import std/strutils
import std/tables

import monoucha/fromjs
import monoucha/javascript
import monoucha/jserror
import monoucha/quickjs
import monoucha/tojs
import types/opt
import types/url
import utils/twtstr

type
  HeaderGuard* = enum
    hgNone = "none"
    hgImmutable = "immutable"
    hgRequest = "request"
    hgRequestNoCors = "request-no-cors"
    hgResponse = "response"

  Headers* = ref object
    table: Table[string, seq[string]]
    guard*: HeaderGuard

  HeadersInitType = enum
    hitSequence, hitTable

  HeadersInit* = object
    case t: HeadersInitType
    of hitSequence:
      s: seq[(string, string)]
    of hitTable:
      tab: Table[string, string]

jsDestructor(Headers)

func isForbiddenResponseHeaderName*(name: string): bool

iterator pairs*(this: Headers): (string, string) =
  for k, vs in this.table:
    if this.guard == hgResponse and k.isForbiddenResponseHeaderName():
      continue
    for v in vs:
      yield (k, v)

iterator allPairs*(headers: Headers): (string, string) =
  for k, vs in headers.table:
    for v in vs:
      yield (k, v)

proc fromJS(ctx: JSContext; val: JSValueConst; res: var HeadersInit):
    Err[void] =
  if JS_IsUndefined(val) or JS_IsNull(val):
    return err()
  var headers: Headers
  if ctx.fromJS(val, headers).isSome:
    res = HeadersInit(t: hitSequence, s: @[])
    for k, v in headers.table:
      for vv in v:
        res.s.add((k, vv))
    return ok()
  if ctx.isSequence(val):
    res = HeadersInit(t: hitSequence)
    if ctx.fromJS(val, res.s).isSome:
      return ok()
  res = HeadersInit(t: hitTable)
  ?ctx.fromJS(val, res.tab)
  return ok()

const TokenChars = {
  '!', '#', '$', '%', '&', '\'', '*', '+', '-', '.', '^', '_', '`', '|', '~'
} + AsciiAlphaNumeric

func isValidHeaderName*(s: string): bool =
  return s.len > 0 and AllChars - TokenChars notin s

func isValidHeaderValue*(s: string): bool =
  return s.len == 0 or s[0] notin {' ', '\t'} and s[^1] notin {' ', '\t'} and
    '\n' notin s

func isForbiddenRequestHeader*(name, value: string): bool =
  const ForbiddenNames = [
    "Accept-Charset",
    "Accept-Encoding",
    "Access-Control-Request-Headers",
    "Access-Control-Request-Method",
    "Connection",
    "Content-Length",
    "Cookie",
    "Cookie2",
    "Date",
    "DNT",
    "Expect",
    "Host",
    "Keep-Alive",
    "Origin",
    "Referer",
    "Set-Cookie",
    "TE",
    "Trailer",
    "Transfer-Encoding",
    "Upgrade",
    "Via"
  ]
  for x in ForbiddenNames:
    if name.equalsIgnoreCase(x):
      return true
  if name.startsWithIgnoreCase("proxy-") or name.startsWithIgnoreCase("sec-"):
    return true
  if name.equalsIgnoreCase("X-HTTP-Method") or
      name.equalsIgnoreCase("X-HTTP-Method-Override") or
      name.equalsIgnoreCase("X-Method-Override"):
    return true # meh
  return false

func isForbiddenResponseHeaderName*(name: string): bool =
  return name.equalsIgnoreCase("Set-Cookie") or
    name.equalsIgnoreCase("Set-Cookie2")

proc validate(this: Headers; name, value: string): JSResult[bool] =
  if not name.isValidHeaderName() or not value.isValidHeaderValue():
    return errTypeError("Invalid header name or value")
  if this.guard == hgImmutable:
    return errTypeError("Tried to modify immutable Headers object")
  if this.guard == hgRequest and isForbiddenRequestHeader(name, value):
    return ok(false)
  if this.guard == hgResponse and name.isForbiddenResponseHeaderName():
    return ok(false)
  return ok(true)

func isNoCorsSafelistedName(name: string): bool =
  return name.equalsIgnoreCase("Accept") or
    name.equalsIgnoreCase("Accept-Language") or
    name.equalsIgnoreCase("Content-Language") or
    name.equalsIgnoreCase("Content-Type")

const CorsUnsafeRequestByte = {
  char(0x00)..char(0x08), char(0x10)..char(0x1F), '"', '(', ')', ':', '<', '>',
  '?', '@', '[', '\\', ']', '{', '}', '\e'
}

func isNoCorsSafelisted(name, value: string): bool =
  if value.len > 128:
    return false
  if name.equalsIgnoreCase("Accept"):
    return CorsUnsafeRequestByte notin value
  if name.equalsIgnoreCase("Accept-Language") or
      name.equalsIgnoreCase("Content-Language"):
    const Forbidden = AllChars - AsciiAlphaNumeric -
      {' ', '*', ',', '-', '.', ';', '='}
    return Forbidden notin value
  if name.equalsIgnoreCase("Content-Type"):
    return value.strip(chars = AsciiWhitespace).toLowerAscii() in [
      "multipart/form-data",
      "text/plain",
      "application-x-www-form-urlencoded"
    ]
  return false

func get0(this: Headers; name: string): string =
  return this.table[name].join(", ")

proc get*(ctx: JSContext; this: Headers; name: string): JSValue {.jsfunc.} =
  if not name.isValidHeaderName():
    JS_ThrowTypeError(ctx, "Invalid header name")
    return JS_EXCEPTION
  let name = name.toHeaderCase()
  if name notin this.table:
    return JS_NULL
  return ctx.toJS(this.get0(name))

proc removeRange(this: Headers) =
  if this.guard == hgRequestNoCors:
    #TODO do this case insensitively
    this.table.del("Range") # privileged no-CORS request headers
    this.table.del("range")

proc append(this: Headers; name, value: string): JSResult[void] {.jsfunc.} =
  let value = value.strip(chars = HTTPWhitespace)
  if not ?this.validate(name, value):
    return ok()
  let name = name.toHeaderCase()
  if this.guard == hgRequestNoCors:
    if name in this.table:
      let tmp = this.get0(name) & ", " & value
      if not name.isNoCorsSafelisted(tmp):
        return ok()
  if name in this.table:
    this.table[name].add(value)
  else:
    this.table[name] = @[value]
  this.removeRange()
  ok()

proc delete(this: Headers; name: string): JSResult[void] {.jsfunc.} =
  let name = name.toHeaderCase()
  if not ?this.validate(name, "") or name notin this.table:
    return ok()
  if not name.isNoCorsSafelistedName() and not name.equalsIgnoreCase("Range"):
    return ok()
  this.table.del(name)
  this.removeRange()
  ok()

proc has(this: Headers; name: string): JSResult[bool] {.jsfunc.} =
  if not name.isValidHeaderName():
    return errTypeError("Invalid header name")
  let name = name.toHeaderCase()
  return ok(name in this.table)

proc set(this: Headers; name, value: string): JSResult[void] {.jsfunc.} =
  let value = value.strip(chars = HTTPWhitespace)
  if not ?this.validate(name, value):
    return ok()
  if this.guard == hgRequestNoCors and not name.isNoCorsSafelisted(value):
    return ok()
  this.table[name.toHeaderCase()] = @[value]
  this.removeRange()
  ok()

proc fill(headers: Headers; s: seq[(string, string)]): JSResult[void] =
  for (k, v) in s:
    ?headers.append(k, v)
  ok()

proc fill(headers: Headers; tab: Table[string, string]): JSResult[void] =
  for k, v in tab:
    ?headers.append(k, v)
  ok()

proc fill*(headers: Headers; init: HeadersInit): JSResult[void] =
  case init.t
  of hitSequence: return headers.fill(init.s)
  of hitTable: return headers.fill(init.tab)

func newHeaders*(guard: HeaderGuard): Headers =
  return Headers(guard: guard)

func newHeaders*(guard: HeaderGuard; table: openArray[(string, string)]):
    Headers =
  let headers = newHeaders(guard)
  for (k, v) in table:
    let k = k.toHeaderCase()
    headers.table.withValue(k, vs):
      vs[].add(v)
    do:
      headers.table[k] = @[v]
  return headers

func newHeaders*(guard: HeaderGuard; table: Table[string, string]): Headers =
  let headers = newHeaders(guard)
  for k, v in table:
    let k = k.toHeaderCase()
    headers.table.withValue(k, vs):
      vs[].add(v)
    do:
      headers.table[k] = @[v]
  return headers

func newHeaders(obj = none(HeadersInit)): JSResult[Headers] {.jsctor.} =
  let headers = Headers(guard: hgNone)
  if obj.isSome:
    ?headers.fill(obj.get)
  return ok(headers)

func clone*(headers: Headers): Headers =
  return Headers(table: headers.table)

proc add*(headers: Headers; k: string; v: sink string) =
  let k = k.toHeaderCase()
  headers.table.withValue(k, p):
    p[].add(v)
  do:
    headers.table[k] = @[v]

proc `[]=`*(headers: Headers; k: string; v: sink string) =
  let k = k.toHeaderCase()
  headers.table[k] = @[v]

func `[]`*(headers: Headers; k: string): var string =
  let k = k.toHeaderCase()
  return headers.table[k][0]

func contains*(headers: Headers; k: string): bool =
  return k.toHeaderCase() in headers.table

func getOrDefault*(headers: Headers; k: string; default = ""): string =
  let k = k.toHeaderCase()
  headers.table.withValue(k, p):
    return p[][0]
  do:
    return default

proc del*(headers: Headers; k: string) =
  headers.table.del(k)

func getAllCommaSplit*(headers: Headers; k: string): seq[string] =
  headers.table.withValue(k, p):
    return p[].join(",").split(',')
  return @[]

func getAllNoComma*(headers: Headers; k: string): seq[string] =
  headers.table.withValue(k, p):
    return p[]
  return @[]

type CheckRefreshResult* = object
  # n is timeout in millis. -1 => not found
  n*: int
  # url == nil => self
  url*: URL

func parseRefresh*(s: string; baseURL: URL): CheckRefreshResult =
  var i = s.skipBlanks(0)
  let s0 = s.until(AllChars - AsciiDigit, i)
  let x = parseUInt32(s0, allowSign = false)
  if s0 != "":
    if x.isNone and (i >= s.len or s[i] != '.'):
      return CheckRefreshResult(n: -1)
  var n = int(x.get(0) * 1000)
  i = s.skipBlanks(i + s0.len)
  if i < s.len and s[i] == '.':
    inc i
    let s1 = s.until(AllChars - AsciiDigit, i)
    if s1 != "":
      n += int(parseUInt32(s1, allowSign = false).get(0))
      i = s.skipBlanks(i + s1.len)
  elif s0 == "": # empty string or blanks
    return CheckRefreshResult(n: -1)
  if i >= s.len: # just reload this page
    return CheckRefreshResult(n: n)
  if s[i] notin {',', ';'}:
    return CheckRefreshResult(n: -1)
  i = s.skipBlanks(i + 1)
  if s.toOpenArray(i, s.high).startsWithIgnoreCase("url="):
    i = s.skipBlanks(i + "url=".len)
  var q = false
  if i < s.len and s[i] in {'"', '\''}:
    q = true
    inc i
  var s2 = s.substr(i)
  if q and s2.len > 0 and s[^1] in {'"', '\''}:
    s2.setLen(s2.high)
  let url = parseURL(s2, some(baseURL))
  if url.isNone:
    return CheckRefreshResult(n: -1)
  return CheckRefreshResult(n: n, url: url.get)

proc addHeadersModule*(ctx: JSContext) =
  ctx.registerType(Headers)