// Loaded from https://deno.land/x/tinyhttp@0.1.18/extensions/res/headers.ts


import { vary, encodeUrl, charset, lookup, Req, Res } from '../../deps.ts'
import { getRequestHeader } from '../req/headers.ts'

const charsetRegExp = /;\s*charset\s*=/

export const setHeader = <Response extends Res = Res>(res: Response) => (
  field: string | Record<string, string | number | string[]>,
  val?: string | number | readonly string[]
): Response => {
  if (typeof field === 'string') {
    let value = Array.isArray(val) ? val.map(String) : String(val)

    // add charset to content-type
    if (field.toLowerCase() === 'content-type') {
      if (Array.isArray(value)) {
        throw new TypeError('Content-Type cannot be set to an Array')
      }

      if (!charsetRegExp.test(value)) {
        const ch = charset(value.split(';')[0])

        if (typeof ch === 'string') value += '; charset=' + ch.toLowerCase()
      }
    }

    res.headers.set(field, value as string)
  } else {
    for (const key in field) {
      setHeader(res)(key, field[key] as string)
    }
  }
  return res
}

export const getResponseHeader = <Response extends Res = Res>(res: Response) => (field: string) => {
  return res.headers?.get(field)
}

export const setLocationHeader = <Request extends Req = Req, Response extends Res = Res>(
  req: Request,
  res: Response
) => (url: string): Response => {
  let loc = url

  // "back" is an alias for the referrer
  if (url === 'back') loc = (getRequestHeader(req)('Referrer') as string) || '/'

  // set location
  res.headers.set('Location', encodeUrl(loc))
  return res
}

export const setLinksHeader = <Response extends Res = Res>(res: Response) => (links: {
  [key: string]: string
}): Response => {
  let link = res.headers?.get('Link') || ''
  if (link) link += ', '
  res.headers.set(
    'Link',
    link +
      Object.keys(links)
        .map((rel) => '<' + links[rel] + '>; rel="' + rel + '"')
        .join(', ')
  )

  return res
}

export const setVaryHeader = <Response extends Res = Res>(res: Response) => (field: string): Response => {
  vary(res.headers || new Headers({}), field)

  return res
}

export const setContentType = <Response extends Res = Res>(res: Response) => (type: string): Response => {
  const ct = type.indexOf('/') === -1 ? lookup(type) : type

  setHeader(res)('Content-Type', ct)

  return res
}