittrends-app/core/blob/main/src/entities/base/Node.ts): domain schema base · Shared node, actor, and repository-scoped concepts. · `src/entities/base/Node.ts`

## Connections

- Library consumer → Package exports: imports
- Package exports → Service contract: exports
- Package exports → GitHub service: exports
- Package exports → Cache decorator: exports optional decorator
- Package exports → Buffered decorator: exports optional decorator
- Cache decorator → Delegating base: extends delegation
- Buffered decorator → Delegating base: extends delegation
- Delegating base → Service contract: preserves
- GitHub service → Service contract: implements
- Cache decorator → GitHub service: wraps source
- Buffered decorator → GitHub service: wraps source
- GitHub service → Async pagination: exposes resources()
- GitHub service → Resource handlers: dispatches resources
- Resource handlers → Nested enrichment: applies nested data
- Resource handlers → GraphQL lookups: uses
- GraphQL lookups → Repository lookup: specializes
- GraphQL lookups → Connection lookup: specializes
- GraphQL lookups → GraphQL fragments: composes
- GraphQL lookups → Query runner: executes through
- Nested enrichment → Query runner: queries through
- Query runner → GitHub client: uses transport
- GitHub client → Shared throttler: shares concurrency
- GitHub client → GitHub GraphQL API: GraphQL requests
- Resource handlers → Validated entities: maps and validates
- Validated entities → Repository entity: exports
- Validated entities → Issue entity: exports
- Repository entity → Entity base schemas: builds on
- Issue entity → Entity base schemas: builds on