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#include "PhysicsObject.hh"

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#include "Engine.hh"

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#include <cmath>

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PhysicsObject::PhysicsObject (PhysicsWorld &world, float mass, Vector position, Vector velocity, ObjectType type, bool enabled) :

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    world(world), position(position), velocity(velocity), mass(mass), inAir(true), aim(0), facing(FACING_RIGHT), 

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    alive(false), shouldDelete(false), type(type), pivot(NULL)

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{  

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    if (enabled)

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        enable();  

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}

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PhysicsObject::~PhysicsObject (void) {

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//    Engine::log(DEBUG, "PhysicsObject.destructor") << this /* << ": objects.size=" << ((int) world.objects.size()) */;

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}

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/**

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 * Player walks on floor.

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 */

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Vector PhysicsObject::walk_one_step (float partial, bool right) {

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    // which way we are walking

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    float deltaX = right ? partial : -partial;

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    Vector reached = this->position;

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    if(reached.roundToInt() == (reached+Vector(deltaX, 0)).roundToInt()) {

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        return reached+Vector(deltaX, 0);

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    }

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    // Is there upward ramp

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    if(!possibleLocation(position+Vector(deltaX, 0))) {

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        // Yes. Then we check n pixels up

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        for(int i = 1; i < 3; i++) {

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            if(possibleLocation(position+Vector(deltaX, -i))) {

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                // and when there is finally EMPTY, we can walk

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                reached = position+Vector(deltaX, -i);

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                break;

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            }

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        }

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    } else {

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        // Or downward ramp or flat

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        for(int i = 0; 1; i++) {

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            // And when there is finally ground we can step on

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            // it. If there is no gound we still step there,

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            // but will fall one pixel down

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            if(possibleLocation(position+Vector(deltaX, i))) {

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                reached = position+Vector(deltaX, i);

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            } else {

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                break;

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            }

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            // If the fall is big enough, set the worm in the air

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            if (i >= 2) {

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//                Vector back = walk(dt, !right);

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                this->inAir = true;

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//                this->velocity.x = right ? velocity : -velocity;

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                // Avoid stepping two pixels down when it starts to free fall

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                reached.y -= 2;

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//                this->velocity = (reached-back)*1000/dt;

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                break;

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            }

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        }

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    }

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    // And we return where we got

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    return reached;

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}

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void PhysicsObject::walk (TimeMS dt, bool right) {

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    float velocity = PLAYER_WALK_SPEED;

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    float walkAmount = (velocity*dt)/1000;

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    Vector reached = this->position;

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    while (walkAmount > 0 && !this->inAir) {

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        this->position = walk_one_step((1 < walkAmount ? 1 : walkAmount), right);

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        walkAmount--;

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    }

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    // TODO: Should the remaining walkAmount be handled somehow?

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}

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/**

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 * Makes the player jump in the air.

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 * @param direction -1: jump left, 0: jump up, 1: jump right

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 */

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void PhysicsObject::jump (int direction) {

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    // Jump only if player is "on the ground"

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    if (!this->inAir) {

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 	    velocity.y = -100;

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        switch (direction) {

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            case 1:

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                velocity.x += 20;

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                break;

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            case -1:

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                velocity.x -= 20;

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                break;

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            case 0:

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                break;

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            default:

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                throw std::logic_error("Invalid jump direction");

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        }

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	    inAir = true;

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    }

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}

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bool PhysicsObject::possibleLocation (Vector loc) {

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    for(unsigned int i = 0; i < this->shape.size(); i++) {

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        if(world.collides(loc+shape[i]))

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            return false;

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    }

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    return true;

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}

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/**

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 * Updates object speed and position. This function organises force

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 * integration and collision detection.

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 */   

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void PhysicsObject::updatePosition (TimeMS dt) {

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    // Add gravity to the force queue

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    forceq.push(world.gravity);

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    // If the object (practically player) has a pivot point add

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    // a force towards that

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    if (pivot != NULL) {

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        Vector direction(pivot->getPosition()-position);

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        float magnitude = pivot->getPivotForce(this);

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        float length = direction.length();

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        if (length > 0) {

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            direction = direction / length * magnitude;

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            forceq.push(direction);

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        }

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    }

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    Force total;

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    while (!forceq.empty()) {

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        total += forceq.front();

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        forceq.pop();

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    }

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    // If the player has stopped and there's some ground under some of the 3 some of the 3t

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    // set inAir false

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    if (this->velocity == Vector(0,0)) {

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        this->inAir = !world.collides(this->position+shape[1]+Vector(0, 1))

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                      && !world.collides(this->position+shape[2]+Vector(0, 1))

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                      && !world.collides(this->position+shape[3]+Vector(0, 1));

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        // If, however, there's a force caused by a bomb, e.g., set it in air.

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        // Still, we have to be able to separate forces caused by walking attempts

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        // and bombs etc (+0.1 because float comparison can be dangerous)

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        if (total.y < 0.01 || abs(total.x) > PLAYER_MOVE_FORCE + 0.1)

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            this->inAir = true;

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    }

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    if(!possibleLocation(position)) {

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        //if we are trapped in ground form dirtball or something

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        //we might want to just return and set velocity to some value

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        //return;

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    }

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    // If the worm is not in the air make it walk,

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    // otherwise integrate the new position and velocity

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    if (!this->inAir) {

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        // It walks only if there's some vertical force

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        if (total.x != 0) {

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            walk(dt, total.x > 0);

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            this->velocity = Vector(0,0);

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        }   

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        // Now the possible walking has been done so we can return from this function.

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        // In walk inAir could have been set true, but that will be handled in the next tick.

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        return;

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    }

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    if (!possibleLocation(position))

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        Engine::log(DEBUG, "PhysicsObject.updatePosition") << "impossible location: " << position;

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    Vector newPosition;

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    Vector velAfterTick;

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    // Calculate new position and velocity to the given references

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    integrate(total, dt, newPosition, velAfterTick);

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    this->velocity = velAfterTick;

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    // Collision detection

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    bool collided = false;

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    Vector collisionPoint;

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    const Vector diffVec = newPosition-position;

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    const Vector unitVector = diffVec / diffVec.length();

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    Vector reached = position;

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    while ((position-reached).sqrLength() < diffVec.sqrLength()) {

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        reached += unitVector;

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        // Check if any of the shapes points collide

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        for (uint64_t i = 0; i < shape.size(); i++) {

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            if (world.collides(reached+shape[i])) {  // Collision

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                collisionPoint = reached+shape[i];

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                if (inAir) {

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                    this->bounce(world.getNormal(reached+shape[i], 

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                                                 reached-unitVector+shape[i]));

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                }

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                reached = reached - unitVector; // Return to last point

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                collided = true;

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                if (this->velocity.sqrLength() < PLAYER_MIN_SPEED * PLAYER_MIN_SPEED) {

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                    this->velocity = Vector(0,0);

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                }

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                break;

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            }

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        }

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        if (collided)

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            break;

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    }

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    if (!possibleLocation(reached))

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        Engine::log(DEBUG, "PhysicsObject.updatePosition") << "impossible location: " << position << ", diffVec=" << diffVec;

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    // In case of some float error check the final coordinate

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    if (!collided) {

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        if (!possibleLocation(newPosition)) {

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            newPosition = reached;

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        } else {

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            // This means everything was ok, so no need to do anything

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        }

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        this->position = newPosition;

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    } else {

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        newPosition = reached;

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        this->position = newPosition;

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        // the following may delete this object, so it must be the last thing called

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        return;

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    }

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}

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/**

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 * Bounces from straight wall in any direction.

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 * Direction given as normal of that wall

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 */

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void PhysicsObject::bounce (Vector normal) {

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    // normal.sqrLength can't be 0 when got from getNormal()

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    if (normal.sqrLength() != 0) {

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        Vector nvel = velocity;

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        // We project the velocity on normal and remove twice that much from velocity

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        nvel = nvel - ((2)*((nvel*normal)/(normal*normal))*normal);

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        velocity = nvel;

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        // We lose some of our speed on collision

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        this->velocity *= this->collision_elasticity;

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    }

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}

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/**

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 * Integrates given force over time and stores new position to

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 * posAfterTick and new velocity to velAfterTick.

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 * @param force Force vector.

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 * @param dt The time the force is applied (<=PHYSICS_TICK_MS)

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 */

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void PhysicsObject::integrate(Force force, TimeMS dt, Vector &posAfterTick, Vector &velAfterTick) {

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    posAfterTick = position;

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    velAfterTick = velocity;

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    Derivative tmpd;

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    Derivative k1 = evaluate(force, 0, tmpd, posAfterTick, velAfterTick);

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    Derivative k2 = evaluate(force, 0.5f*dt, k1, posAfterTick, velAfterTick);

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    Derivative k3 = evaluate(force, 0.5f*dt, k2, posAfterTick, velAfterTick);

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    Derivative k4 = evaluate(force, dt, k3, posAfterTick, velAfterTick);

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    const Vector dxdt = (k1.dx + (k2.dx + k3.dx) * 2.0f + k4.dx) * 1.0f/6.0f;

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    const Vector dvdt = (k1.dv + (k2.dv + k3.dv) * 2.0f + k4.dv) * 1.0f/6.0f;

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    //    Engine::log(DEBUG, "PhysicsObject.integrate") << "Changes: "<< dxdt << " " << dvdt << " Time: " <<dt;

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    posAfterTick = posAfterTick + (dxdt * dt)/1000;

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    velAfterTick = velAfterTick + (dvdt * dt)/1000;

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    //Engine::log(DEBUG, "PhysicsObject.integrate") << "velAfterTick: " << velAfterTick;

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}

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Derivative PhysicsObject::evaluate(Force force, TimeMS dt, Derivative &d, const Vector &posAfterTick, const Vector &velAfterTick) {

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    Vector curPos = posAfterTick + (d.dx*dt)/1000;

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    Vector curVel = velAfterTick + (d.dv*dt)/1000;

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    Derivative out;

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    out.dx = curVel;

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    out.dv = acceleration(force);

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    //Engine::log(DEBUG, "PhysicsObject.evaluate") << "Out.dx: " << out.dx;

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    return out;

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}

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Vector PhysicsObject::acceleration(const Force &force) {

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    return (force/mass);

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}

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void PhysicsObject::applyForce (Force force) {

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    // Add applied force to the queue

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    forceq.push(force);

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}

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void PhysicsObject::changeAim(float da) {

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    this->aim += da;

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    if (this->aim > PLAYER_AIM_MAX) this->aim = PLAYER_AIM_MAX;

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    if (this->aim < PLAYER_AIM_MIN) this->aim = PLAYER_AIM_MIN;

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    //Engine::log(DEBUG, "PhysicsObject.changeAim") << "Player aim: " << this->aim;

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}

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void PhysicsObject::setFacing (FacingDirection facing) {

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    this->facing = facing;

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}

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void PhysicsObject::updatePhysics (Vector position, Vector velocity, bool inAir, FacingDirection facing, float aim) {

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    this->position = position;

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    this->velocity = velocity;

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    this->inAir = inAir;

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    this->facing = facing;

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    this->aim = aim;

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}

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Vector PhysicsObject::getPosition (void) const {

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    return position;

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}

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PixelCoordinate PhysicsObject::getCoordinate (void) const {

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    return world.getPixelCoordinate(position);

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}

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Vector PhysicsObject::getVelocity (void) const {

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    return velocity;

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}

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FacingDirection PhysicsObject::getFacing (void) const {

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    return facing;

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}

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float PhysicsObject::getAim (void) const {

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    return aim;

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}

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Vector PhysicsObject::getDirection (void) const {

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    return facing == FACING_RIGHT ? Vector(cos(aim), -sin(aim)) : Vector(-cos(aim), -sin(aim));

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}

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const std::vector<Vector>& PhysicsObject::getShape () const {

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    return shape;

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}

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void PhysicsObject::setShape (std::vector<Vector> shape) {

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    this->shape = shape;

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}

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void PhysicsObject::setPivot (PhysicsObject *pivot) {

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    this->pivot = pivot;

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}

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void PhysicsObject::tick (TimeMS tick_length) {

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    this->updatePosition(tick_length);

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}

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void PhysicsObject::enable (void) {

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    // only enable once until disabled

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    if (alive)

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        return;

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    // mark as alive

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    alive = true;

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    // add the world objects list

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    world.addPhysicsObject(this);

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}

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void PhysicsObject::disable (void) {

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    // mark as disabled

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    alive = false;

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}

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void PhysicsObject::destroy (void) {

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    // mark as disabled and for deletion

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    alive = false;

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    shouldDelete = true;

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}

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bool PhysicsObject::isDestroyed (void) {

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    return !alive;

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}

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bool PhysicsObject::removeIfDestroyed (void) {

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    if (!alive) {

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        if (shouldDelete)

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            delete this;

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        return true;

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    } else {

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        return false;

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    }

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}

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float PhysicsObject::getPivotForce (PhysicsObject *bob) { 

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    return 0.0; 

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}

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bool PhysicsObject::collides (const PhysicsObject &obj) {

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    const std::vector<Vector> oShape = obj.getShape();

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    Vector p1, p2, p3;

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    int8_t sign, nsign;

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    for (std::vector<Vector>::const_iterator i = oShape.begin(); i != oShape.end(); i++) { // For every point in other shape

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        p3 = *i + obj.getPosition();

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        sign = 0;

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        for (std::vector<Vector>::const_iterator j = shape.begin(); j != shape.end(); j++) {

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            p1 = *j + position;

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            if ( (j+1) == shape.end() ) p2 = *shape.begin() + position;

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            else p2 = *(j+1) + position;

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            nsign = crossProduct(p1, p2, p3);

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            if ( sign == 0 ) sign = nsign;

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            else if ( ((sign < 0) && (nsign < 0)) || ((sign > 0) && (nsign > 0)) ) continue;

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            else return false;

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        }

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    }

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    return true;

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}

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int8_t crossProduct (const Vector &p1, const Vector &p2, const Vector &p3) {

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    float p = (p2.x - p1.x)*(p3.y - p1.y) - (p2.y - p1.y)*(p3.x - p1.x);

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    if (p < 0)

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        return -1;

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    else

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        return 1;

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}