/* Copyright (C) 2020  C. 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/>.
 */

#include <err.h>
#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sysexits.h>
#include <unistd.h>

#include "imap.h"

#define ENV_PASSWORD "BUBGER_IMAP_PASSWORD"

static void checkValidity(uint32_t validity) {
	FILE *file = fopen("UIDVALIDITY", "r");
	if (file) {
		uint32_t previous;
		int n = fscanf(file, "%" SCNu32, &previous);
		if (n < 1) errx(EX_DATAERR, "invalid UIDVALIDITY file");

		if (validity != previous) {
			errx(EX_TEMPFAIL, "UIDVALIDITY changed; fresh export required");
		}

	} else {
		FILE *file = fopen("UIDVALIDITY", "w");
		if (!file) err(EX_CANTCREAT, "UIDVALIDITY");

		int n = fprintf(file, "%" PRIu32 "\n", validity);
		if (n < 0) err(EX_IOERR, "UIDVALIDITY");

		int error = fclose(file);
		if (error) err(EX_IOERR, "UIDVALIDITY");
	}
}

int main(int argc, char *argv[]) {
	const char *host = NULL;
	const char *port = "imaps";
	const char *user = NULL;
	const char *passPath = NULL;

	const char *mailbox = "Archive";
	const char *algo = "REFERENCES";
	const char *search = "ALL";

	const char *title = NULL;
	const char *headPath = NULL;

	for (int opt; 0 < (opt = getopt(argc, argv, "C:a:h:p:s:t:vw:"));) {
		switch (opt) {
			break; case 'C': {
				int error = chdir(optarg);
				if (error) err(EX_NOINPUT, "%s", optarg);
			}
			break; case 'a': algo = optarg;
			break; case 'h': headPath = optarg;
			break; case 'p': port = optarg;
			break; case 's': search = optarg;
			break; case 't': title = optarg;
			break; case 'v': imapVerbose = true;
			break; case 'w': passPath = optarg;
		}
	}
	if (optind < argc) host = argv[optind++];
	if (optind < argc) user = argv[optind++];
	if (optind < argc) mailbox = argv[optind++];

	if (!host) errx(EX_USAGE, "host required");
	if (!user) errx(EX_USAGE, "user required");
	if (!title) title = mailbox;

	char *pass = NULL;
	if (passPath) {
		FILE *file = fopen(passPath, "r");
		if (!file) err(EX_NOINPUT, "%s", passPath);

		size_t cap = 0;
		ssize_t len = getline(&pass, &cap, file);
		if (len < 0) err(EX_IOERR, "%s", passPath);
		if (len && pass[len - 1] == '\n') pass[len - 1] = '\0';
		fclose(file);
	} else {
		pass = getenv(ENV_PASSWORD);
		if (!pass) errx(EX_CONFIG, ENV_PASSWORD " unset");
	}

	enum Atom login = 0;
	enum Atom examine = atom("examine");

	FILE *imap = imapOpen(host, port);
	for (struct Resp resp; resp = imapResp(imap), resp.resp != AtomBye;) {
		if (resp.resp == AtomNo || resp.resp == AtomBad) {
			errx(EX_CONFIG, "%s %s", Atoms[resp.resp], resp.text);
		}

		if (!login) {
			login = atom("login");
			fprintf(
				imap, "%s LOGIN \"%s\" \"%s\"\r\n",
				Atoms[login], user, pass
			);
		}

		if (resp.tag == login) {
			fprintf(imap, "%s EXAMINE \"%s\"\r\n", Atoms[examine], mailbox);
		}

		if (
			resp.resp == AtomOk &&
			resp.code.len > 1 &&
			resp.code.ptr[0].type == Atom &&
			resp.code.ptr[0].atom == AtomUIDValidity
		) {
			if (resp.code.ptr[1].type != Number) {
				errx(EX_PROTOCOL, "invalid UIDVALIDITY");
			}
			checkValidity(resp.code.ptr[1].number);
		}
	}
	fclose(imap);
}