eliasdb/examples/game/res/scripts/engine.ecal

import "./const.ecal" as const
import "./helper.ecal" as hlp

/*
 Constant rate for moving. The higher the less movement we do in a given time.
*/
moveRate := 30

/*
 Time the move loop was executed last (used for time correction)
*/
lastMoveCycleTime := 0

/*
 Game engine object which moves objects in a game world.
*/
GameEngine := {

    /*
     Partition to manage
     */
    "part" : null,

    /*
     Game world
     */
    "world" : null,

    /*
     Game state
     */
    gameState : null,

    /*
     Active websocket connections
     */
    websocket : null,

    /*
     Constructor
     */
    "init" : func (part, world, gameState, websocket) {
        this.part := part
        this.world := world
        this.gameState := gameState
        this.websocket := websocket
    },

    /*
     updateStat updates a statistic value.
     */
    "updateStat" : func (key, value) {
        mutex GameStateMutex {
            this.gameState[this.part][key] := value
        }

    },

    /*
     moveLoop handles object movement in the game world.
     */
    "moveLoop" : func () {
        let moveLoopTime := now()
        let timeDelta := moveLoopTime - lastMoveCycleTime # Do the move
        mutex GameStateMutex {
            if this.gameState == null or this.gameState[this.part] == null {
                return null
            }
        }


        /*
         Do a single move step with compensation for the time delta
         */
        time := now()

        this.move(timeDelta)

        this.updateStat("time_total_move", now() - time)

        lastMoveCycleTime := moveLoopTime
    },

    /*
     move calculates one move step
     */
    "move" : func (timeDelta) {

        /*
         Calculate a correction multiplier for the time lag
         */
        let timeCorrection := timeDelta / moveRate

        if math.isNaN(timeCorrection) or math.isInf(timeCorrection, 0) or timeCorrection > 10000 {
            timeCorrection := 1
        }

        mutex GameStateMutex {
            this.updateStat("time_move_correction", timeCorrection)

            entitiesToRemove := []

            /* First move things a step */
            for [playername, obj] in this.gameState[this.part].players {
                if not this.moveObject(timeCorrection, obj) {
                    entitiesToRemove := add(entitiesToRemove, obj)
                }
                this.executeAction(obj)
            }

            for obj in this.gameState[this.part].sprites {
                if not this.moveObject(timeCorrection, obj) {
                    entitiesToRemove := add(entitiesToRemove, obj)
                }
                this.executeAction(obj)
            }

            /* Detect collisions */
            for [playername, obj] in this.gameState[this.part].players {
                entitiesToRemove := concat(entitiesToRemove, this.collisionDetection(obj))
            }

            for obj in this.gameState[this.part].sprites {
                entitiesToRemove := concat(entitiesToRemove, this.collisionDetection(obj))
            }

            /* Remove things from the world */
            if len(entitiesToRemove) > 0 {

                let toRemoveSpriteIds := []
                let toRemovePlayerIds := []

                for e in entitiesToRemove {
                    if e.kind == const.ObjectKinds.Player {
                        log("Removing player: {{e.id}}")
                        toRemovePlayerIds := add(toRemovePlayerIds, e.id)
                        this.gameState[this.part].players := del(this.gameState[this.part].players, e.id)
                    } else {
                        toRemoveSpriteIds := add(toRemoveSpriteIds, e.id)
                    }
                }

                for [commID, data] in this.websocket {
                    if data.gamename == this.part {
                        addEventAndWait("StateUpdate", "db.web.sock.msg", {"commID" : commID, "payload" : {"toRemovePlayerIds" : toRemovePlayerIds}})
                    }
                }

                this.gameState[this.part].sprites := hlp.filter(this.gameState[this.part].sprites, func (i) {
                    return not i.id in toRemoveSpriteIds
                })

                for [commID, data] in this.websocket {
                    if data.gamename == this.part {
                        addEventAndWait("StateUpdate", "db.web.sock.msg", {"commID" : commID, "payload" : {"toRemoveSpriteIds" : toRemoveSpriteIds}})
                    }
                }
            }
        }

    },

    /*
     Move a specific object in the game world. Return false if the object
     should be removed from the world.
     */
    "moveObject" : func (timeCorrection, obj) {
        let keepObj := true

        /*
         Calculate new entity coordinates
         */
        let moveStep := timeCorrection * obj.speed * obj.moveSpeed
        let strafeStep := timeCorrection * obj.strafe * obj.moveSpeed * 0.02

        /*
         Forward / backward movement
         */
        let newX := obj.x + math.cos(obj.rot) * moveStep
        let newY := obj.y + math.sin(obj.rot) * moveStep

        /*
         Left / right strafe movement
         */
        newX := newX - math.sin(obj.rot) * strafeStep
        newY := newY + math.cos(obj.rot) * strafeStep

        /*
         Rotate the entity
         */
        obj.rot := obj.rot + timeCorrection * obj.dir * obj.rotSpeed

        obj.x := math.floor(newX)
        obj.y := math.floor(newY)

        /*
         Ensure the entity does not move outside the boundaries
         */
        if obj.displayLoop {
            hmin := 0 - obj.dim - 20
            hmax := this.world.screenWidth + obj.dim + 20

            if obj.x > hmax {
                obj.x := 0 - obj.dim - 10
            } elif obj.x < hmin {
                obj.x := this.world.screenWidth + obj.dim + 10
            }

            vmin := 0 - obj.dim - 20
            vmax := this.world.screenHeight + obj.dim + 20

            if obj.y > vmax {
                obj.y := 0 - obj.dim - 10
            } elif obj.y < vmin {
                obj.y := this.world.screenHeight + obj.dim + 10
            }
        } elif obj.x > this.world.screenWidth or obj.x < 0 or obj.y > this.world.screenHeight or obj.y < 0 {

            keepObj := false
        }

        mutex WebsocketMutex {
            for [commID, data] in this.websocket {
                if data.gamename == this.part {
                    res := addEventAndWait("StateUpdate", "db.web.sock.msg", {"commID" : commID, "payload" : {"state" : obj}})
                    if len(res) > 0 {
                        log("Removing unknown websocket", commID)
                        del(this.websocket, commID)
                    }
                }
            }
        }


        return keepObj
    },

    /*
     Detect collisions with other objects. Return false if the object
     should be removed from the world.
     */
    "collisionDetection" : func (entity) {
        let entitiesToRemove := []

        checkCollision := func (e1, e2) {
            let e1dh := e1.dim / 2
            let e2dh := e2.dim / 2

            return e1.x + e1dh > e2.x - e2dh and e1.x - e1dh < e2.x + e2dh and e1.y + e1dh > e2.y - e2dh and e1.y - e1dh < e2.y + e2dh
        }

        for [playername, obj] in this.gameState[this.part].players {
            if entity.id == obj.id {
                break
            }

            if checkCollision(entity, obj) {
                entitiesToRemove := concat(entitiesToRemove, entity.collision(entity, obj, this), obj.collision(obj, entity, this))
            }
        }

        for obj in this.gameState[this.part].sprites {
            if entity.id == obj.id {
                break
            }

            if checkCollision(entity, obj) {
                entitiesToRemove := concat(entitiesToRemove, entity.collision(entity, obj, this), obj.collision(obj, entity, this))
            }
        }

        return entitiesToRemove
    },

    /*
     Execute an action for a given object.
     */
    "executeAction" : func (entity) {

        if entity.action != null {
            entity.doAction(entity, entity.action, this)
            entity.action := null
        }
    }
}