/* Copyright (C) 2019  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 <errno.h>
#include <limits.h>
#include <sqlite3.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sysexits.h>

#define SQL(...) #__VA_ARGS__
#define ARRAY_LEN(a) (sizeof(a) / sizeof((a)[0]))

#define DATABASE_PATH "litterbox/litterbox.sqlite"

enum { DatabaseVersion = 2 };

#define ENUM_TYPE \
	X(Privmsg, "privmsg") \
	X(Notice, "notice") \
	X(Action, "action") \
	X(Join, "join") \
	X(Part, "part") \
	X(Quit, "quit") \
	X(Kick, "kick") \
	X(Nick, "nick") \
	X(Topic, "topic")

enum Type {
#define X(id, _) id,
	ENUM_TYPE
#undef X
};

static inline uint32_t hash(const char *user) {
	if (*user == '~') user++;
	uint32_t hash = 0;
	for (; *user; ++user) {
		hash = (hash << 5) | (hash >> 27);
		hash ^= *user;
		hash *= 0x27220A95;
	}
	return hash;
}

static bool verbose;
static sqlite3 *db;

static inline void dbExec(const char *sql) {
	int error = sqlite3_exec(db, sql, NULL, NULL, NULL);
	if (error) errx(EX_SOFTWARE, "%s: %s", sqlite3_errmsg(db), sql);
}

static inline void dbOpen(char *path, int flags) {
	char *base = strrchr(path, '/');
	if (flags & SQLITE_OPEN_CREATE && base) {
		*base = '\0';
		int error = mkdir(path, 0700);
		if (error && errno != EEXIST) err(EX_CANTCREAT, "%s", path);
		*base = '/';
	}

	int error = sqlite3_open_v2(path, &db, flags, NULL);
	if (error == SQLITE_CANTOPEN) {
		sqlite3_close(db);
		db = NULL;
		return;
	}
	if (error) errx(EX_NOINPUT, "%s: %s", path, sqlite3_errmsg(db));

	sqlite3_busy_timeout(db, 10000);
	dbExec(SQL(PRAGMA journal_mode = WAL;));
	dbExec(SQL(PRAGMA foreign_keys = true;));
}

static inline void dbFind(char *path, int flags) {
	if (path) {
		dbOpen(path, flags);
		if (db) return;
		errx(EX_NOINPUT, "%s: database not found", path);
	}

	const char *home = getenv("HOME");
	const char *dataHome = getenv("XDG_DATA_HOME");
	const char *dataDirs = getenv("XDG_DATA_DIRS");

	char buf[PATH_MAX];
	if (dataHome) {
		snprintf(buf, sizeof(buf), "%s/" DATABASE_PATH, dataHome);
	} else {
		if (!home) errx(EX_CONFIG, "HOME unset");
		snprintf(buf, sizeof(buf), "%s/.local/share/" DATABASE_PATH, home);
	}
	dbOpen(buf, flags);
	if (db) return;

	if (!dataDirs) dataDirs = "/usr/local/share:/usr/share";
	while (*dataDirs) {
		size_t len = strcspn(dataDirs, ":");
		snprintf(buf, sizeof(buf), "%.*s/" DATABASE_PATH, (int)len, dataDirs);
		dbOpen(buf, flags);
		if (db) return;
		dataDirs += len;
		if (*dataDirs) dataDirs++;
	}
	errx(EX_NOINPUT, "database not found");
}

static struct Persist {
	sqlite3_stmt *stmt;
	struct Persist *prev;
} *persistHead;

static inline void dbPersist(sqlite3_stmt **stmt, const char *sql) {
	if (*stmt) return;

	int error = sqlite3_prepare_v3(
		db, sql, -1, SQLITE_PREPARE_PERSISTENT, stmt, NULL
	);
	if (error) errx(EX_SOFTWARE, "%s: %s", sqlite3_errmsg(db), sql);

	struct Persist *persist = malloc(sizeof(*persist));
	persist->stmt = *stmt;
	persist->prev = persistHead;
	persistHead = persist;
}

static inline void dbClose(void) {
	for (struct Persist *persist = persistHead; persist;) {
		sqlite3_finalize(persist->stmt);
		struct Persist *prev = persist->prev;
		free(persist);
		persist = prev;
	}
	dbExec(SQL(PRAGMA optimize;));
	sqlite3_close(db);
}

static inline sqlite3_stmt *dbPrepare(const char *sql) {
	sqlite3_stmt *stmt;
	int error = sqlite3_prepare_v2(db, sql, -1, &stmt, NULL);
	if (error) err(EX_SOFTWARE, "%s: %s", sqlite3_errmsg(db), sql);
	return stmt;
}

static inline int dbParam(sqlite3_stmt *stmt, const char *param) {
	int index = sqlite3_bind_parameter_index(stmt, param);
	if (index) return index;
	errx(EX_SOFTWARE, "no such parameter %s: %s", param, sqlite3_sql(stmt));
}

static inline void dbBindNull(sqlite3_stmt *stmt, const char *param) {
	if (!sqlite3_bind_null(stmt, dbParam(stmt, param))) return;
	errx(EX_SOFTWARE, "sqlite3_bind_null: %s", sqlite3_errmsg(db));
}

static inline void
dbBindInt(sqlite3_stmt *stmt, const char *param, sqlite3_int64 value) {
	if (!sqlite3_bind_int64(stmt, dbParam(stmt, param), value)) return;
	errx(EX_SOFTWARE, "sqlite3_bind_int64: %s", sqlite3_errmsg(db));
}

static inline void dbBindText5(
	sqlite3_stmt *stmt, const char *param,
	const char *text, int len, bool copy
) {
	int error = sqlite3_bind_text(
		stmt, dbParam(stmt, param), text, len, (copy ? SQLITE_TRANSIENT : NULL)
	);
	if (error) err(EX_SOFTWARE, "sqlite3_bind_text: %s", sqlite3_errmsg(db));
}

static inline void
dbBindText(sqlite3_stmt *stmt, const char *param, const char *text) {
	dbBindText5(stmt, param, text, -1, false);
}

static inline void
dbBindTextLen(sqlite3_stmt *stmt, const char *param, const char *text, int len) {
	dbBindText5(stmt, param, text, len, false);
}

static inline void
dbBindTextCopy(sqlite3_stmt *stmt, const char *param, const char *text) {
	dbBindText5(stmt, param, text, -1, true);
}

static inline int dbStep(sqlite3_stmt *stmt) {
	int error = sqlite3_step(stmt);
	if (error == SQLITE_ROW || error == SQLITE_DONE) return error;
	errx(EX_SOFTWARE, "%s: %s", sqlite3_errmsg(db), sqlite3_expanded_sql(stmt));
}

static inline void dbRun(sqlite3_stmt *stmt) {
	dbStep(stmt);
	if (verbose && sqlite3_changes(sqlite3_db_handle(stmt))) {
		char *sql = sqlite3_expanded_sql(stmt);
		if (sql) fprintf(stderr, "%s\n", sql);
		sqlite3_free(sql);
	}
	sqlite3_reset(stmt);
}

static inline int dbVersion(void) {
	sqlite3_stmt *stmt = dbPrepare(SQL(PRAGMA user_version;));
	dbStep(stmt);
	int version = sqlite3_column_int(stmt, 0);
	sqlite3_finalize(stmt);
	return version;
}

static const char *InitSQL = SQL(
	BEGIN TRANSACTION;

	CREATE TABLE motds (
		time DATETIME NOT NULL,
		network TEXT NOT NULL,
		motd TEXT NOT NULL,
		UNIQUE (network, motd)
	);

	CREATE TABLE contexts (
		context INTEGER PRIMARY KEY,
		network TEXT NOT NULL,
		name TEXT NOT NULL,
		query BOOLEAN NOT NULL,
		UNIQUE (network, name)
	);

	CREATE TABLE topics (
		time DATETIME NOT NULL,
		context INTEGER NOT NULL REFERENCES contexts,
		topic TEXT NOT NULL,
		UNIQUE (context, topic)
	);

	CREATE TABLE names (
		name INTEGER PRIMARY KEY,
		nick TEXT NOT NULL,
		user TEXT NOT NULL,
		host TEXT NOT NULL,
		UNIQUE (nick, user, host)
	);

	CREATE TABLE events (
		event INTEGER PRIMARY KEY,
		time DATETIME NOT NULL,
		type INTEGER NOT NULL,
		context INTEGER NOT NULL REFERENCES contexts,
		name INTEGER NOT NULL REFERENCES names,
		target TEXT,
		message TEXT
	);

	CREATE VIEW text (
		event, network, channel, query, nick, user, target, message
	) AS
	SELECT
		event, network,
		CASE WHEN query THEN NULL ELSE contexts.name END,
		CASE WHEN query THEN contexts.name ELSE NULL END,
		nick, user, target, message
	FROM events
	JOIN contexts USING (context)
	JOIN names USING (name);

	CREATE VIRTUAL TABLE search USING fts5 (
		network, channel, query, nick, user, target, message,
		content = text,
		content_rowid = event,
		tokenize = 'porter',
		columnsize = 0
	);

	CREATE TRIGGER eventsInsert AFTER INSERT ON events BEGIN
		INSERT INTO search (
			rowid, network, channel, query, nick, user, target, message
		) SELECT * FROM text WHERE event = new.event;
	END;

	CREATE TRIGGER eventsDelete AFTER DELETE ON events BEGIN
		INSERT INTO search (
			search, rowid, network, channel, query, nick, user, target, message
		) SELECT 'delete', * FROM text WHERE event = old.event;
	END;

	CREATE TABLE consumers (
		host STRING NOT NULL,
		port INTEGER NOT NULL,
		pos INTEGER NOT NULL,
		UNIQUE (host, port)
	);

	PRAGMA user_version = 2;

	COMMIT TRANSACTION;
);

static inline void dbInit(void) {
	dbExec(InitSQL);
}

static const char *MigrationSQL[] = {
	// Added columnsize = 0 option.
	SQL(
		BEGIN TRANSACTION;
		DROP TABLE search;
		CREATE VIRTUAL TABLE search USING fts5 (
			network, channel, query, nick, user, target, message,
			content = text,
			content_rowid = event,
			tokenize = 'porter',
			columnsize = 0
		);
		INSERT INTO search (
			rowid, network, channel, query, nick, user, target, message
		) SELECT * FROM text;
		PRAGMA user_version = 1;
		COMMIT TRANSACTION;
	),

	SQL(
		BEGIN TRANSACTION;
		CREATE TABLE consumers (
			host STRING NOT NULL,
			port INTEGER NOT NULL,
			pos INTEGER NOT NULL,
			UNIQUE (host, port)
		);
		PRAGMA user_version = 2;
		COMMIT TRANSACTION;
	),
};

static inline void dbMigrate(void) {
	for (int version = dbVersion(); version < DatabaseVersion; ++version) {
		dbExec(MigrationSQL[version]);
	}
}

static inline void dbBackup(const char *path) {
	if (sqlite3_libversion_number() < 3027000) {
		errx(EX_CONFIG, "SQLite version 3.27.0 or newer required");
	}
	sqlite3_stmt *stmt = dbPrepare(SQL(VACUUM INTO :path;));
	dbBindText(stmt, ":path", path);
	dbRun(stmt);
	sqlite3_finalize(stmt);
}