// The browser side of `money serve`. It renders what the API returns and
// nothing more: amounts arrive formatted, globs are matched on the server, and
// every tag still comes from rules.toml — there is no control here that tags a
// transaction, only the builder that writes a rule for it.
'use strict';

const VIEWS = [
  { id: 'accounts', title: 'Accounts', mount: mountAccounts },
  { id: 'txns', title: 'Transactions', mount: mountTxns },
  { id: 'report', title: 'Report', mount: mountReport },
  { id: 'rule', title: 'Rule builder', mount: mountRuleBuilder },
  { id: 'rules', title: 'Rules', mount: mountRules },
  { id: 'transfer', title: 'Transfer builder', mount: mountTransferBuilder },
  { id: 'transfers', title: 'Transfers', mount: mountTransfers },
];

const state = {
  view: 'accounts',
  overview: null,
  // The scope the transaction list and the report share. The report's period
  // lives apart from it on purpose: it narrows the report and nothing else.
  filter: { account: '', search: '', untagged: false },
  wide: false,
  report: { period: '', sort: 'out' },
  rule: blankRule(),
  ruleSort: 'name',
  transfer: blankTransfer(),
  status: '',
  error: '',
  busy: false,
};

function blankRule() {
  return { match: '', account: '', tag: '', note: '', editing: null };
}

function blankTransfer() {
  return { fromAccount: '', fromDesc: '', toAccount: '', toDesc: '', tolerance: '', note: '' };
}

// --- plumbing -------------------------------------------------------------

// h builds an element. Text always goes in as a text node, never as HTML,
// since descriptions come straight off bank statements. Children flatten all
// the way down: a map that yields a group of rows — the report's transfers
// and their fee — would otherwise be stringified into the page.
function h(tag, attrs, ...children) {
  const el = document.createElement(tag);
  for (const [k, v] of Object.entries(attrs || {})) {
    if (v === null || v === undefined || v === false) continue;
    if (k.startsWith('on')) el.addEventListener(k.slice(2), v);
    else if (k === 'class') el.className = v;
    else if (k === 'value') el.value = v;
    else el.setAttribute(k, v === true ? '' : v);
  }
  for (const c of children.flat(Infinity)) {
    if (c === null || c === undefined || c === false) continue;
    el.append(c instanceof Node ? c : document.createTextNode(String(c)));
  }
  return el;
}

async function api(method, path, body) {
  const opts = { method, headers: {} };
  if (body !== undefined) {
    opts.headers['Content-Type'] = 'application/json';
    opts.body = JSON.stringify(body);
  }
  const res = await fetch(path, opts);
  const data = await res.json().catch(() => ({ error: `${res.status} ${res.statusText}` }));
  if (!res.ok) throw new Error(data.error || `${res.status} ${res.statusText}`);
  return data;
}

// latest wraps a loader so only the most recent call's answer is used: typing
// fires one request per keystroke, and they do not always come back in order.
function latest(fn) {
  let seq = 0;
  return async (...args) => {
    const mine = ++seq;
    const out = await fn(...args);
    return mine === seq ? out : undefined;
  };
}

function debounce(fn, ms) {
  let t;
  return (...args) => {
    clearTimeout(t);
    t = setTimeout(() => fn(...args), ms);
  };
}

function query(params) {
  const q = new URLSearchParams();
  for (const [k, v] of Object.entries(params)) {
    if (v === '' || v === false || v === null || v === undefined) continue;
    q.set(k, v === true ? '1' : v);
  }
  const s = q.toString();
  return s ? '?' + s : '';
}

function amount(m) {
  return h('td', { class: 'num' + (m.negative ? ' neg' : '') }, m.text);
}

function setStatus(msg) {
  state.status = msg;
  state.error = '';
  renderBanners();
}

function setError(err) {
  state.error = err instanceof Error ? err.message : String(err);
  renderBanners();
}

function renderBanners() {
  const box = document.getElementById('banners');
  box.replaceChildren();
  const o = state.overview;
  if (o && o.stale) {
    const text = o.rulesError
      ? `rules.toml does not load: ${o.rulesError}`
      : 'rules.toml has changed on disk since the index was last derived from it.';
    box.append(h('div', { class: 'banner warn' }, h('span', {}, text),
      o.rulesError ? null : h('button', { type: 'button', onclick: retag }, 'Retag to apply it')));
  }
  if (state.error) {
    box.append(h('div', { class: 'banner error' }, h('span', {}, state.error),
      h('button', { type: 'button', class: 'link', onclick: () => setError('') }, 'dismiss')));
  } else if (state.status) {
    box.append(h('div', { class: 'banner info' }, h('span', {}, state.status),
      h('button', { type: 'button', class: 'link', onclick: () => setStatus('') }, 'dismiss')));
  }
}

async function loadOverview() {
  state.overview = await api('GET', '/api/overview');
  renderBanners();
  fillDatalists();
}

// The account and tag fields complete natively, from lists the server
// builds. (transfer) is never among the tags: it is a label.
function fillDatalists() {
  const o = state.overview;
  if (!o) return;
  for (const [id, values] of [['dl-accounts', o.accountSlugs], ['dl-tags', o.tags]]) {
    let dl = document.getElementById(id);
    if (!dl) {
      dl = h('datalist', { id });
      document.body.append(dl);
    }
    dl.replaceChildren(...values.map((v) => h('option', { value: v })));
  }
}

function scopeLabel() {
  const f = state.filter;
  let s = f.account || 'all accounts';
  if (f.untagged) s += ' · untagged';
  if (f.search) s += ' · /' + f.search;
  return s;
}

// --- navigation -----------------------------------------------------------

let current = null; // the mounted view, whose refresh() reloads its data

function renderNav() {
  const nav = document.getElementById('nav');
  nav.replaceChildren(...VIEWS.map((v, i) => h('a', {
    href: '#' + v.id,
    class: v.id === state.view ? 'active' : null,
  }, h('kbd', {}, String(i + 1)), v.title)));
}

function go(id) {
  if (location.hash !== '#' + id) {
    location.hash = id; // hashchange calls show()
    return;
  }
  show();
}

function show() {
  const id = location.hash.slice(1) || 'accounts';
  const view = VIEWS.find((v) => v.id === id) || VIEWS[0];
  // Leaving the builder mid-edit abandons the edit, as esc does: a new rule
  // must not start out as a copy of the one being edited.
  if (view.id !== 'rule' && state.rule.editing) state.rule = blankRule();
  state.view = view.id;
  renderNav();
  const main = document.getElementById('main');
  main.replaceChildren();
  current = view.mount(main) || null;
}

async function refreshAll() {
  await loadOverview();
  if (current && current.refresh) await current.refresh();
}

// --- import and retag -----------------------------------------------------

function runImport(force) {
  return importing(() => api('POST', '/api/import', { force: !!force }));
}

// importing runs a request that ends in an import — the Import button, or an
// upload — and reports it the same way. It answers whether the request
// succeeded; per-file failures inside the import still count as success.
async function importing(request) {
  if (state.busy) return false;
  state.busy = true;
  const btn = document.getElementById('import');
  btn.disabled = true;
  btn.textContent = 'Importing…';
  setStatus('importing… parsing PDF statements can take a while');
  try {
    const res = await request();
    state.status = res.status;
    state.error = res.failed ? `${res.failed} file(s) failed to import` : '';
    renderBanners();
    showImportDetails(res);
    await refreshAll();
    return true;
  } catch (e) {
    setError(e);
    return false;
  } finally {
    state.busy = false;
    btn.disabled = false;
    btn.textContent = 'Import';
  }
}

// showImportDetails lists what each file contributed, like `money import`
// does. Files skipped by checksum are not listed: unchanged is not news.
function showImportDetails(res) {
  if (!res.files.length) return;
  const items = res.files.map((f) => h('li', {},
    f.error ? h('span', { class: 'neg' }, `${f.path}: ${f.error}`)
      : `${f.path}: ${f.new} new, ${f.skipped} duplicate (${f.parsed} parsed)`,
    (f.warnings || []).map((w) => h('div', { class: 'warn' }, 'warning: ' + w))));
  const box = document.getElementById('banners');
  box.append(h('div', { class: 'banner info' },
    h('ul', { class: 'import-files' }, items),
    h('button', { type: 'button', class: 'link', onclick: (e) => e.target.parentElement.remove() }, 'dismiss')));
}

async function retag() {
  if (state.busy) return;
  try {
    const res = await api('POST', '/api/retag', {});
    setStatus(res.status);
    await refreshAll();
  } catch (e) {
    setError(e);
  }
}

// --- accounts -------------------------------------------------------------

function mountAccounts(main) {
  const body = h('div');
  const upload = h('div');
  main.append(h('h2', {}, 'Accounts'), body, upload);

  async function refresh() {
    if (!state.overview) await loadOverview();
    const o = state.overview;
    upload.replaceChildren(uploader(o));
    if (!o.accounts.length) {
      // An account.toml is not enough on its own: folders reach the index
      // only through an import, so say that rather than show nothing.
      body.replaceChildren(h('div', { class: 'panel empty' }, o.folders.length
        ? `No accounts imported yet.\n\n${o.folders.length} account folder(s) in ${o.root}.\nAdd statements below, or put them in the folders and press Import.`
        : `No account folders found in ${o.root}.\n\nAn account is a folder containing an account.toml.\nCreate one, then add statements to it here.`));
      return;
    }
    body.replaceChildren(h('div', { class: 'panel' }, h('table', {},
      h('thead', {}, h('tr', {}, h('th', {}, 'Account'), h('th', {}, 'Slug'),
        h('th', { class: 'num' }, 'Balance'), h('th', {}, 'Cur'), h('th', { class: 'num' }, 'Txns'))),
      h('tbody', {}, o.accounts.map((a) => h('tr', {
        class: 'clickable',
        title: 'Show this account\'s transactions',
        onclick: () => { state.filter.account = a.slug; go('txns'); },
      }, h('td', {}, a.name), h('td', { class: 'muted' }, a.slug), amount(a.balance),
      h('td', {}, a.currency), h('td', { class: 'num' }, a.count)))))));
  }
  refresh().catch(setError);
  return { refresh };
}

// uploader puts statement files into an account folder and imports them. The
// folder is where they belong: the index is rebuilt from it, so a statement
// that lived only in the index would be lost the next time it is deleted.
function uploader(o) {
  const panel = h('div', { class: 'panel upload' }, h('h3', {}, 'Add statements'));
  if (!o.folders.length) {
    panel.append(h('div', { class: 'muted' }, o.foldersError
      ? `Account folders do not load: ${o.foldersError}`
      : `There is no account folder to add statements to. Create one in ${o.root} with an account.toml.`));
    return panel;
  }

  let files = [];
  const account = h('select', { 'aria-label': 'Account to add statements to' },
    o.folders.map((f) => h('option', { value: f }, f)));
  // Default to the account being browsed, since that is usually the one.
  account.value = o.folders.includes(state.filter.account) ? state.filter.account : o.folders[0];

  const picker = h('input', {
    type: 'file', multiple: true, hidden: true,
    onchange: (e) => choose(e.target.files),
  });
  const chosen = h('div', { class: 'chosen muted' }, 'No files chosen');
  const send = h('button', { type: 'button', class: 'primary', disabled: true, onclick: submit }, 'Upload and import');
  const zone = h('div', {
    class: 'dropzone',
    tabindex: 0,
    role: 'button',
    onclick: () => picker.click(),
    onkeydown: (e) => { if (e.key === 'Enter' || e.key === ' ') { e.preventDefault(); picker.click(); } },
    ondragover: (e) => { e.preventDefault(); zone.classList.add('over'); },
    ondragleave: () => zone.classList.remove('over'),
    ondrop: (e) => { e.preventDefault(); zone.classList.remove('over'); choose(e.dataTransfer.files); },
  }, 'Drop statement files here, or click to choose');

  function choose(list) {
    files = Array.from(list || []);
    send.disabled = !files.length;
    chosen.textContent = files.length
      ? files.map((f) => `${f.name} (${Math.ceil(f.size / 1024)} KB)`).join(' · ')
      : 'No files chosen';
  }

  async function submit() {
    send.disabled = true;
    try {
      const payload = {
        account: account.value,
        files: await Promise.all(files.map(async (f) => ({ name: f.name, data: await base64(f) }))),
      };
      if (await importing(() => api('POST', '/api/upload', payload))) {
        picker.value = '';
        choose([]);
      }
    } catch (e) {
      setError(e);
    } finally {
      send.disabled = !files.length;
    }
  }

  panel.append(
    h('div', { class: 'toolbar' }, h('label', {}, 'Account ', account), send),
    zone, picker, chosen,
    h('div', { class: 'hint muted' },
      'Files are saved into the account folder, next to the statements already there, and imported. ' +
      'A file with the same name and different contents is refused rather than replaced.'));
  return panel;
}

// base64 encodes a file for the JSON body. Chunked, because spreading a whole
// statement into String.fromCharCode overflows the call stack.
async function base64(file) {
  const bytes = new Uint8Array(await file.arrayBuffer());
  let bin = '';
  for (let i = 0; i < bytes.length; i += 0x8000) {
    bin += String.fromCharCode.apply(null, bytes.subarray(i, i + 0x8000));
  }
  return btoa(bin);
}

// --- shared scope toolbar ---------------------------------------------------

function scopeToolbar(onChange) {
  const accounts = (state.overview && state.overview.accounts) || [];
  const select = h('select', {
    'aria-label': 'Account',
    onchange: (e) => { state.filter.account = e.target.value; onChange(); },
  }, h('option', { value: '' }, 'All accounts'),
  accounts.map((a) => h('option', { value: a.slug }, a.slug)));
  select.value = state.filter.account;

  const search = h('input', {
    type: 'search', id: 'search', placeholder: 'Filter by description  ( / )',
    value: state.filter.search,
    oninput: debounce((e) => { state.filter.search = e.target.value.trim(); onChange(); }, 200),
  });
  const untagged = h('input', {
    type: 'checkbox', checked: state.filter.untagged,
    onchange: (e) => { state.filter.untagged = e.target.checked; onChange(); },
  });
  return h('div', { class: 'toolbar' }, select, search,
    h('label', { class: 'check', title: 'No tag and not a matched transfer leg (u)' }, untagged, 'Untagged only'));
}

// --- transactions ---------------------------------------------------------

const PAGE = 500;

function mountTxns(main) {
  const title = h('h2');
  const body = h('div');
  let shown = PAGE;
  let rows = [];

  const wide = h('input', {
    type: 'checkbox', checked: state.wide,
    onchange: (e) => { state.wide = e.target.checked; draw(); },
  });
  const toolbar = scopeToolbar(() => { shown = PAGE; refresh(); });
  toolbar.append(h('label', { class: 'check', title: 'Also show type and reported balance' }, wide, 'Wide'),
    h('button', { type: 'button', onclick: () => go('rule') }, 'New rule…'));
  main.append(title, toolbar, body);

  const load = latest(() => api('GET', '/api/transactions' + query(state.filter)));

  function emptyMessage() {
    const f = state.filter;
    if (f.search) return `No transactions match /${f.search}.`;
    if (f.untagged) return 'Nothing untagged.\n\nEvery transaction here has a tag or belongs to a transfer.';
    if (f.account) return `No transactions in ${f.account}.\n\nImport, or choose all accounts.`;
    return 'No transactions yet.\n\nPress Import to read your statements.';
  }

  function draw() {
    title.replaceChildren(`Transactions `, h('span', { class: 'sub' }, `· ${scopeLabel()} · ${rows.length} rows`));
    if (!rows.length) {
      body.replaceChildren(h('div', { class: 'panel empty' }, emptyMessage()));
      return;
    }
    const head = ['Date', 'Account', 'Amount', 'Tag'];
    if (state.wide) head.push('Balance', 'Type');
    head.push('Description');
    const visible = rows.slice(0, shown);
    body.replaceChildren(h('div', { class: 'panel' },
      h('table', {},
        h('thead', {}, h('tr', {}, head.map((c) => h('th', { class: c === 'Amount' || c === 'Balance' ? 'num' : null }, c)))),
        h('tbody', {}, visible.map((t) => h('tr', {},
          h('td', {}, t.date), h('td', {}, t.account), amount(t.amount),
          h('td', { class: t.supplied ? 'muted' : null }, t.tag),
          state.wide ? [h('td', { class: 'num' }, t.balance), h('td', { class: 'muted' }, t.type)] : null,
          h('td', { class: 'desc' }, t.description))))),
      rows.length > shown ? h('div', { class: 'more' },
        h('button', { type: 'button', onclick: () => { shown += PAGE; draw(); } },
          `Show more (${rows.length - shown} hidden)`)) : null));
  }

  async function refresh() {
    try {
      const res = await load();
      if (!res) return;
      rows = res.rows;
      draw();
    } catch (e) { setError(e); }
  }
  refresh();
  return { refresh };
}

// --- report ---------------------------------------------------------------

const TRANSFERS_ROW = '(transfers)';
const FEES_ROW = '⤷ fees';

function mountReport(main) {
  const title = h('h2');
  const body = h('div');
  main.append(title, scopeToolbar(() => refresh()), body);
  let data = null;

  const load = latest(() => api('GET', '/api/report' + query({
    ...state.filter, period: state.report.period, sort: state.report.sort,
  })));

  function setPeriod(i) {
    if (!data || i < 0 || i >= data.periods.length || i === data.period) return;
    state.report.period = data.periods[i].label;
    refresh();
  }

  function draw() {
    const period = data.periods[data.period];
    title.replaceChildren('Report ', h('span', { class: 'sub' }, `· ${period.name} · ${scopeLabel()}`));

    const periods = h('div', { class: 'panel periods' }, h('div', { class: 'head' }, 'Period'),
      data.periods.map((p, i) => h('button', {
        type: 'button', class: i === data.period ? 'active' : null, title: p.name,
        onclick: () => setPeriod(i),
      }, p.label)));

    let content;
    if (!data.rows.length && !data.excluded.length) {
      // An empty period is not an empty index, and the default window is the
      // one most likely to be empty: last month's statement may not be in yet.
      content = h('div', { class: 'panel empty' }, period.bounded && !data.indexEmpty
        ? `Nothing in ${period.name}.\n\nChoose another period (← →), or import.`
        : 'Nothing to report yet.\n\nImport some statements first.');
    } else {
      const order = data.orders.find((o) => o.name === data.order);
      const cols = [['Tag', false], ['Cur', false], ['Out', true], ['In', true], ['Net', true], ['N', true]];
      const header = h('tr', {}, cols.map(([c, num]) => {
        const o = data.orders.find((x) => x.column === c);
        const marked = order && order.column === c;
        return h('th', {
          class: [num ? 'num' : '', o ? 'sortable' : ''].join(' ').trim() || null,
          title: o ? 'Sort: ' + o.label : null,
          onclick: o ? () => { state.report.sort = o.name; refresh(); } : null,
        }, c + (marked ? (order.ascending ? ' ▴' : ' ▾') : ''));
      }));
      const row = (cls, tag, r, n) => h('tr', { class: cls }, h('td', {}, tag), h('td', {}, r.currency),
        amount(r.out), amount(r.in), amount(r.net), h('td', { class: 'num' }, n));
      const blank = { text: '', negative: false };
      content = h('div', { class: 'panel' }, h('table', {}, h('thead', {}, header), h('tbody', {},
        data.rows.map((r) => row(r.tag === '(untagged)' ? 'muted' : null, r.tag, r, r.count)),
        data.totals.map((r) => row('total', 'TOTAL', r, '')),
        // What the report held out, so it agrees with the balances: the legs
        // moved between accounts, and any fee a tolerant definition admitted.
        data.excluded.map((x, i) => [
          row('excluded' + (i === 0 ? ' first' : ''), TRANSFERS_ROW, x, x.legs),
          x.fee ? row('excluded', FEES_ROW, { currency: x.currency, out: x.fee, in: blank, net: x.feeNet }, x.pairs) : null,
        ]))));
    }
    body.replaceChildren(h('div', { class: 'report' }, periods, content));
  }

  async function refresh() {
    try {
      const res = await load();
      if (!res) return;
      data = res;
      state.report.period = data.periods[data.period].label;
      draw();
    } catch (e) { setError(e); }
  }
  refresh();
  return {
    refresh,
    key(e, typing) {
      if (typing || !data || e.ctrlKey || e.metaKey || e.altKey) return false;
      if (e.key === 'ArrowLeft') { setPeriod(data.period - 1); return true; }
      if (e.key === 'ArrowRight') { setPeriod(data.period + 1); return true; }
      if (e.key === 's') {
        const i = data.orders.findIndex((o) => o.name === data.order);
        state.report.sort = data.orders[(i + 1) % data.orders.length].name;
        refresh();
        return true;
      }
      return false;
    },
  };
}

// --- form helpers ---------------------------------------------------------

function field(label, input, hint) {
  return h('div', { class: 'field' }, h('label', { for: input.id }, label), input,
    hint ? h('div', { class: 'hint' }, hint) : null);
}

function textInput(id, value, placeholder, oninput, list) {
  return h('input', {
    type: 'text', id, value, placeholder, list, autocomplete: 'off', spellcheck: 'false', oninput,
  });
}

// --- rule builder ---------------------------------------------------------

function mountRuleBuilder(main) {
  const r = state.rule;
  const editing = r.editing;
  // A new rule starts on the account being browsed.
  if (!editing && !r.account && state.filter.account) r.account = state.filter.account;

  const summary = h('div', { class: 'summary' });
  const preview = h('div', { class: 'panel preview' });
  const update = (k) => (e) => { r[k] = e.target.value; refreshPreview(); };

  const inputs = {
    match: textInput('rule-match', r.match, '*LIDL*', update('match')),
    account: textInput('rule-account', r.account, 'blank = every account', update('account'), 'dl-accounts'),
    tag: textInput('rule-tag', r.tag, 'groceries', update('tag'), 'dl-tags'),
    note: textInput('rule-note', r.note, 'optional', update('note')),
  };
  const save = h('button', { type: 'submit', class: 'primary' }, editing ? 'Save changes' : 'Save rule');

  const form = h('form', {
    class: 'panel form',
    onsubmit: (e) => { e.preventDefault(); submit(); },
  },
  field('Glob', inputs.match, 'vs. the description · * any run, ? one character'),
  // The form has no type field, so a rule that sets one says it is kept
  // rather than looking broader than it is.
  editing && editing.expect.type ? h('div', { class: 'kept' }, `+ type:${editing.expect.type} · kept`) : null,
  field('Account', inputs.account, 'blank = all accounts'),
  field('Tag', inputs.tag, 'applied to matches'),
  field('Note', inputs.note, 'why this rule exists'),
  summary,
  h('div', { class: 'buttons' }, save,
    editing ? h('button', { type: 'button', onclick: () => { state.rule = blankRule(); go('rules'); } }, 'Cancel') : null));

  main.append(
    h('h2', {}, editing ? `Editing rule ${editing.pos + 1} ` : 'Rule builder ',
      h('span', { class: 'sub' }, editing ? '· rewrites it in rules.toml' : '· writes to rules.toml')),
    h('div', { class: 'builder' }, form, preview));

  const load = latest(() => api('POST', '/api/rules/preview', {
    glob: r.match, account: r.account, sort: state.ruleSort,
    edit: editing ? editing.pos : null,
  }));

  async function refreshNow() {
    try {
      const res = await load();
      if (!res) return;
      draw(res);
    } catch (e) { setError(e); }
  }
  const refreshPreview = debounce(refreshNow, 120);

  function draw(res) {
    let text = `${res.matches} of ${res.candidates} descriptions match`;
    if (!r.match.trim() && !editing) text = `${res.candidates} untagged descriptions`;
    if (res.dropped) text += `\n${res.dropped} no longer claimed`;
    summary.textContent = text;

    const byCount = state.ruleSort === 'count';
    const toggle = () => { state.ruleSort = byCount ? 'name' : 'count'; refreshNow(); };
    const descTitle = (editing ? 'Description' : 'Untagged description') + (byCount ? '' : ' ↓');
    if (!res.rows.length) {
      preview.replaceChildren(h('div', { class: 'empty' }, r.match.trim()
        ? 'The glob matches nothing still waiting for a rule.'
        : 'Nothing untagged — every transaction has a tag or belongs to a transfer.'));
      return;
    }
    preview.replaceChildren(h('table', {},
      h('thead', {}, h('tr', {}, h('th', {}, ''),
        h('th', { class: 'sortable', onclick: toggle, title: 'Sort by name / by count (ctrl+s)' }, descTitle),
        h('th', { class: 'num sortable', onclick: toggle, title: 'Sort by name / by count (ctrl+s)' }, 'N' + (byCount ? ' ↓' : '')))),
      h('tbody', {}, res.rows.map((row) => h('tr', {
        class: 'clickable',
        title: 'Use this description as the glob',
        onclick: () => {
          // Collapsed as the engine normalises it, or a doubled space on the
          // statement would make a glob that never matches.
          inputs.match.value = r.match = '*' + row.description.trim().split(/\s+/).join(' ') + '*';
          inputs.match.focus();
          refreshNow();
        },
      }, h('td', { class: 'mark' + (row.marker === '−' ? ' neg' : '') }, row.marker),
      h('td', { class: 'desc' }, row.description), h('td', { class: 'num' }, row.count))))));
  }

  async function submit() {
    save.disabled = true;
    try {
      const form = { match: r.match, account: r.account, tag: r.tag, note: r.note };
      if (editing) {
        const res = await api('PUT', `/api/rules/${editing.pos}`, { rule: form, expect: editing.expect });
        state.rule = blankRule();
        setStatus(res.status);
        await loadOverview();
        // An edit is a round trip from the rules screen, so it ends there.
        go('rules');
        return;
      }
      const res = await api('POST', '/api/rules', form);
      // The account stays: the next rule is usually for the same one.
      Object.assign(r, { match: '', tag: '', note: '' });
      inputs.match.value = inputs.tag.value = inputs.note.value = '';
      inputs.match.focus();
      setStatus(res.status);
      await loadOverview();
      await refreshNow();
    } catch (e) {
      setError(e);
    } finally {
      save.disabled = false;
    }
  }

  inputs.match.focus();
  refreshNow();
  return {
    refresh: refreshNow,
    form: true,
    key(e) {
      if (e.key === 's' && e.ctrlKey) {
        state.ruleSort = state.ruleSort === 'count' ? 'name' : 'count';
        refreshNow();
        return true;
      }
      if (e.key === 'Escape' && editing) {
        state.rule = blankRule();
        go('rules');
        return true;
      }
      return false;
    },
  };
}

// --- rules ----------------------------------------------------------------

function ruleExpect(r) {
  return { match: r.match, type: r.type, account: r.account, tag: r.tag, note: r.note };
}

function mountRules(main) {
  const title = h('h2');
  const body = h('div');
  const prune = h('button', { type: 'button', class: 'danger' }, 'Prune unused');
  main.append(title, h('div', { class: 'toolbar' },
    h('button', { type: 'button', onclick: () => go('rule') }, 'New rule…'),
    prune,
    h('button', { type: 'button', onclick: () => refresh().then(() => setStatus('counts refreshed')) }, 'Refresh counts')),
  body);
  let rules = [];

  async function del(positions, question) {
    if (!confirm(question)) return;
    try {
      const res = await api('POST', '/api/rules/delete', {
        positions, expect: positions.map((p) => ruleExpect(rules[p])),
      });
      setStatus(res.status);
      await refreshAll();
    } catch (e) { setError(e); }
  }

  function edit(r) {
    state.rule = {
      match: r.match, account: r.account, tag: r.tag, note: r.note,
      editing: { pos: r.pos, expect: ruleExpect(r) },
    };
    go('rule');
  }

  async function refresh() {
    try {
      rules = (await api('GET', '/api/rules')).rules;
    } catch (e) { setError(e); return; }
    const unused = rules.filter((r) => r.usage === 0);
    title.replaceChildren('Rules ', h('span', { class: 'sub' }, unused.length
      ? `· ${rules.length} rules · ${unused.length} match nothing`
      : `· ${rules.length} rules, all in use`));
    prune.disabled = !unused.length;
    prune.onclick = () => del(unused.map((r) => r.pos), `Delete all ${unused.length} rules that match nothing?`);

    if (!rules.length) {
      body.replaceChildren(h('div', { class: 'panel empty' }, 'No rules yet.\n\nBuild one, or write rules.toml by hand.'));
      return;
    }
    // File order, numbered as in rules.toml. Precedence is not read off this:
    // the most specific rule wins wherever it sits.
    body.replaceChildren(h('div', { class: 'panel' }, h('table', {},
      h('thead', {}, h('tr', {}, h('th', { class: 'num' }, '#'), h('th', {}, ''), h('th', {}, 'Pattern'),
        h('th', {}, 'Account'), h('th', {}, 'Tag'), h('th', { class: 'num', title: 'Transactions this rule wins' }, 'Txns'),
        h('th', {}, 'Note'), h('th', {}, ''))),
      h('tbody', {}, rules.map((r) => h('tr', {},
        h('td', { class: 'num muted' }, r.pos + 1),
        h('td', { class: 'mark neg', title: r.usage ? null : 'Claims nothing: matches nothing, or a more specific rule wins' }, r.usage ? '' : '✗'),
        h('td', { class: 'desc', style: 'font-family: var(--mono)' }, r.pattern),
        h('td', { class: r.account ? null : 'muted' }, r.account || '(all)'),
        h('td', {}, r.tag), h('td', { class: 'num' }, r.usage),
        h('td', { class: 'desc muted' }, r.note),
        h('td', { class: 'actions' },
          h('button', { type: 'button', onclick: () => edit(r) }, 'Edit'), ' ',
          h('button', {
            type: 'button', class: 'danger',
            onclick: () => del([r.pos], `Delete rule ${r.pos + 1} (${r.pattern} → ${r.tag}), used by ${r.usage} transactions?`),
          }, 'Delete'))))))));
  }
  refresh();
  return { refresh };
}

// --- transfer builder -----------------------------------------------------

function mountTransferBuilder(main) {
  const t = state.transfer;
  const summary = h('div', { class: 'summary' });
  const preview = h('div', { class: 'panel preview' });
  const update = (k) => (e) => { t[k] = e.target.value; refreshPreview(); };

  const inputs = {
    fromAccount: textInput('tr-from', t.fromAccount, 'nlb', update('fromAccount'), 'dl-accounts'),
    fromDesc: textInput('tr-from-desc', t.fromDesc, '*TO REVOLUT*', update('fromDesc')),
    toAccount: textInput('tr-to', t.toAccount, 'revolut', update('toAccount'), 'dl-accounts'),
    toDesc: textInput('tr-to-desc', t.toDesc, '*FROM NLB*', update('toDesc')),
    tolerance: textInput('tr-tol', t.tolerance, '0', update('tolerance')),
    note: textInput('tr-note', t.note, 'optional', update('note')),
  };
  const save = h('button', { type: 'submit', class: 'primary' }, 'Save transfer');

  main.append(
    h('h2', {}, 'Transfer builder ', h('span', { class: 'sub' }, '· writes to rules.toml')),
    h('div', { class: 'builder' },
      h('form', { class: 'panel form', onsubmit: (e) => { e.preventDefault(); submit(); } },
        field('From account', inputs.fromAccount, 'money leaves here'),
        field('From desc', inputs.fromDesc, 'glob vs. the leaving leg'),
        field('To account', inputs.toAccount, 'money arrives here'),
        field('To desc', inputs.toDesc, 'glob vs. the arriving leg'),
        field('Tolerance %', inputs.tolerance, '0 = amounts must match exactly; only for a route that charges a fee'),
        field('Note', inputs.note, 'why this transfer exists'),
        summary,
        h('div', { class: 'buttons' }, save)),
      preview));

  const load = latest(() => api('POST', '/api/transfers/preview', t));

  async function refreshNow() {
    try {
      const res = await load();
      if (!res) return;
      draw(res);
    } catch (e) { setError(e); }
  }
  const refreshPreview = debounce(refreshNow, 120);

  function draw(res) {
    let text = res.pairs || res.unpaired ? `${res.pairs} pairs · ${res.unpaired} unpaired` : 'nothing matches yet';
    // Fees are why the tolerance exists, so the preview says what it admits.
    if (res.fees) text += ` · ${res.fees} in fees`;
    summary.textContent = text;
    if (!res.rows.length) {
      preview.replaceChildren(h('div', { class: 'empty' },
        'Fill in either side to see which legs it catches.\n▸ a matched pair · ⚠ a leg with no other side'));
      return;
    }
    preview.replaceChildren(h('table', {},
      h('thead', {}, h('tr', {}, h('th', {}, ''), h('th', {}, 'Date'), h('th', { class: 'num' }, 'Amount'),
        h('th', {}, 'Movement'), h('th', {}, 'Description'))),
      h('tbody', {}, res.rows.map((row) => h('tr', {},
        h('td', { class: 'mark' + (row.marker === '⚠' ? ' warn' : '') }, row.marker),
        h('td', {}, row.date), h('td', { class: 'num' }, row.amount),
        h('td', {}, row.movement), h('td', { class: 'desc' }, row.description))))));
  }

  async function submit() {
    save.disabled = true;
    try {
      const res = await api('POST', '/api/transfers', t);
      // The accounts stay — the next definition is usually the same route the
      // other way. The tolerance goes with the globs: carried over silently it
      // would loosen a route that never asked for one.
      for (const k of ['fromDesc', 'toDesc', 'tolerance', 'note']) {
        t[k] = '';
        inputs[k].value = '';
      }
      inputs.fromDesc.focus();
      setStatus(res.status);
      await loadOverview();
      await refreshNow();
    } catch (e) {
      setError(e);
    } finally {
      save.disabled = false;
    }
  }

  inputs.fromAccount.focus();
  refreshNow();
  return { refresh: refreshNow, form: true };
}

// --- transfers ------------------------------------------------------------

function transferExpect(t) {
  return {
    fromAccount: t.fromAccount, fromDesc: t.fromDesc, toAccount: t.toAccount,
    toDesc: t.toDesc, tolerancePct: t.tolerancePct, note: t.note,
  };
}

function mountTransfers(main) {
  const title = h('h2');
  const body = h('div');
  const prune = h('button', { type: 'button', class: 'danger' }, 'Prune unmatched');
  main.append(title, h('div', { class: 'toolbar' },
    h('button', { type: 'button', onclick: () => go('transfer') }, 'New transfer…'),
    prune,
    h('button', { type: 'button', onclick: () => refresh().then(() => setStatus('pairing refreshed')) }, 'Refresh pairing')),
  body);
  let defs = [];

  async function del(positions, question) {
    if (!confirm(question)) return;
    try {
      const res = await api('POST', '/api/transfers/delete', {
        positions, expect: positions.map((p) => transferExpect(defs[p])),
      });
      setStatus(res.status);
      await refreshAll();
    } catch (e) { setError(e); }
  }

  async function refresh() {
    let res;
    try {
      res = await api('GET', '/api/transfers');
    } catch (e) { setError(e); return; }
    defs = res.transfers;
    title.replaceChildren('Transfers ', h('span', { class: 'sub' }, res.unpaired
      ? `· ${defs.length} definitions · ${res.unpaired} leg(s) unpaired`
      : `· ${defs.length} definitions · every leg paired`));
    // Only definitions catching nothing at all are pruned. One with unpaired
    // legs is doing something, and deleting it would hide the problem.
    const unused = defs.filter((d) => d.paired === 0 && d.orphaned === 0);
    prune.disabled = !unused.length;
    prune.onclick = () => del(unused.map((d) => d.pos), `Delete all ${unused.length} transfers that match nothing?`);

    if (!defs.length) {
      body.replaceChildren(h('div', { class: 'panel empty' },
        'No transfers yet.\n\nA transfer names both legs of money moved between your own accounts,\n' +
        'so the report can leave the pair out instead of counting it as spending.'));
      return;
    }
    body.replaceChildren(h('div', { class: 'panel' }, h('table', {},
      h('thead', {}, h('tr', {}, h('th', { class: 'num' }, '#'), h('th', {}, ''), h('th', {}, 'From'), h('th', {}, 'To'),
        h('th', { class: 'num' }, 'Pairs'), h('th', { class: 'num' }, 'Unpaired'), h('th', { class: 'num' }, 'Tol'),
        h('th', {}, 'Note'), h('th', {}, ''))),
      h('tbody', {}, defs.map((d) => {
        let mark = '', cls = 'mark', tip = null;
        if (d.orphaned > 0) [mark, cls, tip] = ['⚠', 'mark warn', 'Catches legs it cannot pair'];
        else if (d.paired === 0) [mark, cls, tip] = ['✗', 'mark neg', 'Matches nothing at all'];
        return h('tr', {},
          h('td', { class: 'num muted' }, d.pos + 1),
          h('td', { class: cls, title: tip }, mark),
          h('td', {}, d.fromAccount, ' ', h('span', { style: 'font-family: var(--mono)' }, d.fromDesc)),
          h('td', {}, d.toAccount, ' ', h('span', { style: 'font-family: var(--mono)' }, d.toDesc)),
          h('td', { class: 'num' }, d.paired),
          h('td', { class: 'num' + (d.orphaned ? ' warn' : '') }, d.orphaned),
          h('td', { class: 'num' }, d.tolerance),
          h('td', { class: 'desc muted' }, d.note),
          h('td', { class: 'actions' }, h('button', {
            type: 'button', class: 'danger',
            onclick: () => del([d.pos], `Delete transfer ${d.pos + 1} (${d.fromAccount} → ${d.toAccount}), ${d.paired} matched?`),
          }, 'Delete')));
      })))));
  }
  refresh();
  return { refresh };
}

// --- keyboard -------------------------------------------------------------

// Single-key shortcuts, where they do not fight the browser. A builder is a
// form, so outside of chords its keys belong to the field being typed in.
document.addEventListener('keydown', (e) => {
  const t = e.target;
  const typing = t instanceof HTMLInputElement || t instanceof HTMLSelectElement || t instanceof HTMLTextAreaElement;
  if (current && current.key && current.key(e, typing)) {
    e.preventDefault();
    return;
  }
  if (typing || e.ctrlKey || e.metaKey || e.altKey) return;

  if (e.key >= '1' && e.key <= String(VIEWS.length)) {
    go(VIEWS[Number(e.key) - 1].id);
  } else if (e.key === '/') {
    if (state.view !== 'txns' && state.view !== 'report') go('txns');
    setTimeout(() => { const s = document.getElementById('search'); if (s) s.focus(); });
  } else if (e.key === 'u') {
    state.filter.untagged = !state.filter.untagged;
    if (state.view === 'txns' || state.view === 'report') show();
    else go('txns');
  } else if (e.key === 'a') {
    state.filter.account = '';
    if (state.view === 'txns' || state.view === 'report') show();
  } else if (e.key === 'i') {
    runImport(false);
  } else if (e.key === 'r') {
    retag();
  } else {
    return;
  }
  e.preventDefault();
});

document.getElementById('import').addEventListener('click', (e) => runImport(e.shiftKey));
document.getElementById('import').title += ' (shift-click re-parses unchanged files too)';
document.getElementById('retag').addEventListener('click', retag);
window.addEventListener('hashchange', show);

loadOverview().catch(setError).finally(show);