#pragma once
// Only compiled when KPN_WEB_DEBUG is defined. network.hpp includes this conditionally.

#include "diagnostics.hpp"
#include <httplib.h>

#include <atomic>
#include <sstream>
#include <string>
#include <thread>
#include <vector>

namespace kpn::web_debug {

// ── Minimal JSON serialiser ───────────────────────────────────────────────────

static std::string escape_json(const std::string& s) {
    std::string out;
    out.reserve(s.size());
    for (char c : s) {
        if      (c == '"')  out += "\\\"";
        else if (c == '\\') out += "\\\\";
        else if (c == '\n') out += "\\n";
        else if (c == '\r') out += "\\r";
        else if (c == '\t') out += "\\t";
        else                out += c;
    }
    return out;
}

// Parse "src_name:N → dst_name:M" into {src_name, dst_name}.
// Stored separately so the browser doesn't need to regex-parse a UTF-8 arrow.
static std::pair<std::string,std::string> parse_edge_name(const std::string& name) {
    // Format: "<src>:<idx> → <dst>:<idx>"
    auto arrow = name.find(" \xe2\x86\x92 "); // UTF-8 for →
    if (arrow == std::string::npos) return {name, name};
    std::string src_part = name.substr(0, arrow);
    std::string dst_part = name.substr(arrow + 5); // " → " = 5 bytes (space + 3-byte arrow + space)
    // Strip ":N" index suffix
    auto sc1 = src_part.rfind(':');
    auto sc2 = dst_part.rfind(':');
    if (sc1 != std::string::npos) src_part = src_part.substr(0, sc1);
    if (sc2 != std::string::npos) dst_part = dst_part.substr(0, sc2);
    return {src_part, dst_part};
}

static std::string to_json(const std::vector<NodeSnapshot>& nodes,
                            const std::vector<ChannelSnapshot>& channels,
                            const std::vector<ResourceSnapshot>& resources = {},
                            double elapsed_s = 0.0,
                            const std::vector<PoolSnapshot>& pools = {}) {
    std::ostringstream o;
    o << std::fixed;
    o.precision(2);

    o << "{\"nodes\":[";
    for (std::size_t i = 0; i < nodes.size(); ++i) {
        const auto& n = nodes[i];
        if (i) o << ',';
        o << "{\"id\":\"" << escape_json(n.name) << "\""
          << ",\"frames\":"       << n.frames_processed
          << ",\"ema_exec_ms\":"  << n.ema_exec_ms
          << ",\"max_exec_ms\":"  << n.max_exec_ms
          << ",\"blocked_ms\":"   << n.total_blocked_ms
          << ",\"fps\":"          << n.throughput_fps
          << ",\"total_cpu_ms\":" << n.total_cpu_ms
          << ",\"cpu_util_pct\":" << n.cpu_util_pct
          << "}";
    }
    o << "],\"edges\":[";
    for (std::size_t i = 0; i < channels.size(); ++i) {
        const auto& c = channels[i];
        if (i) o << ',';
        auto [src, dst] = parse_edge_name(c.name);
        o << "{\"name\":\"" << escape_json(c.name) << "\""
          << ",\"source\":\""    << escape_json(src) << "\""
          << ",\"target\":\""    << escape_json(dst) << "\""
          << ",\"capacity\":"    << c.capacity
          << ",\"current\":"     << c.current_fill
          << ",\"fill_pct\":"    << c.fill_pct()
          << ",\"peak_pct\":"    << c.peak_pct()
          << ",\"pushes\":"      << c.pushes
          << ",\"drops\":"       << c.drops
          << ",\"overflows\":"   << c.overflows
          << ",\"item_bytes\":"  << c.item_bytes
          << ",\"bw_mbs\":"      << c.bandwidth_mbs(elapsed_s)
          << "}";
    }
    o << "],\"resources\":[";
    for (std::size_t i = 0; i < resources.size(); ++i) {
        const auto& r = resources[i];
        if (i) o << ',';
        o << "{\"name\":\""          << escape_json(r.name) << "\""
          << ",\"acquisitions\":"    << r.acquisitions
          << ",\"avg_wait_ms\":"     << r.avg_wait_ms
          << ",\"peak_waiters\":"    << r.peak_waiters
          << ",\"current_waiters\":" << r.current_waiters
          << ",\"held\":"            << (r.held ? "true" : "false")
          << "}";
    }
    o << "],\"pools\":[";
    for (std::size_t i = 0; i < pools.size(); ++i) {
        const auto& p = pools[i];
        if (i) o << ',';
        double in_rate  = elapsed_s > 0.0 ? p.tasks_submitted / elapsed_s : 0.0;
        double out_rate = elapsed_s > 0.0 ? p.tasks_completed / elapsed_s : 0.0;
        o << "{\"name\":\""        << escape_json(p.name) << "\""
          << ",\"thread_count\":"  << p.thread_count
          << ",\"queue_depth\":"   << p.queue_depth
          << ",\"active_count\":"  << p.active_count
          << ",\"in_rate\":"       << in_rate
          << ",\"out_rate\":"      << out_rate
          << "}";
    }
    o << "]}";
    return o.str();
}

// ── Embedded single-page HTML ─────────────────────────────────────────────────

static const char* HTML = R"html(<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>KPN++ Web Debug</title>
<style>
  body { margin: 0; background: #1a1a2e; color: #eee; font-family: monospace; }
  #header { padding: 12px 20px; background: #16213e; border-bottom: 1px solid #0f3460; }
  #header h1 { margin: 0; font-size: 18px; color: #e94560; }
  #header span { font-size: 12px; color: #888; margin-left: 16px; }
  #graph { width: 100vw; height: calc(100vh - 50px); }
  .node circle { stroke: #fff; stroke-width: 1.5px; }
  .node text { font-size: 11px; fill: #eee; pointer-events: none; text-anchor: middle; }
  .node .stats { font-size: 9px; fill: #aaa; }
  .link { fill: none; stroke-width: 2px; }
  .link-label { font-size: 9px; fill: #ccc; }
  .arrowhead { fill: #888; }
  #tooltip {
    position: absolute; background: #0f3460; border: 1px solid #e94560;
    border-radius: 4px; padding: 8px 12px; font-size: 11px; pointer-events: none;
    display: none; white-space: pre; line-height: 1.6;
  }
  #resources {
    position: absolute; bottom: 12px; right: 12px;
    background: #16213e; border: 1px solid #0f3460; border-radius: 4px;
    padding: 8px 12px; font-size: 10px; min-width: 220px;
    display: none;
  }
  #resources h2 { margin: 0 0 6px; font-size: 11px; color: #e94560; }
  .res-row { display: flex; justify-content: space-between; gap: 12px; margin-top: 3px; }
  .res-name { color: #eee; }
  .res-held-y { color: #e94560; }
  .res-held-n { color: #4CAF50; }
</style>
</head>
<body>
<div id="header"><h1>KPN++ Web Debug</h1><span id="status">connecting...</span></div>
<svg id="graph"></svg>
<div id="tooltip"></div>
<div id="resources"><h2>Shared Resources</h2><div id="res-list"></div></div>
<script src="https://d3js.org/d3.v7.min.js"></script>
<script>
const nodeRadius = 30;

const svg = d3.select('#graph');
const width  = () => window.innerWidth;
const height = () => window.innerHeight - 50;

// Arrow marker defs
const defs = svg.append('defs');
['green','#f0c040','#e94560'].forEach((col, i) => {
  defs.append('marker')
    .attr('id', 'arrow' + i)
    .attr('viewBox', '0 -5 10 10').attr('refX', 10).attr('refY', 0)
    .attr('markerWidth', 6).attr('markerHeight', 6).attr('orient', 'auto')
    .append('path').attr('d', 'M0,-5L10,0L0,5').attr('fill', col);
});

const g = svg.append('g');
svg.call(d3.zoom().on('zoom', e => g.attr('transform', e.transform)));

let sim, linkSel, nodeSel, labelSel, edgeLabelSel, edgeLabelBwSel;
let nodes = [], links = [];

function edgeColor(fill_pct) {
  if (fill_pct >= 80) return '#e94560';
  if (fill_pct >= 50) return '#f0c040';
  return '#4CAF50';
}
function edgeArrow(fill_pct) {
  if (fill_pct >= 80) return 'url(#arrow2)';
  if (fill_pct >= 50) return 'url(#arrow1)';
  return 'url(#arrow0)';
}
function nodeColor(ema) {
  if (ema > 100) return '#e94560';
  if (ema > 50)  return '#e07040';
  if (ema > 10)  return '#f0c040';
  return '#4CAF50';
}

function init(data) {
  nodes = data.nodes.map(n => ({ ...n, x: width()/2, y: height()/2 }));
  const nodeById = Object.fromEntries(nodes.map(n => [n.id, n]));

  links = data.edges.map(e => ({
    ...e,
    source: nodeById[e.source],
    target: nodeById[e.target],
  })).filter(e => e.source && e.target);

  sim = d3.forceSimulation(nodes)
    .force('link',    d3.forceLink(links).distance(160).strength(0.5))
    .force('charge',  d3.forceManyBody().strength(-400))
    .force('center',  d3.forceCenter(width()/2, height()/2))
    .force('collide', d3.forceCollide(nodeRadius + 20))
    .on('tick', ticked);

  // Links
  linkSel = g.append('g').selectAll('line').data(links).join('line')
    .attr('class', 'link')
    .attr('stroke', d => edgeColor(d.fill_pct))
    .attr('marker-end', d => edgeArrow(d.fill_pct));

  edgeLabelSel = g.append('g').selectAll('text').data(links).join('text')
    .attr('class', 'link-label')
    .text(d => `${d.fill_pct.toFixed(0)}%`);

  edgeLabelBwSel = g.append('g').selectAll('text').data(links).join('text')
    .attr('class', 'link-label')
    .text(d => `${d.bw_mbs.toFixed(1)} MB/s`);

  // Nodes
  const nodeG = g.append('g').selectAll('g').data(nodes).join('g')
    .attr('class', 'node')
    .call(d3.drag()
      .on('start', (e,d) => { if (!e.active) sim.alphaTarget(0.3).restart(); d.fx=d.x; d.fy=d.y; })
      .on('drag',  (e,d) => { d.fx=e.x; d.fy=e.y; })
      .on('end',   (e,d) => { if (!e.active) sim.alphaTarget(0); d.fx=null; d.fy=null; }));

  nodeG.append('circle').attr('r', nodeRadius).attr('fill', d => nodeColor(d.ema_exec_ms));
  nodeG.append('text').attr('dy', 4).text(d => d.id);
  nodeG.append('text').attr('class', 'stats').attr('dy', 18)
    .text(d => `${d.ema_exec_ms.toFixed(1)}ms ${d.fps.toFixed(1)}fps`);

  nodeSel = nodeG;
  renderResources(data.resources);

  // Tooltips
  const tip = d3.select('#tooltip');
  nodeG.on('mousemove', (e, d) => {
    tip.style('display','block')
       .style('left', (e.pageX+12)+'px').style('top', (e.pageY+12)+'px')
       .text(
         `node: ${d.id}\nframes: ${d.frames}\nexec (ema): ${d.ema_exec_ms.toFixed(2)} ms` +
         `\nexec (max): ${d.max_exec_ms.toFixed(2)} ms\nblocked: ${d.blocked_ms.toFixed(2)} ms` +
         `\nfps: ${d.fps.toFixed(2)}\ncpu total: ${d.total_cpu_ms.toFixed(1)} ms` +
         `\ncpu util: ${d.cpu_util_pct.toFixed(1)}%`);
  }).on('mouseleave', () => tip.style('display','none'));

  g.selectAll('.link').on('mousemove', (e, d) => {
    tip.style('display','block')
       .style('left', (e.pageX+12)+'px').style('top', (e.pageY+12)+'px')
       .text(
         `channel: ${d.name}\nfill: ${d.fill_pct.toFixed(1)}%  peak: ${d.peak_pct.toFixed(1)}%` +
         `\ncapacity: ${d.capacity}  current: ${d.current}` +
         `\npushes: ${d.pushes}  drops: ${d.drops}  overflows: ${d.overflows}` +
         `\nbandwidth: ${d.bw_mbs.toFixed(2)} MB/s  item: ${d.item_bytes} B`);
  }).on('mouseleave', () => tip.style('display','none'));
}

function renderResources(resources) {
  const panel = document.getElementById('resources');
  const list  = document.getElementById('res-list');
  if (!resources || resources.length === 0) { panel.style.display = 'none'; return; }
  panel.style.display = 'block';
  list.innerHTML = resources.map(r => {
    const heldCls = r.held ? 'res-held-y' : 'res-held-n';
    const heldTxt = r.held ? 'HELD' : 'free';
    return `<div class="res-row">
      <span class="res-name">${r.name}</span>
      <span class="${heldCls}">${heldTxt}</span>
      <span>wait ${r.avg_wait_ms.toFixed(1)}ms</span>
      <span>waiters ${r.current_waiters}/${r.peak_waiters}</span>
    </div>`;
  }).join('');
}

function update(data) {
  renderResources(data.resources);
  // Update node stats in-place (preserve simulation x/y positions)
  const byId = Object.fromEntries(data.nodes.map(n => [n.id, n]));
  nodes.forEach(n => {
    const fresh = byId[n.id];
    if (fresh) {
      n.frames = fresh.frames; n.ema_exec_ms = fresh.ema_exec_ms;
      n.max_exec_ms = fresh.max_exec_ms; n.blocked_ms = fresh.blocked_ms;
      n.fps = fresh.fps; n.total_cpu_ms = fresh.total_cpu_ms;
      n.cpu_util_pct = fresh.cpu_util_pct;
    }
  });

  // Update edge stats in-place (source/target are already D3 node refs — don't overwrite)
  data.edges.forEach((e, i) => {
    if (!links[i]) return;
    links[i].fill_pct  = e.fill_pct;  links[i].peak_pct = e.peak_pct;
    links[i].pushes    = e.pushes;    links[i].drops     = e.drops;
    links[i].overflows = e.overflows; links[i].current   = e.current;
    links[i].bw_mbs    = e.bw_mbs;
  });

  // Re-color
  nodeSel.select('circle').attr('fill', d => nodeColor(d.ema_exec_ms));
  nodeSel.select('.stats').text(d => `${d.ema_exec_ms.toFixed(1)}ms ${d.fps.toFixed(1)}fps`);
  linkSel.attr('stroke', d => edgeColor(d.fill_pct))
         .attr('marker-end', d => edgeArrow(d.fill_pct));
  edgeLabelSel.text(d => `${d.fill_pct.toFixed(0)}%`);
  edgeLabelBwSel.text(d => `${d.bw_mbs.toFixed(1)} MB/s`);
}

function ticked() {
  // Clamp nodes to viewport
  nodes.forEach(d => {
    d.x = Math.max(nodeRadius, Math.min(width()  - nodeRadius, d.x));
    d.y = Math.max(nodeRadius, Math.min(height() - nodeRadius, d.y));
  });

  linkSel
    .attr('x1', d => d.source.x).attr('y1', d => d.source.y)
    .attr('x2', d => { // shorten to node edge
      const dx = d.target.x - d.source.x, dy = d.target.y - d.source.y;
      const dist = Math.sqrt(dx*dx+dy*dy) || 1;
      return d.target.x - (dx/dist)*(nodeRadius+8);
    })
    .attr('y2', d => {
      const dx = d.target.x - d.source.x, dy = d.target.y - d.source.y;
      const dist = Math.sqrt(dx*dx+dy*dy) || 1;
      return d.target.y - (dy/dist)*(nodeRadius+8);
    });

  edgeLabelSel
    .attr('x', d => (d.source.x + d.target.x)/2)
    .attr('y', d => (d.source.y + d.target.y)/2 - 6);

  edgeLabelBwSel
    .attr('x', d => (d.source.x + d.target.x)/2)
    .attr('y', d => (d.source.y + d.target.y)/2 + 8);

  nodeSel.attr('transform', d => `translate(${d.x},${d.y})`);
}

let initialised = false;

async function poll() {
  try {
    const r = await fetch('/api/snapshot');
    if (!r.ok) throw new Error(r.status);
    const data = await r.json();
    document.getElementById('status').textContent =
      `last update: ${new Date().toLocaleTimeString()}  •  ${data.nodes.length} nodes, ${data.edges.length} edges`;
    if (!initialised) { init(data); initialised = true; }
    else               { update(data); }
  } catch(e) {
    document.getElementById('status').textContent = `error: ${e}`;
  }
}

poll();
setInterval(poll, 500);
window.addEventListener('resize', () => sim && sim.force('center', d3.forceCenter(width()/2, height()/2)).alpha(0.1).restart());
</script>
</body>
</html>
)html";

// ── WebDebugServer ────────────────────────────────────────────────────────────

class WebDebugServer {
public:
    using SnapshotFn = std::function<std::string()>;

    explicit WebDebugServer(uint16_t port, SnapshotFn fn,
                            const char* custom_html = nullptr)
        : port_(port), snapshot_fn_(std::move(fn))
        , html_(custom_html ? custom_html : HTML) {}

    void start() {
        svr_.Get("/", [this](const httplib::Request&, httplib::Response& res) {
            res.set_content(html_, "text/html");
        });
        svr_.Get("/api/snapshot", [this](const httplib::Request&, httplib::Response& res) {
            res.set_content(snapshot_fn_(), "application/json");
        });
        thread_ = std::thread([this] {
            svr_.listen("0.0.0.0", static_cast<int>(port_));
        });
    }

    void stop() {
        svr_.stop();
        if (thread_.joinable()) thread_.join();
    }

    ~WebDebugServer() { stop(); }

    WebDebugServer(const WebDebugServer&) = delete;
    WebDebugServer& operator=(const WebDebugServer&) = delete;

private:
    uint16_t        port_;
    SnapshotFn      snapshot_fn_;
    const char*     html_;
    httplib::Server svr_;
    std::thread     thread_;
};

} // namespace kpn::web_debug