import { Canvas } from "@/canvas";
import { clamp } from "@/common/functions";
import { Vec } from "@/common/vec";
import { desiredDensity, particleSize } from "@/game/fluids/fluids";
import { Swarm } from "@/game/swarm/swarm";
import { fillCircle, strokeLine } from "@/graphics";

const padding = 50;
const allowedSteer = 2 / 180;
const idlingUrgency = 0.001;
const idlingDistance = 20;
const desiredDistanceToEveryone = 30;
const flockPerceptionDistance = 150;
const behaveLikeFlockDoesUrgency = 0.8;
const epsilon = 1e-5;
export type NavigationType = 'stayInBounds' | 'doNotBumpIntoFlock' | 'keepFlockClose' | 'behaveLikeFlockDoes' | 'idling';
export type NavigatingDesire = {
    pos: Vec;
    urgency: number; // [0,1]
    type: NavigationType;
}
const navigationColorMap = {
    stayInBounds: 'red',
    doNotBumpIntoFlock: 'blue',
    keepFlockClose: 'green',
    behaveLikeFlockDoes: 'yellow',
    idling: 'purple'
};
export class Agent {
    dir: Vec;
    pos: Vec;
    swarm: Swarm;
    idlingGoal: Vec|null = null;
    lastNavigation: NavigatingDesire;
    constructor(pos: Vec, swarm: Swarm) {
        this.pos = pos;
        this.swarm = swarm;
        this.lastNavigation = {
            pos: pos,
            urgency: 0,
            type: 'idling'
        }
        this.dir = Vec.randomUnit();
    }

    update(canvas: Canvas, delta: DOMHighResTimeStamp) {
        const nextPos = this.pos.add(this.dir);
        const navigations = [];
        /**if (nextPos.y >= canvas.height - padding || nextPos.y < padding) {
            this.vel.y *= -1;
            nextPos.y = clamp(nextPos.y, padding, canvas.height - padding);
        }
        if (nextPos.x >= canvas.width - padding || nextPos.x < padding) {
            this.vel.x *= -1;
            nextPos.x = clamp(nextPos.x, padding, canvas.width - padding);
        }*/
        navigations.push(this.stayInBounds(nextPos));
        navigations.push(this.doNotBumpIntoFlock(nextPos));
        navigations.push(this.keepFlockClose(nextPos));
        navigations.push(this.behaveLikeFlockDoes(nextPos));
        navigations.push(this.idling(nextPos));
        const navigation = this.mostUrgentNavigation(navigations);
        this.steerTowards(navigation.pos);
        this.lastNavigation = navigation;
        this.pos = nextPos;
    }

    steerTowards(target: Vec) {
        const targetDir = target.sub(this.pos);
        // no division by zero!
        if (targetDir.length() < epsilon) {
            return;
        }
        const alpha = this.dir.clockwiseAngleBetween(targetDir.normalize());
        this.dir = this.dir.rotate(Math.min(allowedSteer, Math.abs(alpha)) * Math.sign(alpha)).normalize();
    }

    mostUrgentNavigation(navigations: NavigatingDesire[]) {
        return navigations
            .reduce((a, b) => a.urgency > b.urgency ? a : b);
    }

    stayInBounds(nextPos: Vec): NavigatingDesire {
        const {rect} = this.swarm;
        if (rect.contains(this.pos.add(this.dir.scale(padding)))) {
            return {
                pos: nextPos,
                urgency: 0,
                type: 'stayInBounds'
            };
        }
        return {
            pos: rect.center,
            urgency: 1,
            type: 'stayInBounds'
        };
    }

    doNotBumpIntoFlock(nextPos: Vec): NavigatingDesire {
        const {agents} = this.swarm;
        const visibleAgentsNotMe = agents
            .filter(a => a.pos.distance(this.pos) < flockPerceptionDistance && a !== this);
        const visibleAgentsInBounds = visibleAgentsNotMe
            .filter(a => this.swarm.rect.contains(a.pos));
        let closestAgent: Agent|null = null;
        for (const a of visibleAgentsInBounds) {
            if (!closestAgent || a.pos.distance(this.pos) < closestAgent.pos.distance(this.pos)) {
                closestAgent = a;
            }
        }
        if (!closestAgent) {
            return {
                pos: nextPos,
                urgency: 0,
                type: 'doNotBumpIntoFlock'
            };
        }
        const awayFromClosestAgentDir = this.pos.sub(closestAgent.pos).normalize();
        return {
            pos: this.pos.add(awayFromClosestAgentDir),
            urgency: (desiredDistanceToEveryone - closestAgent.pos.distance(this.pos)) / desiredDistanceToEveryone,
            type: 'doNotBumpIntoFlock'
        };
    }

    keepFlockClose(nextPos: Vec): NavigatingDesire {
        const {agents} = this.swarm;
        const visibleAgents = agents
            .filter(a => a.pos.distance(this.pos) < flockPerceptionDistance);
        const visibleAgentsInBounds = visibleAgents
            .filter(a => this.swarm.rect.contains(a.pos));
        const center = visibleAgentsInBounds
            .reduce((sum, a) => sum.add(a.pos), new Vec)
            .scale(1 / visibleAgentsInBounds.length);
        const distanceToCenter = this.pos.distance(center);
        return {
            pos: center,
            urgency: distanceToCenter / flockPerceptionDistance,
            type: 'keepFlockClose'
        };
    }

    behaveLikeFlockDoes(nextPos: Vec): NavigatingDesire {
        const {agents} = this.swarm;
        const visibleAgents = agents
            .filter(a => a.pos.distance(this.pos) < flockPerceptionDistance);
        const visibleAgentsInBounds = visibleAgents
            .filter(a => this.swarm.rect.contains(a.pos));
        const averageDir = visibleAgentsInBounds
            .reduce((sum, a) => sum.add(a.dir), new Vec)
            .scale(1 / visibleAgentsInBounds.length);
        const angleDiff = this.dir.clockwiseAngleBetween(averageDir);
        return {
            pos: nextPos.add(averageDir),
            urgency: behaveLikeFlockDoesUrgency * Math.abs(angleDiff) / Math.PI,
            type: 'behaveLikeFlockDoes'
        };
    }

    idling(nextPos: Vec): NavigatingDesire {
        if (this.idlingGoal && this.idlingGoal.distance(nextPos) > idlingDistance) {
            return {
                pos: this.idlingGoal,
                urgency: idlingUrgency,
                type: 'idling'
            };
        }
        this.idlingGoal = Vec.random(this.swarm.rect);
        return {
            pos: this.idlingGoal,
            urgency: idlingUrgency,
            type: 'idling'
        }
    }

    /**
     * @returns {Number} between 0 and 255
     */
    satisfaction(): number {
        return 255 - this.lastNavigation.urgency * 255;
    }

    /**render({ctx}: Canvas) {
        const satisfaction = this.satisfaction();
        const dissatisfaction = 255 - satisfaction;
        fillCircle(ctx, this.pos, particleSize, `rgb(${dissatisfaction}, 0, ${satisfaction})`);
        strokeLine(ctx, this.pos, this.pos.add(this.dir.scale(30)));
    }*/

    render({ctx}: Canvas) {
        const color = navigationColorMap[this.lastNavigation.type];
        fillCircle(ctx, this.pos, particleSize, color);
        strokeLine(ctx, this.pos, this.pos.add(this.dir.scale(30)));
    }
}