import type { Op, OpSet, ResolvedOptions } from '../core.js';
import type { Line, Point } from '../geometry.js';
import { lineLength } from '../geometry.js';
import type { PatternFiller, RenderHelper } from './filler-interface.js';
import { polygonHachureLines } from './scan-line-hachure.js';

export class DashedFiller implements PatternFiller {
  private helper: RenderHelper;

  constructor(helper: RenderHelper) {
    this.helper = helper;
  }

  fillPolygons(polygonList: Point[][], o: ResolvedOptions): OpSet {
    const lines = polygonHachureLines(polygonList, o);
    return { type: 'fillSketch', ops: this.dashedLine(lines, o) };
  }

  private dashedLine(lines: Line[], o: ResolvedOptions): Op[] {
    const offset =
      o.dashOffset < 0
        ? o.hachureGap < 0
          ? o.strokeWidth * 4
          : o.hachureGap
        : o.dashOffset;
    const gap =
      o.dashGap < 0
        ? o.hachureGap < 0
          ? o.strokeWidth * 4
          : o.hachureGap
        : o.dashGap;
    const ops: Op[] = [];
    lines.forEach(line => {
      const length = lineLength(line);
      const count = Math.floor(length / (offset + gap));
      const startOffset = (length + gap - count * (offset + gap)) / 2;
      let p1 = line[0];
      let p2 = line[1];
      if (p1[0] > p2[0]) {
        p1 = line[1];
        p2 = line[0];
      }
      const alpha = Math.atan((p2[1] - p1[1]) / (p2[0] - p1[0]));
      for (let i = 0; i < count; i++) {
        const lstart = i * (offset + gap);
        const lend = lstart + offset;
        const start: Point = [
          p1[0] + lstart * Math.cos(alpha) + startOffset * Math.cos(alpha),
          p1[1] + lstart * Math.sin(alpha) + startOffset * Math.sin(alpha),
        ];
        const end: Point = [
          p1[0] + lend * Math.cos(alpha) + startOffset * Math.cos(alpha),
          p1[1] + lend * Math.sin(alpha) + startOffset * Math.sin(alpha),
        ];
        ops.push(
          ...this.helper.doubleLineOps(start[0], start[1], end[0], end[1], o)
        );
      }
    });
    return ops;
  }
}