(*
  OCaml HTTP - do it yourself (fully OCaml) HTTP daemon

  Copyright (C) <2002> Stefano Zacchiroli <zack@cs.unibo.it>

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*)

open Printf;;

open Http_common;;
open Http_types;;
open Http_constants;;

let (bindings_sep, binding_sep, pieces_sep, header_sep) =
  (Pcre.regexp "&", Pcre.regexp "=", Pcre.regexp " ", Pcre.regexp ":")
let header_RE = Pcre.regexp "([^:]*):(.*)"

let url_decode url = Netencoding.Url.decode ~plus:true url

  (** given an HTTP like query string (e.g. "name1=value1&name2=value2&...")
  @return a list of pairs [("name1", "value1"); ("name2", "value2")]
  @raise Malformed_query if the string isn't a valid query string
  @raise Malformed_query_part if some piece of the query isn't valid
  *)
let split_query_params query =
  let bindings = Pcre.split ~rex:bindings_sep query in
  match bindings with
  | [] -> raise (Malformed_query query)
  | bindings ->
      List.map
        (fun binding ->
          match Pcre.split ~rex:binding_sep binding with
          | [ ""; b ] -> (* '=b' *)
              raise (Malformed_query_part (binding, query))
          | [ a; b ]  -> (* 'a=b' *) (url_decode a, url_decode b)
          | [ a ]     -> (* 'a=' || 'a' *) (url_decode a, "")
          | _ -> raise (Malformed_query_part (binding, query)))
        bindings

  (** internal, used by generic_input_line *)
exception Line_completed;;

  (** given an input channel and a separator
  @return a line read from it (like Pervasives.input_line)
  line is returned only after reading a separator string; separator string isn't
  included in the returned value
  TODO what about efficiency?, input is performed char-by-char
  *)
let generic_input_line ~sep ~ic =
  let sep_len = String.length sep in
  if sep_len < 1 then
    failwith ("Separator '" ^ sep ^ "' is too short!")
  else  (* valid separator *)
    let line = ref "" in
    let sep_pointer = ref 0 in
    try
      while true do
        if !sep_pointer >= String.length sep then (* line completed *)
          raise Line_completed
        else begin (* incomplete line: need to read more *)
          let ch = input_char ic in
          if ch = String.get sep !sep_pointer then  (* next piece of sep *)
            incr sep_pointer
          else begin  (* useful char *)
            for i = 0 to !sep_pointer - 1 do
              line := !line ^ (String.make 1 (String.get sep i))
            done;
            sep_pointer := 0;
            line := !line ^ (String.make 1 ch)
          end
        end
      done;
      assert false  (* unreacheable statement *)
    with Line_completed -> !line

let patch_empty_path = function "" -> "/" | s -> s
let debug_dump_request path params =
  debug_print
    (sprintf
      "recevied request; path: %s; params: %s"
      path
      (String.concat ", " (List.map (fun (n, v) -> n ^ "=" ^ v) params)))

let parse_request_fst_line ic =
  let request_line = generic_input_line ~sep:crlf ~ic in
  match Pcre.split ~rex:pieces_sep request_line with
  | [ meth_raw; uri_raw; http_version_raw ] ->
      (try
        (method_of_string meth_raw,                 (* method *)
        Http_parser_sanity.url_of_string uri_raw,   (* uri *)
        version_of_string http_version_raw)         (* version *)
      with Neturl.Malformed_URL -> raise (Malformed_request_URI uri_raw))
  | _ -> raise (Malformed_request request_line)

let parse_path uri = patch_empty_path (String.concat "/" (Neturl.url_path uri))
let parse_query_get_params uri =
  try (* act on HTTP encoded URIs *)
    split_query_params (Neturl.url_query ~encoded:true uri)
  with Not_found -> []

let parse_headers ic =
  (* consume also trailing "^\r\n$" line *)
  let rec parse_headers' headers =
    match generic_input_line ~sep:crlf ~ic with
    | "" -> List.rev headers
    | line ->
        (let subs =
          try
            Pcre.extract ~rex:header_RE line
          with Not_found -> raise (Invalid_header line)
        in
        let header =
          try
            subs.(1)
          with Invalid_argument "Array.get" -> raise (Invalid_header line)
        in
        let value =
          try
            Http_parser_sanity.normalize_header_value subs.(2) 
          with Invalid_argument "Array.get" -> ""
        in
        Http_parser_sanity.heal_header (header, value);
        parse_headers' ((header, value) :: headers))
  in
  parse_headers' []

let parse_request ic =
  let (meth, uri, version) = parse_request_fst_line ic in
  let path = parse_path uri in
  let query_get_params = parse_query_get_params uri in
  debug_dump_request path query_get_params;
  (path, query_get_params)