// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (C) 2019 Daniel Borkmann <daniel@iogearbox.net> */

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <wordexp.h>
#include <stdbool.h>

#include <sys/resource.h>

#include "l2md.h"

enum {
	STATE_NONE = 0,
	STATE_GENERAL,
	STATE_REPO,
	STATE_MAX,
};

static void config_dump(struct config *cfg)
{
	struct config_repo *repo;
	struct config_url *url;
	uint32_t i, j;

	if (!verbose_enabled)
		return;

	verbose("general.base = %s\n", cfg->general.base);
	verbose("general.mode = %s\n", cfg->ops->name);
	verbose("general.%s = %s\n", cfg->ops->name, cfg->general.out);
	verbose("general.period = %u\n", cfg->general.period);

	repo_for_each(cfg, repo, i) {
		verbose("repos.%s.%s = %s\n", repo->name, cfg->ops->name, repo->out);
		verbose("repos.%s.initial_import = %u\n", repo->name, repo->initial_import);
		url_for_each(repo, url, j) {
			verbose("repos.%s.url = %s\n", repo->name, url->path);
			verbose("repos.%s.oid = %s\n", repo->name,
				url->oid_known ? url->oid : "[unknown]");
		}
	}

	verbose("oneshot = %d\n", cfg->oneshot);
}

static void config_probe_oids(struct config *cfg)
{
	struct config_repo *repo;
	struct config_url *url;
	char path[PATH_MAX];
	uint32_t i, j;
	int ret;

	repo_for_each(cfg, repo, i) {
		url_for_each(repo, url, j) {
			repo_local_oid(cfg, repo, url, path, sizeof(path));
			ret = xread_file(path, url->oid, sizeof(url->oid) - 1,
					 false);
			if (!ret)
				url->oid_known = true;
		}
	}
}

static void config_set_basedir(struct config *cfg, const char *dir)
{
	wordexp_t p;

	wordexp(dir, &p, 0);
	dir = p.we_wordv[0];
	__strlcpy(cfg->general.base, dir, sizeof(cfg->general.base));
	wordfree(&p);
}

static void config_set_ops(struct config *cfg, const struct mail_ops* ops)
{
	cfg->ops = ops;
}

static void config_check_ops(struct config *cfg, const struct mail_ops* ops)
{
	if (cfg->ops != ops)
		panic("mode %s in [general] must match [repo *] mode %s\n",
		      cfg->ops->name, ops->name);
}

static void config_set_mode(struct config *cfg, const char *mode)
{
	if (!strncmp(mode, "maildir", sizeof("maildir")))
		config_set_ops(cfg, &ops_maildir);
	else if (!strncmp(mode, "pipe", sizeof("pipe")))
		config_set_ops(cfg, &ops_pipe);
	else
		panic("Unknown mode: %s!\n", mode);
}

static void config_set_out(struct config *cfg, const char *ctx, bool root)
{
	struct config_repo *repo = repo_last(cfg);
	char *out = root ? cfg->general.out : repo->out;
	wordexp_t p;

	wordexp(ctx, &p, 0);
	ctx = p.we_wordv[0];
	__strlcpy(out, ctx, sizeof(repo->out));
	wordfree(&p);
}

static void config_set_initial_import(struct config *cfg, uint32_t limit)
{
	struct config_repo *repo = repo_last(cfg);

	repo->initial_import = limit;
	if (repo->initial_import > 0)
		repo->limit = true;
}

static void config_set_repo_status(struct config *cfg, bool status)
{
	struct config_repo *repo = repo_last(cfg);

	repo->sync_enabled = status;
}

static void config_new_url(struct config *cfg, const char *git_url)
{
	struct config_repo *repo = repo_last(cfg);
	struct config_url *url;

	repo->urls_num++;
	repo->urls = xrealloc(repo->urls, sizeof(*repo->urls) *
			      repo->urls_num);
	url = url_last(repo);
	memset(url, 0, sizeof(*url));
	__strlcpy(url->path, git_url, sizeof(url->path));
}

static void config_new_repo(struct config *cfg, const char *name)
{
	struct config_repo *repo;

	cfg->repos_num++;
	cfg->repos = xrealloc(cfg->repos, sizeof(*cfg->repos) *
			      cfg->repos_num);
	repo = repo_last(cfg);
	memset(repo, 0, sizeof(*repo));
	config_set_out(cfg, cfg->general.out, false);
	config_set_repo_status(cfg, true);
	__strlcpy(repo->name, name, sizeof(repo->name));
}

static void config_set_defaults(struct config *cfg, const char *homedir)
{
	char default_data_dir[PATH_MAX];
	char *data_dir;

	cfg->general.period = 60;

	/* Default base is ~/.l2md/ if it exists, otherwise
	 * ~/${XDG_DATA_HOME}/l2md/. Fallback for empty XDG_DATA_DIR is
	 * ~/.local/share/.
	 */
	slprintf(default_data_dir, sizeof(default_data_dir), "%s/.l2md",
		 homedir);
	if (access(default_data_dir, F_OK) >= 0)
		data_dir = default_data_dir;
	else if (!(data_dir = getenv("XDG_DATA_HOME"))) {
		slprintf(default_data_dir, sizeof(default_data_dir),
			 "%s/.local/share/l2md", homedir);
		data_dir = default_data_dir;
	}

	verbose("Using base dir %s\n", default_data_dir);
	__strlcpy(cfg->general.base, data_dir, sizeof(cfg->general.base));

	config_set_ops(cfg, &ops_maildir);
	cfg->ops->set_defaults(cfg);
}

static void config_ulimits(void)
{
	struct rlimit limit;
	int ret;

	ret = getrlimit(RLIMIT_NOFILE, &limit);
	if (ret < 0)
		panic("Cannot retrieve rlimit!\n");

	/* The git repos we're dealing with can have a lot of
	 * pack files potentially, hence increase open file limit
	 * to help libgit2's revwalk.
	 *
	 * If there is a better API supported by native libgit2
	 * for doing repack, we should use that instead:
	 *
	 * https://github.com/libgit2/libgit2/issues/3247
	 */
	limit.rlim_cur = limit.rlim_max;

	ret = setrlimit(RLIMIT_NOFILE, &limit);
	if (ret < 0)
		panic("Cannot set rlimit!\n");
}

void config_uninit(struct config *cfg)
{
	struct config_repo *repo;
	uint32_t i;

	repo_for_each(cfg, repo, i)
		xfree(repo->urls);
	xfree(cfg->repos);
	xfree(cfg);
}

static FILE *config_open(const char *homedir)
{
	struct dirinfo {
		const char *env;
		const char *suffix;
		const char *fallback;
		bool prefix_home_to_fallback;
	};
	struct dirinfo dirinfo[] = {
		{ "XDG_CONFIG_HOME", "l2md/config", ".config", true, },
		{ "HOME", ".l2mdconfig", },
		{ },
	};
	struct dirinfo *cur;
	char path[PATH_MAX];
	FILE *fp;

	for (cur = dirinfo; cur->suffix; cur++) {
		char *env = getenv(cur->env);

		if (env)
			slprintf(path, sizeof(path), "%s/%s", env,
				 cur->suffix);
		else if (cur->fallback) {
			if (cur->prefix_home_to_fallback)
				slprintf(path, sizeof(path), "%s/%s/%s",
					 homedir, cur->fallback, cur->suffix);
			else
				slprintf(path, sizeof(path), "%s/%s",
					 cur->fallback, cur->suffix);
		}

		verbose("Attempting to open config file %s\n", path);
		fp = fopen(path, "r");
		if (fp)
			return fp;
		if (errno != ENOENT)
			panic("Cannot open config %s: %s\n", path, strerror(errno));
	}

	return panic("Unable to find config. Please check l2md README.\n"),
	       NULL;
}

struct config *config_init(int argc, char **argv)
{
	const char *homedir = getenv("HOME");
	char buff[1024], tmp[1024] = {};
	bool seen[STATE_MAX] = {};
	int state = STATE_NONE;
	struct config *cfg;
	FILE *fp;

	if (argc > 1) {
		if (argc == 2 && !strncmp(argv[1], "--verbose",
					  sizeof("--verbose")))
			verbose_enabled = true;
		else
			panic("Usage: %s [--verbose]\n", argv[0]);
	}

	if (!homedir)
		panic("Cannot retrieve $HOME from env!\n");

	fp = config_open(homedir);

	config_ulimits();

	cfg = xzmalloc(sizeof(*cfg));
	config_set_defaults(cfg, homedir);

	while (fgets(buff, sizeof(buff), fp)) {
		uint32_t val;

		if (buff[0] == '#' || buff[0] == '\n')
			continue;

		seen[state] = true;
		switch (state) {
		case STATE_NONE:
		state_next:
			if (!strcmp(buff, "[general]\n")) {
				state = STATE_GENERAL;
			} else if (sscanf(buff, "[repo %1023[a-z0-9-]]\n",
					  tmp) == 1) {
				state = STATE_REPO;
				config_new_repo(cfg, tmp);
			} else {
				panic("Cannot parse: '%s'\n", buff);
			}
			break;

		case STATE_GENERAL:
			if (seen[STATE_REPO]) {
				panic("[general] config must be before [repo *] config\n");
			} else if (sscanf(buff, "\tperiod = %u", &val) == 1) {
				cfg->general.period = val;
			} else if (sscanf(buff, "\tmode = %1023s", tmp) == 1) {
				config_set_mode(cfg, tmp);
			} else if (sscanf(buff, "\tmaildir = %1023s", tmp) == 1) {
				config_set_ops(cfg, &ops_maildir);
				config_set_out(cfg, tmp, true);
			} else if (sscanf(buff, "\tpipe = %1023s", tmp) == 1) {
				config_set_ops(cfg, &ops_pipe);
				config_set_out(cfg, tmp, true);
			} else if (sscanf(buff, "\tbase = %1023s", tmp) == 1) {
				config_set_basedir(cfg, tmp);
			} else if (sscanf(buff, "\toneshot = %u", &val) == 1) {
				cfg->oneshot = val;
			} else {
				goto state_next;
			}
			break;

		case STATE_REPO:
			if (sscanf(buff, "\turl = %1023s", tmp) == 1) {
				config_new_url(cfg, tmp);
			} else if (sscanf(buff, "\tmaildir = %1023s", tmp) == 1) {
				config_check_ops(cfg, &ops_maildir);
				config_set_out(cfg, tmp, false);
			} else if (sscanf(buff, "\tpipe = %1023s", tmp) == 1) {
				config_check_ops(cfg, &ops_pipe);
				config_set_out(cfg, tmp, false);
			} else if (sscanf(buff, "\tinitial_import = %u", &val) == 1) {
				config_set_initial_import(cfg, val);
			} else if (sscanf(buff, "\tsync_enabled = %u", &val) == 1) {
				config_set_repo_status(cfg, val);
			} else {
				goto state_next;
			}
			break;

		default:
			panic("Invalid parser state: %d\n", state);
		};
	}

	fclose(fp);

	config_probe_oids(cfg);
	config_dump(cfg);

	return cfg;
}