// Everything `web/app.js` decides that is not painting: no DOM, no browser
// API, one `node --test` away. What belongs here: context/code/clients.md.

/** The websocket URL for `?ws=`, defaulting to TLS. Why, and when an explicit
 *  `ws://` is upgraded rather than honoured: context/code/clients.md. */
export function socketUrl(peer, pageProtocol) {
  const secure = pageProtocol === "https:";
  if (/^wss:\/\//i.test(peer)) return peer;
  if (/^ws:\/\//i.test(peer)) return secure ? peer.replace(/^ws:/i, "wss:") : peer;
  return `${secure ? "wss" : "ws"}://${peer}`;
}

/** `#status` carries two independent facts, composed rather than overwritten:
 *  a repaint must not quietly erase a connection error. */
export function composeStatus(shell, model) {
  return [shell, model].filter(Boolean).join(" · ");
}

/** The title bar's one line, in the order and spelling `src/draw.rs::draw_title`
 *  uses. The three facts are the host's; only the joining is here (clients.md). */
export function documentTitle(name, dirty, storedAs) {
  return `${name}${storedAs ? ` (${storedAs})` : ""}${dirty ? " [+]" : ""}`;
}

/** The collapse glyph. `collapsed` is the fact, decided by the view and
 *  carried on the frame; only this spelling is the page's (gotcha 26). */
export function indicator(collapsed) {
  return collapsed ? "▶" : "▼";
}

/** Where the deployment notice's open/closed state is remembered. Per-viewer
 *  and per-origin by construction: it never reaches Rust and never travels. */
export const NOTICE_KEY = "improvise.notice.open";

/** Whether a visitor who has never answered sees the notice OPEN. It is a
 *  product call and the argument for `false` is in context/code/clients.md. */
export const NOTICE_OPEN_BY_DEFAULT = false;

/** What a stored notice state MEANS. Everything that is not one of the two
 *  spellings — absent, empty, a value from an older page, a string a private
 *  window handed back — is "unanswered", which is the default and not an
 *  error: storage is allowed to forget, and a page that treated forgetting as
 *  a third state would flicker between them. */
export function noticeOpen(stored) {
  if (stored === "open") return true;
  if (stored === "closed") return false;
  return NOTICE_OPEN_BY_DEFAULT;
}

/** …and the inverse, so the two spellings have exactly one home. */
export function noticeState(open) {
  return open ? "open" : "closed";
}

// Rough character metrics, used only to turn the window size into an extent.
// Being wrong here costs a row of over- or under-fetch, nothing more.
export const ROW_PX = 26;
export const COL_PX = 110;

/** How long a peer has to answer the handshake. Exported because the harness
 *  must jump *past* it: a spec with its own copy can understate it silently
 *  and every watchdog assertion then passes vacuously (clients.md). */
export const HANDSHAKE_TIMEOUT_MS = 8000;

/** The extent a box of this size can show, in whole DATA cells: the frame is
 *  charged for first, and at least one cell is always asked for. */
export function extentOf(box, frameCost, metrics = { rowPx: ROW_PX, colPx: COL_PX }) {
  return {
    rows: Math.max(1, Math.floor(box.height / metrics.rowPx) - frameCost.rows),
    cols: Math.max(1, Math.floor(box.width / metrics.colPx) - frameCost.cols),
  };
}

/** What the grid's own frame costs, in whole cells — measured off the painted
 *  model, never predicted. Inline group ROWS are deliberately not counted. */
export function frameCostOf(model) {
  return {
    // The totals strip is chrome on the same terms as a header level: always
    // there when there are totals, and never a data row (improvise-p7lh).
    rows:
      model.col_levels.length +
      (model.col_groups.length > 0 ? 1 : 0) +
      (model.totals.length > 0 ? 1 : 0),
    cols: model.row_levels,
  };
}

/** The page bar: one entry per category fixing which records are visible. The
 *  Page/Filter split is `cycle`, decided in Rust — gotcha 27, clients.md. */
export function pageEntries(model) {
  return model.page_coords.map((axis) => ({
    // The TUI's own spelling (`src/ui/grid.rs`); only the spelling is local,
    // exactly as `indicator`'s is.
    text: `${axis.cat} = ${axis.selected}`,
    // `cycle` is null for a Filter axis, which constrains without being
    // navigable: there is no position to show and no key that would move it.
    position: axis.cycle ? `${axis.cycle.at + 1}/${axis.cycle.count}` : "",
    navigable: Boolean(axis.cycle),
  }));
}

/** The grid, as a description: every decision made, nothing created. The page
 *  decides nothing here and neither does this — which labels repeat, how many
 *  header levels there are and which columns share a group all arrive
 *  answered, by the same `AxisFrame` the TUI widget reads (improvise-anr9). */
export function gridPlan(model) {
  const cornerSpan = model.row_levels;
  const groups = model.col_groups.map((group) => ({
    span: group.span,
    // `label` is null for a run in no group; an empty STRING is a legal group
    // name, so this is a null check and not a truthiness test.
    text: group.label === null ? "" : `${indicator(group.collapsed)} ${group.label}`,
  }));

  // The cell coordinates a click sends are DATA row indices and a group header
  // is not a data row, so this counts rather than trusting the row's position.
  let dataRow = -1;
  const body = model.rows.map((row) => {
    if (row.kind === "group") {
      return {
        kind: "group",
        colSpan: model.row_levels + model.col_levels[0].length,
        text: `${indicator(row.collapsed)} ${row.label}`,
      };
    }
    dataRow += 1;
    return {
      kind: "data",
      row: dataRow,
      labels: row.labels,
      cells: row.cells.map((cell, col) => {
        // A keyboard edit is open when `model.editing` is a string, and it
        // holds what has been typed. Both facts are decided in Rust.
        const typing = cell.selected && typeof model.editing === "string";
        return {
          row: dataRow,
          col,
          text: typing ? `${model.editing}▏` : cell.text,
          editText: cell.edit_text,
          editable: cell.editable,
          classes: {
            numeric: cell.numeric && !typing,
            error: cell.error,
            selected: cell.selected,
            typing,
            // `editable` is the server's answer relayed through Rust: a stored
            // cell. Drill is not on the wire, so an aggregate is not offered.
            editable: cell.editable,
          },
        };
      }),
    };
  });

  // An EMPTY strip means this grid has no totals — not a row of blanks, and
  // not "not caught up yet" (gotcha 33). So `null`, not an empty row.
  const totals =
    model.totals.length === 0
      ? null
      : {
          span: cornerSpan,
          // The SECOND spelling of this word — `src/ui/grid.rs` has the other.
          // Named as debt rather than shared: context/code/clients.md.
          label: "Total",
          cells: model.totals.map((cell) => ({
            text: cell.text,
            classes: { numeric: cell.numeric, error: cell.error },
          })),
        };

  return { cornerSpan, groups, levels: model.col_levels, body, totals };
}

/** What a data cell carries on its node, so one delegated handler can read
 *  back the answers `gridPlan` already made (improvise-b8ot, clients.md). */
export function cellAttrs(cell) {
  return { row: String(cell.row), col: String(cell.col), edit: cell.editText };
}

/** …and the inverse: what a delegated mousedown MEANS. `null` where the event
 *  did not land on a data cell, which is every header and the corner. */
export function cellAction(dataset, editable) {
  const row = whole(dataset.row);
  const col = whole(dataset.col);
  // A node that carries no coordinates is not a cell: every header and the
  // corner reach here, and none of them means anything.
  if (row === null || col === null) return null;
  return { row, col, editable, editText: dataset.edit ?? "" };
}

/** The same, for the surfaces whose rows are named by one index: the panels,
 *  the tile bar and the category tree. `null` where there is no row. */
export function indexAction(dataset) {
  return whole(dataset.index);
}

/** A non-negative whole number off an attribute, or `null`. An ABSENT
 *  attribute and the string `""` are both "no index", and `Number` says 0. */
function whole(text) {
  if (typeof text !== "string" || text.trim() === "") return null;
  const value = Number(text);
  return Number.isInteger(value) && value >= 0 ? value : null;
}

/** What the worker just posted. A protocol frame is a STRING and a shell
 *  notice is an OBJECT; nothing else crosses that port (clients.md). */
export function classifyWorkerMessage(data) {
  if (typeof data === "string") return { kind: "frame", text: data };
  if (data && typeof data === "object" && typeof data.kind === "string") {
    return { kind: "notice", notice: data };
  }
  return { kind: "unknown", data };
}

/** What a boot or save notice READS AS. The kinds are decided in Rust
 *  (`improvise_worker_server::boot`); only the wording is the page's. */
export function noticeText(notice) {
  const where = notice.document ? ` — ${notice.document}` : "";
  const why = notice.detail ? ` (${notice.detail})` : "";
  switch (notice.kind) {
    case "ReadOnly":
      return `read-only${where}: another tab or window has it open. Close it and reload to edit.`;
    case "BootFailed":
      return `the in-page worker could not start${where}${why}`;
    case "SeedMissing":
      return `started an EMPTY document${where}: its starting copy could not be fetched${why}`;
    case "SaveFailed":
      return `NOT SAVED${where}${why}`;
    // A kind this page does not know is still a failure, and saying so beats
    // saying nothing — the reason it carries is the point (improvise-1wft).
    default:
      return `the in-page worker reported ${notice.kind}${where}${why}`;
  }
}

/** Whether a notice means the session is unusable, as opposed to degraded.
 *  Only `BootFailed` is fatal: read-only, empty and unsaved all still paint. */
export function isFatal(notice) {
  return notice.kind === "BootFailed";
}

/** The page's two status facts and the handshake watchdog, which share a home
 *  because the one rule between them is that a *failure disarms the timer*. */
export function createShell({ onStatus, timeoutMs, setTimer = setTimeout, clearTimer = clearTimeout }) {
  let shell = "";
  let model = "";
  let watchdog = null;
  let arms = 0;
  const paint = () => onStatus(composeStatus(shell, model));

  return {
    setShell(text) {
      shell = text;
      paint();
    },
    setModel(text) {
      model = text;
      paint();
    },
    /** A peer that never answers the handshake. Deliberately about the *first
     *  frame*, not either peer's own failure modes — clients.md. */
    arm(message) {
      arms += 1;
      clearTimer(watchdog);
      watchdog = setTimer(() => {
        watchdog = null;
        this.setShell(message);
      }, timeoutMs);
    },
    /** A frame arrived, so the peer answered: the watchdog has no question
     *  left to ask. */
    sawFrame() {
      clearTimer(watchdog);
      watchdog = null;
    },
    /** A peer that failed *loudly* has already said something more precise, so
     *  the watchdog must be DISARMED and not merely pre-empted (PR #13). */
    fail(text) {
      this.sawFrame();
      this.setShell(text);
    },
    armed: () => watchdog !== null,
    /** The window this shell was built with. Exposed so a spec can compare the
     *  RUNNING page's value against the one it imported — improvise-669b. */
    timeoutMs: () => timeoutMs,
    /** How many times the watchdog has been armed. A test denying its message
     *  needs this to be nonzero, or it is denying an unreachable event. */
    timesArmed: () => arms,
  };
}