/* Copyright 2016 Software Freedom Conservancy Inc.
 *
 * This software is licensed under the GNU LGPL (version 2.1 or later).
 * See the COPYING file in this distribution.
 */

public errordomain DatabaseError {
    ERROR,
    BACKING,
    MEMORY,
    ABORT,
    LIMITS,
    TYPESPEC
}

public abstract class DatabaseTable {
    /*** 
     * This number should be incremented every time any database schema is altered.
     * 
     * NOTE: Adding or removing tables or removing columns do not need a new schema version, because
     * tables are created on demand and tables and columns are easily ignored when already present.
     * However, the change should be noted in upgrade_database() as a comment.
     ***/
    public const int SCHEMA_VERSION = 20;
    
    protected static Sqlite.Database db;
    
    private static int in_transaction = 0;
    
    public string table_name = null;

    private static void prepare_db(string filename) {
        // Open DB.
        int res = Sqlite.Database.open_v2(filename, out db, Sqlite.OPEN_READWRITE | Sqlite.OPEN_CREATE, 
            null);
        if (res != Sqlite.OK)
            AppWindow.panic(_("Unable to open/create photo database %s: error code %d").printf(filename,
                res));
        
        // Check if we have write access to database.
        if (filename != Db.IN_MEMORY_NAME) {
            try {
                File file_db = File.new_for_path(filename);
                FileInfo info = file_db.query_info(FileAttribute.ACCESS_CAN_WRITE, FileQueryInfoFlags.NONE);
                if (!info.get_attribute_boolean(FileAttribute.ACCESS_CAN_WRITE))
                    AppWindow.panic(_("Unable to write to photo database file:\n %s").printf(filename));
            } catch (Error e) {
                AppWindow.panic(_("Error accessing database file:\n %s\n\nError was: \n%s").printf(filename,
                    e.message));
            }
        }
    }

    public static void init(string filename) {
        // Open DB.
        prepare_db(filename);
        
        // Try a query to make sure DB is intact; if not, try to use the backup
        Sqlite.Statement stmt;
        int res = db.prepare_v2("CREATE TABLE IF NOT EXISTS VersionTable ("
            + "id INTEGER PRIMARY KEY, "
            + "schema_version INTEGER, "
            + "app_version TEXT, "
            + "user_data TEXT NULL"
            + ")", -1, out stmt);

        // Query on db failed, copy over backup and open it
        if(res != Sqlite.OK) {
            db = null;
            
            string backup_path = filename + ".bak";

            try {
                File src = File.new_for_commandline_arg(backup_path);
                File dest = File.new_for_commandline_arg(filename);
                src.copy(dest,
                         FileCopyFlags.OVERWRITE |
                         FileCopyFlags.ALL_METADATA);
                prepare_db(filename);
            } catch (Error error) {
                AppWindow.panic(_("Unable to restore photo database %s").printf(error.message));
            }
        }

        // disable synchronized commits for performance reasons ... this is not vital, hence we
        // don't error out if this fails
        res = db.exec("PRAGMA synchronous=OFF");
        if (res != Sqlite.OK)
            warning("Unable to disable synchronous mode", res);
    }
    
    public static void terminate() {
        // freeing the database closes it
        db = null;
    }
    
    // XXX: errmsg() is global, and so this will not be accurate in a threaded situation
    protected static void fatal(string op, int res) {
        error("%s: [%d] %s", op, res, db.errmsg());
    }
    
    // XXX: errmsg() is global, and so this will not be accurate in a threaded situation
    protected static void warning(string op, int res) {
        GLib.warning("%s: [%d] %s", op, res, db.errmsg());
    }
    
    protected void set_table_name(string table_name) {
        this.table_name = table_name;
    }
    
    // This method will throw an error on an SQLite return code unless it's OK, DONE, or ROW, which
    // are considered normal results.
    protected static void throw_error(string method, int res) throws DatabaseError {
        string msg = "(%s) [%d] - %s".printf(method, res, db.errmsg());
        
        switch (res) {
            case Sqlite.OK:
            case Sqlite.DONE:
            case Sqlite.ROW:
                return;
            
            case Sqlite.PERM:
            case Sqlite.BUSY:
            case Sqlite.READONLY:
            case Sqlite.IOERR:
            case Sqlite.CORRUPT:
            case Sqlite.CANTOPEN:
            case Sqlite.NOLFS:
            case Sqlite.AUTH:
            case Sqlite.FORMAT:
            case Sqlite.NOTADB:
                throw new DatabaseError.BACKING(msg);
            
            case Sqlite.NOMEM:
                throw new DatabaseError.MEMORY(msg);
            
            case Sqlite.ABORT:
            case Sqlite.LOCKED:
            case Sqlite.INTERRUPT:
                throw new DatabaseError.ABORT(msg);
            
            case Sqlite.FULL:
            case Sqlite.EMPTY:
            case Sqlite.TOOBIG:
            case Sqlite.CONSTRAINT:
            case Sqlite.RANGE:
                throw new DatabaseError.LIMITS(msg);
            
            case Sqlite.SCHEMA:
            case Sqlite.MISMATCH:
                throw new DatabaseError.TYPESPEC(msg);
            
            case Sqlite.ERROR:
            case Sqlite.INTERNAL:
            case Sqlite.MISUSE:
            default:
                throw new DatabaseError.ERROR(msg);
        }
    }
    
    protected bool exists_by_id(int64 id) {
        Sqlite.Statement stmt;
        int res = db.prepare_v2("SELECT id FROM %s WHERE id=?".printf(table_name), -1, out stmt);
        assert(res == Sqlite.OK);
        
        res = stmt.bind_int64(1, id);
        assert(res == Sqlite.OK);
        
        res = stmt.step();
        if (res != Sqlite.ROW && res != Sqlite.DONE)
            fatal("exists_by_id [%s] %s".printf(id.to_string(), table_name), res);
        
        return (res == Sqlite.ROW);
    }
    
    protected bool select_by_id(int64 id, string columns, out Sqlite.Statement stmt) {
        string sql = "SELECT %s FROM %s WHERE id=?".printf(columns, table_name);

        int res = db.prepare_v2(sql, -1, out stmt);
        assert(res == Sqlite.OK);
        
        res = stmt.bind_int64(1, id);
        assert(res == Sqlite.OK);
        
        res = stmt.step();
        if (res != Sqlite.ROW && res != Sqlite.DONE)
            fatal("select_by_id [%s] %s %s".printf(id.to_string(), table_name, columns), res);
        
        return (res == Sqlite.ROW);
    }
    
    // Caller needs to bind value #1 before calling execute_update_by_id()
    private void prepare_update_by_id(int64 id, string column, out Sqlite.Statement stmt) {
        string sql = "UPDATE %s SET %s=? WHERE id=?".printf(table_name, column);
        
        int res = db.prepare_v2(sql, -1, out stmt);
        assert(res == Sqlite.OK);
        
        res = stmt.bind_int64(2, id);
        assert(res == Sqlite.OK);
    }
    
    private bool execute_update_by_id(Sqlite.Statement stmt) {
        int res = stmt.step();
        if (res != Sqlite.DONE) {
            fatal("execute_update_by_id", res);
            
            return false;
        }
        
        return true;
    }
    
    protected bool update_text_by_id(int64 id, string column, string text) {
        Sqlite.Statement stmt;
        prepare_update_by_id(id, column, out stmt);
        
        int res = stmt.bind_text(1, text);
        assert(res == Sqlite.OK);
        
        return execute_update_by_id(stmt);
    }
    
    protected void update_text_by_id_2(int64 id, string column, string text) throws DatabaseError {
        Sqlite.Statement stmt;
        prepare_update_by_id(id, column, out stmt);
        
        int res = stmt.bind_text(1, text);
        assert(res == Sqlite.OK);
        
        res = stmt.step();
        if (res != Sqlite.DONE)
            throw_error("DatabaseTable.update_text_by_id_2 %s.%s".printf(table_name, column), res);
    }
    
    protected bool update_int_by_id(int64 id, string column, int value) {
        Sqlite.Statement stmt;
        prepare_update_by_id(id, column, out stmt);
        
        int res = stmt.bind_int(1, value);
        assert(res == Sqlite.OK);
        
        return execute_update_by_id(stmt);
    }

    protected void update_int_by_id_2(int64 id, string column, int value) throws DatabaseError {
        Sqlite.Statement stmt;
        prepare_update_by_id(id, column, out stmt);
        
        int res = stmt.bind_int(1, value);
        assert(res == Sqlite.OK);
        
        res = stmt.step();
        if (res != Sqlite.DONE)
            throw_error("DatabaseTable.update_int_by_id_2 %s.%s".printf(table_name, column), res);
    }

    protected bool update_int64_by_id(int64 id, string column, int64 value) {
        Sqlite.Statement stmt;
        prepare_update_by_id(id, column, out stmt);
        
        int res = stmt.bind_int64(1, value);
        assert(res == Sqlite.OK);
        
        return execute_update_by_id(stmt);
    }
    
    protected void update_int64_by_id_2(int64 id, string column, int64 value) throws DatabaseError {
        Sqlite.Statement stmt;
        prepare_update_by_id(id, column, out stmt);
        
        int res = stmt.bind_int64(1, value);
        assert(res == Sqlite.OK);
        
        res = stmt.step();
        if (res != Sqlite.DONE)
            throw_error("DatabaseTable.update_int64_by_id_2 %s.%s".printf(table_name, column), res);
    }
    
    protected void delete_by_id(int64 id) throws DatabaseError {
        Sqlite.Statement stmt;
        int res = db.prepare_v2("DELETE FROM %s WHERE id=?".printf(table_name), -1, out stmt);
        assert(res == Sqlite.OK);

        res = stmt.bind_int64(1, id);
        assert(res == Sqlite.OK);
        
        res = stmt.step();
        if (res != Sqlite.DONE)
            throw_error("%s.remove".printf(table_name), res);
    }
    
    public static bool has_column(string table_name, string column_name) {
        Sqlite.Statement stmt;
        int res = db.prepare_v2("PRAGMA table_info(%s)".printf(table_name), -1, out stmt);
        assert(res == Sqlite.OK);
        
        for (;;) {
            res = stmt.step();
            if (res == Sqlite.DONE) {
                break;
            } else if (res != Sqlite.ROW) {
                fatal("has_column %s".printf(table_name), res);
                
                break;
            } else {
                string column = stmt.column_text(1);
                if (column != null && column == column_name)
                    return true;
            }
        }
        
        return false;
    }
    
    public static bool has_table(string table_name) {
        Sqlite.Statement stmt;
        int res = db.prepare_v2("PRAGMA table_info(%s)".printf(table_name), -1, out stmt);
        assert(res == Sqlite.OK);
        
        res = stmt.step();

        return (res != Sqlite.DONE);
    }
    
    public static bool add_column(string table_name, string column_name, string column_constraints) {
        Sqlite.Statement stmt;
        int res = db.prepare_v2("ALTER TABLE %s ADD COLUMN %s %s".printf(table_name, column_name,
            column_constraints), -1, out stmt);
        assert(res == Sqlite.OK);
        
        res = stmt.step();
        if (res != Sqlite.DONE) {
            critical("Unable to add column %s %s %s: (%d) %s", table_name, column_name, column_constraints,
                res, db.errmsg());
            
            return false;
        }
        
        return true;
    }
    
    // This method will only add the column if a table exists (relying on the table object
    // to build a new one when first referenced) and only if the column does not exist.  In essence,
    // it's a cleaner way to run has_table(), has_column(), and add_column().
    public static bool ensure_column(string table_name, string column_name, string column_constraints,
        string upgrade_msg) {
        if (!has_table(table_name) || has_column(table_name, column_name))
            return true;
        
        message("%s", upgrade_msg);
        
        return add_column(table_name, column_name, column_constraints);
    }
    
    public int get_row_count() {
        Sqlite.Statement stmt;
        int res = db.prepare_v2("SELECT COUNT(id) AS RowCount FROM %s".printf(table_name), -1, out stmt);
        assert(res == Sqlite.OK);
        
        res = stmt.step();
        if (res != Sqlite.ROW) {
            critical("Unable to retrieve row count on %s: (%d) %s", table_name, res, db.errmsg());
            
            return 0;
        }
        
        return stmt.column_int(0);
    }
    
    // This is not thread-safe.
    public static void begin_transaction() {
        if (in_transaction++ != 0)
            return;
        
        int res = db.exec("BEGIN TRANSACTION");
        assert(res == Sqlite.OK);
    }
    
    // This is not thread-safe.
    public static void commit_transaction() throws DatabaseError {
        assert(in_transaction > 0);
        if (--in_transaction != 0)
            return;
        
        int res = db.exec("COMMIT TRANSACTION");
        if (res != Sqlite.DONE)
            throw_error("commit_transaction", res);
    }
}