package data.scripts.weapons;

import com.fs.starfarer.api.Global;
import com.fs.starfarer.api.combat.CombatEntityAPI;
import com.fs.starfarer.api.combat.DamageType;
import com.fs.starfarer.api.combat.GuidedMissileAI;
import com.fs.starfarer.api.combat.MissileAIPlugin;
import com.fs.starfarer.api.combat.MissileAPI;
import com.fs.starfarer.api.combat.ShipAPI;
import com.fs.starfarer.api.combat.ShipCommand;
import java.util.*;
import org.lazywizard.lazylib.CollectionUtils;
import org.lazywizard.lazylib.MathUtils;
import org.lazywizard.lazylib.VectorUtils;
import org.lazywizard.lazylib.combat.AIUtils;
import org.lazywizard.lazylib.combat.CombatUtils;
import org.lwjgl.util.vector.Vector2f;

//Based on LazyWizard's script
public class SeekerAI implements MissileAIPlugin, GuidedMissileAI {

    // Our missile object
    private final MissileAPI missile;
    // Our current target (can be null)
    private CombatEntityAPI target;

    private final static float VELOCITY_DAMPING_FACTOR = 0.2f; // Lower numbers means it will snap in place more abruptly; set it to some negative number if you want it to corkscrew drunkenly

    public static ShipAPI findBestTarget(MissileAPI missile) {
        ShipAPI source = missile.getSource();
        if (source != null && source.getShipTarget() != null
                && !source.getShipTarget().isHulk()) {
            return source.getShipTarget();
        }

        return AIUtils.getNearestEnemy(missile);
    }

    public SeekerAI(MissileAPI missile, ShipAPI launchingShip) {
        this.missile = missile;

        // Support for 'fire at target by clicking on them' behavior
        List directTargets = CombatUtils.getShipsWithinRange(
                launchingShip.getMouseTarget(), 100f);
        if (!directTargets.isEmpty()) {
            Collections.sort(directTargets, new CollectionUtils.SortEntitiesByDistance(launchingShip.getMouseTarget()));
            for (Iterator<ShipAPI> iter = directTargets.iterator(); iter.hasNext();) {
                ShipAPI tmp = iter.next();
                if (!tmp.isHulk() && tmp.getOwner() != launchingShip.getOwner()) {
                    setTarget(tmp);
                    break;
                }
            }
        }

        // Otherwise, use default Sidewinder targeting AI
        if (target == null) {
            setTarget(findBestTarget(missile));
        }
    }

    @Override
    public void advance(float amount) {
        // Apparently commands still work while fizzling
        if (missile.isFading() || missile.isFizzling()) {
            Global.getCombatEngine().applyDamage(missile, missile.getLocation(), missile.getHitpoints() * 2f, DamageType.FRAGMENTATION, 0f, false, false, missile);
            return;
        }

        // If our current target is lost, assign a new one
        if (target == null // unset
                || (target instanceof ShipAPI && ((ShipAPI) target).isHulk()) // dead
                || (missile.getOwner() == target.getOwner()) // friendly
                || !Global.getCombatEngine().isEntityInPlay(target)) // completely removed
        {
            setTarget(findBestTarget(missile));
            missile.giveCommand(ShipCommand.ACCELERATE);
            return;
        }

        // Head towards the target, with target leading
        Vector2f guidedTarget = intercept(missile.getLocation(), missile.getVelocity().length(), target.getLocation(), target.getVelocity());
        if (guidedTarget == null) {
            // If the target is unreachable, try to lead anyway
            Vector2f projection = new Vector2f(target.getVelocity());
            float scalar = MathUtils.getDistance(target.getLocation(), missile.getLocation()) / missile.getVelocity().length();
            projection.x *= scalar;
            projection.y *= scalar;
            guidedTarget = Vector2f.add(target.getLocation(), projection, null);
        }

        float angularDistance = MathUtils.getShortestRotation(missile.getFacing(), VectorUtils.getAngle(missile.getLocation(), guidedTarget));
        float absAngD = Math.abs(angularDistance);

        // Turn in the correct direction
        missile.giveCommand(angularDistance < 0 ? ShipCommand.TURN_RIGHT : ShipCommand.TURN_LEFT);

        // Always accelerate
        missile.giveCommand(ShipCommand.ACCELERATE);

        // Course correction
        if (absAngD < 5) {
            float MFlightAng = VectorUtils.getAngle(new Vector2f(0, 0), missile.getVelocity());
            float MFlightCC = MathUtils.getShortestRotation(missile.getFacing(), MFlightAng);
            if (Math.abs(MFlightCC) > 20) {
                missile.giveCommand(MFlightCC < 0 ? ShipCommand.STRAFE_LEFT : ShipCommand.STRAFE_RIGHT);
            }
        }

        //Damp angular velocity if we're getting close to the target angle
        if (Math.abs(angularDistance) < Math.abs(missile.getAngularVelocity()) * VELOCITY_DAMPING_FACTOR) {
            missile.setAngularVelocity(angularDistance / VELOCITY_DAMPING_FACTOR);
        }
    }

    // Will be in the next LazyLib, courtesy of DarkRevenant
    public static Vector2f intercept(Vector2f point, float speed, Vector2f target, Vector2f targetVel) {
        Vector2f difference = new Vector2f(target.x - point.x, target.y - point.y);

        float a = targetVel.x * targetVel.x + targetVel.y * targetVel.y - speed * speed;
        float b = 2 * (targetVel.x * difference.x + targetVel.y * difference.y);
        float c = difference.x * difference.x + difference.y * difference.y;

        Vector2f solutionSet = quad(a, b, c);

        Vector2f intercept = null;
        if (solutionSet != null) {
            float bestFit = Math.min(solutionSet.x, solutionSet.y);
            if (bestFit < 0) {
                bestFit = Math.max(solutionSet.x, solutionSet.y);
            }
            if (bestFit > 0) {
                intercept = new Vector2f(target.x + targetVel.x * bestFit, target.y + targetVel.y * bestFit);
            }
        }

        return intercept;
    }

    public static Vector2f quad(float a, float b, float c) {
        Vector2f solution = null;
        if (Float.compare(Math.abs(a), 0) == 0) {
            if (Float.compare(Math.abs(b), 0) == 0) {
                solution = (Float.compare(Math.abs(c), 0) == 0) ? new Vector2f(0, 0) : null;
            } else {
                solution = new Vector2f(-c / b, -c / b);
            }
        } else {
            float d = b * b - 4 * a * c;
            if (d >= 0) {
                d = (float) Math.sqrt(d);
                a = 2 * a;
                solution = new Vector2f((-b - d) / a, (-b + d) / a);
            }
        }
        return solution;
    }

    @Override
    public CombatEntityAPI getTarget() {
        return target;
    }

    @Override
    public void setTarget(CombatEntityAPI target) {
        this.target = target;
    }
}