/* 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 <stdio.h>
#include <stdlib.h>
#include <sysexits.h>

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

static struct Address parseAddress(struct List list) {
	if (list.len < 4) {
		errx(EX_PROTOCOL, "missing address structure fields");
	}
	struct Address addr = {0};
	if (list.ptr[0].type == String) {
		// TODO: Decode UTF-8 in name.
		addr.name = strdup(list.ptr[0].string);
		if (!addr.name) err(EX_OSERR, "strdup");
	}
	if (list.ptr[2].type == String) addr.mailbox = list.ptr[2].string;
	if (list.ptr[3].type == String) addr.host = list.ptr[3].string;
	return addr;
}

static struct AddressList parseAddressList(struct List list) {
	struct Address *addrs = calloc(list.len, sizeof(*addrs));
	if (!addrs) err(EX_OSERR, "calloc");
	for (size_t i = 0; i < list.len; ++i) {
		addrs[i] = parseAddress(dataCheck(list.ptr[i], List).list);
	}
	return (struct AddressList) { list.len, addrs };
}

static char *parseID(char *id) {
	size_t len = strlen(id);
	if (id[0] != '<' || !len || id[len - 1] != '>') {
		errx(EX_PROTOCOL, "invalid message ID");
	}
	id[len - 1] = '\0';
	return &id[1];
}

void parseEnvelope(struct Envelope *envelope, struct List list) {
	enum {
		Date, Subject, From, Sender, ReplyTo,
		To, Cc, Bcc, InReplyTo, MessageID,
		EnvelopeLen,
	};
	if (list.len < EnvelopeLen) {
		errx(EX_PROTOCOL, "missing envelope structure fields");
	}

	const char *date = dataCheck(list.ptr[Date], String).string;
	date = strptime(date, "%a, %e %b %Y %H:%M:%S %z", &envelope->date);
	if (!date) errx(EX_PROTOCOL, "invalid envelope date format");

	envelope->date.tm_isdst = -1;
	envelope->utc = mktime(&envelope->date);

	// TODO: Decode UTF-8 in subject.
	envelope->subject = strdup(dataCheck(list.ptr[Subject], String).string);
	if (!envelope->subject) err(EX_OSERR, "strdup");

	for (size_t i = From; i <= Bcc; ++i) {
		if (list.ptr[i].type == List) continue;
		if (list.ptr[i].type == Atom && list.ptr[i].atom == AtomNil) {
			list.ptr[i].type = List;
			list.ptr[i].list = (struct List) {0};
			continue;
		}
		errx(EX_PROTOCOL, "invalid envelope address field");
	}
	for (size_t i = From; i <= ReplyTo; ++i) {
		if (!list.ptr[i].list.len || list.ptr[i].list.ptr[0].type != List) {
			errx(EX_PROTOCOL, "invalid envelope address field");
		}
	}
	envelope->from = parseAddress(list.ptr[From].list.ptr[0].list);
	envelope->sender = parseAddress(list.ptr[Sender].list.ptr[0].list);
	envelope->replyTo = parseAddress(list.ptr[ReplyTo].list.ptr[0].list);
	envelope->to = parseAddressList(list.ptr[To].list);
	envelope->cc = parseAddressList(list.ptr[Cc].list);
	envelope->bcc = parseAddressList(list.ptr[Bcc].list);

	if (list.ptr[InReplyTo].type == String) {
		envelope->inReplyTo = parseID(list.ptr[InReplyTo].string);
	}
	envelope->messageID = parseID(dataCheck(list.ptr[MessageID], String).string);
}