/* 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 <errno.h>
#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sysexits.h>
#include <unistd.h>

#include "archive.h"
#include "imap.h"

#define ENV_PASSWORD "BUBGER_IMAP_PASSWORD"

static uint32_t uidRead(const char *path) {
	FILE *file = fopen(path, "r");
	if (!file) return 0;
	uint32_t uid;
	int n = fscanf(file, "%" SCNu32, &uid);
	if (n < 1) errx(EX_DATAERR, "%s: invalid UID", path);
	return uid;
}

static void uidWrite(const char *path, uint32_t uid) {
	FILE *file = fopen(path, "w");
	if (!file) err(EX_CANTCREAT, "%s", path);
	int n = fprintf(file, "%" PRIu32 "\n", uid);
	if (n < 0) err(EX_IOERR, "%s", path);
	int error = fclose(file);
	if (error) err(EX_IOERR, "%s", path);
}

static void createDir(const char *path) {
	int error = mkdir(path, 0775);
	if (error && errno != EEXIST) err(EX_CANTCREAT, "%s", path);
}

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");
	}

	uint32_t uidNext = 0;
	enum Atom login = 0;
	enum Atom examine = atom("EXAMINE");
	enum Atom thread = atom("THREAD");
	enum Atom export = 0;

	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
		) {
			enum Atom code = resp.code.ptr[0].atom;
			if (code == AtomUIDValidity || code == AtomUIDNext) {
				if (resp.code.ptr[1].type != Number) {
					errx(EX_PROTOCOL, "invalid %s", Atoms[code]);
				}
			}
			if (code == AtomUIDValidity) {
				uint32_t validity = resp.code.ptr[1].number;
				uint32_t previous = uidRead("UIDVALIDITY");
				if (previous && validity != previous) {
					errx(
						EX_TEMPFAIL,
						"UIDVALIDITY changed; fresh export required"
					);
				}
				if (!previous) uidWrite("UIDVALIDITY", validity);
			}
			if (code == AtomUIDNext) {
				uint32_t next = resp.code.ptr[1].number;
				uint32_t prev = uidRead("UIDNEXT");
				if (next == prev) {
					examine = 0;
					fprintf(imap, "ayy LOGOUT\r\n");
				}
			}
		}

		if (resp.tag == examine) {
			fprintf(
				imap, "%s UID THREAD %s UTF-8 %s\r\n",
				Atoms[thread], algo, search
			);
		}

		if (resp.resp == thread) {
			if (!resp.data.len) {
				errx(EX_TEMPFAIL, "no messages matching %s", search);
			}
			createDir("UID");
			createDir("message");
			export = exportThreads(imap, resp.data);
		}

		if (export && resp.resp == AtomFetch) {
			if (!resp.data.len || resp.data.ptr[0].type != List) {
				errx(EX_PROTOCOL, "invalid FETCH data");
			}
			exportData(resp.data.ptr[0].list);
		}

		respFree(resp);
	}
	fclose(imap);
	uidWrite("UIDNEXT", uidNext);
}