gem-hunter

echt

Why echt?

Installation

npm install echt
# or
yarn add echt
# or
pnpm add echt

Quick Start

import express from 'express'
import { validate } from 'echt'
import { z } from 'zod'

const app = express()
app.use(express.json())

// Define your schema once, get full type safety
const userSchema = {
  body: z.object({
    name: z.string(),
    age: z.number()
  }),
  response: z.object({
    id: z.string(),
    name: z.string(),
    age: z.number()
  })
}

// Validation and type inference work automatically
app.post('/users', validate(userSchema), (req, res) => {
  const { name, age } = req.body // ✅ Fully typed
  res.json({ id: '123', name, age }) // ✅ Response validated
})

Validation Types

Request Validation

const schema = {
  // Request body validation
  body: z.object({
    username: z.string(),
    age: z.number()
  }),

  // URL parameters (e.g., /users/:id)
  params: z.object({
    id: z.string().uuid()
  }),

  // Query string parameters (e.g., ?page=1&limit=10)
  query: z.object({
    page: z.string().transform(Number),
    limit: z.string().transform(Number)
  }),

  // HTTP headers
  headers: z.object({
    'api-key': z.string(),
    'content-type': z.string().optional()
  }),

  // Express locals (useful for middleware communication)
  locals: z.object({
    userId: z.string(),
    permissions: z.array(z.string())
  })
}

app.get('/users/:id', validate(schema), (req, res) => {
  // All properties are fully typed
  const { id } = req.params
  const { page, limit } = req.query
  const { userId } = res.locals
  // ...
})

Response Validation

Simple Response Validation

const schema = {
  response: z.object({
    success: z.boolean(),
    data: z.any()
  })
}

app.get('/data', validate(schema), (req, res) => {
  res.json({
    success: true,
    data: {
      /* ... */
    }
  })
})

Status-Aware Response Validation

const schema = {
  useResponse: {
    200: z.object({ data: z.array(z.string()) }),
    404: z.object({ error: z.string() }),
    500: z.object({
      message: z.string(),
      code: z.literal('INTERNAL_SERVER_ERROR'),
      requestId: z.string()
    })
  }
}

// ❌ This will throw an error
app.get('/data', validate(schema), (req, res) => {})

// ✅ This is the correct way
app.get(
  '/data',
  validate(schema).use((req, res) => {
    if (!data) {
      return res.status(404).json({ error: 'Not found' })
    }

    try {
      // your logic here
      res.json({ data: ['item1', 'item2'] })
    } catch (error) {
      res.status(500).json({
        message: 'Internal server error occurred',
        code: 'INTERNAL_SERVER_ERROR',
        requestId: generateRequestId()
      })
    }
  })
)

Troubleshooting

Contributing

License

MIT License

Copyright (c) 2025 Armagan Amcalar

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.