import { vec2 } from 'gl-matrix';

import { appConfig } from '../config';
import { AGENT_FLOAT_COUNT } from '../pipelines/agents/agent-generation/agent';
import { AgentGenerationPipeline } from '../pipelines/agents/agent-generation/agent-generation-pipeline';
import { settings } from '../settings';
import { createIntroTitleAgents } from './intro-title-agents';

export const GLOBAL_AGENT_CAP = appConfig.simulation.globalAgentCap;

const INITIAL_AGENT_COUNT = appConfig.simulation.initialAgentCount;
const MIN_STROKE_AGENT_COUNT = appConfig.simulation.stroke.minAgentCount;
const MAX_STROKE_AGENT_COUNT = appConfig.simulation.stroke.maxAgentCount;
const STROKE_AGENT_DENSITY_MULTIPLIER = appConfig.simulation.stroke.densityMultiplier;
const ADAPTIVE_CAP_MAX = appConfig.simulation.budget.adaptiveCapMax;
const ADAPTIVE_CAP_MIN = appConfig.simulation.budget.adaptiveCapMin;
const ADAPTIVE_CAP_DECREASE_AGENTS_PER_SECOND =
  appConfig.simulation.budget.adaptiveCapDecreaseAgentsPerSecond;

export class AgentPopulation {
  private activeCount = 0;
  private replacementCursor = 0;
  private canExpandAdaptiveCap = true;
  private shouldCompactAfterErase = false;
  private isCompacting = false;
  private readonly strokeAgentData = new Float32Array(
    MAX_STROKE_AGENT_COUNT * AGENT_FLOAT_COUNT
  );

  public constructor(private readonly pipeline: AgentGenerationPipeline) {}

  public get activeAgentCount(): number {
    return this.activeCount;
  }

  public get maxAgentCount(): number {
    return this.pipeline.maxAgentCount;
  }

  public initializeIntroAgents(canvasSize: vec2): void {
    settings.agentBudgetMax = this.clampAdaptiveCap(settings.agentBudgetMax);
    const introAgentCount = Math.min(settings.agentBudgetMax, INITIAL_AGENT_COUNT);
    this.writeAgentBatch(
      createIntroTitleAgents({
        count: introAgentCount,
        width: canvasSize[0],
        height: canvasSize[1],
      })
    );
  }

  public onVibeChanged(): void {
    settings.agentBudgetMax = this.clampAdaptiveCap(settings.agentBudgetMax);
    this.trimActiveCountToBudget();
  }

  public growBudget(
    deltaTime: number,
    smoothedFps: number,
    refreshTargetFps: number
  ): void {
    this.updateAdaptiveCap(deltaTime, smoothedFps, refreshTargetFps);
  }

  public resizeAgents(scale: vec2): void {
    this.pipeline.resizeAgents(this.activeCount, scale);
  }

  public requestCompactionAfterErase(): void {
    this.shouldCompactAfterErase = true;
  }

  public async compactAfterErase(isSwipeActive: boolean): Promise<void> {
    if (!this.shouldCompactAfterErase || this.isCompacting || isSwipeActive) {
      return;
    }

    this.shouldCompactAfterErase = false;
    if (this.activeCount === 0) {
      return;
    }

    this.isCompacting = true;
    try {
      const compactedAgentCount = await this.pipeline.compactAgents(this.activeCount);
      this.activeCount = compactedAgentCount;
      this.replacementCursor =
        compactedAgentCount === 0 ? 0 : this.replacementCursor % compactedAgentCount;
    } finally {
      this.isCompacting = false;
    }
  }

  public spawnStrokeAgents(from: vec2, to: vec2): void {
    const length = Math.max(1, vec2.dist(from, to));
    const count = Math.max(
      MIN_STROKE_AGENT_COUNT,
      Math.min(
        MAX_STROKE_AGENT_COUNT,
        Math.ceil(length * settings.spawnPerPixel * STROKE_AGENT_DENSITY_MULTIPLIER)
      )
    );
    const direction = vec2.sub(vec2.create(), to, from);
    const baseAngle = Math.atan2(direction[1], direction[0]);

    for (let i = 0; i < count; i++) {
      const t = count === 1 ? 1 : i / (count - 1);
      const x = from[0] + (to[0] - from[0]) * t;
      const y = from[1] + (to[1] - from[1]) * t;
      const angle =
        (Number.isFinite(baseAngle) ? baseAngle : Math.random() * Math.PI * 2) +
        (Math.random() - 0.5) * appConfig.simulation.stroke.angleJitterRadians;
      const base = i * AGENT_FLOAT_COUNT;
      this.strokeAgentData[base] = x + (Math.random() - 0.5) * settings.brushSize;
      this.strokeAgentData[base + 1] = y + (Math.random() - 0.5) * settings.brushSize;
      this.strokeAgentData[base + 2] = angle;
      this.strokeAgentData[base + 3] = settings.selectedColorIndex;
      this.strokeAgentData[base + 4] = -1;
      this.strokeAgentData[base + 5] = -1;
      this.strokeAgentData[base + 6] = angle;
      this.strokeAgentData[base + 7] = 0;
    }

    this.writeAgentBatch(this.strokeAgentData.subarray(0, count * AGENT_FLOAT_COUNT));
  }

  private writeAgentBatch(data: Float32Array): void {
    if (data.length === 0) {
      return;
    }

    const count = data.length / AGENT_FLOAT_COUNT;
    settings.agentBudgetMax = this.clampAdaptiveCap(settings.agentBudgetMax);
    this.expandAdaptiveCapForPendingAgents(count);

    const available = Math.max(0, settings.agentBudgetMax - this.activeCount);
    const appendCount = Math.min(count, available);

    if (appendCount > 0) {
      this.pipeline.writeAgents(
        this.activeCount,
        data.subarray(0, appendCount * AGENT_FLOAT_COUNT)
      );
      this.activeCount += appendCount;
    }

    let sourceAgentOffset = appendCount;
    while (sourceAgentOffset < count && this.activeCount > 0) {
      const targetAgentOffset = this.replacementCursor % this.activeCount;
      const chunkAgentCount = Math.min(
        count - sourceAgentOffset,
        this.activeCount - targetAgentOffset
      );

      this.pipeline.writeAgents(
        targetAgentOffset,
        data.subarray(
          sourceAgentOffset * AGENT_FLOAT_COUNT,
          (sourceAgentOffset + chunkAgentCount) * AGENT_FLOAT_COUNT
        )
      );

      sourceAgentOffset += chunkAgentCount;
      this.replacementCursor = (targetAgentOffset + chunkAgentCount) % this.activeCount;
    }
  }

  private updateAdaptiveCap(
    deltaTime: number,
    smoothedFps: number,
    refreshTargetFps: number
  ): void {
    const previousCap = this.clampAdaptiveCap(settings.agentBudgetMax);
    this.canExpandAdaptiveCap =
      refreshTargetFps <= 0 ||
      smoothedFps >= refreshTargetFps * appConfig.simulation.budget.fpsHeadroom;

    if (this.canExpandAdaptiveCap) {
      settings.agentBudgetMax = previousCap;
      this.trimActiveCountToBudget();
      return;
    }

    const decrease = Math.max(
      1,
      Math.ceil(ADAPTIVE_CAP_DECREASE_AGENTS_PER_SECOND * deltaTime)
    );
    const nextCap = this.clampAdaptiveCap(previousCap - decrease);
    settings.agentBudgetMax = nextCap;
    this.trimActiveCountToBudget(decrease);
  }

  private expandAdaptiveCapForPendingAgents(requestedAgentCount: number): void {
    const available = Math.max(0, settings.agentBudgetMax - this.activeCount);
    if (requestedAgentCount <= available || !this.canExpandAdaptiveCap) {
      return;
    }

    const currentCap = this.clampAdaptiveCap(settings.agentBudgetMax);
    const pendingAgentCount = requestedAgentCount - available;
    settings.agentBudgetMax = this.clampAdaptiveCap(currentCap + pendingAgentCount);
  }

  private trimActiveCountToBudget(maxDecrease = Number.POSITIVE_INFINITY): void {
    if (this.activeCount <= settings.agentBudgetMax) {
      return;
    }

    this.activeCount = Math.max(
      settings.agentBudgetMax,
      this.activeCount - Math.max(1, Math.ceil(maxDecrease))
    );
    this.replacementCursor =
      this.activeCount === 0 ? 0 : this.replacementCursor % this.activeCount;
  }

  private clampAdaptiveCap(value: number): number {
    const pipelineCap = Math.max(0, Math.floor(this.pipeline.maxAgentCount));
    const maxCap = Math.min(ADAPTIVE_CAP_MAX, pipelineCap);
    const minCap = Math.min(ADAPTIVE_CAP_MIN, maxCap);
    const finiteValue = Number.isFinite(value) ? value : minCap;
    return Math.min(maxCap, Math.max(minCap, Math.round(finiteValue)));
  }
}