import {Part} from "./part";
import {RNG} from "@/utils/rng";

export type Region = {
  id: string;
  axes: RegionAxis[];
  childIds: string[];
  partMap: Record<string, string>;
}

export type RegionAxis = {
  name: string;
  min?: number;
  max?: number;
  align?: 'start' | 'end' | 'center';
}

export function createRegion(id: string, axes: RegionAxis[]): Region {
  return {
    id,
    axes,
    childIds: [],
    partMap: {},
  };
}

function buildPartMap<TMeta>(region: Region, parts: Record<string, Part<TMeta>>) {
  const map: Record<string, string> = {};
  for (const childId of region.childIds) {
    const part = parts[childId];
    if (part) {
      map[part.position.join(',')] = childId;
    }
  }
  return map;
}

export function applyAlign<TMeta>(region: Region, parts: Record<string, Part<TMeta>>) {
  if (region.childIds.length === 0) return;

  for (let axisIndex = 0; axisIndex < region.axes.length; axisIndex++) {
    const axis = region.axes[axisIndex];
    if (!axis.align) continue;

    const positionValues = new Set<number>();
    for (const childId of region.childIds) {
      const part = parts[childId];
      if (part) {
        positionValues.add(part.position[axisIndex] ?? 0);
      }
    }

    const sortedPositions = Array.from(positionValues).sort((a, b) => a - b);
    const positionMap = new Map<number, number>();

    if (axis.align === 'start' && axis.min !== undefined) {
      sortedPositions.forEach((pos, index) => {
        positionMap.set(pos, axis.min! + index);
      });
    } else if (axis.align === 'end' && axis.max !== undefined) {
      const count = sortedPositions.length;
      sortedPositions.forEach((pos, index) => {
        positionMap.set(pos, axis.max! - (count - 1 - index));
      });
    } else if (axis.align === 'center') {
      const count = sortedPositions.length;
      const min = axis.min ?? 0;
      const max = axis.max ?? count - 1;
      const range = max - min;
      const center = min + range / 2;

      sortedPositions.forEach((pos, index) => {
        const offset = index - (count - 1) / 2;
        positionMap.set(pos, center + offset);
      });
    }

    for (const childId of region.childIds) {
      const part = parts[childId];
      if (part) {
        const currentPos = part.position[axisIndex] ?? 0;
        part.position[axisIndex] = positionMap.get(currentPos) ?? currentPos;
      }
    }
  }

  region.childIds.sort((aId, bId) => {
    const a = parts[aId];
    const b = parts[bId];
    if (!a || !b) return 0;
    for (let i = 0; i < region.axes.length; i++) {
      const diff = (a.position[i] ?? 0) - (b.position[i] ?? 0);
      if (diff !== 0) return diff;
    }
    return 0;
  });

  region.partMap = buildPartMap(region, parts);
}

export function shuffle<TMeta>(region: Region, parts: Record<string, Part<TMeta>>, rng: RNG){
  if (region.childIds.length <= 1) return;

  const childIds = [...region.childIds];
  for (let i = childIds.length - 1; i > 0; i--) {
    const j = rng.nextInt(i + 1);
    const partI = parts[childIds[i]];
    const partJ = parts[childIds[j]];
    if (!partI || !partJ) continue;

    const posI = [...partI.position];
    const posJ = [...partJ.position];
    partI.position = posJ;
    partJ.position = posI;
  }

  region.partMap = buildPartMap(region, parts);
}

export function moveToRegion<TMeta>(part: Part<TMeta>, sourceRegion: Region | null, targetRegion: Region, position?: number[]) {
  if (sourceRegion && part.regionId === sourceRegion.id) {
    sourceRegion.childIds = sourceRegion.childIds.filter(id => id !== part.id);
    delete sourceRegion.partMap[part.position.join(',')];
  }

  targetRegion.childIds.push(part.id);
  if (position) {
    part.position = position;
  }
  targetRegion.partMap[part.position.join(',')] = part.id;

  part.regionId = targetRegion.id;
}

export function moveToRegionAll<TMeta>(parts: Record<string, Part<TMeta>>, sourceRegion: Region | null, targetRegion: Region, positions?: number[][]) {
  const partIds = Object.keys(parts);
  for (let i = 0; i < partIds.length; i++) {
    const part = parts[partIds[i]];
    if (sourceRegion && part.regionId === sourceRegion.id) {
      sourceRegion.childIds = sourceRegion.childIds.filter(id => id !== part.id);
      delete sourceRegion.partMap[part.position.join(',')];
    }

    targetRegion.childIds.push(part.id);
    if (positions && positions[i]) {
      part.position = positions[i];
    }
    targetRegion.partMap[part.position.join(',')] = part.id;

    part.regionId = targetRegion.id;
  }
}

export function removeFromRegion<TMeta>(part: Part<TMeta>, region: Region) {
  region.childIds = region.childIds.filter(id => id !== part.id);
  delete region.partMap[part.position.join(',')];
}