This code is a small code-snippet that will allow you to pass in a center position, and a size, as well as a room object to get back the nearest position where your search will fit, excluding any terrain. and structures. Useful for dynamic bases. It also has an iterator that can be adjusted to your liking, however it should be noted the more of …

Flood Fill - Buildable Area Search - Sizeable - Screeps

    private static validPos(x: number, y: number, size: number, room: Room): boolean {
        if (x < 0 || y < 0) return false
        if (x >= 50 || y >= 50) return false
        if (x - Math.floor(size / 2) < 0 || y - Math.floor(size / 2) < 0) return false
        if (x + Math.floor(size / 2) >= 50 || y + Math.floor(size / 2) >= 50) return false

        let results = room.lookAtArea(
            y - Math.floor(size / 2),
            x - Math.floor(size / 2),
            y + Math.floor(size / 2),
            x + Math.floor(size / 2),
            true
        ).filter( x => x.type != LOOK_CREEPS &&
            x.terrain != 'plain' &&
            x.terrain != 'swamp' &&
            x.type != LOOK_POWER_CREEPS &&
            x.type != LOOK_TOMBSTONES &&
            x.type != LOOK_RUINS &&
            x.type != LOOK_NUKES)

        if (results.length > 0) return false

        return true
    }

    /**
     *
     * @param x - x of Pos/RoomPosition
     * @param y - y of Pos/RoomPosition
     * @param size - EVEN numbers are treated as a radius
     * - (EX: 2 sets a search size of 5x5, 4 sets a search of 9x9).
     *
     * ODD numbers are treated as a diameter
     * - (Ex 5 is 5x5, 7 is 7x7).
     */
    static findPosForStamp(x: number, y: number, size: number, room: Room): RoomPosition | undefined {
        if (size % 2 == 0) {
            size = size * 2 + 1
        }

        let queue: number[][] = []
        queue.push([x, y])
        let iteration = 0
        while (queue.length > 0 && iteration < 100) {
            let currPos = queue[queue.length - 1]
            queue.pop()

            let posX = currPos[0]
            let posY = currPos[1]

            if (this.validPos(posX + 1, posY, size, room)) {
                return new RoomPosition(posX + 1, posY, room.name)
            } else {
                queue.push([posX + 1, posY])
            }

            if (this.validPos(posX - 1, posY, size, room)) {
                return new RoomPosition(posX - 1, posY, room.name)
            } else {
                queue.push([Math.floor(posX - 1), posY])
            }

            if (this.validPos(posX, posY + 1, size, room)) {
                return new RoomPosition(posX, posY + 1, room.name)
            } else {
                queue.push([posX, posY + 1])
            }

            if (this.validPos(posX, posY - 1, size, room)) {
                return new RoomPosition(posX, posY - 1, room.name)
            } else {
                queue.push([posX, posY - 1])
            }
            iteration++
        }
        return
    }