/* Copyright (C) 2019, 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 "compat.h"

#include <err.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <sysexits.h>
#include <unistd.h>

#ifndef NO_READPASSPHRASE_H
#include <readpassphrase.h>
#endif

#include "imap.h"

#if !defined(DIG_PATH) && !defined(DRILL_PATH)
#	ifdef __FreeBSD__
#		define DRILL_PATH "/usr/bin/drill"
#	else
#		define DIG_PATH "dig"
#	endif
#endif

#define FETCH_HEADERS \
	"Date From To Cc Subject Message-Id In-Reply-To References " \
	"Content-Transfer-Encoding"

static void mboxrd(char *headers, char *body) {
	printf("From mboxrd@z Thu Jan  1 00:00:00 1970\n");
	for (char *crlf; (crlf = strstr(headers, "\r\n")); headers = &crlf[2]) {
		*crlf = '\0';
		printf("%s\n", headers);
	}
	for (char *crlf; (crlf = strstr(body, "\r\n")); body = &crlf[2]) {
		*crlf = '\0';
		char *from = body;
		while (*from == '>') from++;
		if (!strncmp(from, "From ", 5)) {
			printf(">%s\n", body);
		} else {
			printf("%s\n", body);
		}
	}
	printf("\n");
}

static void lookup(const char **host, const char **port, const char *domain) {
	static char buf[1024];
	snprintf(buf, sizeof(buf), "_imaps._tcp.%s", domain);

	int rw[2];
	int error = pipe(rw);
	if (error) err(EX_OSERR, "pipe");

	pid_t pid = fork();
	if (pid < 0) err(EX_OSERR, "fork");

	if (!pid) {
		close(rw[0]);
		dup2(rw[1], STDOUT_FILENO);
		dup2(rw[1], STDERR_FILENO);
		close(rw[1]);
#ifdef DRILL_PATH
		execlp(DRILL_PATH, DRILL_PATH, buf, "SRV", NULL);
		err(EX_CONFIG, "%s", DRILL_PATH);
#else
		execlp(DIG_PATH, DIG_PATH, "-t", "SRV", "-q", buf, "+short", NULL);
		err(EX_CONFIG, "%s", DIG_PATH);
#endif
	}

	int status;
	pid = wait(&status);
	if (pid < 0) err(EX_OSERR, "wait");

	close(rw[1]);
	FILE *pipe = fdopen(rw[0], "r");
	if (!pipe) err(EX_IOERR, "fdopen");

	fgets(buf, sizeof(buf), pipe);
	if (ferror(pipe)) err(EX_IOERR, "fgets");

	if (!WIFEXITED(status) || WEXITSTATUS(status)) {
		fprintf(stderr, "%s", buf);
		exit(WEXITSTATUS(status));
	}

	char *ptr = buf;
#ifdef DRILL_PATH
	for (;;) {
		char *line = fgets(buf, sizeof(buf), pipe);
		if (!line || !strcmp(line, ";; ANSWER SECTION:\n")) break;
	}
	fgets(buf, sizeof(buf), pipe);
	if (ferror(pipe)) err(EX_IOERR, "fgets");
	ptr = strrchr(buf, '\t');
	ptr = (ptr ? ptr + 1 : buf);
#endif
	fclose(pipe);

	char *dot = strrchr(ptr, '.');
	if (dot) *dot = '\0';
	strsep(&ptr, " \n"); // priority
	strsep(&ptr, " \n"); // weight
	*port = strsep(&ptr, " \n");
	*host = strsep(&ptr, " \n");
	if (!*host) {
		*host = domain;
		*port = "imaps";
	}
}

int main(int argc, char *argv[]) {
	const char *host = NULL;
	const char *port = "imaps";
	const char *mailbox = "INBOX";
	const char *subject = "[PATCH";
	const char *from = NULL;
	const char *to = NULL;
	const char *cc = NULL;
	int rppFlags = 0;

	int opt;
	while (0 < (opt = getopt(argc, argv, "C:F:S:T:h:m:p:vw"))) {
		switch (opt) {
			break; case 'C': cc = optarg;
			break; case 'F': from = optarg;
			break; case 'S': subject = optarg;
			break; case 'T': to = optarg;
			break; case 'h': host = optarg;
			break; case 'm': mailbox = optarg;
			break; case 'p': port = optarg;
			break; case 'v': imapVerbose = true;
			break; case 'w': rppFlags |= RPP_STDIN;
			break; default:  return EX_USAGE;
		}
	}

	const char *user = argv[optind];
	if (!user) errx(EX_USAGE, "username required");

	if (!host) {
		const char *domain = strchr(user, '@');
		if (!domain) errx(EX_USAGE, "no domain in username");
		lookup(&host, &port, &domain[1]);
	}

	char buf[1024];
	char *pass = readpassphrase(
		(rppFlags & RPP_STDIN ? "" : "Password: "),
		buf, sizeof(buf), rppFlags
	);
	if (!pass) err(EX_UNAVAILABLE, "readpassphrase");

	enum Atom login = 0;
	enum Atom examine = atom("examine");
	enum Atom headerFields = atom("HEADER.FIELDS");
	enum Atom text = atom("TEXT");

	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.tag == examine) {
			fprintf(
				imap,
				"%s SEARCH CHARSET UTF-8 OR "
				"NOT HEADER Content-Type \"\" "
				"HEADER Content-Type \"text/plain\"",
				Atoms[AtomSearch]
			);
			if (subject) fprintf(imap, " SUBJECT \"%s\"", subject);
			if (from) fprintf(imap, " FROM \"%s\"", from);
			if (to) fprintf(imap, " TO \"%s\"", to);
			if (cc) fprintf(imap, " CC \"%s\"", cc);
			fprintf(imap, "\r\n");
		}

		if (resp.resp == AtomSearch) {
			if (!resp.data.len) errx(EX_TEMPFAIL, "no matching messages");
			fprintf(imap, "%s FETCH ", Atoms[AtomFetch]);
			for (size_t i = 0; i < resp.data.len; ++i) {
				struct Data data = resp.data.ptr[i];
				if (data.type != Number) {
					errx(EX_PROTOCOL, "invalid search result");
				}
				fprintf(imap, "%s%" PRIu32, (i ? "," : ""), data.number);
			}
			fprintf(
				imap,
				" (BODY[HEADER.FIELDS (" FETCH_HEADERS ")] BODY[TEXT])\r\n"
			);
		}

		if (resp.resp == AtomFetch) {
			if (!resp.data.len) {
				errx(EX_PROTOCOL, "no fetch data");
			}
			if (resp.data.ptr[0].type != List) {
				errx(EX_PROTOCOL, "invalid fetch data");
			}

			struct Data headers = {0};
			struct Data body = {0};
			struct List items = resp.data.ptr[0].list;
			for (size_t i = 0; i < items.len; ++i) {
				struct Data item = items.ptr[i];
				if (item.type != List) continue;
				if (!item.list.len) continue;
				if (item.list.ptr[0].type != Atom) continue;
				if (item.list.ptr[0].atom == headerFields) {
					if (i + 1 < items.len) headers = items.ptr[i + 1];
				}
				if (item.list.ptr[0].atom == text) {
					if (i + 1 < items.len) body = items.ptr[i + 1];
				}
			}

			if (headers.type != String) {
				errx(EX_PROTOCOL, "invalid header data");
			}
			if (body.type != String) {
				errx(EX_PROTOCOL, "invalid body data");
			}
			mboxrd(headers.string, body.string);
		}

		if (resp.tag == AtomFetch) {
			fprintf(imap, "ayy LOGOUT\r\n");
		}

		respFree(resp);
	}
	fclose(imap);
}