Custom Fetcher

// Default behavior
const response = await fetch(url, {
  method,
  headers: body ? { 'Content-Type': 'application/json' } : {},
  body: body ? JSON.stringify(body) : undefined
})

interface FetcherOptions {
  method: string
  url:    string
  body?:  any     // already-parsed body object (not stringified)
}

type Fetcher = (options: FetcherOptions) => Promise<Response>

const kweri = new Kweri({
  baseURL: 'https://api.example.com',
  fetcher: async ({ method, url, body }) => {
    const token = getAuthToken()  // your auth mechanism

    return fetch(url, {
      method,
      headers: {
        'Content-Type': 'application/json',
        ...(token ? { Authorization: `Bearer ${token}` } : {})
      },
      body: body ? JSON.stringify(body) : undefined
    })
  }
})

const kweri = new Kweri({
  baseURL: 'https://api.example.com',
  fetcher: async ({ method, url, body }) => {
    let token = getAccessToken()

    const res = await fetch(url, {
      method,
      headers: { Authorization: `Bearer ${token}`, 'Content-Type': 'application/json' },
      body: body ? JSON.stringify(body) : undefined
    })

    // Attempt a single refresh on 401
    if (res.status === 401) {
      token = await refreshAccessToken()
      return fetch(url, {
        method,
        headers: { Authorization: `Bearer ${token}`, 'Content-Type': 'application/json' },
        body: body ? JSON.stringify(body) : undefined
      })
    }

    return res
  }
})

const kweri = new Kweri({
  baseURL: 'https://api.example.com',
  fetcher: async ({ method, url, body }) => {
    const controller = new AbortController()
    const timeout = setTimeout(() => controller.abort(), 10_000)  // 10s

    try {
      return await fetch(url, {
        method,
        signal: controller.signal,
        headers: { 'Content-Type': 'application/json' },
        body: body ? JSON.stringify(body) : undefined
      })
    } finally {
      clearTimeout(timeout)
    }
  }
})

import { fetch } from 'undici'

const kweri = new Kweri({
  baseURL: 'https://api.example.com',
  fetcher: async ({ method, url, body }) =>
    fetch(url, {
      method,
      headers: { 'Content-Type': 'application/json' },
      body: body ? JSON.stringify(body) : undefined
    }) as unknown as Response
})

const kweri = new Kweri({
  baseURL: 'https://api.example.com',
  fetcher: async ({ method, url, body }) => {
    const res = await fetch(url, {
      method,
      headers: { 'Content-Type': 'application/json' },
      body: body ? JSON.stringify(body) : undefined
    })

    if (!res.ok) throw new Error(`HTTP ${res.status}`)

    const envelope = await res.json()

    // Return a fake Response that kweri can call .json() on
    return new Response(JSON.stringify(envelope.data), {
      status: 200,
      headers: { 'Content-Type': 'application/json' }
    })
  }
})