/* notmuch - Not much of an email program, (just index and search)
 *
 * Copyright © 2012 Jameson Rollins
 *
 * 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/ .
 *
 * Authors: Jameson Rollins <jrollins@finestructure.net>
 */

#include "notmuch-client.h"

#ifdef GMIME_ATLEAST_26

#define NOTMUCH_PASSWORD_DATA_KEY "notmuch-password-data"

typedef struct
{
    int status_fd;
    GIOChannel *command_channel;
} notmuch_password_data_t;

static void
free_password_data_cb (void *data_ptr)
{
    notmuch_password_data_t *data = data_ptr;

    g_io_channel_unref (data->command_channel);
    free (data);
}

static void
escape_string (GString *buf,
	       const char *str)
{
    const char *p;

    g_string_append_c (buf, '"');

    for (p = str; *p; p++)
	switch (*p) {
	case '\n':
	    g_string_append (buf, "\\n");
	    break;
	case '\t':
	    g_string_append (buf, "\\t");
	    break;
	case '\r':
	    g_string_append (buf, "\\t");
	    break;
	case '"':
	    g_string_append (buf, "\\\"");
	    break;
	default:
	    if (*p < 32)
		g_string_append_printf (buf, "\\0%o", *p);
	    else
		g_string_append_c (buf, *p);
	    break;
	}

    g_string_append_c (buf, '"');
}

static gboolean
write_all (const char *buf,
	   size_t length,
	   int fd)
{
    ssize_t wrote;

    while (length > 0) {
	wrote = write (fd, buf, length);
	if (wrote == -1)
	    return FALSE;
	buf += wrote;
	length -= wrote;
    }

    return TRUE;
}

static gboolean
password_request_cb (GMimeCryptoContext *ctx,
		     const char *user_id,
		     const char *prompt_ctx,
		     gboolean reprompt,
		     GMimeStream *response,
		     GError **err)
{
    notmuch_password_data_t *data;
    GString *buf;
    gboolean write_result;
    char *line = NULL;
    gsize line_length;
    ssize_t wrote;

    data = g_object_get_data (G_OBJECT (ctx), NOTMUCH_PASSWORD_DATA_KEY);

    buf = g_string_new ("[NOTMUCH:] GET_HIDDEN ");
    escape_string (buf, user_id);
    g_string_append_c (buf, ' ');
    escape_string (buf, prompt_ctx);
    g_string_append_c (buf, ' ');
    g_string_append_c (buf, (!!reprompt) + '0');
    g_string_append_c (buf, '\n');

    write_result = write_all (buf->str, buf->len, data->status_fd);

    g_string_free (buf, TRUE);

    if (!write_result) {
	g_set_error_literal (err,
			     G_FILE_ERROR,
			     g_file_error_from_errno (errno),
			     strerror (errno));
	return FALSE;
    }

    if (!g_io_channel_read_line (data->command_channel,
				 &line,
				 &line_length,
				 NULL, /* terminator_pos */
				 err))
	return FALSE;

    wrote = g_mime_stream_write (response, line, line_length);

    /* TODO: is there a more reliable way to clear the memory
     * containing a password? */
    memset (line, 0, line_length);

    g_free (line);

    if (wrote < (ssize_t) line_length) {
	g_set_error_literal (err,
			     G_FILE_ERROR,
			     G_FILE_ERROR_FAILED,
			     "Failed to write password response");
	return FALSE;
    }

    return TRUE;
}

/* Create a GPG context (GMime 2.6) */
static notmuch_bool_t
create_gpg_context (notmuch_crypto_t *crypto)
{
    notmuch_crypto_context_t *gpgctx;
    GMimePasswordRequestFunc password_func;
    notmuch_password_data_t *password_data;

    /* If the --status-fd and --command-fd options were specified then
     * we can handle password requests by forwarding them on to the
     * application that invoked notmuch */
    if (crypto->status_fd != -1 && crypto->command_fd != -1) {
	password_func = password_request_cb;
	password_data = malloc (sizeof (*password_data));
	if (password_data == NULL)
	    return FALSE;
	password_data->status_fd = crypto->status_fd;
	password_data->command_channel =
	    g_io_channel_unix_new (crypto->command_fd);
    } else {
	password_func = NULL;
	password_data = NULL;
    }

    gpgctx = g_mime_gpg_context_new (password_func, "gpg");
    if (! gpgctx)
	return FALSE;

    /* The password callback for GMime doesn't seem to provide any
     * user data pointer so we'll work around it by attaching the data
     * to the gpg context, which it does pass */
    if (password_data) {
	g_object_set_data_full (G_OBJECT (gpgctx),
				NOTMUCH_PASSWORD_DATA_KEY,
				password_data,
				free_password_data_cb);
    }

    g_mime_gpg_context_set_use_agent ((GMimeGpgContext *) gpgctx, TRUE);
    g_mime_gpg_context_set_always_trust ((GMimeGpgContext *) gpgctx, FALSE);

    crypto->gpgctx = gpgctx;

    return TRUE;
}

#else /* GMIME_ATLEAST_26 */

/* Create a GPG context (GMime 2.4) */
static notmuch_bool_t
create_gpg_context (notmuch_crypto_t *crypto)
{
    GMimeSession *session;
    notmuch_crypto_context_t *gpgctx;

    session = g_object_new (g_mime_session_get_type (), NULL);
    gpgctx = g_mime_gpg_context_new (session, "gpg");
    g_object_unref (session);

    if (! gpgctx)
	return FALSE;

    g_mime_gpg_context_set_always_trust ((GMimeGpgContext *) gpgctx, FALSE);

    crypto->gpgctx = gpgctx;

    return TRUE;
}

#endif /* GMIME_ATLEAST_26 */

/* for the specified protocol return the context pointer (initializing
 * if needed) */
notmuch_crypto_context_t *
notmuch_crypto_get_context (notmuch_crypto_t *crypto, const char *protocol)
{
    notmuch_crypto_context_t *cryptoctx = NULL;

    /* As per RFC 1847 section 2.1: "the [protocol] value token is
     * comprised of the type and sub-type tokens of the Content-Type".
     * As per RFC 1521 section 2: "Content-Type values, subtypes, and
     * parameter names as defined in this document are
     * case-insensitive."  Thus, we use strcasecmp for the protocol.
     */
    if (strcasecmp (protocol, "application/pgp-signature") == 0 ||
	strcasecmp (protocol, "application/pgp-encrypted") == 0) {
	if (! crypto->gpgctx) {
	    create_gpg_context (crypto);
	    if (! crypto->gpgctx)
		fprintf (stderr, "Failed to construct gpg context.\n");
	}
	cryptoctx = crypto->gpgctx;
    } else {
	fprintf (stderr, "Unknown or unsupported cryptographic protocol.\n");
    }

    return cryptoctx;
}

int
notmuch_crypto_cleanup (notmuch_crypto_t *crypto)
{
    if (crypto->gpgctx) {
	g_object_unref (crypto->gpgctx);
	crypto->gpgctx = NULL;
    }

    return 0;
}