/* Copyright (C) 2020  June McEnroe <june@causal.agency>
 *
 * 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 <https://www.gnu.org/licenses/>.
 *
 * Additional permission under GNU GPL version 3 section 7:
 *
 * If you modify this Program, or any covered work, by linking or
 * combining it with OpenSSL (or a modified version of that library),
 * containing parts covered by the terms of the OpenSSL License and the
 * original SSLeay license, the licensors of this Program grant you
 * additional permission to convey the resulting work. Corresponding
 * Source for a non-source form of such a combination shall include the
 * source code for the parts of OpenSSL used as well as that of the
 * covered work.
 */

#include <err.h>
#include <inttypes.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sysexits.h>
#include <time.h>
#include <unistd.h>

#ifdef __APPLE__
#include <sys/random.h>
#endif

#ifdef DECLARE_RPP
#define RPP_STDIN 1
char * readpassphrase(const char *prompt, char *buf, size_t bufsiz, int flags);
#else
#include <readpassphrase.h>
#endif

#include "imap.h"

typedef unsigned char byte;

static const char *uuidGen(void) {
	byte uuid[16];
	int error = getentropy(uuid, sizeof(uuid));
	if (error) err(EX_OSERR, "getentropy");

	uuid[6] &= 0x0F;
	uuid[6] |= 0x40;
	uuid[8] &= 0x3F;
	uuid[8] |= 0x80;

	static char str[sizeof("00000000-0000-0000-0000-000000000000")];
	snprintf(
		str, sizeof(str),
		"%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
		uuid[0], uuid[1], uuid[2], uuid[3],
		uuid[4], uuid[5], uuid[6], uuid[7],
		uuid[8], uuid[9], uuid[10], uuid[11],
		uuid[12], uuid[13], uuid[14], uuid[15]
	);
	return str;
}

static bool uuidCheck(const char *uuid) {
	if (strlen(uuid) != 36) return false;
	if (strspn(uuid, "0123456789abcdef-") != 36) return false;
	return true;
}

#define DATE_FORMAT "%a, %e %b %Y %H:%M:%S %z"

static char *format(const char *from, const char *uuid, const char *path) {
	FILE *note = fopen(path, "r");
	if (!note) err(EX_NOINPUT, "%s", path);

	struct stat status;
	int error = fstat(fileno(note), &status);
	if (error) err(EX_IOERR, "%s", path);

	char date[sizeof("Mon, 00 Jan 0000 00:00:00 -0000")];
	strftime(
		date, sizeof(date), DATE_FORMAT,
		localtime(&status.st_mtime)
	);

	char *buf;
	size_t buflen;
	FILE *msg = open_memstream(&buf, &buflen);
	if (!msg) err(EX_OSERR, "open_memstream");

	fprintf(
		msg,
		"From: <%s>\r\n"
		"Date: %s\r\n"
		"X-Universally-Unique-Identifier: %s\r\n"
		"X-Uniform-Type-Identifier: com.apple.mail-note\r\n"
		"X-Mailer: notemap\r\n"
		"MIME-Version: 1.0\r\n"
		"Content-Type: text/plain; charset=\"utf-8\"\r\n"
		"Content-Transfer-Encoding: quoted-printable\r\n"
		"Subject: =?utf-8?Q?",
		from, date, uuid
	);
	for (const char *ch = path; *ch; ++ch) {
		if ((uint8_t)*ch & 0x80) {
			fprintf(msg, "=%02hhX", (uint8_t)*ch);
		} else if (*ch == ' ') {
			fprintf(msg, "_");
		} else {
			fprintf(msg, "%c", *ch);
		}
	}
	fprintf(msg, "?=\r\n\r\n");

	int ch;
	int len = 0;
	bool ws = false;
	while (EOF != (ch = fgetc(note))) {
		if (len == 75 && ch != '\n') {
			fprintf(msg, "=\r\n");
			len = 0;
		}
		if (ch == '\n') {
			fprintf(msg, "%s\r\n", (ws ? "=\r\n" : ""));
			len = 0;
		} else if (ch == '\t' || (ch >= ' ' && ch <= '~' && ch != '=')) {
			fprintf(msg, "%c", ch);
			len++;
		} else {
			fprintf(msg, "=%02X", ch);
			len += 3;
		}
		ws = (ch == '\t' || ch == ' ');
	}
	if (ferror(note)) err(EX_IOERR, "%s", path);
	fclose(note);

	error = fclose(msg);
	if (error) err(EX_IOERR, "fclose");

	return buf;
}

int main(int argc, char *argv[]) {
	const char *path = ".notemap";
	bool add = false;
	bool force = false;

	const char *user = NULL;
	const char *host = NULL;
	const char *port = "imaps";
	const char *mailbox = "Notes";
	int rppFlags = 0;

	int opt;
	while (0 < (opt = getopt(argc, argv, "M:afh:m:p:vw"))) {
		switch (opt) {
			break; case 'M': mailbox = optarg;
			break; case 'a': add = true;
			break; case 'f': force = true;
			break; case 'h': host = optarg;
			break; case 'm': path = optarg;
			break; case 'p': port = optarg;
			break; case 'u': user = optarg;
			break; case 'v': imapVerbose = true;
			break; case 'w': rppFlags |= RPP_STDIN;
			break; default:  return EX_USAGE;
		}
	}
	if (optind < argc) user = argv[optind++];
	argv += optind;
	argc -= optind;
	
	if (!user) errx(EX_USAGE, "username required");
	if (!host) {
		host = strchr(user, '@');
		if (!host) errx(EX_USAGE, "no domain in username");
		host++;
	}

	char buf[1024];
	char *pass = readpassphrase(
		(rppFlags & RPP_STDIN ? "" : "Password: "),
		buf, sizeof(buf), rppFlags
	);
	if (!pass) err(EX_UNAVAILABLE, "readpassphrase");

	if (add) {
		FILE *map = fopen(path, "a");
		if (!map) err(EX_CANTCREAT, "%s", path);
		for (int i = 0; i < argc; ++i) {
			if (access(argv[i], R_OK)) err(EX_NOINPUT, "%s", argv[i]);
			fprintf(map, "%s %s\n", uuidGen(), argv[i]);
			if (ferror(map)) err(EX_IOERR, "%s", path);
		}
		int error = fclose(map);
		if (error) err(EX_IOERR, "%s", path);
	}

	FILE *map = fopen(path, "r");
	if (!map) err(EX_NOINPUT, "%s", path);

	struct Resp resp;
	struct IMAP imap = imapOpen(host, port);
	respFree(respOk(imapResp(&imap)));

	enum Atom login = atom("login");
	fprintf(imap.w, "%s LOGIN \"%s\" \"%s\"\r\n", Atoms[login], user, pass);
	for (; (resp = respOk(imapResp(&imap))).tag != login; respFree(resp));
	respFree(resp);

	enum Atom select = atom("select");
	fprintf(imap.w, "%s SELECT \"%s\"\r\n", Atoms[select], mailbox);
	for (; (resp = respOk(imapResp(&imap))).tag != select; respFree(resp));
	respFree(resp);

	size_t cap = 0;
	char *entry = NULL;
	for (ssize_t len; 0 < (len = getline(&entry, &cap, map));) {
		if (entry[len - 1] == '\n') entry[len - 1] = '\0';

		char *note = entry;
		char *uuid = strsep(&note, " ");
		if (!note || !uuid || !uuidCheck(uuid)) {
			errx(EX_CONFIG, "invalid map entry: %s", entry);
		}

		if (argc) {
			int i;
			for (i = 0; i < argc; ++i) {
				if (!argv[i]) continue;
				if (strcmp(argv[i], note)) continue;
				argv[i] = NULL;
				break;
			}
			if (i == argc) continue;
		}

		uint32_t seq = 0;
		enum Atom search = atom("search");
		fprintf(
			imap.w,
			"%s SEARCH HEADER X-Universally-Unique-Identifier \"%s\"\r\n",
			Atoms[search], uuid
		);
		for (; (resp = respOk(imapResp(&imap))).tag != search; respFree(resp)) {
			if (resp.resp != AtomSearch) continue;
			if (resp.data.len > 1) {
				errx(EX_CONFIG, "multiple messages matching %s", uuid);
			}
			if (resp.data.len) {
				seq = dataCheck(resp.data.ptr[0], Number).number;
			}
		}
		respFree(resp);

		if (!seq) goto append;

		struct tm date = {0};
		enum Atom fetch = atom("fetch");
		fprintf(
			imap.w, "%s FETCH %" PRIu32 " ENVELOPE\r\n",
			Atoms[fetch], seq
		);
		for (; (resp = respOk(imapResp(&imap))).tag != fetch; respFree(resp)) {
			if (resp.resp != AtomFetch) continue;
			if (!resp.data.len) errx(EX_PROTOCOL, "missing fetch data");
			struct List items = dataCheck(resp.data.ptr[0], List).list;
			if (items.len < 2) errx(EX_PROTOCOL, "missing fetch data items");
			enum Atom item = dataCheck(items.ptr[0], Atom).atom;
			if (item != AtomEnvelope) continue;
			struct List envelope = dataCheck(items.ptr[1], List).list;
			if (!envelope.len) errx(EX_PROTOCOL, "missing envelope date");
			const char *rest = strptime(
				dataCheck(envelope.ptr[0], String).string, DATE_FORMAT, &date
			);
			if (!rest) errx(EX_PROTOCOL, "invalid envelope date format");
		}
		respFree(resp);

		struct stat status;
		int error = stat(note, &status);
		if (error) err(EX_NOINPUT, "%s", note);
		if (status.st_mtime < mktime(&date) && !force) {
			errx(
				EX_TEMPFAIL,
				"%s: note modified in mailbox; use -f to overwrite", note
			);
		} else if (status.st_mtime == mktime(&date)) {
			continue;
		}

append:;
		char *message = format(user, uuid, note);
		enum Atom append = atom("append");
		fprintf(
			imap.w, "%s APPEND %s (\\Seen) {%zu}\r\n",
			Atoms[append], mailbox, strlen(message)
		);
		for (; (resp = respOk(imapResp(&imap))).tag != append; respFree(resp)) {
			if (resp.tag == AtomContinue) fprintf(imap.w, "%s\r\n", message);
		}
		respFree(resp);
		free(message);

		if (!seq) {
			printf("+ %s\n", note);
			continue;
		}

		enum Atom delete = atom("delete");
		fprintf(
			imap.w, "%s STORE %" PRIu32 " +FLAGS (\\Deleted)\r\n",
			Atoms[delete], seq
		);
		for (; (resp = respOk(imapResp(&imap))).tag != delete; respFree(resp));
		respFree(resp);
		printf("~ %s\n", note);
	}
	if (ferror(map)) err(EX_IOERR, "%s", path);

	fprintf(imap.w, "ayy LOGOUT\r\n");
	fclose(imap.r);
	fclose(imap.w);

	int ret = EX_OK;
	for (int i = 0; i < argc; ++i) {
		if (!argv[i]) continue;
		warnx("%s: unmapped note; use -a to add", argv[i]);
		ret = EX_CONFIG;
	}
	return ret;
}