const { all, audit, json, now, one, parseJson, run, tx } = require('../db');
const { computeNextDue, projectUsageDue } = require('./pmScheduling');

const FREQUENCY_UNITS = ['days', 'weeks', 'months', 'quarters', 'semiannual', 'years'];

function todayStr() {
  return new Date().toISOString().slice(0, 10);
}

function addInterval(dateStr, value, unit) {
  const date = new Date(`${dateStr || todayStr()}T00:00:00`);
  const v = Math.max(1, Number(value) || 1);
  switch (unit) {
    case 'days': date.setDate(date.getDate() + v); break;
    case 'weeks': date.setDate(date.getDate() + v * 7); break;
    case 'quarters': date.setMonth(date.getMonth() + v * 3); break;
    case 'semiannual': date.setMonth(date.getMonth() + v * 6); break;
    case 'years': date.setFullYear(date.getFullYear() + v); break;
    case 'months':
    default: date.setMonth(date.getMonth() + v); break;
  }
  return date.toISOString().slice(0, 10);
}

// ---- PM plan templates -----------------------------------------------------

function round2(value) {
  return Math.round((Number(value || 0) + Number.EPSILON) * 100) / 100;
}

function yearOf(value) {
  return value ? Number(String(value).slice(0, 4)) : null;
}

function planSteps(planId) {
  return all('SELECT id, step_order, title, details, est_minutes FROM pm_plan_steps WHERE plan_id = ? ORDER BY step_order, id', [planId]);
}

function planComponents(planId) {
  return all('SELECT id, sort_order, part_number, description, supplier, cost FROM pm_plan_components WHERE plan_id = ? ORDER BY sort_order, id', [planId]);
}

// Usage meters declared on a plan template (e.g. Operating Hours / hrs / due every 500).
function planMeters(planId) {
  return all('SELECT id, sort_order, label, unit, usage_interval FROM pm_plan_meters WHERE plan_id = ? ORDER BY sort_order, id', [planId]);
}

// Per-schedule meters with their reading log, used by the engine and surfaced to the UI.
function assetPmMeters(apId) {
  return all('SELECT * FROM asset_pm_meters WHERE asset_pm_id = ? ORDER BY sort_order, id', [apId]).map((m) => {
    const readings = all(
      'SELECT reading, reading_date FROM pm_meter_readings WHERE asset_pm_meter_id = ? ORDER BY reading_date, id',
      [m.id]
    );
    return { ...m, readings, projected_usage_due_date: projectUsageDue(m, readings, todayStr()) };
  });
}

function writePlanMeters(planId, meters) {
  run('DELETE FROM pm_plan_meters WHERE plan_id = ?', [planId]);
  (meters || []).forEach((meter, index) => {
    const label = (meter.label || '').trim();
    if (!label) return;
    run(
      'INSERT INTO pm_plan_meters (plan_id, sort_order, label, unit, usage_interval) VALUES (?, ?, ?, ?, ?)',
      [planId, index, label, (meter.unit || '').trim() || null, Number(meter.usage_interval) || 0]
    );
  });
}

// Guidance photos for a plan. `withData` is false for list views (omits the base64 blob).
function planPhotos(planId, withData = true) {
  const columns = withData ? 'id, name, mime_type, caption, data_base64, sort_order' : 'id, name, mime_type, caption, sort_order';
  return all(`SELECT ${columns} FROM pm_plan_photos WHERE plan_id = ? ORDER BY sort_order, id`, [planId])
    .map((p) => ({ id: p.id, name: p.name, mime: p.mime_type, caption: p.caption, ...(withData ? { data: p.data_base64 } : {}) }));
}

function stepsMinutes(steps) {
  return (steps || []).reduce((sum, step) => sum + (Number(step.est_minutes) || 0), 0);
}

function componentsTotal(components) {
  return round2((components || []).reduce((sum, component) => sum + (Number(component.cost) || 0), 0));
}

function planFromRow(row, { withPhotoData = true } = {}) {
  if (!row) return null;
  const components = planComponents(row.id);
  const photos = planPhotos(row.id, withPhotoData);
  return {
    ...row,
    lifespan_adjust: Boolean(row.lifespan_adjust),
    steps: planSteps(row.id),
    components,
    components_total: componentsTotal(components),
    meters: planMeters(row.id),
    photos,
    photo_count: photos.length
  };
}

function listPlans(companyId) {
  return all('SELECT * FROM pm_plans WHERE (? IS NULL OR entity_id = ?) ORDER BY name', [companyId || null, companyId || null])
    .map((row) => planFromRow(row, { withPhotoData: false }));
}

function getPlan(id) {
  return planFromRow(one('SELECT * FROM pm_plans WHERE id = ?', [id]));
}

function writeSteps(planId, steps) {
  run('DELETE FROM pm_plan_steps WHERE plan_id = ?', [planId]);
  (steps || []).forEach((step, index) => {
    const title = (step.title || '').trim();
    if (!title) return;
    const est = step.est_minutes === '' || step.est_minutes == null ? null : Number(step.est_minutes);
    run('INSERT INTO pm_plan_steps (plan_id, step_order, title, details, est_minutes) VALUES (?, ?, ?, ?, ?)', [planId, index, title, step.details || null, est]);
  });
}

function writeComponents(planId, components) {
  run('DELETE FROM pm_plan_components WHERE plan_id = ?', [planId]);
  (components || []).forEach((component, index) => {
    const part = (component.part_number || '').trim();
    const description = (component.description || '').trim();
    if (!part && !description && !Number(component.cost)) return;
    run(
      'INSERT INTO pm_plan_components (plan_id, sort_order, part_number, description, supplier, cost) VALUES (?, ?, ?, ?, ?, ?)',
      [planId, index, component.part_number || null, component.description || null, component.supplier || null, Number(component.cost) || 0]
    );
  });
}

// Reconcile guidance photos: existing items (carry an id) keep their stored blob and
// only update caption/order; new items (carry data) are inserted; missing ones are removed.
function writePhotos(planId, photos) {
  const existing = all('SELECT id FROM pm_plan_photos WHERE plan_id = ?', [planId]).map((r) => r.id);
  const keep = new Set();
  (photos || []).forEach((photo, index) => {
    if (photo.id && existing.includes(photo.id)) {
      keep.add(photo.id);
      run('UPDATE pm_plan_photos SET caption = ?, sort_order = ? WHERE id = ? AND plan_id = ?', [photo.caption || null, index, photo.id, planId]);
    } else if (photo.data) {
      const result = run(
        'INSERT INTO pm_plan_photos (plan_id, name, mime_type, caption, data_base64, sort_order, created_at) VALUES (?, ?, ?, ?, ?, ?, ?)',
        [planId, photo.name || null, photo.mime || photo.mime_type || 'image/jpeg', photo.caption || null, photo.data, index, now()]
      );
      keep.add(result.lastInsertRowid);
    }
  });
  for (const id of existing) {
    if (!keep.has(id)) run('DELETE FROM pm_plan_photos WHERE id = ?', [id]);
  }
}

// Estimated minutes are derived from the step times when steps are supplied.
function resolveEstimatedMinutes(body, fallback) {
  if (Array.isArray(body.steps)) {
    const total = stepsMinutes(body.steps);
    if (total > 0) return total;
  }
  if (body.estimated_minutes != null && body.estimated_minutes !== '') return Number(body.estimated_minutes);
  return fallback ?? null;
}

function createPlan(body, userId, companyId) {
  const ts = now();
  return tx(() => {
    const result = run(
      `INSERT INTO pm_plans (entity_id, name, description, category, frequency_value, frequency_unit, estimated_minutes, instructions, lifespan_adjust, created_by, created_at, updated_at)
       VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
      [
        companyId || null,
        body.name || 'PM plan', body.description || null, body.category || null,
        Number(body.frequency_value) || 1, FREQUENCY_UNITS.includes(body.frequency_unit) ? body.frequency_unit : 'months',
        resolveEstimatedMinutes(body, null), body.instructions || null, body.lifespan_adjust ? 1 : 0,
        userId, ts, ts
      ]
    );
    writeSteps(result.lastInsertRowid, body.steps);
    writeComponents(result.lastInsertRowid, body.components);
    writePlanMeters(result.lastInsertRowid, body.meters);
    writePhotos(result.lastInsertRowid, body.photos);
    audit(userId, 'create', 'pm_plan', result.lastInsertRowid, null, { name: body.name });
    return getPlan(result.lastInsertRowid);
  });
}

function updatePlan(id, body, userId) {
  const before = one('SELECT * FROM pm_plans WHERE id = ?', [id]);
  if (!before) return null;
  return tx(() => {
    run(
      `UPDATE pm_plans SET name = ?, description = ?, category = ?, frequency_value = ?, frequency_unit = ?,
         estimated_minutes = ?, instructions = ?, lifespan_adjust = ?, updated_at = ? WHERE id = ?`,
      [
        body.name ?? before.name, body.description ?? before.description, body.category ?? before.category,
        body.frequency_value != null ? Number(body.frequency_value) : before.frequency_value,
        FREQUENCY_UNITS.includes(body.frequency_unit) ? body.frequency_unit : before.frequency_unit,
        resolveEstimatedMinutes(body, before.estimated_minutes),
        body.instructions ?? before.instructions,
        body.lifespan_adjust !== undefined ? (body.lifespan_adjust ? 1 : 0) : before.lifespan_adjust,
        now(), id
      ]
    );
    if (Array.isArray(body.steps)) writeSteps(id, body.steps);
    if (Array.isArray(body.components)) writeComponents(id, body.components);
    if (Array.isArray(body.meters)) writePlanMeters(id, body.meters);
    if (Array.isArray(body.photos)) writePhotos(id, body.photos);
    audit(userId, 'update', 'pm_plan', id, before, { name: body.name });
    return getPlan(id);
  });
}

function deletePlan(id, userId) {
  const before = one('SELECT * FROM pm_plans WHERE id = ?', [id]);
  if (!before) return false;
  run('DELETE FROM pm_plans WHERE id = ?', [id]);
  audit(userId, 'delete', 'pm_plan', id, before, null);
  return true;
}

// ---- Per-asset PM schedules ------------------------------------------------

function assetPmRows(assetId) {
  const settings = engineSettings();
  return all(
    `SELECT ap.*, p.name AS plan_name, p.description AS plan_description, p.instructions AS plan_instructions,
       u.name AS assigned_to_name, a.in_service_date AS asset_in_service_date, a.useful_life_months AS asset_useful_life_months
     FROM asset_pm_plans ap
     LEFT JOIN pm_plans p ON p.id = ap.plan_id
     LEFT JOIN users u ON u.id = ap.assigned_to
     LEFT JOIN assets a ON a.id = ap.asset_id
     WHERE ap.asset_id = ?
     ORDER BY ap.active DESC, ap.next_due_date IS NULL, ap.next_due_date`,
    [assetId]
  ).map((row) => {
    const components = row.plan_id ? planComponents(row.plan_id) : [];
    const completions = all(
      `SELECT c.id, c.completed_at, c.notes, c.notes_json, c.steps_json, c.cost, c.components_json,
         c.rating_safety, c.rating_physical, c.rating_operating,
         CASE WHEN c.signature IS NOT NULL THEN 1 ELSE 0 END AS has_signature, c.next_due_date,
         u.name AS completed_by_name,
         (SELECT COUNT(*) FROM pm_completion_photos ph WHERE ph.completion_id = c.id) AS photo_count
       FROM pm_completions c LEFT JOIN users u ON u.id = c.completed_by
       WHERE c.asset_pm_id = ? ORDER BY c.completed_at DESC LIMIT 12`,
      [row.id]
    ).map((c) => ({
      ...c,
      has_signature: Boolean(c.has_signature),
      notes: parseJson(c.notes_json, c.notes ? [c.notes] : []),
      steps: parseJson(c.steps_json, []),
      components: parseJson(c.components_json, []),
      ratings: { safety: c.rating_safety, physical: c.rating_physical, operating: c.rating_operating }
    }));
    const totalCost = round2(completions.reduce((sum, c) => sum + Number(c.cost || 0), 0));
    const meters = assetPmMeters(row.id);
    // Re-derive the per-signal breakdown for display (the persisted next_due_date stays authoritative).
    const projection = computeNextDue(
      { lastDate: row.last_completed_date || row.start_date, frequency_value: row.frequency_value, frequency_unit: row.frequency_unit, lifespan_adjust: Boolean(row.lifespan_adjust) },
      { in_service_date: row.asset_in_service_date, useful_life_months: row.asset_useful_life_months },
      meters,
      settings,
      todayStr()
    );
    return {
      ...row,
      active: Boolean(row.active),
      lifespan_adjust: Boolean(row.lifespan_adjust),
      steps: row.plan_id ? planSteps(row.plan_id) : [],
      plan_photos: row.plan_id ? planPhotos(row.plan_id) : [],
      components,
      meters,
      signals: projection.signals,
      due_driver: projection.driver,
      expected_cost: componentsTotal(components),
      total_cost: totalCost,
      last_cost: completions[0] ? round2(completions[0].cost) : 0,
      completions
    };
  });
}

function attachPlan(assetId, body, userId) {
  const ts = now();
  const plan = body.plan_id ? one('SELECT * FROM pm_plans WHERE id = ?', [body.plan_id]) : null;
  const value = Number(body.frequency_value) || (plan ? plan.frequency_value : 1);
  const unit = FREQUENCY_UNITS.includes(body.frequency_unit) ? body.frequency_unit : (plan ? plan.frequency_unit : 'months');
  const startDate = body.start_date || todayStr();
  const nextDue = body.next_due_date || startDate;
  const lifespanAdjust = body.lifespan_adjust !== undefined ? (body.lifespan_adjust ? 1 : 0) : (plan && plan.lifespan_adjust ? 1 : 0);
  const result = run(
    `INSERT INTO asset_pm_plans (asset_id, plan_id, frequency_value, frequency_unit, start_date, end_date, next_due_date, assigned_to, active, notes, lifespan_adjust, created_at, updated_at)
     VALUES (?, ?, ?, ?, ?, ?, ?, ?, 1, ?, ?, ?, ?)`,
    [assetId, body.plan_id || null, value, unit, startDate, body.end_date || null, nextDue, body.assigned_to || null, body.notes || null, lifespanAdjust, ts, ts]
  );
  // Copy the plan's meter definitions onto the schedule; the first threshold is one interval out.
  const meters = Array.isArray(body.meters) ? body.meters : (body.plan_id ? planMeters(body.plan_id) : []);
  meters.forEach((meter, index) => {
    const label = (meter.label || '').trim();
    if (!label) return;
    const interval = Number(meter.usage_interval) || 0;
    run(
      `INSERT INTO asset_pm_meters (asset_pm_id, sort_order, label, unit, usage_interval, baseline_reading, due_at_reading)
       VALUES (?, ?, ?, ?, ?, 0, ?)`,
      [result.lastInsertRowid, index, label, (meter.unit || '').trim() || null, interval, interval > 0 ? interval : null]
    );
  });
  audit(userId, 'attach', 'asset_pm', result.lastInsertRowid, null, { asset_id: assetId, plan_id: body.plan_id });
  return one('SELECT * FROM asset_pm_plans WHERE id = ?', [result.lastInsertRowid]);
}

function updateAssetPm(assetId, apId, body, userId) {
  const before = one('SELECT * FROM asset_pm_plans WHERE id = ? AND asset_id = ?', [apId, assetId]);
  if (!before) return null;
  run(
    `UPDATE asset_pm_plans SET frequency_value = ?, frequency_unit = ?, start_date = ?, end_date = ?,
       next_due_date = ?, assigned_to = ?, active = ?, notes = ?, lifespan_adjust = ?, updated_at = ? WHERE id = ?`,
    [
      body.frequency_value != null ? Number(body.frequency_value) : before.frequency_value,
      FREQUENCY_UNITS.includes(body.frequency_unit) ? body.frequency_unit : before.frequency_unit,
      body.start_date ?? before.start_date,
      body.end_date !== undefined ? body.end_date : before.end_date,
      body.next_due_date ?? before.next_due_date,
      body.assigned_to !== undefined ? body.assigned_to : before.assigned_to,
      body.active === undefined ? before.active : (body.active ? 1 : 0),
      body.notes ?? before.notes,
      body.lifespan_adjust !== undefined ? (body.lifespan_adjust ? 1 : 0) : before.lifespan_adjust,
      now(), apId
    ]
  );
  audit(userId, 'update', 'asset_pm', apId, before, body);
  return one('SELECT * FROM asset_pm_plans WHERE id = ?', [apId]);
}

function detachAssetPm(assetId, apId, userId) {
  const result = run('DELETE FROM asset_pm_plans WHERE id = ? AND asset_id = ?', [apId, assetId]);
  if (!result.changes) return false;
  audit(userId, 'detach', 'asset_pm', apId, null, { asset_id: assetId });
  return true;
}

function clampRating(value) {
  if (value == null || value === '') return null;
  return Math.max(1, Math.min(5, Number(value)));
}

// Composite next-due for a schedule given the date it was last serviced. Loads the schedule's meters
// (with their reading history) and the owning asset's life, runs the earliest-wins engine, and applies
// the asset's maintenance end-date cutoff. Shared by completion and standalone reading logs.
function scheduleNextDue(ap, lastDate) {
  const asset = one('SELECT in_service_date, useful_life_months FROM assets WHERE id = ?', [ap.asset_id]) || {};
  const projection = computeNextDue(
    { lastDate, frequency_value: ap.frequency_value, frequency_unit: ap.frequency_unit, lifespan_adjust: Boolean(ap.lifespan_adjust) },
    asset,
    assetPmMeters(ap.id),
    engineSettings(),
    todayStr()
  );
  let nextDue = projection.next_due_date;
  let active = ap.active;
  if (ap.end_date && nextDue && nextDue > ap.end_date) {
    nextDue = null;
    active = 0; // schedule complete — past the asset's maintenance end date
  }
  return { nextDue, active };
}

// Record a meter reading against a schedule's meter (resets its baseline/threshold when this is a
// service completion). Insert into the log so the usage-rate projection stays current.
function recordMeterReading(meter, reading, readingDate, source, completionId, userId) {
  const value = Number(reading);
  if (!Number.isFinite(value)) return;
  if (source === 'completion') {
    // Completing service resets the cycle: the next threshold is one interval past this reading.
    const dueAt = Number(meter.usage_interval) > 0 ? value + Number(meter.usage_interval) : null;
    run('UPDATE asset_pm_meters SET baseline_reading = ?, due_at_reading = ?, last_reading = ?, last_reading_date = ? WHERE id = ?',
      [value, dueAt, value, readingDate, meter.id]);
  } else {
    run('UPDATE asset_pm_meters SET last_reading = ?, last_reading_date = ? WHERE id = ?', [value, readingDate, meter.id]);
  }
  run('INSERT INTO pm_meter_readings (asset_pm_meter_id, reading, reading_date, source, completion_id, created_by, created_at) VALUES (?, ?, ?, ?, ?, ?, ?)',
    [meter.id, value, readingDate, source, completionId || null, userId || null, now()]);
}

function completePm(assetId, apId, body, userId) {
  const ap = one('SELECT * FROM asset_pm_plans WHERE id = ? AND asset_id = ?', [apId, assetId]);
  if (!ap) return null;
  if (!body.signature) throw Object.assign(new Error('A signature is required to complete a PM'), { status: 400 });

  const ts = now();
  const completedDate = (body.completed_at || ts).slice(0, 10);
  const planComps = ap.plan_id ? planComponents(ap.plan_id) : [];
  const components = Array.isArray(body.components) ? body.components : planComps;
  const cost = body.cost != null && body.cost !== '' ? round2(body.cost) : componentsTotal(planComps);
  const notesList = Array.isArray(body.notes_list) ? body.notes_list.filter((n) => String(n || '').trim()) : (body.notes ? [body.notes] : []);
  const ratings = body.ratings || {};
  const photos = Array.isArray(body.photos) ? body.photos.filter((p) => p && p.data) : [];
  const meterReadings = Array.isArray(body.meter_readings) ? body.meter_readings : [];

  return tx(() => {
    const inserted = run(
      `INSERT INTO pm_completions (asset_pm_id, completed_at, completed_by, notes, notes_json, steps_json, cost, components_json,
         signature, rating_safety, rating_physical, rating_operating, next_due_date, created_at)
       VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
      [
        apId, ts, userId, notesList.join('\n') || null, json(notesList), json(body.steps || []), cost, json(components),
        body.signature, clampRating(ratings.safety), clampRating(ratings.physical), clampRating(ratings.operating), null, ts
      ]
    );
    for (const photo of photos) {
      run('INSERT INTO pm_completion_photos (completion_id, name, mime_type, data_base64, created_at) VALUES (?, ?, ?, ?, ?)', [
        inserted.lastInsertRowid, photo.name || null, photo.mime || photo.mime_type || 'image/jpeg', photo.data, ts
      ]);
    }
    // Reset each meter's cycle from the reading captured during service.
    for (const entry of meterReadings) {
      const meter = one('SELECT * FROM asset_pm_meters WHERE id = ? AND asset_pm_id = ?', [entry.asset_pm_meter_id, apId]);
      if (meter && entry.reading != null && entry.reading !== '') {
        recordMeterReading(meter, entry.reading, completedDate, 'completion', inserted.lastInsertRowid, userId);
      }
    }
    // Earliest-wins next-due now reflects the reset meters and the lifespan curve.
    const { nextDue, active } = scheduleNextDue(ap, completedDate);
    run('UPDATE pm_completions SET next_due_date = ? WHERE id = ?', [nextDue, inserted.lastInsertRowid]);
    run('UPDATE asset_pm_plans SET last_completed_date = ?, next_due_date = ?, active = ?, updated_at = ? WHERE id = ?', [completedDate, nextDue, active, ts, apId]);
    audit(userId, 'complete', 'asset_pm', apId, null, { next_due_date: nextDue, completion_id: inserted.lastInsertRowid });
    return one('SELECT * FROM asset_pm_plans WHERE id = ?', [apId]);
  });
}

// Standalone usage reading (quick-log / inspection) — updates the meter's current reading and
// recomputes the schedule's next-due so a faster-than-expected usage rate pulls service in sooner.
function logReading(assetId, apId, body, userId) {
  const ap = one('SELECT * FROM asset_pm_plans WHERE id = ? AND asset_id = ?', [apId, assetId]);
  if (!ap) return null;
  const meter = one('SELECT * FROM asset_pm_meters WHERE id = ? AND asset_pm_id = ?', [body.asset_pm_meter_id, apId]);
  if (!meter) throw Object.assign(new Error('Meter not found on this schedule'), { status: 404 });
  if (body.reading == null || body.reading === '' || !Number.isFinite(Number(body.reading))) {
    throw Object.assign(new Error('A numeric reading is required'), { status: 400 });
  }
  const readingDate = (body.reading_date || now()).slice(0, 10);
  const source = body.source === 'inspection' ? 'inspection' : 'manual';
  return tx(() => {
    recordMeterReading(meter, body.reading, readingDate, source, null, userId);
    const lastDate = ap.last_completed_date || ap.start_date || readingDate;
    const { nextDue, active } = scheduleNextDue(ap, lastDate);
    run('UPDATE asset_pm_plans SET next_due_date = ?, active = ?, updated_at = ? WHERE id = ?', [nextDue, active, now(), apId]);
    audit(userId, 'reading', 'asset_pm', apId, null, { meter: meter.label, reading: Number(body.reading), next_due_date: nextDue });
    return one('SELECT * FROM asset_pm_plans WHERE id = ?', [apId]);
  });
}

function listCompletions(query = {}) {
  return all(
    `SELECT c.id, c.completed_at, c.cost, c.notes_json, c.rating_safety, c.rating_physical, c.rating_operating,
       CASE WHEN c.signature IS NOT NULL THEN 1 ELSE 0 END AS has_signature,
       u.name AS completed_by_name, a.asset_id AS asset_code, a.description AS asset_description, p.name AS plan_name,
       (SELECT COUNT(*) FROM pm_completion_photos ph WHERE ph.completion_id = c.id) AS photo_count
     FROM pm_completions c
     JOIN asset_pm_plans ap ON ap.id = c.asset_pm_id
     JOIN assets a ON a.id = ap.asset_id
     LEFT JOIN pm_plans p ON p.id = ap.plan_id
     LEFT JOIN users u ON u.id = c.completed_by
     WHERE (? IS NULL OR ap.asset_id = ?)
     ORDER BY c.completed_at DESC, c.id DESC
     LIMIT 500`,
    [query.asset_id || null, query.asset_id || null]
  ).map((r) => ({ ...r, has_signature: Boolean(r.has_signature), notes: parseJson(r.notes_json, []) }));
}

function getCompletion(id) {
  const row = one(
    `SELECT c.*, u.name AS completed_by_name, a.asset_id AS asset_code, a.description AS asset_description, p.name AS plan_name
     FROM pm_completions c
     JOIN asset_pm_plans ap ON ap.id = c.asset_pm_id
     JOIN assets a ON a.id = ap.asset_id
     LEFT JOIN pm_plans p ON p.id = ap.plan_id
     LEFT JOIN users u ON u.id = c.completed_by
     WHERE c.id = ?`,
    [id]
  );
  if (!row) return null;
  return {
    id: row.id,
    asset_code: row.asset_code,
    asset_description: row.asset_description,
    plan_name: row.plan_name,
    completed_at: row.completed_at,
    completed_by_name: row.completed_by_name,
    cost: row.cost,
    notes: parseJson(row.notes_json, row.notes ? [row.notes] : []),
    steps: parseJson(row.steps_json, []),
    components: parseJson(row.components_json, []),
    signature: row.signature || null,
    ratings: { safety: row.rating_safety, physical: row.rating_physical, operating: row.rating_operating },
    photos: all('SELECT id, name, mime_type, data_base64 FROM pm_completion_photos WHERE completion_id = ? ORDER BY id', [row.id])
      .map((p) => ({ id: p.id, name: p.name, mime: p.mime_type, data: p.data_base64 }))
  };
}

// ---- Settings & alert candidates ------------------------------------------

function getSettings() {
  const rows = all("SELECT key, value FROM app_settings WHERE key LIKE 'pm_%'");
  const map = Object.fromEntries(rows.map((r) => [r.key, r.value]));
  return {
    pm_default_frequency_value: Number(map.pm_default_frequency_value || 3),
    pm_default_frequency_unit: map.pm_default_frequency_unit || 'months',
    pm_lead_days: Number(map.pm_lead_days || 7),
    pm_usage_tracking_enabled: map.pm_usage_tracking_enabled === '1',
    pm_lifespan_curve_enabled: map.pm_lifespan_curve_enabled === '1',
    pm_lifespan_min_factor: map.pm_lifespan_min_factor != null ? Number(map.pm_lifespan_min_factor) : 0.5,
    pm_lifespan_curve_exponent: map.pm_lifespan_curve_exponent != null ? Number(map.pm_lifespan_curve_exponent) : 2,
    // Nightly recompute job: refreshes projected due-dates so dynamic schedules don't drift between
    // completions/readings. pm_last_recompute_at is job-managed (read-only to clients).
    pm_recompute_enabled: map.pm_recompute_enabled === '1',
    pm_recompute_hour: map.pm_recompute_hour != null ? Number(map.pm_recompute_hour) : 2,
    pm_last_recompute_at: map.pm_last_recompute_at || null
  };
}

function saveSettings(body, userId) {
  const set = (k, v) => run('INSERT INTO app_settings (key, value, updated_at) VALUES (?, ?, ?) ON CONFLICT(key) DO UPDATE SET value = excluded.value, updated_at = excluded.updated_at', [k, String(v), now()]);
  if (body.pm_default_frequency_value !== undefined) set('pm_default_frequency_value', Number(body.pm_default_frequency_value) || 3);
  if (body.pm_default_frequency_unit !== undefined) set('pm_default_frequency_unit', FREQUENCY_UNITS.includes(body.pm_default_frequency_unit) ? body.pm_default_frequency_unit : 'months');
  if (body.pm_lead_days !== undefined) set('pm_lead_days', Number(body.pm_lead_days) || 7);
  if (body.pm_usage_tracking_enabled !== undefined) set('pm_usage_tracking_enabled', body.pm_usage_tracking_enabled ? 1 : 0);
  if (body.pm_lifespan_curve_enabled !== undefined) set('pm_lifespan_curve_enabled', body.pm_lifespan_curve_enabled ? 1 : 0);
  // Floor multiplier is clamped to a sane 0.1–1.0; exponent to 0.5–6.
  if (body.pm_lifespan_min_factor !== undefined) set('pm_lifespan_min_factor', Math.min(1, Math.max(0.1, Number(body.pm_lifespan_min_factor) || 0.5)));
  if (body.pm_lifespan_curve_exponent !== undefined) set('pm_lifespan_curve_exponent', Math.min(6, Math.max(0.5, Number(body.pm_lifespan_curve_exponent) || 2)));
  if (body.pm_recompute_enabled !== undefined) set('pm_recompute_enabled', body.pm_recompute_enabled ? 1 : 0);
  if (body.pm_recompute_hour !== undefined) set('pm_recompute_hour', Math.min(23, Math.max(0, Math.round(Number(body.pm_recompute_hour)) || 0)));
  audit(userId, 'update', 'pm_settings', null, null, body);
  return getSettings();
}

// Map persisted settings into the shape pmScheduling.computeNextDue expects.
function engineSettings(settings = getSettings()) {
  return {
    usage_enabled: settings.pm_usage_tracking_enabled,
    curve_enabled: settings.pm_lifespan_curve_enabled,
    min_factor: settings.pm_lifespan_min_factor,
    curve_exponent: settings.pm_lifespan_curve_exponent
  };
}

// Alert candidates for PM schedules that are due/overdue.
function pmAlertCandidates() {
  const lead = getSettings().pm_lead_days;
  const today = todayStr();
  const horizon = new Date(Date.now() + lead * 86400000).toISOString().slice(0, 10);
  const rows = all(
    `SELECT ap.*, p.name AS plan_name, a.asset_id AS asset_code
     FROM asset_pm_plans ap
     LEFT JOIN pm_plans p ON p.id = ap.plan_id
     LEFT JOIN assets a ON a.id = ap.asset_id
     WHERE ap.active = 1 AND ap.next_due_date IS NOT NULL`
  );
  const list = [];
  for (const ap of rows) {
    const name = ap.plan_name || 'Preventative maintenance';
    const where = ap.asset_code ? ` on ${ap.asset_code}` : '';
    // Meters at/over their threshold are reported in the alert text (e.g. "Operating Hours 512/500").
    const crossed = assetPmMeters(ap.id)
      .filter((m) => m.last_reading != null && m.due_at_reading != null && Number(m.last_reading) >= Number(m.due_at_reading))
      .map((m) => `${m.label} ${Math.round(m.last_reading)}/${Math.round(m.due_at_reading)}${m.unit ? ' ' + m.unit : ''}`);
    const usageNote = crossed.length ? ` Usage threshold reached: ${crossed.join('; ')}.` : '';
    if (ap.next_due_date < today || crossed.length) {
      list.push({ type: 'pm_overdue', reference_type: 'asset_pm', reference_id: ap.id, asset_id: ap.asset_id, severity: 'critical', title: `PM overdue: ${name}`, message: `${name}${where} was due ${ap.next_due_date}.${usageNote}`, due_date: ap.next_due_date });
    } else if (ap.next_due_date <= horizon) {
      list.push({ type: 'pm_due', reference_type: 'asset_pm', reference_id: ap.id, asset_id: ap.asset_id, severity: 'warning', title: `PM due: ${name}`, message: `${name}${where} is due ${ap.next_due_date}.${usageNote}`, due_date: ap.next_due_date });
    }
  }
  return list;
}

// ---- Nightly recompute -----------------------------------------------------

// Re-derive next_due_date for every active schedule. Usage projections shift as time passes (a meter
// that has crossed its threshold becomes due "today"), so without a periodic sweep a schedule that
// isn't completed or read keeps a stale projected date. Cheap: one engine pass per active schedule.
function recomputeAllSchedules(userId) {
  const rows = all('SELECT * FROM asset_pm_plans WHERE active = 1');
  let updated = 0;
  for (const ap of rows) {
    const lastDate = ap.last_completed_date || ap.start_date || todayStr();
    const { nextDue, active } = scheduleNextDue(ap, lastDate);
    if (nextDue !== ap.next_due_date || (active ? 1 : 0) !== (ap.active ? 1 : 0)) {
      run('UPDATE asset_pm_plans SET next_due_date = ?, active = ?, updated_at = ? WHERE id = ?', [nextDue, active, now(), ap.id]);
      updated += 1;
    }
  }
  const ranAt = now();
  run(
    "INSERT INTO app_settings (key, value, updated_at) VALUES ('pm_last_recompute_at', ?, ?) ON CONFLICT(key) DO UPDATE SET value = excluded.value, updated_at = excluded.updated_at",
    [ranAt, ranAt]
  );
  if (userId) audit(userId, 'recompute', 'asset_pm', null, null, { scanned: rows.length, updated });
  return { scanned: rows.length, updated, ran_at: ranAt };
}

// Self-gating entry point for the scheduler: runs once per day at the configured hour when enabled.
function runScheduledRecompute() {
  const s = getSettings();
  if (!s.pm_recompute_enabled) return { skipped: 'disabled' };
  if (new Date().getHours() !== s.pm_recompute_hour) return { skipped: 'off-hour' };
  if (s.pm_last_recompute_at && String(s.pm_last_recompute_at).slice(0, 10) === todayStr()) return { skipped: 'already-ran-today' };
  return recomputeAllSchedules(null);
}

// Maintenance-cost "ledger" for the PM book: actual PM spend per asset for a year.
function pmBookLedger(year, companyId) {
  const rows = all(
    `SELECT c.cost, c.completed_at, a.asset_id, a.description
     FROM pm_completions c
     JOIN asset_pm_plans ap ON ap.id = c.asset_pm_id
     JOIN assets a ON a.id = ap.asset_id
     WHERE (? IS NULL OR a.entity_id = ?)`,
    [companyId || null, companyId || null]
  );
  const byAsset = {};
  let total = 0;
  let count = 0;
  for (const row of rows) {
    if (yearOf(row.completed_at) !== Number(year)) continue;
    const cost = Number(row.cost || 0);
    const entry = byAsset[row.asset_id] || (byAsset[row.asset_id] = { asset_id: row.asset_id, description: row.description, completions: 0, cost: 0, last_service: null });
    entry.completions += 1;
    entry.cost += cost;
    const day = String(row.completed_at).slice(0, 10);
    if (!entry.last_service || day > entry.last_service) entry.last_service = day;
    total += cost;
    count += 1;
  }
  const assets = Object.values(byAsset).map((a) => ({ ...a, cost: round2(a.cost) })).sort((a, b) => b.cost - a.cost);
  const accounts = [
    { account: '6450', type: 'PM / maintenance expense', debit: round2(total), credit: 0 },
    { account: '2000', type: 'Maintenance clearing', debit: 0, credit: round2(total) }
  ];
  return {
    year: Number(year),
    kind: 'maintenance',
    rule_set: {},
    summary: { assets: assets.length, completions: count, cost: round2(total) },
    accounts,
    accountTotals: { debit: round2(total), credit: round2(total) },
    assets
  };
}

module.exports = {
  FREQUENCY_UNITS,
  addInterval,
  assetPmRows,
  pmBookLedger,
  attachPlan,
  completePm,
  createPlan,
  deletePlan,
  detachAssetPm,
  getCompletion,
  getPlan,
  listCompletions,
  getSettings,
  listPlans,
  logReading,
  pmAlertCandidates,
  recomputeAllSchedules,
  runScheduledRecompute,
  saveSettings,
  updateAssetPm,
  updatePlan
};