/* 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 "archive.h"
#include "imap.h"

bool exportFetch(FILE *imap, enum Atom tag, struct List threads) {
	struct List uids = {0};
	listFlatten(&uids, threads);
	for (size_t i = uids.len - 1; i < uids.len; --i) {
		uint32_t uid = dataCheck(uids.ptr[i], Number).number;
		int error = 0
			|| access(pathUID(uid, "atom"), F_OK)
			|| access(pathUID(uid, "html"), F_OK)
			|| access(pathUID(uid, "mbox"), F_OK);
		if (!error) uids.ptr[i] = uids.ptr[--uids.len];
	}
	if (!uids.len) {
		listFree(uids);
		return false;
	}

	fprintf(imap, "%s UID FETCH ", Atoms[tag]);
	for (size_t i = 0; i < uids.len; ++i) {
		fprintf(imap, "%s%" PRIu32, (i ? "," : ""), uids.ptr[i].number);
	}
	fprintf(
		imap,
		" (UID ENVELOPE BODYSTRUCTURE"
		" BODY[HEADER.FIELDS (" MBOX_HEADERS ")] BODY[TEXT])\r\n"
	);
	return true;
}

static void exportMbox(
	uint32_t uid, const struct Envelope *envelope,
	const char *header, const char *body
) {
	const char *path = pathUID(uid, "mbox");
	FILE *file = fopen(path, "w");
	if (!file) err(EX_CANTCREAT, "%s", path);
	int error = 0
		|| mboxFrom(file)
		|| mboxHeader(file, header)
		|| mboxBody(file, body)
		|| fclose(file);
	if (error) err(EX_IOERR, "%s", path);

	const char *msg = pathMessage(envelope->messageID, "mbox");
	unlink(msg);
	error = link(path, msg);
	if (error) err(EX_CANTCREAT, "%s", msg);
}

static void exportAtom(
	uint32_t uid, const struct Envelope *envelope,
	const struct BodyPart *structure, const char *body
) {
	const char *path = pathUID(uid, "atom");
	FILE *file = fopen(path, "w");
	if (!file) err(EX_CANTCREAT, "%s", path);

	int error = atomEntryOpen(file, envelope);
	if (error) err(EX_IOERR, "%s", path);

	if (
		!structure->multipart &&
		!strcmp(structure->type, "TEXT") &&
		!strcmp(structure->subtype, "PLAIN")
	) {
		error = 0
			|| atomContentOpen(file)
			|| decodeContent(file, escapeXML, structure, body)
			|| atomContentClose(file);
		if (error) err(EX_IOERR, "%s", path);
	}

	error = atomEntryClose(file) || fclose(file);
	if (error) err(EX_IOERR, "%s", path);
}

static void exportFetchParts(
	FILE *imap, struct List *parts, const struct BodyPart *structure
) {
	if (structure->multipart) {
		for (size_t i = 0; i < structure->parts.len; ++i) {
			struct Data part = { .type = Number, .number = 1 + i };
			listPush(parts, part);
			exportFetchParts(imap, parts, &structure->parts.ptr[i]);
			parts->len--;
		}
	} else if (
		structure->message.structure &&
		structure->message.structure->multipart
	) {
		exportFetchParts(imap, parts, structure->message.structure);
	} else {
		fprintf(imap, " BODY[");
		for (size_t i = 0; i < parts->len; ++i) {
			fprintf(imap, "%s%" PRIu32, (i ? "." : ""), parts->ptr[i].number);
		}
		if (structure->message.structure) {
			fprintf(imap, ".TEXT");
		}
		fprintf(imap, "]");
	}
}

bool exportData(FILE *imap, enum Atom tag, struct List items) {
	uint32_t uid = 0;
	struct Envelope envelope = {0};
	struct BodyPart structure = {0};
	const char *bodyHeader = NULL;
	const char *bodyText = NULL;
	struct Data bodyParts = {0};

	for (size_t i = 0; i + 1 < items.len; i += 2) {
		enum Atom name = dataCheck(items.ptr[i], Atom).atom;
		struct Data data = items.ptr[i + 1];
		if (name == AtomUID) {
			uid = dataCheck(data, Number).number;
		} else if (name == AtomEnvelope) {
			parseEnvelope(&envelope, dataCheck(data, List).list);
		} else if (name == AtomBodyStructure) {
			parseBodyPart(&structure, dataCheck(data, List).list);
		}
		if (name != AtomBody) continue;

		struct List section = dataCheck(data, List).list;
		if (!section.len) {
			errx(EX_PROTOCOL, "missing body data item section");
		}
		i++;
		if (i + 1 >= items.len) {
			errx(EX_PROTOCOL, "missing body data item value");
		}
		data = items.ptr[i + 1];

		if (section.ptr[0].type == Atom) {
			name = section.ptr[0].atom;
			if (name == AtomHeaderFields) {
				bodyHeader = dataCheck(data, String).string;
			} else if (name == AtomText) {
				bodyText = dataCheck(data, String).string;
			}
			continue;
		}

		data = dataTake(&items.ptr[i + 1]);
		struct Data *dest = &bodyParts;
		for (size_t i = 0; i < section.len; ++i) {
			if (section.ptr[i].type != Number) continue;
			uint32_t num = section.ptr[i].number;
			*dest = (struct Data) { .type = List };
			while (dest->list.len < num) {
				listPush(&dest->list, (struct Data) {0});
			}
			dest = &dest->list.ptr[num - 1];
			*dest = data;
		}
	}

	if (!uid) {
		errx(EX_PROTOCOL, "missing UID data item");
	}
	if (!structure.subtype) {
		errx(EX_PROTOCOL, "missing BODYSTRUCTURE data item");
	}

	bool fetch = false;
	if (envelope.subject) {
		if (!bodyHeader) {
			errx(EX_PROTOCOL, "missing BODY[HEADER.FIELDS] data item");
		}
		if (!bodyText) {
			errx(EX_PROTOCOL, "missing BODY[TEXT] data item");
		}
		exportMbox(uid, &envelope, bodyHeader, bodyText);
		exportAtom(uid, &envelope, &structure, bodyText);

		if (structure.multipart) {
			fetch = true;
			fprintf(
				imap, "%s UID FETCH %" PRIu32 " (UID BODYSTRUCTURE",
				Atoms[tag], uid
			);
			struct List parts = {0};
			exportFetchParts(imap, &parts, &structure);
			listFree(parts);
			fprintf(imap, ")\r\n");
		}
	} else {
		// TODO: Correlate body parts to body data.
	}

	envelopeFree(envelope);
	bodyPartFree(structure);
	dataFree(bodyParts);
	return fetch;
}