type HttpVerbs = 'GET' | 'POST' | 'PATCH' | 'DELETE'

const board = () => '/boards'
const id = ({ id }: { id: number }) => id.toString()
// const id = ({ id, fuga }: { id: number, fuga: number }) => id.toString() + fuga.toString()
const boards = { pathSpec: [board, id] as const } as {
  Methods?: {
    PATCH: { id: number; title: string },
    DELETE: { id: number }
  }
}

type Resource = {
  Methods?: { [verb in HttpVerbs]?: any }
  pathSpec?: ((args: any) => string)[]
}
function f<
  M extends keyof Exclude<T['Methods'], undefined>,
  T extends Resource,
  P extends Exclude<T['Methods'], undefined>[M]
>(method: M, { pathSpec }: T, params: P): string {
  const paths = pathSpec.map(f => f(params))
  return method + paths.join('/')
}

type P = Exclude<(typeof boards)['Methods'], undefined>['DELETE']
// const params = { id: 1, title: 'hi' }
const params = { id: 1 }
type AP = typeof params

type XP = Exclude<keyof AP, keyof P> extends never ? P : never

f('PATCH', boards, { id: 1, title: 'hi' })
f('PATCH', boards, { title: 'hi' })
f('DELETE', boards, { id: 1 })
f('DELETE', boards, { id: 1, title: 'hi' })
f('GET', boards, { id: 1 })
f('FUGA', boards, { id: 1, title: 'hi' })