/**
 * Renders the board graph as SVG, laid out entirely from board.spaces data —
 * no hand-placed coordinates. Column = longest-path distance from Start;
 * lane = branch offset that fans out at a 'choice' space and re-centers
 * (averages) at whichever space its branches rejoin. This means the layout
 * keeps working unmodified as shared/board.js grows.
 */

const SVG_NS = 'http://www.w3.org/2000/svg';

const COL_WIDTH = 108;
const ROW_HEIGHT = 168;
const LANE_HEIGHT = 64;
const MARGIN_X = 70;
const MARGIN_Y = 80;
const NODE_W = 88;
const NODE_H = 60;
const PLAYER_TOKEN_R = 12;

const TYPE_STYLE = {
  start: { icon: '🚩', shape: 'circle' },
  finish: { icon: '🏁', shape: 'circle' },
  choice: { icon: '🔀', shape: 'diamond' },
  money: { icon: '💰', shape: 'rect' },
  event: { icon: '✨', shape: 'rect' },
};

/** Pure layout computation — no DOM. Returns { positions, edges, width, height }. */
export function computeLayout(board, colsPerRow = 14) {
  const ids = Object.keys(board.spaces);
  const outEdges = new Map(ids.map((id) => [id, []]));
  const predecessors = new Map(ids.map((id) => [id, []]));

  for (const id of ids) {
    const space = board.spaces[id];
    const targets = space.type === 'choice' ? space.choices : (space.next ? [space.next] : []);
    for (const t of targets) {
      outEdges.get(id).push(t);
      predecessors.get(t).push(id);
    }
  }

  const col = new Map([[board.startSpaceId, 0]]);
  const laneSum = new Map([[board.startSpaceId, 0]]);
  const remaining = new Map(ids.map((id) => [id, predecessors.get(id).length]));
  const queue = [board.startSpaceId];

  while (queue.length) {
    const id = queue.shift();
    const space = board.spaces[id];
    const children = outEdges.get(id);

    children.forEach((childId, i) => {
      col.set(childId, Math.max(col.get(childId) ?? -Infinity, col.get(id) + 1));

      // Choice spaces fan their N branches out symmetrically around the
      // parent's lane (works for 2-way, 3-way, ... forks alike); anything
      // else just inherits the parent's lane unchanged. A join (>1
      // predecessor) accumulates every incoming contribution and averages
      // once all of its predecessors have been processed (guaranteed by the
      // time `remaining` hits 0, since that only happens after every
      // in-edge is visited).
      const offset = space.type === 'choice' ? i - (children.length - 1) / 2 : 0;
      const contribution = laneSum.get(id) + offset;
      laneSum.set(childId, (laneSum.get(childId) ?? 0) + contribution);

      remaining.set(childId, remaining.get(childId) - 1);
      if (remaining.get(childId) === 0) {
        const n = predecessors.get(childId).length || 1;
        laneSum.set(childId, laneSum.get(childId) / n);
        queue.push(childId);
      }
    });
  }

  const positions = new Map();
  for (const id of ids) {
    const c = col.get(id) ?? 0;
    const lane = laneSum.get(id) ?? 0;
    const row = Math.floor(c / colsPerRow);
    let colInRow = c % colsPerRow;
    if (row % 2 === 1) colInRow = colsPerRow - 1 - colInRow; // snake/boustrophedon
    positions.set(id, {
      x: MARGIN_X + colInRow * COL_WIDTH,
      y: MARGIN_Y + row * ROW_HEIGHT + lane * LANE_HEIGHT,
      col: c,
      row,
    });
  }

  const maxRow = Math.max(0, ...[...positions.values()].map((p) => p.row));
  return {
    positions,
    edges: outEdges,
    width: MARGIN_X * 2 + (colsPerRow - 1) * COL_WIDTH,
    height: MARGIN_Y * 2 + maxRow * ROW_HEIGHT + 3 * LANE_HEIGHT,
  };
}

function svgEl(tag, attrs = {}) {
  const el = document.createElementNS(SVG_NS, tag);
  for (const [k, v] of Object.entries(attrs)) el.setAttribute(k, v);
  return el;
}

function escapeHtml(str) {
  return String(str).replace(/[&<>"']/g, (c) => (
    { '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;' }[c]
  ));
}

export class BoardView {
  constructor(container, board) {
    this.board = board;
    this.layout = computeLayout(board);
    this.container = container;
    this.tokenEls = new Map(); // playerId -> <g>
    this._build();
  }

  _build() {
    const { width, height } = this.layout;
    const svg = svgEl('svg', {
      viewBox: `0 0 ${width} ${height}`,
      class: 'board-svg',
      role: 'img',
      'aria-label': 'Life Journey board',
    });
    svg.appendChild(this._buildBackdrop(width, height));
    svg.appendChild(this._buildEdges());
    svg.appendChild(this._buildNodes());
    this.tokenLayer = svgEl('g', { class: 'token-layer' });
    svg.appendChild(this.tokenLayer);

    this.svg = svg;
    this.container.innerHTML = '';
    this.container.appendChild(svg);
  }

  _buildBackdrop(width, height) {
    const g = svgEl('g', { class: 'backdrop' });
    let seed = 7; // deterministic — stable across re-renders, not flickering
    const rand = () => { seed = (seed * 9301 + 49297) % 233280; return seed / 233280; };
    const count = Math.max(6, Math.floor((width * height) / 11000));
    for (let i = 0; i < count; i++) {
      g.appendChild(svgEl('circle', {
        cx: rand() * width, cy: rand() * height, r: 16 + rand() * 26, class: 'tree-blob',
      }));
    }
    return g;
  }

  _buildEdges() {
    const g = svgEl('g', { class: 'edges' });
    for (const [id, children] of this.layout.edges) {
      const from = this.layout.positions.get(id);
      for (const childId of children) {
        const to = this.layout.positions.get(childId);
        const cx = from.x + (to.x - from.x) * 0.5;
        const d = `M ${from.x} ${from.y} C ${cx} ${from.y}, ${cx} ${to.y}, ${to.x} ${to.y}`;
        g.appendChild(svgEl('path', { d, class: 'edge-path' }));
      }
    }
    return g;
  }

  _buildNodes() {
    const g = svgEl('g', { class: 'nodes' });
    for (const id of Object.keys(this.board.spaces)) {
      g.appendChild(this._buildNode(this.board.spaces[id], this.layout.positions.get(id)));
    }
    return g;
  }

  _buildNode(space, pos) {
    const style = TYPE_STYLE[space.type] ?? TYPE_STYLE.event;
    const node = svgEl('g', {
      class: `space space-${space.type}`,
      transform: `translate(${pos.x}, ${pos.y})`,
      'data-space-id': space.id,
    });

    if (style.shape === 'circle') {
      node.appendChild(svgEl('circle', { r: NODE_H / 2, class: 'space-shape' }));
    } else if (style.shape === 'diamond') {
      const r = NODE_H / 2 + 6;
      node.appendChild(svgEl('rect', {
        x: -r, y: -r, width: r * 2, height: r * 2, rx: 8,
        transform: 'rotate(45)', class: 'space-shape',
      }));
    } else {
      node.appendChild(svgEl('rect', {
        x: -NODE_W / 2, y: -NODE_H / 2, width: NODE_W, height: NODE_H, rx: 14, class: 'space-shape',
      }));
    }

    const fo = svgEl('foreignObject', { x: -NODE_W / 2, y: -NODE_H / 2, width: NODE_W, height: NODE_H });
    const div = document.createElement('div');
    div.className = 'space-label';
    div.innerHTML = `<span class="space-icon">${style.icon}</span><span class="space-text">${escapeHtml(space.label)}</span>`;
    fo.appendChild(div);
    node.appendChild(fo);

    if (space.cash) {
      const badge = svgEl('text', {
        class: `cash-badge ${space.cash > 0 ? 'pos' : 'neg'}`, y: NODE_H / 2 + 17, 'text-anchor': 'middle',
      });
      badge.textContent = `${space.cash > 0 ? '+' : ''}${space.cash}`;
      node.appendChild(badge);
    }

    return node;
  }

  /** Move tokens to current positions, highlight+wire up any pending choice. */
  update(state, self, { onChoose } = {}) {
    this.svg.querySelectorAll('.space.highlight').forEach((el) => {
      el.classList.remove('highlight', 'clickable');
      el.onclick = null;
    });

    const grouped = new Map(); // spaceId -> player[]
    for (const p of Object.values(state.players)) {
      if (!grouped.has(p.position)) grouped.set(p.position, []);
      grouped.get(p.position).push(p);
    }

    const seen = new Set();
    for (const [position, occupants] of grouped) {
      const pos = this.layout.positions.get(position);
      if (!pos) continue;
      occupants.forEach((p, i) => {
        seen.add(p.id);
        const angle = (i / occupants.length) * Math.PI * 2;
        const spread = occupants.length > 1 ? 16 : 0;
        const tx = pos.x + Math.cos(angle) * spread;
        const ty = pos.y + NODE_H / 2 + 16 + Math.sin(angle) * (spread / 2);

        let el = this.tokenEls.get(p.id);
        if (!el) {
          el = this._buildToken(p);
          this.tokenLayer.appendChild(el);
          this.tokenEls.set(p.id, el);
        }
        el.setAttribute('transform', `translate(${tx}, ${ty})`);
        el.classList.toggle('current-turn', state.currentTurn === p.id);
      });
    }
    for (const [id, el] of this.tokenEls) {
      if (!seen.has(id)) { el.remove(); this.tokenEls.delete(id); }
    }

    const decidingPlayer = Object.values(state.players).find((p) => p.pendingChoice);
    if (decidingPlayer) {
      for (const optionId of decidingPlayer.pendingChoice.options) {
        const el = this.svg.querySelector(`.space[data-space-id="${cssEscape(optionId)}"]`);
        if (!el) continue;
        el.classList.add('highlight');
        if (decidingPlayer.id === self?.playerId) {
          el.classList.add('clickable');
          el.onclick = () => onChoose?.(optionId);
        }
      }
    }
  }

  _buildToken(player) {
    const g = svgEl('g', { class: 'token' });
    g.appendChild(svgEl('circle', { r: PLAYER_TOKEN_R, class: 'token-dot', fill: player.color }));
    const text = svgEl('text', { class: 'token-label', 'text-anchor': 'middle', dy: '0.35em' });
    text.textContent = (player.name || '?').trim().charAt(0).toUpperCase();
    g.appendChild(text);
    return g;
  }
}

function cssEscape(str) {
  return String(str).replace(/["\\]/g, '\\$&');
}