params.ts

type PathConverter<P> = (params: P) => string
type routes = {
  boards: {
    GET: {
      pathParams: {}
      bodyParams: {}
    },
    POST: {
      pathParams: {}
      bodyParams: { title: string }
    }
  },
  board: {
    GET: {
      pathParams: { id: number }
      bodyParams: {}
    },
    PATCH: {
      pathParams: { id: number }
      bodyParams: { title: string }
    }
  }
}
type HttpVerbs = 'GET' | 'POST' | 'PATCH'
type Verbs<R> = keyof R & HttpVerbs
type Resources = keyof routes

function f<
  V extends Verbs<routes[R]>,
  R extends Resources,
  P extends routes[R][V] extends { pathParams: infer PP, bodyParams: infer BP } ? PP & BP : {}
>(verb: V, name: R, params: P) {
  return verb + name + JSON.stringify(params)
}

const updateBoard = ['PATCH', 'board']
f('PATCH', 'board', { id: 1, title: 'hi' })

params2.ts

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' })

params3.ts

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

const boards = { path: ({ id }: { id: number }) => `/boards/${id}` } as {
  path?: ({ id: number}) => string
  Methods?: {
    PATCH: {
      names: { id: number }
      params: { title: string }
    }
    DELETE: {
      names: { id: number }
    }
  }
}

type Resource = {
  path?: (names: any, opts?: any) => string
  Methods?: { [verb in HttpVerbs]?: any }
}
function f<
  M extends keyof Exclude<T['Methods'], undefined>,
  T extends Resource,
  P extends Exclude<T['Methods'], undefined>[M]
>(method: M, { path }: T, params: P): string {
  return method + path(params)
}

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