import gleam/bytes_tree
import gleam/http/response
import gleam/int
import gleam/list

/// Encodes an HTTP response into bytes.
/// 
pub fn encode_response(
  response: response.Response(BitArray),
) -> bytes_tree.BytesTree {
  bytes_tree.new()
  |> bytes_tree.append(encode_status_line(response.status))
  |> bytes_tree.append(encode_headers(response.headers))
  |> bytes_tree.append(response.body)
}

/// Encodes the HTTP status line and headers of an HTTP response.
/// 
pub fn encode_response_partially(
  response: response.Response(a),
) -> bytes_tree.BytesTree {
  bytes_tree.new()
  |> bytes_tree.append(encode_status_line(response.status))
  |> bytes_tree.append(encode_headers(response.headers))
}

/// Encodes the HTTP status line.
/// 
fn encode_status_line(status: Int) -> BitArray {
  let status_name = status_to_bit_array(status)
  let status = int.to_string(status)

  <<"HTTP/1.1 ", status:utf8, " ", status_name:bits, "\r\n">>
}

/// Encodes HTTP headers into bytes.
/// 
fn encode_headers(headers: List(#(String, String))) -> BitArray {
  let headers =
    list.fold(headers, <<>>, fn(acc, headers) {
      let #(key, value) = headers

      <<acc:bits, key:utf8, ": ", value:utf8, "\r\n">>
    })

  <<headers:bits, "\r\n">>
}

/// Maps HTTP status codes to their text descriptions.
/// 
fn status_to_bit_array(status: Int) -> BitArray {
  case status {
    100 -> <<"Continue">>
    101 -> <<"Switching Protocols">>
    102 -> <<"Processing">>
    103 -> <<"Early Hints">>
    200 -> <<"OK">>
    201 -> <<"Created">>
    202 -> <<"Accepted">>
    203 -> <<"Non-Authoritative Information">>
    204 -> <<"No Content">>
    205 -> <<"Reset Content">>
    206 -> <<"Partial Content">>
    207 -> <<"Multi-Status">>
    208 -> <<"Already Reported">>
    226 -> <<"IM Used">>
    300 -> <<"Multiple Choices">>
    301 -> <<"Moved Permanently">>
    302 -> <<"Found">>
    303 -> <<"See Other">>
    304 -> <<"Not Modified">>
    307 -> <<"Temporary Redirect">>
    308 -> <<"Permanent Redirect">>
    400 -> <<"Bad Request">>
    401 -> <<"Unauthorized">>
    403 -> <<"Forbidden">>
    404 -> <<"Not Found">>
    405 -> <<"Method Not Allowed">>
    406 -> <<"Not Acceptable">>
    407 -> <<"Proxy Authentication Required">>
    408 -> <<"Request Timeout">>
    409 -> <<"Conflict">>
    410 -> <<"Gone">>
    411 -> <<"Length Required">>
    412 -> <<"Precondition Failed">>
    413 -> <<"Payload Too Large">>
    414 -> <<"URI Too Long">>
    415 -> <<"Unsupported Media Type">>
    416 -> <<"Range Not Satisfiable">>
    417 -> <<"Expectation Failed">>
    418 -> <<"I'm a teapot">>
    421 -> <<"Misdirected Request">>
    422 -> <<"Unprocessable Entity">>
    423 -> <<"Locked">>
    424 -> <<"Failed Dependency">>
    425 -> <<"Too Early">>
    426 -> <<"Upgrade Required">>
    428 -> <<"Precondition Required">>
    429 -> <<"Too Many Requests">>
    431 -> <<"Request Header Fields Too Large">>
    451 -> <<"Unavailable For Legal Reasons">>
    500 -> <<"Internal Server Error">>
    501 -> <<"Not Implemented">>
    502 -> <<"Bad Gateway">>
    503 -> <<"Service Unavailable">>
    504 -> <<"Gateway Timeout">>
    505 -> <<"HTTP Version Not Supported">>
    506 -> <<"Variant Also Negotiates">>
    507 -> <<"Insufficient Storage">>
    508 -> <<"Loop Detected">>
    510 -> <<"Not Extended">>
    511 -> <<"Network Authentication Required">>
    _ -> <<"Unknown HTTP Status">>
  }
}