### Installing Express OpenAPI Middleware

Source: https://github.com/wesleytodd/express-openapi/blob/main/README.md

Command to install the @wesleytodd/openapi package using npm.

```shell
$ npm install --save @wesleytodd/openapi
```

--------------------------------

### Defining OpenAPI Component - JavaScript

Source: https://github.com/wesleytodd/express-openapi/blob/main/README.md

Shows how to use the `oapi.component` method to define a new reusable component in the OpenAPI document. This example defines an 'examples' component named 'FooExample' with a summary and value.

```javascript
oapi.component('examples', 'FooExample', {
  summary: 'An example of foo',
  value: 'bar'
})
```

--------------------------------

### Getting Full Component Definition - JavaScript

Source: https://github.com/wesleytodd/express-openapi/blob/main/README.md

Shows how to use `oapi.component` with only the component type to retrieve the full JSON definition of the component previously defined with that type and name.

```javascript
oapi.component('examples')
// { summary: 'An example of foo', value: 'bar' }
```

--------------------------------

### Getting Component Reference Object - JavaScript

Source: https://github.com/wesleytodd/express-openapi/blob/main/README.md

Illustrates using `oapi.component` with only the component type and name (or variable holding the name) to retrieve an OpenAPI Reference Object (`{ '$ref': '#/components/examples/FooExample' }`) pointing to the defined component.

```javascript
oapi.component('examples', FooExample)
// { '$ref': '#/components/examples/FooExample' }
```

--------------------------------

### Registering Validated Path with Custom Keywords - Express/JavaScript

Source: https://github.com/wesleytodd/express-openapi/blob/main/README.md

Shows how to use `oapi.validPath` with the `pathOpts` parameter to enable custom AJV keywords like 'regexp'. It defines a request body schema with a validation rule using `not: { regexp: '/^[A-Z]/' }`. An error handler middleware is included to process validation errors, similar to the previous example.

```javascript
app.get('/zoom', oapi.validPath({
  ...
  requestBody: {
    required: true,
    content: {
      'application/json': {
        schema: {
          type: 'object',
          properties: {
            name: { type: 'string', not: { regexp: '/^[A-Z]/' } }
          }
        }
      }
    }
  },
  ...
}, { keywords: ['regexp'] }), (err, req, res, next) => {
  res.status(err.status).json({
    error: err.message,
    validation: err.validationErrors,
    schema: err.validationSchema
  })
})
```

--------------------------------

### Initializing and Using Express OpenAPI Middleware

Source: https://github.com/wesleytodd/express-openapi/blob/main/README.md

Demonstrates how to require the middleware, initialize it with basic OpenAPI info, apply it to an Express app, and define a route with inline OpenAPI response schema.

```javascript
const openapi = require('@wesleytodd/openapi')
const app = require('express')()

const oapi = openapi({
  openapi: '3.0.0',
  info: {
    title: 'Express Application',
    description: 'Generated docs from an Express api',
    version: '1.0.0',
  }
})

// This will serve the generated json document(s)
// (as well as the swagger-ui if configured)
app.use(oapi)

// To add path specific schema you can use the .path middleware
app.get('/', oapi.path({
  responses: {
    200: {
      description: 'Successful response',
      content: {
        'application/json': {
          schema: {
            type: 'object',
            properties: {
              hello: { type: 'string' }
            }
          }
        }
      }
    }
  }
}), (req, res) => {
  res.json({
    hello: 'world'
  })
})

app.listen(8080)
```

--------------------------------

### Serving Swagger UI Middleware (JavaScript)

Source: https://github.com/wesleytodd/express-openapi/blob/main/README.md

This snippet demonstrates how to mount the `swaggerui` middleware provided by `express-openapi` onto a specific path (`/swaggerui`) in an Express application.

```javascript
app.use('/swaggerui', oapi.swaggerui())
```

--------------------------------

### Registering Path with OpenAPI Document - Express/JavaScript

Source: https://github.com/wesleytodd/express-openapi/blob/main/README.md

Shows how to use `oapi.path` middleware within an Express `app.get` route. It defines the OpenAPI `OperationObject` for the path, specifying the response schema for a 200 OK response. The subsequent route handler demonstrates accessing request parameters and sending a JSON response.

```javascript
app.get('/:foo', oapi.path({
  description: 'Get a foo',
  responses: {
    200: {
      content: {
        'application/json': {
          schema: {
            type: 'object',
            properties: {
              foo: { type: 'string' }
            }
          }
        }
      }
    }
  }
}), (req, res) => {
  res.json({
    foo: req.params.foo
  })
})
```

--------------------------------

### Fetching Generated OpenAPI Spec

Source: https://github.com/wesleytodd/express-openapi/blob/main/README.md

Shell command using curl to retrieve the generated OpenAPI JSON document from the running Express application and jq to format the output.

```shell
$ curl -s http://localhost:8080/openapi.json | jq .
```

--------------------------------

### Registering Validated Path and Handling Errors - Express/JavaScript

Source: https://github.com/wesleytodd/express-openapi/blob/main/README.md

Illustrates using `oapi.validPath` middleware to register a path and automatically validate incoming requests against the defined schema. It includes an error handling middleware function that catches validation errors (`err`) and sends a formatted JSON response containing error details, validation errors, and the schema.

```javascript
app.get('/:foo', oapi.validPath({
  description: 'Get a foo',
  responses: {
    200: {
      content: {
        'application/json': {
          schema: {
            type: 'object',
            properties: {
              foo: { type: 'string' }
            }
          }
        }
      }
    },
    400: {
      content: {
        'application/json': {
          schema: {
            type: 'object',
            properties: {
              error: { type: 'string' }
            }
          }
        }
      }
    }
  }
}), (err, req, res, next) => {
  res.status(err.status).json({
    error: err.message,
    validation: err.validationErrors,
    schema: err.validationSchema
  })
})
```

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