/*
 * Copyright © 2009 Carl Worth
 *
 * 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/ .
 *
 * Author: Carl Worth <cworth@cworth.org>
 */

/* This indexer creates a Xapian mail index that is remarkably similar
 * to that created by sup. The big difference, (and the thing that
 * will keep a notmuch index from being used by sup directly), is that
 * sup expects a serialized ruby data structure in the document's data
 * field, but notmuch just puts the mail's filename there (trusting
 * that the email client can get the data in needs from the filename).
 *
 * Note: One bug here is that sup actually merges together fields such
 * as To, CC, Bcc etc. when finding multiple emails with the same
 * message ID. To support something similar, notmuch should list
 * multiple files in the data field.
 *
 * Other differences between sup and notmuch-index identified so far:
 *
 *   o sup supports encrypted mime parts by prompting for a passphrase
 *     to decrypt the message. So far, notmuch doesn't support this,
 *     both because I'm lazy to code it, and I also think doing so
 *     would present a security leak.
 *
 *   o sup and notmuch have different heuristics for identifying (and
 *     thus ignoring) signatures. For example, sup considers a line
 *     consisting of two hypens as a signature separator, while
 *     notmuch expects those two hyphens to be followed by a space
 *     character.
 *
 *   o sup as been seen to split some numbers before indexing
 *     them. For example, the number 1754 in an email message was
 *     indexed by sup as separate terms 17 and 54. I couldn't find any
 *     explanation for this behavior and did not try to replicate it
 *     in notmuch.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <time.h>

#include <iostream>

#include <gmime/gmime.h>

#include <xapian.h>

using namespace std;

#define ARRAY_SIZE(arr) (sizeof (arr) / sizeof (arr[0]))

/* Xapian complains if we provide a term longer than this. */
#define NOTMUCH_MAX_TERM 245

/* These prefix values are specifically chosen to be compatible
 * with sup, (http://sup.rubyforge.org), written by
 * William Morgan <wmorgan-sup@masanjin.net>, and released
 * under the GNU GPL v2.
 */

typedef struct {
    const char *name;
    const char *prefix;
} prefix_t;

prefix_t NORMAL_PREFIX[] = {
    { "subject", "S" },
    { "body", "B" },
    { "from_name", "FN" },
    { "to_name", "TN" },
    { "name", "N" },
    { "attachment", "A" }
};

prefix_t BOOLEAN_PREFIX[] = {
    { "type", "K" },
    { "from_email", "FE" },
    { "to_email", "TE" },
    { "email", "E" },
    { "date", "D" },
    { "label", "L" },
    { "source_id", "I" },
    { "attachment_extension", "O" },
    { "msgid", "Q" },
    { "thread", "H" },
    { "ref", "R" }
};

/* Similarly, these value numbers are also chosen to be sup
 * compatible. */

typedef enum {
    NOTMUCH_VALUE_MESSAGE_ID = 0,
    NOTMUCH_VALUE_THREAD = 1,
    NOTMUCH_VALUE_DATE = 2
} notmuch_value_t;

static const char *
find_prefix (const char *name)
{
    unsigned int i;

    for (i = 0; i < ARRAY_SIZE (NORMAL_PREFIX); i++)
	if (strcmp (name, NORMAL_PREFIX[i].name) == 0)
	    return NORMAL_PREFIX[i].prefix;

    for (i = 0; i < ARRAY_SIZE (BOOLEAN_PREFIX); i++)
	if (strcmp (name, BOOLEAN_PREFIX[i].name) == 0)
	    return BOOLEAN_PREFIX[i].prefix;

    return "";
}

int TERM_COMBINED = 0;

static void
add_term (Xapian::Document doc,
	  const char *prefix_name,
	  const char *value)
{
    const char *prefix;
    char *term;

    if (value == NULL)
	return;

    prefix = find_prefix (prefix_name);

    term = g_strdup_printf ("%s%s", prefix, value);

    if (strlen (term) <= NOTMUCH_MAX_TERM)
	doc.add_term (term);

    g_free (term);
}

static void
gen_terms (Xapian::TermGenerator term_gen,
	   const char *prefix_name,
	   const char *text)
{
    const char *prefix;

    if (text == NULL)
	return;

    prefix = find_prefix (prefix_name);

    term_gen.index_text (text, 1, prefix);
}

static void
gen_terms_address_name (Xapian::TermGenerator term_gen,
			InternetAddress *address,
			const char *prefix_name)
{
    const char *name;
    int own_name = 0;

    name = internet_address_get_name (address);

    /* In the absence of a name, we'll strip the part before the @
     * from the address. */
    if (! name) {
	InternetAddressMailbox *mailbox = INTERNET_ADDRESS_MAILBOX (address);
	const char *addr = internet_address_mailbox_get_addr (mailbox);
	const char *at;

	at = strchr (addr, '@');
	if (at) {
	    name = strndup (addr, at - addr);
	    own_name = 1;
	}
    }

    if (name)
	gen_terms (term_gen, prefix_name, name);

    if (own_name)
	free ((void *) name);
}

static void
gen_terms_address_names (Xapian::TermGenerator term_gen,
			 InternetAddressList *addresses,
			 const char *address_type)
{
    int i;
    InternetAddress *address;

    if (addresses == NULL)
	return;

    for (i = 0; i < internet_address_list_length (addresses); i++) {
	address = internet_address_list_get_address (addresses, i);
	gen_terms_address_name (term_gen, address, address_type);
	gen_terms_address_name (term_gen, address, "name");
	gen_terms_address_name (term_gen, address, "body");
    }
}

static void
add_term_address_addr (Xapian::Document doc,
		       InternetAddress *address,
		       const char *prefix_name)
{
    InternetAddressMailbox *mailbox = INTERNET_ADDRESS_MAILBOX (address);
    const char *addr;

    addr = internet_address_mailbox_get_addr (mailbox);

    if (addr)
	add_term (doc, prefix_name, addr);
}

static void
add_terms_address_addrs (Xapian::Document doc,
			 InternetAddressList *addresses,
			 const char *address_type)
{
    int i;
    InternetAddress *address;

    if (addresses == NULL)
	return;

    for (i = 0; i < internet_address_list_length (addresses); i++) {
	address = internet_address_list_get_address (addresses, i);
	add_term_address_addr (doc, address, address_type);
	add_term_address_addr (doc, address, "email");
    }
}

static const char *
skip_re_in_subject (const char *subject)
{
    const char *s = subject;

    while (*s) {
	while (*s && isspace (*s))
	    s++;
	if (strncasecmp (s, "re:", 3) == 0)
	    s += 3;
	else
	    break;
    }

    return s;
}

static void
find_messages_by_term (Xapian::Database db,
		       const char *prefix_name,
		       const char *value,
		       Xapian::PostingIterator *begin,
		       Xapian::PostingIterator *end)
{
    Xapian::PostingIterator i;
    char *term;

    term = g_strdup_printf ("%s%s", find_prefix (prefix_name), value);

    *begin = db.postlist_begin (term);

    if (end)
	*end = db.postlist_end (term);

    free (term);
}

Xapian::Document
find_message_by_docid (Xapian::Database db, Xapian::docid docid)
{
    return db.get_document (docid);
}

Xapian::Document
find_message_by_message_id (Xapian::Database db, const char *message_id)
{
    Xapian::PostingIterator i, end;

    find_messages_by_term (db, "msgid", message_id, &i, &end);

    if (i != end)
	return find_message_by_docid (db, *i);
    else
	return Xapian::Document ();
}

static void
insert_thread_id (GHashTable *thread_ids, Xapian::Document doc)
{
    string value_string;
    const char *value, *id, *comma;

    value_string = doc.get_value (NOTMUCH_VALUE_THREAD);
    value = value_string.c_str();
    if (strlen (value)) {
	id = value;
	while (*id) {
	    comma = strchr (id, ',');
	    if (comma == NULL)
		comma = id + strlen (id);
	    g_hash_table_insert (thread_ids,
				 strndup (id, comma - id), NULL);
	    id = comma;
	    if (*id)
		id++;
	}
    }
}

/* Return one or more thread_ids, (as a GPtrArray of strings), for the
 * given message based on looking into the database for any messages
 * referenced in parents, and also for any messages in the database
 * referencing message_id.
 *
 * Caller should free all strings in the array and the array itself,
 * (g_ptr_array_free) when done. */
static GPtrArray *
find_thread_ids (Xapian::Database db,
		 GPtrArray *parents,
		 const char *message_id)
{
    Xapian::PostingIterator child, children_end;
    Xapian::Document doc;
    GHashTable *thread_ids;
    GList *keys, *l;
    unsigned int i;
    const char *parent_message_id;
    GPtrArray *result;

    thread_ids = g_hash_table_new (g_str_hash, g_str_equal);

    find_messages_by_term (db, "ref", message_id, &child, &children_end);
    for ( ; child != children_end; child++) {
	doc = find_message_by_docid (db, *child);
	insert_thread_id (thread_ids, doc);
    }

    for (i = 0; i < parents->len; i++) {
	parent_message_id = (char *) g_ptr_array_index (parents, i);
	doc = find_message_by_message_id (db, parent_message_id);
	insert_thread_id (thread_ids, doc);
    }

    result = g_ptr_array_new ();

    keys = g_hash_table_get_keys (thread_ids);
    for (l = keys; l; l = l->next) {
	char *id = (char *) l->data;
	g_ptr_array_add (result, id);
    }

    return result;
}

/* Add a term for each message-id in the References header of the
 * message. */
static void
parse_references (GPtrArray *array,
		  const char *refs_str)
{
    GMimeReferences *refs, *r;
    const char *message_id;

    if (refs_str == NULL)
	return;

    refs = g_mime_references_decode (refs_str);

    for (r = refs; r; r = r->next) {
	message_id = g_mime_references_get_message_id (r);
	g_ptr_array_add (array, g_strdup (message_id));
    }

    g_mime_references_free (refs);
}

/* Given a string representing the body of a message, generate terms
 * for it, (skipping quoted portions and signatures). */
static void
gen_terms_body_str (Xapian::TermGenerator term_gen,
		    char *body)
{
    char *line, *line_end, *next_line;

    if (body == NULL)
	return;

    next_line = body;

    while (1) {
	line = next_line;
	if (*line == '\0')
	    break;

	next_line = strchr (line, '\n');
	if (next_line == NULL) {
	    next_line = line + strlen (line);
	}
	line_end = next_line - 1;

	/* Get to the next non-blank line. */
	while (*next_line == '\n')
	    next_line++;

	/* Skip lines that are quotes. */
	if (*line == '>')
	    continue;

	/* Also skip lines introducing a quote on the next line. */
	if (*line_end == ':' && *next_line == '>')
	    continue;

	/* Finally, bail as soon as we see a signature. */
	/* XXX: Should only do this if "near" the end of the message. */
	if (strncmp (line, "-- ", 3) == 0 ||
	    strncmp (line, "----------", 10) == 0 ||
	    strncmp (line, "__________", 10) == 0)
	    break;

	*(line_end + 1) = '\0';
	gen_terms (term_gen, "body", line);
    }
}


/* Callback to generate terms for each mime part of a message. */
static void
gen_terms_part (Xapian::TermGenerator term_gen,
		GMimeObject *part)
{
    GMimeStream *stream;
    GMimeDataWrapper *wrapper;
    GByteArray *byte_array;
    GMimeContentDisposition *disposition;
    char *body;

    if (GMIME_IS_MULTIPART (part)) {
	GMimeMultipart *multipart = GMIME_MULTIPART (part);
	int i;

	for (i = 0; i < g_mime_multipart_get_count (multipart); i++) {
	    if (GMIME_IS_MULTIPART_SIGNED (multipart)) {
		/* Don't index the signature. */
		if (i == 1)
		    continue;
		if (i > 1)
		    fprintf (stderr, "Warning: Unexpected extra parts of mutlipart/signed. Indexing anyway.\n");
	    }
	    gen_terms_part (term_gen,
			    g_mime_multipart_get_part (multipart, i));
	}
	return;
    }

    if (! GMIME_IS_PART (part)) {
	fprintf (stderr, "Warning: Not indexing unknown mime part: %s.\n",
		 g_type_name (G_OBJECT_TYPE (part)));
	return;
    }

    disposition = g_mime_object_get_content_disposition (part);
    if (disposition &&
	strcmp (disposition->disposition, GMIME_DISPOSITION_ATTACHMENT) == 0)
    {
	const char *filename = g_mime_part_get_filename (GMIME_PART (part));
	const char *extension;

	add_term (term_gen.get_document (), "label", "attachment");
	gen_terms (term_gen, "attachment", filename);

	if (filename) {
	    extension = strchr (filename, '.');
	    if (extension) {
		add_term (term_gen.get_document (), "attachment_extension",
			  extension + 1);
	    }
	}

	return;
    }

    byte_array = g_byte_array_new ();

    stream = g_mime_stream_mem_new_with_byte_array (byte_array);
    g_mime_stream_mem_set_owner (GMIME_STREAM_MEM (stream), FALSE);
    wrapper = g_mime_part_get_content_object (GMIME_PART (part));
    g_mime_data_wrapper_write_to_stream (wrapper, stream);

    g_object_unref (stream);

    g_byte_array_append (byte_array, (guint8 *) "\0", 1);
    body = (char *) g_byte_array_free (byte_array, FALSE);

    gen_terms_body_str (term_gen, body);

    free (body);
}

static void
index_file (Xapian::WritableDatabase db,
	    Xapian::TermGenerator term_gen,
	    const char *filename)
{
    Xapian::Document doc;

    GMimeStream *stream;
    GMimeParser *parser;
    GMimeMessage *message;
    InternetAddressList *addresses;
    GPtrArray *parents, *thread_ids;

    FILE *file;

    const char *subject, *refs, *in_reply_to, *from;
    const char *message_id;

    time_t time;
    struct tm gm_time_tm;
    char date_str[16]; /* YYYYMMDDHHMMSS + 1 for Y100k compatibility ;-) */
    unsigned int i;

    file = fopen (filename, "r");
    if (! file) {
	fprintf (stderr, "Error opening %s: %s\n", filename, strerror (errno));
	exit (1);
    }

    stream = g_mime_stream_file_new (file);

    parser = g_mime_parser_new_with_stream (stream);

    message = g_mime_parser_construct_message (parser);

    doc = Xapian::Document ();

    doc.set_data (filename);

    term_gen.set_stemmer (Xapian::Stem ("english"));

    term_gen.set_document (doc);

    from = g_mime_message_get_sender (message);
    addresses = internet_address_list_parse_string (from);

    gen_terms_address_names (term_gen, addresses, "from_name");

    addresses = g_mime_message_get_all_recipients (message);
    gen_terms_address_names (term_gen, addresses, "to_name");

    subject = g_mime_message_get_subject (message);
    subject = skip_re_in_subject (subject);
    gen_terms (term_gen, "subject", subject);
    gen_terms (term_gen, "body", subject);

    gen_terms_part (term_gen, g_mime_message_get_mime_part (message));

    parents = g_ptr_array_new ();

    refs = g_mime_object_get_header (GMIME_OBJECT (message), "references");
    parse_references (parents, refs);

    in_reply_to = g_mime_object_get_header (GMIME_OBJECT (message),
					    "in-reply-to");
    parse_references (parents, in_reply_to);

    for (i = 0; i < parents->len; i++)
	add_term (doc, "ref", (char *) g_ptr_array_index (parents, i));

    message_id = g_mime_message_get_message_id (message);

    thread_ids = find_thread_ids (db, parents, message_id);

    for (i = 0; i < parents->len; i++)
	g_free (g_ptr_array_index (parents, i));
    g_ptr_array_free (parents, TRUE);

    from = g_mime_message_get_sender (message);
    addresses = internet_address_list_parse_string (from);

    add_terms_address_addrs (doc, addresses, "from_email");

    add_terms_address_addrs (doc,
			     g_mime_message_get_all_recipients (message),
			     "to_email");

    g_mime_message_get_date (message, &time, NULL);

    gmtime_r (&time, &gm_time_tm);

    if (strftime (date_str, sizeof (date_str),
		  "%Y%m%d%H%M%S", &gm_time_tm) == 0) {
	fprintf (stderr, "Internal error formatting time\n");
	exit (1);
    }

    add_term (doc, "date", date_str);

    add_term (doc, "label", "inbox");
    add_term (doc, "label", "unread");
    add_term (doc, "type", "mail");
    add_term (doc, "source_id", "1");

    add_term (doc, "msgid", message_id);
    doc.add_value (NOTMUCH_VALUE_MESSAGE_ID, message_id);

    if (thread_ids->len) {
	unsigned int i;
	GString *thread_id;
	char *id;

	for (i = 0; i < thread_ids->len; i++) {
	    id = (char *) thread_ids->pdata[i];

	    add_term (doc, "thread", id);

	    if (i == 0)
		thread_id = g_string_new (id);
	    else
		g_string_append_printf (thread_id, ",%s", id);

	    free (id);
	}
	g_ptr_array_free (thread_ids, TRUE);

	doc.add_value (NOTMUCH_VALUE_THREAD, thread_id->str);

	g_string_free (thread_id, TRUE);
    } else {
	/* If not referenced thread, use the message ID */
	add_term (doc, "thread", message_id);
	doc.add_value (NOTMUCH_VALUE_THREAD, message_id);
    }

    doc.add_value (NOTMUCH_VALUE_DATE, Xapian::sortable_serialise (time));

    db.add_document (doc);

    g_object_unref (message);
    g_object_unref (parser);
    g_object_unref (stream);
}

static void
usage (const char *argv0)
{
    fprintf (stderr, "Usage: %s <path-to-xapian-database>\n", argv0);
    fprintf (stderr, "\n");
    fprintf (stderr, "Messages to be indexed are read from stdnin as absolute filenames\n");
    fprintf (stderr, "one file per line.");
}

int
main (int argc, char **argv)
{
    const char *database_path;
    char *filename;
    GIOChannel *channel;
    GIOStatus gio_status;
    GError *error = NULL;

    if (argc < 2) {
	usage (argv[0]);
	exit (1);
    }

    database_path = argv[1];

    g_mime_init (0);

    try {
	Xapian::WritableDatabase db;
	Xapian::TermGenerator term_gen;

	db = Xapian::WritableDatabase (database_path,
				       Xapian::DB_CREATE_OR_OPEN);

	term_gen = Xapian::TermGenerator ();

	channel = g_io_channel_unix_new (fileno (stdin));

	while (1) {
	    gio_status = g_io_channel_read_line (channel, &filename,
						 NULL, NULL, &error);
	    if (gio_status == G_IO_STATUS_EOF)
		break;
	    if (gio_status != G_IO_STATUS_NORMAL) {
		fprintf (stderr, "An error occurred reading from stdin: %s\n",
			 error->message);
		exit (1);
	    }

	    g_strchomp (filename);
	    index_file (db, term_gen, filename);

	    g_free (filename);
	}

    } catch (const Xapian::Error &error) {
	cerr << "A Xapian exception occurred: " << error.get_msg () << endl;
	exit (1);
    }

    return 0;
}