'use client';

import { useId } from 'react';
import {
  getLessonDiagrams,
  getModuleDiagrams,
  type DiagramEdge,
  type DiagramNode,
  type DiagramPoint,
  type TeachingDiagram,
} from './diagram-catalog';
import './teaching-diagrams.css';

export { hasLessonDiagrams } from './diagram-catalog';

const NODE_WIDTH = 210;
const NODE_HEIGHT = 104;

// Wide glyphs need more space than Latin glyphs. Never clip educational text.
function linesFor(text: string, maxUnits: number) {
  const lines: string[] = [];
  let line = '';
  let units = 0;
  for (const character of text) {
    const width = /[\u0020-\u007e]/.test(character) ? 1 : 2;
    if (units + width > maxUnits && line) {
      lines.push(line.trim());
      line = '';
      units = 0;
    }
    line += character;
    units += width;
  }
  if (line) lines.push(line.trim());
  return lines;
}

function port(
  node: DiagramNode,
  side: NonNullable<DiagramEdge['fromPort']>,
): DiagramPoint {
  if (side === 'left') return [node.x, node.y + NODE_HEIGHT / 2];
  if (side === 'right') return [node.x + NODE_WIDTH, node.y + NODE_HEIGHT / 2];
  if (side === 'top') return [node.x + NODE_WIDTH / 2, node.y];
  return [node.x + NODE_WIDTH / 2, node.y + NODE_HEIGHT];
}

function edgeGeometry(edge: DiagramEdge, nodes: DiagramNode[]) {
  const source = nodes.find((node) => node.id === edge.from)!;
  const target = nodes.find((node) => node.id === edge.to)!;
  const sameRow = source.y === target.y;
  const sameColumn = source.x === target.x;
  const right = target.x > source.x;
  const down = target.y > source.y;
  const fromSide =
    edge.fromPort ??
    (sameRow ? (right ? 'right' : 'left') : down ? 'bottom' : 'top');
  const toSide =
    edge.toPort ??
    (sameRow ? (right ? 'left' : 'right') : down ? 'top' : 'bottom');
  const start = port(source, fromSide);
  const end = port(target, toSide);
  const middleY = (start[1] + end[1]) / 2;
  const via =
    edge.via ??
    (sameRow || sameColumn
      ? []
      : ([
          [start[0], middleY],
          [end[0], middleY],
        ] as DiagramPoint[]));
  const points: DiagramPoint[] = [start, ...via, end];
  const path = points
    .map(([x, y], index) => `${index ? 'L' : 'M'} ${x} ${y}`)
    .join(' ');
  const labelAt =
    edge.labelAt ??
    (sameRow || sameColumn
      ? ([(start[0] + end[0]) / 2, (start[1] + end[1]) / 2] as DiagramPoint)
      : ([(start[0] + end[0]) / 2, middleY] as DiagramPoint));
  const vertical = sameColumn && !edge.via;
  return { path, labelAt, vertical };
}

function DiagramFigure({
  diagram,
  index,
}: {
  diagram: TeachingDiagram;
  index: number;
}) {
  const reactId = useId().replace(/:/g, '');
  const instanceId = `teaching-${diagram.id}-${reactId}`;
  const titleId = `${instanceId}-title`;
  const descriptionId = `${instanceId}-description`;
  const height = diagram.rows.length * 185 + 60;
  return (
    <figure
      className="teaching-figure"
      aria-labelledby={`${instanceId}-heading`}
    >
      <figcaption className="teaching-caption">
        <span className="teaching-number">
          图解 {String(index + 1).padStart(2, '0')}
        </span>
        <h3 id={`${instanceId}-heading`}>{diagram.title}</h3>
        <p>{diagram.summary}</p>
      </figcaption>
      <ol className="teaching-row-guide" aria-label="图中区域说明">
        {diagram.rows.map((label, row) => (
          <li key={label}>
            <span>区域 {row + 1}</span>
            {label}
          </li>
        ))}
      </ol>
      {/* oxlint-disable jsx-a11y/no-noninteractive-tabindex -- Keyboard users must be able to focus and scroll the full-size diagram. */}
      <section
        className="teaching-scroll"
        tabIndex={0}
        aria-label={`${diagram.title}，窄屏可横向滚动；下方有完整文字说明`}
      >
        {/* oxlint-disable jsx-a11y/prefer-tag-over-role -- Inline SVG needs image semantics and native title/desc labels. */}
        <svg
          className="teaching-svg"
          viewBox={`0 0 900 ${height}`}
          role="img"
          aria-labelledby={`${titleId} ${descriptionId}`}
        >
          {/* oxlint-enable jsx-a11y/no-noninteractive-tabindex, jsx-a11y/prefer-tag-over-role */}
          <title id={titleId}>{diagram.title}</title>
          <desc id={descriptionId}>
            {diagram.summary}{' '}
            {diagram.edges
              .map(
                (edge) =>
                  `${diagram.nodes.find((node) => node.id === edge.from)?.title}，${edge.label}，到${diagram.nodes.find((node) => node.id === edge.to)?.title}。`,
              )
              .join(' ')}{' '}
            完整步骤与边界说明见图下文字。
          </desc>
          <defs>
            {(['sync', 'async', 'risk'] as const).map((kind) => (
              <marker
                key={kind}
                id={`${instanceId}-${kind}`}
                viewBox="0 0 10 10"
                refX="9"
                refY="5"
                markerWidth="7"
                markerHeight="7"
                orient="auto-start-reverse"
              >
                <path
                  d="M 1 1 L 9 5 L 1 9 Z"
                  className={`teaching-arrow-${kind}`}
                />
              </marker>
            ))}
          </defs>
          {diagram.rows.map((label, row) => (
            <g key={label}>
              <rect
                x="12"
                y={row * 185 + 7}
                width="876"
                height="173"
                rx="10"
                className={
                  row % 2
                    ? 'teaching-lane teaching-lane-secondary'
                    : 'teaching-lane'
                }
              />
              <text x="30" y={row * 185 + 30} className="teaching-row-title">
                区域 {row + 1}
              </text>
            </g>
          ))}
          {diagram.edges.map((edge, edgeIndex) => {
            const geometry = edgeGeometry(edge, diagram.nodes);
            return (
              <path
                key={`path-${edgeIndex}`}
                d={geometry.path}
                className={`teaching-edge teaching-edge-${edge.kind}`}
                markerEnd={`url(#${instanceId}-${edge.kind})`}
              />
            );
          })}
          {diagram.nodes.map((node) => {
            const titleLines = linesFor(node.title, 24);
            const detailLines = linesFor(node.detail, 29);
            return (
              <g
                key={node.id}
                className={`teaching-node teaching-node-${node.tone}`}
              >
                <rect
                  x={node.x}
                  y={node.y}
                  width={NODE_WIDTH}
                  height={NODE_HEIGHT}
                  rx="9"
                />
                <rect
                  x={node.x}
                  y={node.y + 15}
                  width="3"
                  height={NODE_HEIGHT - 30}
                  rx="1.5"
                  className="teaching-node-accent"
                />
                <text
                  x={node.x + 16}
                  y={node.y + 26}
                  className="teaching-node-title"
                >
                  {titleLines.map((line, lineIndex) => (
                    <tspan
                      key={lineIndex}
                      x={node.x + 16}
                      dy={lineIndex ? 19 : 0}
                    >
                      {line}
                    </tspan>
                  ))}
                </text>
                <text
                  x={node.x + 16}
                  y={node.y + 26 + titleLines.length * 19 + 5}
                  className="teaching-node-detail"
                >
                  {detailLines.map((line, lineIndex) => (
                    <tspan
                      key={lineIndex}
                      x={node.x + 16}
                      dy={lineIndex ? 16 : 0}
                    >
                      {line}
                    </tspan>
                  ))}
                </text>
              </g>
            );
          })}
          {diagram.edges.map((edge, edgeIndex) => {
            const { labelAt, vertical } = edgeGeometry(edge, diagram.nodes);
            const labelLines = linesFor(edge.label, vertical ? 20 : 17);
            const x = labelAt[0] + (vertical ? 10 : 0);
            const y =
              labelAt[1] -
              (vertical
                ? (labelLines.length - 1) * 7
                : 10 + (labelLines.length - 1) * 14);
            return (
              <text
                key={`label-${edgeIndex}`}
                x={x}
                y={y}
                textAnchor={vertical ? 'start' : 'middle'}
                className={`teaching-edge-label teaching-edge-label-${edge.kind}`}
              >
                {labelLines.map((line, lineIndex) => (
                  <tspan key={lineIndex} x={x} dy={lineIndex ? 14 : 0}>
                    {line}
                  </tspan>
                ))}
              </text>
            );
          })}
        </svg>
      </section>
      <div className="teaching-legend" aria-label="图例">
        <span>
          <i className="teaching-legend-sync" aria-hidden="true" />
          调用 / 数据或状态流向
        </span>
        {diagram.edges.some((edge) => edge.kind === 'async') && (
          <span>
            <i className="teaching-legend-async" aria-hidden="true" />
            异步交接 / 后续处理
          </span>
        )}
        {diagram.edges.some((edge) => edge.kind === 'risk') && (
          <span>
            <i className="teaching-legend-risk" aria-hidden="true" />
            失败 / 恢复分支
          </span>
        )}
        <span>沿箭头与编号阅读，颜色仅辅助区分</span>
      </div>
      <div className="teaching-explanation">
        <h4>顺着图走一遍</h4>
        <ol>
          {diagram.steps.map((step, stepIndex) => (
            <li key={stepIndex}>{step}</li>
          ))}
        </ol>
        <p className="teaching-misconception">
          <strong>容易误解</strong>
          {diagram.misconception}
        </p>
        {diagram.source && (
          <a
            className="teaching-source"
            href={diagram.source.url}
            target="_blank"
            rel="noreferrer"
          >
            进一步核对：{diagram.source.label}
            <span aria-hidden="true"> ↗</span>
          </a>
        )}
      </div>
    </figure>
  );
}

export function ModuleDiagrams({ module }: { module: string }) {
  const diagrams = getModuleDiagrams(module);
  if (!diagrams.length) return null;
  return (
    <section
      id="module-diagrams"
      className="teaching-diagrams"
      aria-labelledby="module-diagrams-heading"
    >
      <div className="teaching-section-heading">
        <span>先建立画面</span>
        <h2 id="module-diagrams-heading">这个模块怎样与其他组件协作</h2>
      </div>
      <p className="teaching-section-intro">
        先认清谁接收请求、谁保存数据、谁负责执行，再进入每节课理解细节。相关课时中还有针对具体机制的图解。
      </p>
      {diagrams.map((diagram, index) => (
        <DiagramFigure key={diagram.id} diagram={diagram} index={index} />
      ))}
    </section>
  );
}

export function LessonDiagrams({
  module,
  lesson,
}: {
  module: string;
  lesson: string;
}) {
  const diagrams = getLessonDiagrams(module, lesson);
  if (!diagrams.length) return null;
  return (
    <section
      id="diagrams"
      className="teaching-diagrams"
      aria-labelledby="lesson-diagrams-heading"
    >
      <div className="teaching-section-heading">
        <span>做过之后，再看整体</span>
        <h2 id="lesson-diagrams-heading">
          {module === 'database' ? '回看数据设计与事务' : '把刚才的过程连起来'}
        </h2>
      </div>
      <p className="teaching-section-intro">
        {module === 'database'
          ? '结合表关系与事务流程，理解数据怎样组织、约束在哪里生效，以及修改何时提交。'
          : '箭头表示信息或控制如何传递；下方步骤说明等待、交接和失败时分别由谁负责。'}
      </p>
      {diagrams.map((diagram, index) => (
        <DiagramFigure key={diagram.id} diagram={diagram} index={index} />
      ))}
    </section>
  );
}