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

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

static const char *exportPath(uint32_t uid, const char *type) {
	static char buf[PATH_MAX];
	char str[32];
	snprintf(str, sizeof(str), "%" PRIu32, uid);
	struct Variable vars[] = {
		{ "uid", str },
		{ "type", type },
		{0},
	};
	templateBuffer(buf, sizeof(buf), PATH_UID, vars, escapePath);
	return buf;
}

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(exportPath(uid, "atom"), F_OK)
			|| access(exportPath(uid, "html"), F_OK)
			|| access(exportPath(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);
	}
	listFree(uids);
	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 = exportPath(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);

	char buf[PATH_MAX];
	struct Variable vars[] = {
		{ "messageID", envelope->messageID },
		{ "type", "mbox" },
		{0},
	};
	templateBuffer(buf, sizeof(buf), PATH_MESSAGE, vars, escapePath);

	unlink(buf);
	error = link(path, buf);
	if (error) err(EX_CANTCREAT, "%s", buf);
}

static bool isInline(const struct BodyPart *part) {
	if (!bodyPartType(part, "text", "plain")) return false;
	if (!part->disposition.type) return true;
	return !strcasecmp(part->disposition.type, "inline");
}

static bool isAttachment(const struct BodyPart *part) {
	if (isInline(part)) return false;
	return !part->multipart && !part->message.structure;
}

static void exportAtom(
	uint32_t uid, const struct Envelope *envelope,
	const struct BodyPart *structure, struct Data body
) {
	const char *path = exportPath(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);

	const struct BodyPart *part = structure;
	while (part->multipart) {
		if (bodyPartType(part, "multipart", "alternative")) {
			for (size_t i = part->parts.len - 1; i < part->parts.len; --i) {
				if (!isInline(&part->parts.ptr[i])) continue;
				part = &part->parts.ptr[i];
				body = dataCheck(body, List).list.ptr[i];
				break;
			}
			if (part->multipart) break;
		} else {
			part = &part->parts.ptr[0];
			body = dataCheck(body, List).list.ptr[0];
		}
	}
	if (isInline(part)) {
		char *content = decodeToString(part, dataCheck(body, String).string);
		error = atomContent(file, content);
		if (error) err(EX_IOERR, "%s", path);
		free(content);
	}

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

static const char *sectionName(struct List section) {
	static char buf[1024];
	char str[32];
	buf[0] = '\0';
	for (size_t i = 0; i < section.len; ++i) {
		snprintf(
			str, sizeof(str), "%s%" PRIu32,
			(i ? "." : ""), dataCheck(section.ptr[i], Number).number
		);
		strlcat(buf, str, sizeof(buf));
	}
	return buf;
}

static int exportHTMLAttachment(
	FILE *file, const struct Envelope *envelope, struct List section,
	const struct BodyPart *part, struct Data body
) {
	const char *name = paramGet(part->disposition.params, "filename");
	if (!name) name = paramGet(part->params, "name");

	const char *disposition = part->disposition.type;
	if (!disposition) disposition = "INLINE";

	char path[PATH_MAX];
	struct Variable vars[] = {
		{ "messageID", envelope->messageID },
		{ "section", sectionName(section) },
		{ "name", (name ? name : "") },
		{ "disposition", (name ? "" : disposition) },
		{ ".", (name ? "" : ".") },
		{ "subtype", (name ? "" : part->subtype) },
		{0},
	};
	templateBuffer(path, sizeof(path), PATH_ATTACHMENT, vars, escapePath);

	for (char *ch = path; (ch = strchr(ch, '/')); ++ch) {
		*ch = '\0';
		int error = mkdir(path, 0775);
		if (error && errno != EEXIST) err(EX_CANTCREAT, "%s", path);
		*ch = '/';
	}

	FILE *attachment = fopen(path, "w");
	if (!file) err(EX_CANTCREAT, "%s", path);

	int error = 0
		|| decodeToFile(attachment, part, dataCheck(body, String).string)
		|| fclose(attachment);
	if (error) err(EX_IOERR, "%s", path);

	return htmlAttachment(file, part, vars);
}

static int exportHTMLBody(
	FILE *file, const struct Envelope *envelope, struct List *section,
	const struct BodyPart *part, struct Data body
) {
	if (bodyPartType(part, "multipart", "alternative")) {
		for (size_t i = part->parts.len - 1; i < part->parts.len; --i) {
			if (!isInline(&part->parts.ptr[i])) continue;
			return exportHTMLBody(
				file, envelope, section,
				&part->parts.ptr[i], dataCheck(body, List).list.ptr[i]
			);
		}
		return exportHTMLBody(
			file, envelope, section,
			&part->parts.ptr[part->parts.len - 1],
			dataCheck(body, List).list.ptr[part->parts.len - 1]
		);

	} else if (part->multipart) {
		int error;
		bool attached = false;
		for (size_t i = 0; i < part->parts.len; ++i) {
			if (attached != isAttachment(&part->parts.ptr[i])) {
				attached ^= true;
				error = attached
					? htmlAttachmentOpen(file)
					: htmlAttachmentClose(file);
				if (error) return error;
			}
			struct Data num = { .type = Number, .number = 1 + i };
			listPush(section, num);
			error = exportHTMLBody(
				file, envelope, section,
				&part->parts.ptr[i], dataCheck(body, List).list.ptr[i]
			);
			if (error) return error;
			section->len--;
		}
		return (attached ? htmlAttachmentClose(file) : 0);

	} else if (part->message.structure) {
		const struct BodyPart *structure = part->message.structure;
		int error = 0
			|| htmlMessageOpen(file, part->message.envelope)
			|| exportHTMLBody(file, envelope, section, structure, body)
			|| htmlMessageClose(file);
		return error;

	} else if (isInline(part)) {
		char *content = decodeToString(part, dataCheck(body, String).string);
		int error = htmlInline(file, part, content);
		free(content);
		return error;

	} else {
		return exportHTMLAttachment(file, envelope, *section, part, body);
	}
}

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

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

	struct List section = {0};
	error = exportHTMLBody(file, envelope, &section, structure, body);
	if (error) err(EX_IOERR, "%s", path);
	listFree(section);

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

static void fetchParts(
	FILE *imap, struct List *section, 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(section, part);
			fetchParts(imap, section, &structure->parts.ptr[i]);
			section->len--;
		}
	} else if (
		structure->message.structure &&
		structure->message.structure->multipart
	) {
		fetchParts(imap, section, structure->message.structure);
	} else {
		fprintf(
			imap, " BODY[%s%s]",
			sectionName(*section), (structure->message.structure ? ".TEXT" : "")
		);
	}
}

static void checkBodyParts(const struct BodyPart *structure, struct Data body) {
	if (structure->multipart) {
		struct List list = dataCheck(body, List).list;
		if (list.len < structure->parts.len) {
			errx(EX_PROTOCOL, "missing body parts");
		}
		for (size_t i = 0; i < structure->parts.len; ++i) {
			checkBodyParts(&structure->parts.ptr[i], list.ptr[i]);
		}
	} else if (
		structure->message.structure &&
		structure->message.structure->multipart
	) {
		checkBodyParts(structure->message.structure, body);
	} else if (body.type != String) {
		errx(EX_PROTOCOL, "missing body part");
	}
}

bool exportData(FILE *imap, enum Atom tag, struct List items) {
	uint32_t uid = 0;
	struct Envelope envelope = {0};
	struct BodyPart structure = {0};
	struct Data bodyHeader = {0};
	struct Data bodyText = {0};
	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 == AtomHeader) {
				bodyHeader = data;
			} else if (name == AtomText) {
				bodyText = data;
			}
			continue;
		}

		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;
			if (dest->type != List) {
				*dest = (struct Data) { .type = List };
			}
			while (dest->list.len < num) {
				listPush(&dest->list, (struct Data) {0});
			}
			dest = &dest->list.ptr[num - 1];
		}
		// Free with bodyParts:
		*dest = dataTake(&items.ptr[i + 1]);
	}

	if (!uid) {
		errx(EX_PROTOCOL, "missing UID data item");
	}
	if (!envelope.subject) {
		errx(EX_PROTOCOL, "missing ENVELOPE data item");
	}
	if (!structure.subtype) {
		errx(EX_PROTOCOL, "missing BODYSTRUCTURE data item");
	}
	if (bodyParts.type == List) {
		checkBodyParts(&structure, bodyParts);
	}

	if (bodyHeader.type == String && bodyText.type == String) {
		exportMbox(uid, &envelope, bodyHeader.string, bodyText.string);
	}

	bool fetch = false;
	if (!structure.multipart) {
		exportAtom(uid, &envelope, &structure, bodyText);
		exportHTML(uid, &envelope, &structure, bodyText);
	} else if (bodyParts.type == List) {
		exportAtom(uid, &envelope, &structure, bodyParts);
		exportHTML(uid, &envelope, &structure, bodyParts);
	} else {
		fetch = true;
		fprintf(
			imap, "%s UID FETCH %" PRIu32 " (UID ENVELOPE BODYSTRUCTURE",
			Atoms[tag], uid
		);
		struct List section = {0};
		fetchParts(imap, &section, &structure);
		listFree(section);
		fprintf(imap, ")\r\n");
	}

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