/**
 * ui.js – browser UI logic for crushdb.
 *
 * Two distinct screens before the app opens:
 *
 *   1. "setup" (first visit): No encrypted records exist on the server
 *      yet. The user picks a NEW passphrase (typed twice to avoid
 *      typos). This passphrase then protects every future record.
 *
 *   2. "unlock" (returning): encrypted records exist, but the user's
 *      key isn't known to the browser (it never is – that's the whole
 *      point of client-side encryption). The user types their
 *      existing passphrase.
 *
 * Which screen to show is decided by a cheap server call:
 *   GET /api/records → empty array ⇒ setup, else unlock.
 *
 * The passphrase itself NEVER leaves the browser: Argon2id derives a
 * 256-bit session key in memory, and that key exists only here.
 */

import {
  deriveKey,
  encryptRecord,
  decryptRecord,
  randomSalt,
  randomUuid,
  wipeKey,
} from "./crypto.js";

// ---------- tiny DOM helpers ----------

const $ = (sel) => document.querySelector(sel);

function el(tag, attrs = {}, children = []) {
  const node = document.createElement(tag);
  for (const [k, v] of Object.entries(attrs)) {
    if (k === "class") node.className = v;
    else if (k === "text") node.textContent = v;
    else if (k.startsWith("on") && typeof v === "function") {
      // Event handlers MUST be assigned as properties: setAttribute(k, fn)
      // stringifies the function ("... => ...") and never binds a listener,
      // which silently killed the Bearbeiten/Löschen buttons.
      node[k] = v;
    }
    else node.setAttribute(k, v);
  }
  for (const child of children) node.appendChild(child);
  return node;
}

function flash(msg, isError = false) {
  const box = $("#flash");
  box.textContent = msg;
  box.className = isError ? "flash error" : "flash";
  setTimeout(() => { box.textContent = ""; }, 5000);
}

// ---------- session state (memory only) ----------

let sessionKey = null; // Uint8Array(32) or null
let busy = false;      // Argon2id takes a second; block double submits

// Salt for the session-key derivation. Fixed domain string, contains
// no secret; the per-record salt is separate (see crypto.js).
const DOMAIN_SALT = new TextEncoder().encode("crushdb://session-key-v1");

function resetSession() {
  wipeKey(sessionKey);
  sessionKey = null;
  $("#records").replaceChildren();
  $("#app").hidden = true;
  location.reload(); // cheapest and safest way back to a clean state
}

// ---------- API helpers ----------

async function api(path, opts = {}) {
  const res = await fetch(path, {
    headers: opts.body ? { "Content-Type": "application/json" } : {},
    ...opts,
  });
  if (!res.ok) {
    let detail = "";
    try { detail = (await res.json()).error ?? ""; } catch { /* noop */ }
    throw new Error(`HTTP ${res.status}${detail ? ": " + detail : ""}`);
  }
  if (res.status === 204) return null;
  return res.json();
}

// ---------- rendering ----------

// Timestamps are free text now ("unknown", "Sommer 2025", …). Display
// them verbatim; nothing to parse or format.
function showTs(value) {
  return (value === null || value === undefined || value === "") ? "–" : String(value);
}

function renderRow(record, payload) {
  const tr = el("tr");
  const cells = [
    payload.personA,
    payload.personB,
    showTs(payload.tsStart),
    showTs(payload.tsEnd),
    showTs(payload.startCause),
    showTs(payload.endCause),
    payload.action,
  ];
  for (const text of cells) {
    const td = el("td");
    td.textContent = text ?? ""; // textContent = no HTML injection
    tr.appendChild(td);
  }

  const ops = el("td");
  ops.appendChild(
    el("button", {
      text: "Bearbeiten",
      type: "button",
      onclick: () => openEditor(record, payload),
    })
  );
  ops.appendChild(
    el("button", {
      text: "Löschen",
      type: "button",
      onclick: () => removeRecord(record),
    })
  );
  tr.appendChild(ops);
  return tr;
}

async function reload() {
  const tbody = $("#records tbody");
  tbody.replaceChildren();
  const raw = await api("/api/records");
  let failures = 0;
  for (const record of raw) {
    try {
      const payload = decryptRecord(sessionKey, record);
      payload.__version = record.version; // used for optimistic locking
      tbody.appendChild(renderRow(record, payload));
    } catch {
      failures++;
      tbody.appendChild(
        el("tr", { class: "row-error" }, [
          el("td", { colspan: "8", text: "Datensatz nicht entschlüsselbar (falsche Passphrase oder manipuliert)." }),
        ])
      );
    }
  }
  $("#new-btn").disabled = false;
  if (failures > 0) flash(`${failures} Datensatz/Datensätze konnten nicht entschlüsselt werden.`, true);
}

function openEditor(record, payload) {
  const form = $("#editor");
  form.dataset.uuid = record.uuid;
  form.dataset.version = payload.__version;
  form.dataset.salt = record.salt;
  $("#editor-title").textContent = "Datensatz bearbeiten";
  $("#f-persona").value = payload.personA ?? "";
  $("#f-personb").value = payload.personB ?? "";
  $("#f-tsstart").value = payload.tsStart ?? "";
  $("#f-tsend").value = payload.tsEnd ?? "";
  $("#f-startcause").value = payload.startCause ?? "";
  $("#f-endcause").value = payload.endCause ?? "";
  $("#f-action").value = payload.action ?? "";
  $("#editor-backdrop").hidden = false;
}

function newRecord() {
  const form = $("#editor");
  form.reset();
  form.dataset.uuid = randomUuid();
  form.dataset.version = "";
  form.dataset.salt = "";
  $("#editor-title").textContent = "Neuer Datensatz";
  $("#editor-backdrop").hidden = false;
}

function closeEditor() {
  $("#editor-backdrop").hidden = true;
  $("#editor").reset();
}

function tsOrNull(inputValue) {
  // Free-text field: trim to null or the plain string.
  const v = inputValue.trim();
  return v === "" ? null : v;
}

// ---------- record operations ----------

async function saveRecord(ev) {
  ev.preventDefault();
  if (!sessionKey) { flash("Bitte zuerst entsperren.", true); return; }

  const form = $("#editor");
  const payload = {
    personA: $("#f-persona").value.trim(),
    personB: $("#f-personb").value.trim(),
    tsStart: tsOrNull($("#f-tsstart").value),
    tsEnd: tsOrNull($("#f-tsend").value),
    startCause: tsOrNull($("#f-startcause").value),
    endCause: tsOrNull($("#f-endcause").value),
    action: $("#f-action").value.trim(),
  };
  if (!payload.personA || !payload.personB || !payload.action) {
    flash("Person A, Person B und Aktion sind erforderlich.", true);
    return;
  }

  const isEdit = form.dataset.version !== "";
  const salt = isEdit ? new Uint8Array(atob(form.dataset.salt).split("").map((c) => c.charCodeAt(0))) : randomSalt();
  const enc = encryptRecord(sessionKey, form.dataset.uuid, payload, salt);

  try {
    if (isEdit) {
      enc.version = Number(form.dataset.version);
      await api(`/api/records/${encodeURIComponent(enc.uuid)}`, { method: "PUT", body: JSON.stringify(enc) });
    } else {
      await api("/api/records", { method: "POST", body: JSON.stringify(enc) });
    }
    closeEditor();
    await reload();
    flash(isEdit ? "Datensatz aktualisiert." : "Datensatz gespeichert.");
  } catch (e) {
    closeEditor();
    if (String(e).includes("409")) {
      flash("Konflikt: Der Datensatz wurde zwischenzeitlich geändert. Liste wird neu geladen.", true);
    } else {
      flash("Speichern fehlgeschlagen: " + e.message, true);
    }
    await reload();
  }
}

async function removeRecord(record) {
  if (!sessionKey) { flash("Bitte zuerst entsperren.", true); return; }
  if (!confirm("Diesen Datensatz wirklich löschen?")) return;
  try {
    const current = await api(`/api/records/${encodeURIComponent(record.uuid)}`);
    await api(`/api/records/${encodeURIComponent(record.uuid)}`, {
      method: "DELETE",
      body: JSON.stringify({ version: current.version }),
    });
    await reload();
    flash("Datensatz gelöscht.");
  } catch (e) {
    if (String(e).includes("409")) flash("Konflikt beim Löschen (Version geändert). Bitte erneut versuchen.", true);
    else flash("Löschen fehlgeschlagen: " + e.message, true);
    await reload();
  }
}

// ---------- first-time setup (create a NEW passphrase) ----------

async function setup(ev) {
  ev.preventDefault();
  if (busy) return;
  const p1 = $("#setup-pass1").value;
  const p2 = $("#setup-pass2").value;

  if (p1 !== p2) { flash("Die beiden Passphrasen stimmen nicht überein.", true); return; }
  if (p1.length < 8) { flash("Bitte mindestens 8 Zeichen verwenden.", true); return; }

  busy = true;
  $("#setup-btn").disabled = true;
  $("#setup-progress").hidden = false;
  try {
    sessionKey = deriveKey(p1, DOMAIN_SALT);
    // Verify no records existed while we were deriving (TOCTOU-safe):
    // if someone else created data in parallel, fall back to unlock.
    const existing = await api("/api/records");
    if (existing.length > 0) {
      flash("Es existieren bereits Daten. Bitte entsperren statt neu einrichten.", true);
      resetSession();
      return;
    }
    $("#setup-pass1").value = "";
    $("#setup-pass2").value = "";
    $("#setup").hidden = true;
    $("#app").hidden = false;
    await reload();
    flash("Konto eingerichtet. Ab jetzt schützt deine Passphrase alle Daten.");
  } finally {
    busy = false;
    $("#setup-btn").disabled = false;
    $("#setup-progress").hidden = true;
  }
}

// ---------- lock (wipe key, back to clean state) ----------

function lock() {
  if (!confirm("Sperren? Alle entschlüsselten Daten werden verworfen.")) return;
  resetSession();
}

// ---------- wire-up ----------

document.addEventListener("DOMContentLoaded", async () => {
  $("#setup-form").addEventListener("submit", setup);
  $("#unlock-form").addEventListener("submit", unlock);
  $("#lock-btn").addEventListener("click", lock);
  $("#new-btn").addEventListener("click", newRecord);
  $("#new-btn").disabled = true; // enabled after reload() succeeds
  $("#editor").addEventListener("submit", saveRecord);
  $("#editor-cancel").addEventListener("click", closeEditor);
  window.addEventListener("beforeunload", () => wipeKey(sessionKey));

  // Decide which pre-screen to show: fresh install vs returning user.
  try {
    const raw = await api("/api/records");
    const firstVisit = raw.length === 0;
    $("#setup").hidden = !firstVisit;
    $("#unlock").hidden = firstVisit;
    if (firstVisit) $("#setup-pass1").focus();
    else $("#passphrase").focus();
  } catch (e) {
    // Server unreachable → default to unlock screen; retry will tell more.
    $("#setup").hidden = true;
    $("#unlock").hidden = false;
    flash("Server nicht erreichbar: " + e.message, true);
  }
});

// ---------- unlock (returning user) ----------

async function unlock(ev) {
  ev.preventDefault();
  if (busy) return;
  const passphrase = $("#passphrase").value;
  if (!passphrase) { flash("Bitte Passphrase eingeben.", true); return; }

  busy = true;
  $("#unlock-btn").disabled = true;
  $("#unlock-progress").hidden = false;
  try {
    sessionKey = deriveKey(passphrase, DOMAIN_SALT);
    $("#passphrase").value = "";
    $("#unlock").hidden = true;
    $("#app").hidden = false;
    await reload();

    // If nothing decrypts, the passphrase is (almost certainly) wrong.
    const tbody = $("#records tbody");
    const failed = tbody.querySelectorAll("tr.row-error").length;
    const total = tbody.children.length;
    if (total > 0 && failed === total) {
      // Everything undecryptable ⇒ wrong passphrase; go back cleanly.
      flash("Entsperren fehlgeschlagen: falsche Passphrase?");
      resetSession();
    }
  } catch (e) {
    flash("Entsperren fehlgeschlagen: " + e.message, true);
    resetSession();
  } finally {
    busy = false;
    $("#unlock-btn").disabled = false;
    $("#unlock-progress").hidden = true;
  }
}