sustatov027-max/url_shortener

Purpose and Entry Point

A Go HTTP API for creating and resolving shortened URLs, backed by PostgreSQL. The process starts in cmd/app/main.go; generated Swagger artifacts are embedded alongside it in cmd/app/docs/docs.go.

Composition Root and Runtime

cmd/app/main.go loads configuration, initializes PostgreSQL, constructs repository/service/handler layers, and starts the HTTP server. Container deployment is supported by Dockerfile and docker-compose.yml; environment inputs are documented by .env.example.

HTTP/API Boundary

Routing and request/response handling live in internal/handler/router.go and internal/handler/url_handler.go. This boundary owns HTTP semantics—route dispatch, input decoding/validation, status codes, and Swagger-facing API behavior—while delegating URL operations to the service layer.

URL Application Service

internal/service/url_service.go implements the core use cases: accepting an original URL, generating or assigning its short identifier, persisting the mapping, and resolving a short identifier back to its destination. It is the business boundary between transport handlers and persistence, and depends on repository abstractions rather than PostgreSQL directly.

Persistence Abstraction and PostgreSQL Adapter

internal/repository/repository.go defines the storage-facing contract used by services. PostgreSQL-specific connection setup is in internal/repository/postgres/postgres.go, with URL mapping queries in internal/repository/postgres/url.go. PostgreSQL is the material external dependency and durable source of URL mappings.

Identifier Generation

pkg/generator/generator.go provides short-code generation independently of HTTP and database concerns. The URL service consumes this capability when creating mappings; generated values must cooperate with persistence uniqueness rules to prevent collisions.

Schema Lifecycle and API Documentation

migrations/000001_init_schema.up.sql and migrations/000001_init_schema.down.sql define creation and rollback of the database schema. API documentation is published as generated OpenAPI/Swagger files at cmd/app/docs/swagger.yaml and cmd/app/docs/swagger.json, exposing the handler contract to clients.

Primary Flow

Create flow: HTTP request → internal/handler/url_handler.go → internal/service/url_service.go → pkg/generator/generator.go plus repository interface → internal/repository/postgres/url.go → PostgreSQL. Resolve flow reverses the lookup path: request handler → service → repository/PostgreSQL → HTTP redirect or response. Configuration is isolated in internal/config/config.go, keeping environment and connection details outside domain flow.