// The browser half of improvise-cr3, talking to either of two peers: five
// string calls, no protocol knowledge. See context/code/clients.md.

import init, { Client } from "./pkg/improvise_wasm_client.js";
import {
  COL_PX,
  ROW_PX,
  createShell,
  extentOf,
  frameCostOf,
  gridPlan,
  indicator,
  socketUrl,
} from "./shell.js";

const params = new URLSearchParams(location.search);
// present => socket, absent => in-page worker. The value is a host:port, and
// the scheme is NOT the caller's to get wrong: see `socketUrl`.
const WS_PEER = params.get("ws");

const WS_URL = WS_PEER ? socketUrl(WS_PEER, location.protocol) : null;
const DOC = params.get("doc") ?? "demo.improv";
const SEED = params.get("seed") ?? "demo.improv";

const el = {
  grid: document.getElementById("grid"),
  categories: document.getElementById("categories"),
  formulas: document.getElementById("formulas"),
  views: document.getElementById("views"),
  tiles: document.getElementById("tiles"),
  mode: document.getElementById("mode"),
  hint: document.getElementById("hint"),
  help: document.getElementById("help"),
  status: document.getElementById("status"),
  viewName: document.getElementById("view-name"),
};

await init();
const client = new Client();

// A peer that never answers the handshake, and the two facts `#status` shows.
// Both are decided in shell.js; this is the wire to the element.
const HANDSHAKE_TIMEOUT_MS = 8000;
const shell = createShell({
  onStatus: (text) => {
    el.status.textContent = text;
  },
  timeoutMs: HANDSHAKE_TIMEOUT_MS,
});

// What the grid's own frame costs, in whole cells, as of the last repaint —
// measured off the painted model, never predicted. context/code/clients.md.
let frameCost = { rows: 1, cols: 1 };

function sendViewport() {
  const box = el.grid.getBoundingClientRect();
  const metrics = { rowPx: ROW_PX, colPx: COL_PX };
  const { rows, cols } = extentOf(box, frameCost, metrics);
  // `client.set_viewport`, NOT the associated `Client.viewport`: the same
  // frame, but it also RECORDS the window. Why that matters: clients.md.
  transport.send(client.set_viewport(rows, cols));
}

/** One frame, one fold, in arrival order. Never batch or reorder these. */
function onFrame(text) {
  shell.sawFrame();
  try {
    client.on_frame(text);
  } catch (err) {
    // `on_frame` returns a Result, which wasm-bindgen throws; thrown in a bare
    // listener it reached the console alone and the grid just stopped.
    shell.setShell("bad frame — the grid has stopped updating (see console)");
    console.error("improvise: frame rejected", text, err);
    return;
  }
  repaint();
}

// Transports.

/** The in-page worker: the standalone deployment, no server process. */
function workerTransport() {
  const query = new URLSearchParams({ doc: DOC, seed: SEED });
  // `type: "module"` is not optional: worker.js is an ES module (it `import`s
  // the worker bundle), and a classic worker would fail to parse it.
  const worker = new Worker(`./worker.js?${query}`, { type: "module" });
  worker.addEventListener("message", (event) => onFrame(event.data));
  worker.addEventListener("messageerror", () =>
    shell.fail("the worker sent a frame this page could not read"),
  );
  worker.addEventListener("error", (event) => {
    shell.fail(`worker failed to start: ${event.message ?? "see console"}`);
    console.error("improvise: worker error", event);
  });
  shell.setShell(`in-page worker · ${DOC}`);
  // Frames posted before the worker has finished `start()` are held by
  // worker.js in arrival order, so the handshake can go out immediately.
  return { send: (text) => worker.postMessage(text), ready: Promise.resolve() };
}

/** A websocket to `improvise-ws-server`: how a TUI-hosted document is shared. */
function socketTransport() {
  const socket = new WebSocket(WS_URL);
  const unreachable = `cannot reach ${WS_URL} — is improvise-ws-server running?`;
  // Did this socket ever open? The page must record it itself: nothing on the
  // close event can discriminate. See context/code/clients.md.
  let opened = false;
  const ready = new Promise((resolve) => {
    socket.addEventListener("open", () => {
      opened = true;
      shell.setShell(`connected · ${WS_URL}`);
      resolve();
    });
  });
  socket.addEventListener("message", (event) => onFrame(event.data));
  // Without this, a connection that never opens left #status blank and
  // "server not running" read exactly like "still connecting".
  socket.addEventListener("error", () => shell.fail(unreachable));
  // A socket that never opened did not "disconnect" (improvise-taxx). BOTH arms
  // route through `shell.fail`, which disarms the watchdog — clients.md.
  socket.addEventListener("close", () =>
    shell.fail(opened ? "disconnected" : unreachable),
  );
  shell.setShell(`connecting to ${WS_URL}…`);
  return {
    send: (text) => {
      if (socket.readyState === WebSocket.OPEN) socket.send(text);
    },
    ready,
  };
}

const transport = WS_URL ? socketTransport() : workerTransport();

// Painting.

let painted = -1;
let editing = null; // {row, col} while an input is open, so a repaint cannot steal it

function repaint() {
  if (editing) return;
  let model;
  try {
    model = JSON.parse(client.render_model());
  } catch (err) {
    shell.setShell("cannot render the current state (see console)");
    console.error("improvise: render failed", err);
    return;
  }
  if (model.revision === painted) return;
  painted = model.revision;

  el.mode.textContent = model.mode;
  // The mode's own hint, off `help::hint_line`. The page spells no keys
  // itself; see `RenderModel::hint`.
  el.hint.textContent = model.hint;
  paintHelp(model);
  shell.setModel(model.status);
  el.viewName.textContent = model.view_name;
  el.grid.replaceChildren(gridTable(model));
  // The flag is the client's answer, not the page's: `C` toggles it and the
  // TUI draws the panel on exactly the same condition (improvise-wsaw).
  el.categories.hidden = !model.category_panel_open;
  el.categories.replaceChildren(categoryList(model));
  paintTiles(model);
  paintPanel(el.views, model.views, viewRow);
  paintPanel(el.formulas, model.formulas, formulaRow);

  // What the frame costs, so the NEXT viewport announcement is honest.
  // Inline group ROWS are deliberately NOT counted — context/code/clients.md.
  const next = frameCostOf(model);
  const changed = next.rows !== frameCost.rows || next.cols !== frameCost.cols;
  frameCost = next;
  if (changed) sendViewport();
}

/** The help overlay. An empty `help` is what says it is closed -- the page
 *  asks no question about the mode, and writes none of the content: the rows,
 *  their keys and the page titles are `improvise_protocol::help`'s, the same
 *  ones the TUI draws (improvise-ktv1). */
function paintHelp(model) {
  el.help.hidden = model.help.length === 0;
  if (el.help.hidden) {
    el.help.replaceChildren();
    return;
  }

  const tabs = document.createElement("div");
  tabs.className = "help-tabs";
  model.help_titles.forEach((title, i) => {
    const tab = document.createElement("span");
    tab.textContent = title;
    tab.className = i === model.help_page ? "help-tab active" : "help-tab";
    tabs.append(tab);
  });

  const body = document.createElement("dl");
  body.className = "help-body";
  for (const row of model.help) {
    const keys = document.createElement("dt");
    keys.textContent = row.keys;
    keys.className = `help-${row.kind}`;
    body.append(keys);
    // A prose row has no description and spans both columns (its class says
    // so); emitting an empty `dd` beside it would leave a blank grid cell.
    if (row.description) {
      const desc = document.createElement("dd");
      desc.textContent = row.description;
      body.append(desc);
    }
  }

  el.help.replaceChildren(tabs, body);
}

/** The grid, painted from a plan in which every decision is already made
 *  (improvise-anr9, and `shell.js::gridPlan`). Nothing below decides anything:
 *  which labels repeat and are therefore blank, how many header levels there
 *  are, which columns share a group and whether it is collapsed all arrive
 *  answered, by the same `AxisFrame` the TUI widget reads. */
function gridTable(model) {
  const plan = gridPlan(model);
  const table = document.createElement("table");
  const head = table.createTHead();
  const corner = () => {
    const th = document.createElement("th");
    th.colSpan = plan.cornerSpan;
    return th;
  };

  // The column-group line, when there is one. An empty `groups` means this
  // grid has no column groups at all -- not that every group is blank.
  if (plan.groups.length > 0) {
    const groups = head.insertRow();
    groups.appendChild(corner());
    for (const group of plan.groups) {
      const th = document.createElement("th");
      th.colSpan = group.span;
      th.textContent = group.text;
      th.classList.add("group");
      groups.appendChild(th);
    }
  }

  // One header line per level. A blank entry is repeat suppression, decided
  // in Rust -- never an absent label.
  for (const level of plan.levels) {
    const tr = head.insertRow();
    tr.appendChild(corner());
    for (const label of level) {
      const th = document.createElement("th");
      th.textContent = label;
      tr.appendChild(th);
    }
  }

  const body = table.createTBody();
  for (const row of plan.body) {
    const tr = body.insertRow();
    if (row.kind === "group") {
      const th = document.createElement("th");
      th.colSpan = row.colSpan;
      th.textContent = row.text;
      th.classList.add("group");
      tr.appendChild(th);
      continue;
    }

    for (const label of row.labels) {
      const header = document.createElement("th");
      header.scope = "row";
      header.textContent = label;
      tr.appendChild(header);
    }

    for (const cell of row.cells) {
      const td = tr.insertCell();
      td.textContent = cell.text;
      for (const [name, on] of Object.entries(cell.classes)) {
        td.classList.toggle(name, on);
      }
      // Every cell moves the selection; an editable one also opens its editor,
      // which is the pointer's `i`. Not repainted in that branch: `edit` has
      // set `editing`, and a repaint would take the <input> away.
      td.addEventListener("click", () => {
        const frame = client.click_cell(cell.row, cell.col);
        if (frame) transport.send(frame);
        if (cell.editable) edit(td, cell.row, cell.col, cell.editText);
        else repaint();
      });
    }
  }
  return table;
}

/** Open an inline editor. Committing sends a frame; the value that comes
 *  back is the server's, never the string typed here. */
function edit(td, row, col, seed) {
  if (editing) return;
  editing = { row, col };
  // `seed` is `RenderCell::edit_text` -- the STORED value, not the drawn one:
  // `td.textContent` has been through the number format.
  const original = seed;
  const input = document.createElement("input");
  input.value = original;
  td.replaceChildren(input);
  input.focus();
  input.select();

  // Enter removes the focused <input>, which fires `blur`, which calls
  // `close` again. Harmless before, but only by accident.
  let closed = false;
  const close = (commit) => {
    if (closed) return;
    closed = true;
    editing = null;
    if (commit) {
      const frame = client.typed_cell(row, col, input.value);
      // null only if the grid moved under the editor; the repaint that
      // follows restores whatever the server now says is there.
      if (frame) transport.send(frame);
    }
    td.replaceChildren(original);
    painted = -1;
    repaint();
  };

  input.addEventListener("keydown", (e) => {
    if (e.key === "Enter") close(true);
    else if (e.key === "Escape") close(false);
    // The editor owns the keyboard while it is open; the page-level handler
    // below must not also see these.
    e.stopPropagation();
  });
  input.addEventListener("blur", () => close(false));
}

/** A side panel. An empty row list is what says it is closed — the page asks
 *  no question about the mode, exactly as `paintHelp` does not. */
function paintPanel(host, rows, build) {
  host.hidden = rows.length === 0;
  const list = document.createElement("ul");
  for (const row of rows) list.appendChild(build(row));
  host.replaceChildren(list);
}

function viewRow(row) {
  const li = document.createElement("li");
  li.classList.toggle("selected", row.selected);
  li.classList.toggle("active", row.active);
  // The active marker is the TUI's, and the axis line is the shared
  // derivation's — the page spells neither the summary nor the axis letters.
  const name = document.createElement("span");
  name.className = "name";
  name.textContent = (row.active ? "▶ " : "  ") + row.name;
  li.append(name);
  if (row.axes) {
    const axes = document.createElement("span");
    axes.className = "axes";
    axes.textContent = row.axes;
    li.append(axes);
  }
  return li;
}

function formulaRow(row) {
  const li = document.createElement("li");
  li.classList.toggle("selected", row.selected);
  li.textContent = row.text;
  return li;
}

/** The tile bar. `selected` is only ever true in tile-select mode, which is
 *  decided in Rust. The strip is always laid out — context/code/clients.md. */
function paintTiles(model) {
  const tiles = model.tiles.map((tile, index) => {
    const span = document.createElement("span");
    span.className = "tile";
    span.classList.toggle("selected", tile.selected);
    span.textContent = `${tile.category} ${tile.axis}`;
    span.addEventListener("click", () => send(client.click_tile(index)));
    return span;
  });
  el.tiles.replaceChildren(...tiles);
}

function categoryList(model) {
  const list = document.createElement("ul");
  model.categories.forEach((row, index) => {
    const li = document.createElement("li");
    li.className = row.is_category ? "category" : "item";
    li.classList.toggle("selected", row.selected);
    // `indicator`, not a second pair of triangles: this inlined U+25B8/U+25BE
    // where the TUI and the page's own group headers draw U+25B6/U+25BC.
    li.textContent = row.is_category
      ? `${indicator(!row.expanded)} ${row.label} (${row.item_count}) ${row.axis}`
      : row.label;
    li.addEventListener("click", () => send(client.click_category(index)));
    list.appendChild(li);
  });
  return list;
}

/** Send what a `click_*` call returned, and repaint. `null` means the click
 *  resolved to nothing, which is an answer and not a failure. */
function send(frame) {
  if (frame) transport.send(frame);
  repaint();
}

// The keyboard. `Client::on_key_event` folds locally where it can; what it
// cannot answer is sent and does nothing, by design (context/code/clients.md).

window.addEventListener("keydown", (e) => {
  // The inline editor owns the keyboard while it is open. It stops
  // propagation, so this is belt and braces for a focus we did not predict.
  if (editing) return;
  // BrowserKey drops anything held with the platform meta key precisely so
  // Cmd-R does not arrive as a bare `r`; do not claim it here either.
  if (e.metaKey) return;

  const frame = client.on_key_event(e.key, e.ctrlKey, e.altKey, e.shiftKey, e.metaKey);
  if (frame) {
    // A frame means the page claimed the key, so the browser must not also act
    // on it. Ctrl/Alt combinations are left alone: they are the browser's.
    if (!e.ctrlKey && !e.altKey) e.preventDefault();
    transport.send(frame);
  }
  repaint();
});

// Start.

await transport.ready;
sendViewport(); // the handshake: the snapshot is built at this extent
shell.arm(
  WS_URL
    ? `${WS_URL} accepted the connection but sent no document`
    : "the in-page worker did not answer — this browser may not allow it (see console)",
);
new ResizeObserver(sendViewport).observe(el.grid);