/* iridium-standard-file.c
 *
 * Copyright 2018 Matthias Vogelgesang
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 */

#include <string.h>
#include <stdio.h>
#include <json-glib/json-glib.h>
#include <libsoup/soup.h>
#include <nettle/aes.h>
#include <nettle/cbc.h>
#include <nettle/sha2.h>
#include <nettle/hmac.h>
#include <nettle/pbkdf2.h>
#include "iridium-standard-file.h"
#include "iridium-note.h"

typedef enum {
  SF_VERSION_001,
  SF_VERSION_002,
} StandardFileVersion;

typedef enum {
  SF_FUNC_PBKDF2,
} StandardFileFunc;

typedef enum {
  SF_HASH_SHA512,
} StandardFileHash;

typedef struct {
  guint cost;
  guint key_size;
  gchar *salt;
  StandardFileFunc func;
  StandardFileFunc hash;
  StandardFileVersion version;
  struct {
    guint8 password[32];
    guint8 master[32];
    guint8 auth[32];
  } keys;
} StandardFileAuthParams;

typedef struct {
  IridiumStandardFile *client;
  gchar *password;
} ReadAuthParams;

struct _IridiumStandardFile
{
  GObject parent_instance;

  gchar         *email;
  gchar         *token;
  SoupSession   *session;
  SoupURI       *base_uri;
  StandardFileAuthParams auth_params;
};

G_DEFINE_TYPE (IridiumStandardFile, iridium_standard_file, G_TYPE_OBJECT)

const SecretSchema *
standard_file_get_schema (void)
{
  static const SecretSchema schema = {
    "net.bloerg.Iridium", SECRET_SCHEMA_NONE,
    {
      { "email", SECRET_SCHEMA_ATTRIBUTE_STRING },
      { "server", SECRET_SCHEMA_ATTRIBUTE_STRING },
      { NULL, 0 },
    }
  };
  return &schema;
}

IridiumStandardFile *
iridium_standard_file_new (void)
{
  return g_object_new (IRIDIUM_TYPE_STANDARD_FILE, NULL);
}

static guint8 *
unhexlify (const gchar *s, gsize length)
{
  guint8 *result;

  result = g_malloc0 (length / 2);

  for (gsize i = 0; i < length / 2; i++)
    sscanf (&s[i * 2], "%2hhx", &result[i]);

  return result;
}

static gchar *
hexlify (const guint8 *s, gsize length)
{
  gchar *result;

  result = g_malloc0 (2 * length + 1);

  for (gsize i = 0; i < length; i++)
    g_snprintf (&result[2 * i], 3, "%02x", s[i]);

  return result;
}

static void
derive_keys (const guint8 *password,
             StandardFileAuthParams *params)
{
  struct hmac_sha512_ctx context;
  guint8 dst[96];

  g_assert_nonnull (params->salt);

  hmac_sha512_set_key (&context, strlen ((gchar *) password), password);

  PBKDF2 (&context, hmac_sha512_update, hmac_sha512_digest, SHA512_DIGEST_SIZE,
          params->cost, strlen (params->salt), (guint8 *) params->salt, 96, dst);

  memcpy (&params->keys, dst, sizeof (dst));
}

static gchar *
decrypt (const gchar *s,
         const gchar *check_uuid,
         const guint8 *enc_key,
         const guint8 *auth_key,
         gsize key_length)
{
  gchar **v;
  gchar *to_auth;
  gchar *hash;
  gsize cipher_length;
  gsize raw_length;
  const gchar *version;
  const gchar *auth_hash;
  const gchar *uuid;
  const gchar *iv;
  const gchar *cipher_text;
  guint8 *iv_bytes;
  guint8 *dst;
  guchar *cipher_raw_text;
  struct hmac_sha256_ctx hmac_contextt;
  guint8 digest[SHA256_DIGEST_SIZE];
  struct aes_ctx aes_context;

  v = g_strsplit (s, ":", 0);
  g_assert_nonnull (v[0]); version = v[0];
  g_assert_nonnull (v[1]); auth_hash = v[1];
  g_assert_nonnull (v[2]); uuid = v[2];
  g_assert_nonnull (v[3]); iv = v[3];
  g_assert_nonnull (v[4]); cipher_text = v[4];

  g_assert_cmpstr (uuid, ==, check_uuid);

  to_auth = g_strjoin (":", version, uuid, iv, cipher_text, NULL);
  hmac_sha256_set_key (&hmac_contextt, key_length, auth_key);
  hmac_sha256_update (&hmac_contextt, strlen (to_auth), (guint8 *) to_auth);
  hmac_sha256_digest (&hmac_contextt, SHA256_DIGEST_SIZE, digest);

  hash = hexlify (digest, sizeof (digest));
  g_assert_cmpstr (hash, ==, (gchar *) auth_hash);
  g_free (hash);

  cipher_length = strlen (cipher_text);
  cipher_length = AES_BLOCK_SIZE * (cipher_length / AES_BLOCK_SIZE + (cipher_length % AES_BLOCK_SIZE ? 1 : 0));
  dst = g_malloc0 (cipher_length);

  aes_set_decrypt_key (&aes_context, key_length, enc_key);
  iv_bytes = unhexlify (iv, strlen (iv));
  cipher_raw_text = g_base64_decode (cipher_text, &raw_length);

  cbc_decrypt (&aes_context, (nettle_cipher_func *) &aes_decrypt, AES_BLOCK_SIZE, iv_bytes,
               raw_length, dst, (guint8 *) cipher_raw_text);

  dst[raw_length] = '\0';
  g_free (cipher_raw_text);
  g_free (iv_bytes);
  g_free (to_auth);
  g_strfreev (v);
  return (gchar *) dst;
}

static gchar *
decrypt_item (JsonObject *item, StandardFileAuthParams *params)
{
  const gchar *enc_item_key;
  const gchar *uuid;
  gchar *enc_auth_key;
  const gchar *enc_key;
  const gchar *auth_key;
  guint8 *enc_key_bytes;
  guint8 *auth_key_bytes;
  gsize enc_key_size;
  const gchar *enc_content;
  gchar *content;

  uuid = json_object_get_string_member (item, "uuid");
  enc_item_key = json_object_get_string_member (item, "enc_item_key");

  if (!g_strcmp0 (enc_item_key, ""))
    return NULL;

  enc_auth_key = decrypt (enc_item_key, uuid, params->keys.master, params->keys.auth, sizeof (params->keys.master));

  enc_key = (gchar *) enc_auth_key;
  enc_key_size = strlen (enc_auth_key) / 2 - 8;
  auth_key = &enc_auth_key[enc_key_size];

  enc_key_bytes = unhexlify (enc_key, enc_key_size);
  auth_key_bytes = unhexlify (auth_key, enc_key_size);

  enc_content = json_object_get_string_member (item, "content");
  content = decrypt (enc_content, uuid, enc_key_bytes, auth_key_bytes, enc_key_size / 2);

  g_free (enc_key_bytes);
  g_free (auth_key_bytes);
  g_free (enc_auth_key);
  return content;
}

static IridiumNote *
deserialize_note (JsonObject *meta, JsonObject *data)
{
  IridiumNote *note;
  GTimeVal time;
  GDateTime *last_modified;

  if (!g_time_val_from_iso8601 (json_object_get_string_member (meta, "created_at"), &time)) {
    g_print ("Problem parsing\n");
  }

  last_modified = g_date_time_new_from_timeval_local (&time);

  note = iridium_note_new (json_object_get_string_member (data, "title"),
                           json_object_get_string_member (data, "text"),
                           last_modified);

  return note;
}

static GObject *
deserialize_item (JsonObject *meta, const gchar *data)
{
  JsonObject *root;
  g_autoptr(JsonParser) parser;
  const gchar *type;
  GError *error = NULL;

  parser = json_parser_new_immutable ();
  json_parser_load_from_data (parser, data, -1, &error);
  type = json_object_get_string_member (meta, "content_type");
  root = json_node_get_object (json_parser_get_root (parser));

  if (!g_strcmp0 (type, "Note"))
    return G_OBJECT (deserialize_note (meta, root));

  return NULL;
}

static gboolean
get_auth_params (JsonParser *parser,
                 ReadAuthParams *params,
                 GError **error)
{
  JsonObject *object;
  const gchar *s;

  object = json_node_get_object (json_parser_get_root (parser));

  params->client->auth_params.func = SF_FUNC_PBKDF2;
  params->client->auth_params.hash = SF_HASH_SHA512;
  params->client->auth_params.cost = json_object_get_int_member (object, "pw_cost");
  params->client->auth_params.key_size = json_object_get_int_member (object, "pw_key_size");
  params->client->auth_params.salt = g_strdup (json_object_get_string_member (object, "pw_salt"));

  if (g_strcmp0 (json_object_get_string_member (object, "pw_alg"), "sha512")) {
    g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
                         "Hash algorithm other than sha512 is not supported");
    return FALSE;
  }

  if (g_strcmp0 (json_object_get_string_member (object, "pw_func"), "pbkdf2")) {
    g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
                         "Password derivative function other than PBKDF2 is not supported");
    return FALSE;
  }

  s = json_object_get_string_member (object, "version");

  if (!g_strcmp0 (s, "001"))
    params->client->auth_params.version = SF_VERSION_001;
  else if (!g_strcmp0 (s, "002"))
    params->client->auth_params.version = SF_VERSION_002;
  else {
    g_set_error_literal (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
                         "StandardFile protocols other than 001 and 002 are not supported");
    return FALSE;
  }

  return TRUE;
}

static void
read_auth_params_data_free (ReadAuthParams *data)
{
  secret_password_free (data->password);
}

static void
on_signin_response_parsed (GObject *object,
                           GAsyncResult *result,
                           gpointer user_data)
{
  GTask *task;
  ReadAuthParams *data;
  JsonParser *parser;
  JsonObject *root_object;
  GError *error = NULL;

  task = user_data;
  data = g_task_get_task_data (task);
  parser = JSON_PARSER (object);

  if (!json_parser_load_from_stream_finish (parser, result, &error)) {
    g_task_return_error (task, error);
    g_object_unref (task);
    return;
  }

  root_object = json_node_get_object (json_parser_get_root (parser));

  g_free (data->client->token);
  data->client->token = g_strdup (json_object_get_string_member (root_object, "token"));

  g_task_return_boolean (task, TRUE);
  g_object_unref (task);
  g_object_unref (parser);
}

static void
on_send_signin_message (GObject *object,
                        GAsyncResult *result,
                        gpointer user_data)
{
  GInputStream *stream;
  GTask *task;
  JsonParser *parser;
  GError *error = NULL;

  task = user_data;
  stream = soup_request_send_finish (SOUP_REQUEST (object), result, &error);

  if (stream == NULL) {
    g_task_return_error (task, error);
    return;
  }

  parser = json_parser_new ();
  json_parser_load_from_stream_async (parser, stream, g_task_get_cancellable (task),
                                      on_signin_response_parsed, task);

  g_object_unref (stream);
}

static void
on_auth_params_response_parsed (GObject *object,
                                GAsyncResult *result,
                                gpointer user_data)
{
  GTask *task;
  JsonParser *parser;
  ReadAuthParams *data;
  SoupURI *uri;
  SoupRequestHTTP *request;
  SoupMessage *msg;
  gchar *password;
  gchar *body;
  GError *error = NULL;

  task = user_data;
  data = g_task_get_task_data (task);
  parser = JSON_PARSER (object);

  if (!json_parser_load_from_stream_finish (parser, result, &error)) {
    g_task_return_error (task, error);
    return;
  }

  if (!get_auth_params (parser, data, &error)) {
    g_task_return_error (task, error);
    return;
  }

  derive_keys ((guint8 *) data->password, &data->client->auth_params);

  g_debug ("StandardFile parameters: version=%i func=%i hash=%i key_size=%u iterations=%u",
           data->client->auth_params.version,
           data->client->auth_params.func,
           data->client->auth_params.hash,
           data->client->auth_params.key_size,
           data->client->auth_params.cost);

  uri = soup_uri_new_with_base (data->client->base_uri, "api/auth/sign_in");
  request = soup_session_request_http_uri (data->client->session, "POST", uri, &error);

  if (request == NULL) {
    g_task_return_error (task, error);
    return;
  }

  password = hexlify (data->client->auth_params.keys.password,
                      sizeof (data->client->auth_params.keys.password));
  body = g_strdup_printf ("{\"email\": \"%s\", \"password\": \"%s\"}", data->client->email, password);
  msg = soup_request_http_get_message (request);
  soup_message_set_request (msg, "application/json", SOUP_MEMORY_TAKE, body, strlen (body));
  soup_request_send_async (SOUP_REQUEST (request), g_task_get_cancellable (task), on_send_signin_message, task);

  g_free (password);
  soup_uri_free (uri);
  g_object_unref (msg);
  g_object_unref (parser);
}

static void
on_send_auth_params_message (GObject *object,
                             GAsyncResult *result,
                             gpointer user_data)
{
  GInputStream *stream;
  GTask *task;
  JsonParser *parser;
  GError *error = NULL;

  task = user_data;
  stream = soup_request_send_finish (SOUP_REQUEST (object), result, &error);

  if (stream == NULL) {
    g_task_return_error (task, error);
    return;
  }

  parser = json_parser_new ();
  json_parser_load_from_stream_async (parser, stream, g_task_get_cancellable (task),          
                                      on_auth_params_response_parsed, task);
  g_object_unref (object);
  g_object_unref (stream);
}

static void
on_sync_response_parsed (GObject *object,
                         GAsyncResult *result,
                         gpointer user_data)
{
  GTask *task;
  StandardFileAuthParams *auth_params;
  JsonParser *parser;
  JsonObject *root;
  JsonArray *array;
  GList *items = NULL;
  GError *error = NULL;

  task = G_TASK (user_data);
  auth_params = g_task_get_task_data (task);
  parser = JSON_PARSER (object);

  if (!json_parser_load_from_stream_finish (parser, result, &error)) {
    g_task_return_error (task, error);
    return;
  }

  root = json_node_get_object (json_parser_get_root (parser));
  array = json_object_get_array_member (root, "retrieved_items");

  for (guint i = 0; i < json_array_get_length (array); i++) {
    JsonObject *data;
    GObject *item;
    gchar *content;

    data = json_array_get_object_element (array, i);
    content = decrypt_item (data, auth_params);

    if (content) {
      item = deserialize_item (data, content);

      if (item)
        items = g_list_append (items, item);
    }

    g_free (content);
  }

  g_task_return_pointer (task, items, NULL);
  g_object_unref (parser);
}

static void
on_send_sync_request (GObject *object,
                      GAsyncResult *result,
                      gpointer user_data)
{
  GInputStream *stream;
  GTask *task;
  JsonParser *parser;
  GError *error = NULL;

  task = user_data;
  stream = soup_request_send_finish (SOUP_REQUEST (object), result, &error);

  if (stream == NULL) {
    g_task_return_error (task, error);
    return;
  }

  parser = json_parser_new ();
  json_parser_load_from_stream_async (parser, stream, g_task_get_cancellable (task),
                                      on_sync_response_parsed, task);
  g_object_unref (stream);
}

GList *
iridium_standard_file_load_finish (IridiumStandardFile *client,
                                   GAsyncResult *result,
                                   GError **error)
{
  g_return_val_if_fail (g_task_is_valid (result, client), FALSE);
  return g_task_propagate_pointer (G_TASK (result), error);
}

void
iridium_standard_file_load_async (IridiumStandardFile *client,
                                  GCancellable *cancellable,
                                  GAsyncReadyCallback callback,
                                  gpointer user_data)
{
  SoupURI *uri;
  SoupRequestHTTP *request;
  SoupMessage *msg;
  SoupMessageHeaders *headers;
  gchar *value;
  const gchar *body;
  GTask *task;
  GError *error = NULL;

  task = g_task_new (client, cancellable, callback, user_data);
  g_task_set_task_data (task, &client->auth_params, NULL);
  uri = soup_uri_new_with_base (client->base_uri, "api/items/sync");
  request = soup_session_request_http_uri (client->session, "POST", uri, &error);

  if (request == NULL) {
    g_task_return_error (task, error);
    return;
  }

  msg = soup_request_http_get_message (request);
  g_object_get (msg, "request-headers", &headers, NULL);
  value = g_strdup_printf ("Bearer %s", client->token);
  soup_message_headers_append (headers, "Authorization", value);

  body = "{\"items\": []}";
  soup_message_set_request (msg, "application/json", SOUP_MEMORY_STATIC, body, strlen (body));
  soup_request_send_async (SOUP_REQUEST (request), cancellable, on_send_sync_request, task);

  g_object_unref (msg);
  soup_uri_free (uri);
}

gboolean
iridium_standard_file_connect_finish (IridiumStandardFile *client,
                                      GAsyncResult *result,
                                      GError **error)
{
  g_return_val_if_fail (g_task_is_valid (result, client), FALSE);
  return g_task_propagate_boolean (G_TASK (result), error);
}

void
iridium_standard_file_connect_async (IridiumStandardFile *client,
                                     const gchar *server,
                                     const gchar *email,
                                     const gchar *password,
                                     GCancellable *cancellable,
                                     GAsyncReadyCallback callback,
                                     gpointer user_data)
{
  SoupURI *uri;
  SoupRequestHTTP *request;
  ReadAuthParams *data;
  GTask *task;
  GError *error = NULL;

  if (client->base_uri)
    soup_uri_free (client->base_uri);

  client->base_uri = soup_uri_new (server);
  client->email = g_strdup (email);

  uri = soup_uri_new_with_base (client->base_uri, "api/auth/params");
  soup_uri_set_query_from_fields (uri, "email", email, NULL);
  task = g_task_new (client, cancellable, callback, user_data);
  request = soup_session_request_http_uri (client->session, "GET", uri, &error);

  if (request == NULL) {
    g_task_return_error (task, error);
    return;
  }

  data = g_new0 (ReadAuthParams, 1);
  data->client = client;
  data->password = g_strdup (password);

  g_task_set_task_data (task, data, (GDestroyNotify) read_auth_params_data_free);
  soup_request_send_async (SOUP_REQUEST (request), cancellable, on_send_auth_params_message, task);
  soup_uri_free (uri);
}

static void
iridium_standard_file_dispose (GObject *object)
{
  IridiumStandardFile *self;

  self = IRIDIUM_STANDARD_FILE (object);
  g_object_unref (self->session);
  soup_uri_free (self->base_uri);
  G_OBJECT_CLASS (iridium_standard_file_parent_class)->dispose (object);
}

static void
iridium_standard_file_finalize (GObject *object)
{
  IridiumStandardFile *self;

  self = IRIDIUM_STANDARD_FILE (object);
  g_free (self->email);
  g_free (self->token);
  G_OBJECT_CLASS (iridium_standard_file_parent_class)->finalize (object);
}

static void
iridium_standard_file_class_init (IridiumStandardFileClass *klass)
{
  GObjectClass *oclass;

  oclass = G_OBJECT_CLASS (klass);
  oclass->dispose = iridium_standard_file_dispose;
  oclass->finalize = iridium_standard_file_finalize;
}

static void
iridium_standard_file_init (IridiumStandardFile *self)
{
  self->base_uri = NULL;
  self->email = NULL;
  self->token = NULL;
  self->session = soup_session_new ();
}