/* 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 Affero 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <err.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sysexits.h>
#include <unistd.h>

#include <kcgi.h>
#include <kcgihtml.h>
#include <sqlite3.h>

#define SQL(...) #__VA_ARGS__

enum { DatabaseVersion = 4 };

static sqlite3 *db;

static struct {
	sqlite3_stmt *networks;
	sqlite3_stmt *contexts;
	sqlite3_stmt *events;
	sqlite3_stmt *search;
} stmt;

static void dbClose(void) {
	if (stmt.networks) sqlite3_finalize(stmt.networks);
	if (stmt.contexts) sqlite3_finalize(stmt.contexts);
	if (stmt.events) sqlite3_finalize(stmt.events);
	if (stmt.search) sqlite3_finalize(stmt.search);
	sqlite3_close(db);
}

#define ENUM_PAGES \
	X(Networks, "networks") \
	X(Contexts, "contexts") \
	X(Events, "events") \
	X(Search, "search")

enum {
#define X(page, path) page,
	ENUM_PAGES
#undef X
	PagesLen,
};

static const char *Pages[PagesLen] = {
#define X(page, path) [page] = path,
	ENUM_PAGES
#undef X
};

#define ENUM_KEYS \
	X(Network, "network", kvalid_stringne) \
	X(Context, "context", kvalid_stringne) \
	X(After, "after", kvalid_stringne) \
	X(Query, "query", kvalid_stringne)

enum {
#define X(key, name, valid) key,
	ENUM_KEYS
#undef X
	KeysLen,
};

static const struct kvalid Keys[KeysLen] = {
#define X(key, name, valid) [key] = { valid, name },
	ENUM_KEYS
#undef X
};

static enum kcgi_err head(struct kreq *req, enum khttp http, enum kmime mime) {
	return khttp_head(req, kresps[KRESP_STATUS], "%s", khttps[http])
		|| khttp_head(req, kresps[KRESP_CONTENT_TYPE], "%s", kmimetypes[mime]);
}

static enum kcgi_err fail(struct kreq *req, enum khttp http) {
	return head(req, http, KMIME_TEXT_PLAIN)
		|| khttp_body(req)
		|| khttp_puts(req, khttps[http])
		|| khttp_putc(req, '\n');
}

static const char *stylesheet;

static enum kcgi_err htmlHead(struct khtmlreq *html, const char *title) {
	enum kcgi_err error = khtml_elem(html, KELEM_DOCTYPE)
		|| khtml_attr(html, KELEM_META, KATTR_CHARSET, "utf-8", KATTR__MAX)
		|| khtml_elem(html, KELEM_TITLE)
		|| khtml_puts(html, title)
		|| khtml_closeelem(html, 1);
	if (error) return error;
	if (stylesheet) {
		error = khtml_attr(
			html, KELEM_LINK,
			KATTR_REL, "stylesheet",
			KATTR_HREF, stylesheet,
			KATTR__MAX
		);
		if (error) return error;
	}
	return khtml_elem(html, KELEM_H1)
		|| khtml_puts(html, title)
		|| khtml_closeelem(html, 1);
}

static const char *NetworksQuery = SQL(
	SELECT DISTINCT network
	FROM contexts
	ORDER BY network;
);

static enum kcgi_err networks(struct kreq *req) {
	struct khtmlreq html;
	enum kcgi_err error = head(req, KHTTP_200, KMIME_TEXT_HTML)
		|| khttp_body(req)
		|| khtml_open(&html, req, KHTML_PRETTY)
		|| htmlHead(&html, "Networks")
		|| khtml_elem(&html, KELEM_UL);
	if (error) goto fail;

	int result;
	while (SQLITE_ROW == (result = sqlite3_step(stmt.networks))) {
		const char *network = sqlite3_column_text(stmt.networks, 0);
		char *href = khttp_urlpart(
			NULL, NULL, Pages[Contexts], Keys[Network].name, network, NULL
		);
		if (!href) err(EX_OSERR, "khttp_urlpart");

		error = khtml_elem(&html, KELEM_LI)
			|| khtml_attr(&html, KELEM_A, KATTR_HREF, href, KATTR__MAX)
			|| khtml_puts(&html, network)
			|| khtml_closeelem(&html, 2);
		free(href);
		if (error) goto fail;
	}
	if (result != SQLITE_DONE) errx(EX_SOFTWARE, "%s", sqlite3_errmsg(db));

	error = khtml_close(&html);

fail:
	sqlite3_reset(stmt.networks);
	return error;
}

static enum kcgi_err contexts(struct kreq *req) {
	return KCGI_OK;
}

static enum kcgi_err events(struct kreq *req) {
	return KCGI_OK;
}

static enum kcgi_err search(struct kreq *req) {
	return KCGI_OK;
}

static enum kcgi_err request(struct kreq *req) {
	if (req->method != KMETHOD_HEAD && req->method != KMETHOD_GET) {
		return fail(req, KHTTP_405);
	}
	switch (req->page) {
		case Networks: return networks(req);
		case Contexts: return contexts(req);
		case Events:   return events(req);
		case Search:   return search(req);
		default:       return fail(req, KHTTP_404);
	}
}

static void prepare(sqlite3_stmt **stmt, const char *query) {
	int error = sqlite3_prepare_v3(
		db, query, -1, SQLITE_PREPARE_PERSISTENT, stmt, NULL
	);
	if (error) errx(EX_SOFTWARE, "%s: %s", sqlite3_errmsg(db), query);
}

int main(int argc, char *argv[]) {
	bool fastCGI = false;
	bool public = false;

	for (int opt; 0 < (opt = getopt(argc, argv, "fps:"));) {
		switch (opt) {
			break; case 'f': fastCGI = true;
			break; case 'p': public = true;
			break; case 's': stylesheet = optarg;
			break; default:  return EX_USAGE;
		}
	}
	if (optind == argc) errx(EX_USAGE, "database path required");

	int error = sqlite3_open_v2(argv[optind], &db, SQLITE_OPEN_READONLY, NULL);
	if (error) errx(EX_NOINPUT, "%s: %s", argv[optind], sqlite3_errmsg(db));
	atexit(dbClose);

	sqlite3_stmt *check;
	error = sqlite3_prepare_v2(
		db, SQL(PRAGMA user_version;), -1, &check, NULL
	);
	if (error) errx(EX_SOFTWARE, "%s", sqlite3_errmsg(db));

	error = sqlite3_step(check);
	if (error != SQLITE_ROW) errx(EX_SOFTWARE, "%s", sqlite3_errmsg(db));

	int version = sqlite3_column_int(check, 0);
	if (version != DatabaseVersion) {
		errx(EX_DATAERR, "unsupported database version %d", version);
	}
	sqlite3_finalize(check);

	prepare(&stmt.networks, NetworksQuery);
	
	if (fastCGI) {
		struct kfcgi *fcgi;
		enum kcgi_err error = khttp_fcgi_init(
			&fcgi, Keys, KeysLen, Pages, PagesLen, Networks
		);
		if (error) errx(EX_CONFIG, "khttp_fcgi_init: %s", kcgi_strerror(error));
		for (
			struct kreq req;
			KCGI_OK == (error = khttp_fcgi_parse(fcgi, &req));
			khttp_free(&req)
		) {
			error = request(&req);
			if (error && error != KCGI_HUP) break;
		}
		errx(EX_PROTOCOL, "khttp_fcgi_parse: %s", kcgi_strerror(error));
	} else {
		struct kreq req;
		enum kcgi_err error = khttp_parse(
			&req, Keys, KeysLen, Pages, PagesLen, Networks
		);
		if (error) errx(EX_PROTOCOL, "khttp_parse: %s", kcgi_strerror(error));
		error = request(&req);
		if (error) errx(EX_PROTOCOL, "%s", kcgi_strerror(error));
		khttp_free(&req);
	}
}