%%% Copyright (c) 2014, NORDUnet A/S.
%%% See LICENSE for licensing information.

%%% @doc Certificate Transparency (RFC 6962)

-module(v1).
%% API (URL)
-export(['add-chain'/3, 'add-pre-chain'/3, 'get-sth'/3,
 'get-sth-consistency'/3, 'get-proof-by-hash'/3, 'get-entries'/3,
 'get-roots'/3, 'get-entry-and-proof'/3]).
%% Testing -- FIXME: remove
-export([hello/3]).

-include("$CTROOT/plop/include/plop.hrl").
-define(PROTOCOL_VERSION, 0).

%% Public functions, i.e. part of URL.
'add-chain'(SessionID, _Env, Input) ->
    Res = case (catch jiffy:decode(Input)) of
              {error, E} -> html("add-chain: bad input:", E);
              {[{<<"chain">>, Chain}]} ->
                  Entry = #plop_entry{type = x509,
                                      data = list_to_binary(Chain)},
                  SPT = plop:add(#timestamped_entry{entry = Entry}),
                  R = [{sct_version, ?PROTOCOL_VERSION},
                       {id, base64:encode(SPT#spt.logid)},
                       {timestamp, SPT#spt.timestamp},
                       {extensions, base64:encode("")},
                       {signature, base64:encode(
                                     plop:serialise(SPT#spt.signature))}],
                  binary_to_list(jiffy:encode({R}));
              _ -> html("add-chain: missing input: chain", Input)
          end,
    deliver(SessionID, Res).

'add-pre-chain'(SessionID, _Env, _Input) ->
    niy(SessionID).

'get-sth'(SessionID, _Env, _Input) ->
    #sth{
       treesize = Treesize,
       timestamp = Timestamp,
       roothash = Roothash,
       signature = Signature} = plop:sth(),
    R = [{tree_size, Treesize},
         {timestamp, Timestamp},
         {sha256_root_hash, base64:encode(Roothash)},
         {tree_head_signature, base64:encode(
                                 plop:serialise(Signature))}],
    deliver(SessionID, binary_to_list(jiffy:encode({R}))).

'get-sth-consistency'(SessionID, _Env, Input) ->
    R = case lists:sort(httpd:parse_query(Input)) of
            [{"first", FirstInput}, {"second", SecondInput}] ->
                {First, _} = string:to_integer(FirstInput),
                {Second, _} = string:to_integer(SecondInput),
                case lists:member(error, [First, Second]) of
                    true ->
                        html("get-sth-consistency: bad input:",
                             [FirstInput, SecondInput]);
                    false ->
                        binary_to_list(
                          jiffy:encode(
                            {[{consistency,
                               [base64:encode(X) ||
                                   X <- plop:consistency(First, Second)]}]}))
                end;
            _ -> html("get-sth-consistency: bad input:", Input)
        end,
    deliver(SessionID, R).

'get-proof-by-hash'(SessionID, _Env, Input) ->
    R = case lists:sort(httpd:parse_query(Input)) of
            [{"hash", HashInput}, {"tree_size", TreeSizeInput}] ->
                Hash = case (catch base64:decode(HashInput)) of
                           {'EXIT', _} -> error;
                           H -> H
                       end,
                {TreeSize, _} = string:to_integer(TreeSizeInput),
                case lists:member(error, [Hash, TreeSize]) of
                    true ->
                        html("get-proof-by-hash: bad input:",
                             [HashInput, TreeSizeInput]);
                    false ->
                        binary_to_list(
                          jiffy:encode(
                            case plop:inclusion(Hash, TreeSize) of
                                {ok, Index, Path} ->
                                    {[{leaf_index, Index},
                                      {audit_path,
                                       [base64:encode(X) || X <- Path]}]};
                                {notfound, Msg} ->
                                    %% FIXME: http status 400
                                    {[{success, false},
                                      {error_message, list_to_binary(Msg)}]}
                            end))
                end;
            _ -> html("get-proof-by-hash: bad input:", Input)
        end,
    deliver(SessionID, R).

'get-entries'(SessionID, _Env, Input) ->
    %% TODO: Limit the number of returned entreis (i.e. start-end) to
    %% something reasonable.
    R = case lists:sort(httpd:parse_query(Input)) of
            [{"end", EndInput}, {"start", StartInput}] ->
                {Start, _} = string:to_integer(StartInput),
                {End, _} = string:to_integer(EndInput),
                case lists:member(error, [Start, End]) of
                    true -> html("get-entries: bad input:", [Start, End]);
                    false -> encode_entries(plop:get(Start, End))
                end;
            _ -> html("get-entries: bad input:", Input)
        end,
    deliver(SessionID, R).

'get-entry-and-proof'(SessionID, _Env, Input) ->
    R = case lists:sort(httpd:parse_query(Input)) of
            [{"leaf_index", IndexInput}, {"tree_size", TreeSizeInput}] ->
                {Index, _} = string:to_integer(IndexInput),
                {TreeSize, _} = string:to_integer(TreeSizeInput),
                case lists:member(error, [Index, TreeSize]) of
                    true -> html("get-entry-and-proof: bad input:", [fixme]);
                    false ->
                        binary_to_list(
                          jiffy:encode(
                            case plop:inclusion_and_leaf(Index, TreeSize) of
                                {ok, Data, Path} ->
                                    {[{leaf_input,
                                       base64:encode(plop:serialise(Data))},
                                      {extra_data, base64:encode([])},
                                      {audit_path,
                                       [base64:encode(X) || X <- Path]}]};
                                {notfound, Msg} ->
                                    {[{success, false},
                                      {error_message, list_to_binary(Msg)}]}
                            end))
                end;
            _ -> html("get-entry-and-proof: bad input:", Input)
        end,
    deliver(SessionID, R).

'get-roots'(SessionID, _Env, _Input) ->
    R = [{certificates, []}],                   % NIY.
    deliver(SessionID, binary_to_list(jiffy:encode({R}))).

%% For testing. FIXME: Remove.
hello(SessionID, Env, Input) ->
    Query = httpd:parse_query(Input),
    mod_esi:deliver(SessionID, io_lib:format(
                                 "Content-Type: text/html\r\n\r\n" ++
                                     "<html><body>hello again, erlang world" ++
                                     "<p>SessionID: ~p~n" ++
                                     "<p>Env: ~p~n" ++
                                     "<p>Input, raw: ~p~n" ++
                                     "<p>Input, parsed: ~p~n" ++
                                     "</body></html>",
                                 [SessionID, Env, Input, Query])).

%% Private functions.
encode_entries(Entries) ->
    binary_to_list(jiffy:encode({[{entries, encode_entries2(Entries)}]})).
encode_entries2([H|T]) ->
    LeafInput = base64:encode(plop:serialise(H)),
    ExtraData = base64:encode(""),
    [{[{leaf_input, LeafInput}, {extra_data, ExtraData}]} | encode_entries2(T)];
encode_entries2([]) ->
    [].

html(Text, Input) ->
    io_lib:format(
      "Content-Type: text/html\r\n\r\n" ++
          "<html><body><p>~n" ++
          "~s~n" ++
          "~p~n" ++
          "</body></html>~n", [Text, Input]).

niy(S) ->
    mod_esi:deliver(S, html("NIY - Not Yet Implemented|", [])).

-spec deliver(any(), string()) -> ok | {error, _Reason}.
deliver(Session, Data) ->
    mod_esi:deliver(Session, Data).