const router = require('express').Router();
const { body } = require('express-validator');
const prisma = require('../lib/prisma');
const cache = require('../lib/cache');
const auditMiddleware = require('../middleware/auditMiddleware');
const { validateRequest } = require('../middleware/errorHandler');
const { v4: uuidv4 } = require('uuid');
const { resolveTemplate, DEFAULT_TEMPLATE, UUID_RE } = require('../lib/defaultTemplate');

const experimentValidation = [
  body('title').trim().notEmpty().withMessage('Title is required').isLength({ max: 255 }).withMessage('Title must be ≤255 characters'),
];

// ── Template validation helpers ────────────────────────────────────────────────

const BUILTIN_FIELD_IDS = new Set(DEFAULT_TEMPLATE.map((f) => f.fieldId));
const BUILTIN_KEYS      = new Set(DEFAULT_TEMPLATE.map((f) => f.key));
const VALID_TYPES       = new Set(['text', 'textarea']);

function validateTemplate(template) {
  if (!Array.isArray(template)) return 'template must be an array';
  if (template.length > 50) return 'template may have at most 50 fields';

  const seenFieldIds = new Set();
  const seenKeys     = new Set();

  for (const field of template) {
    // ── fieldId ────────────────────────────────────────────────────────────────
    if (!field.fieldId || !UUID_RE.test(field.fieldId))
      return `each field must have a valid UUID fieldId (got: ${field.fieldId})`;
    if (seenFieldIds.has(field.fieldId))
      return `duplicate fieldId "${field.fieldId}"`;
    seenFieldIds.add(field.fieldId);

    // Builtin fields must keep their original fieldIds
    if (BUILTIN_KEYS.has(field.key) && !BUILTIN_FIELD_IDS.has(field.fieldId))
      return `builtin field "${field.key}" must keep its original fieldId`;

    // ── key ────────────────────────────────────────────────────────────────────
    if (!field.key || typeof field.key !== 'string') return 'each field must have a string key';
    if (!/^[a-z0-9_]+$/.test(field.key)) return `key "${field.key}" must be lowercase alphanumeric/underscore only`;
    if (field.key.length > 64) return `key "${field.key}" must be ≤64 characters`;
    if (seenKeys.has(field.key)) return `duplicate key "${field.key}"`;
    seenKeys.add(field.key);

    // ── label ──────────────────────────────────────────────────────────────────
    if (!field.label || typeof field.label !== 'string' || !field.label.trim())
      return `field "${field.key}" must have a non-empty label`;
    if (field.label.length > 128) return `label for "${field.key}" must be ≤128 characters`;

    // ── type / active / builtin ────────────────────────────────────────────────
    if (!VALID_TYPES.has(field.type)) return `field "${field.key}" type must be "text" or "textarea"`;
    if (typeof field.active !== 'boolean') return `field "${field.key}" must have a boolean active flag`;

    if (BUILTIN_KEYS.has(field.key) && field.builtin !== true)
      return `field "${field.key}" is a builtin field and cannot be made non-builtin`;
    if (!BUILTIN_KEYS.has(field.key) && field.builtin !== false)
      return `custom field "${field.key}" must have builtin: false`;

    // ── abbr / unit / width ────────────────────────────────────────────────────
    if (field.abbr !== undefined && field.abbr !== null) {
      if (typeof field.abbr !== 'string') return `abbr for "${field.key}" must be a string`;
      if (field.abbr.length > 10) return `abbr for "${field.key}" must be ≤10 characters`;
    }
    if (field.unit !== undefined && field.unit !== null) {
      if (typeof field.unit !== 'string') return `unit for "${field.key}" must be a string`;
      if (field.unit.length > 10) return `unit for "${field.key}" must be ≤10 characters`;
    }
    if (field.width !== undefined && field.width !== null) {
      if (!Number.isInteger(field.width) || field.width < 1 || field.width > 100)
        return `width for "${field.key}" must be an integer between 1 and 100`;
    }

    // ── tags ───────────────────────────────────────────────────────────────────
    if (field.tags !== undefined) {
      if (!Array.isArray(field.tags)) return `tags for "${field.key}" must be an array`;
      if (field.tags.length > 50) return `field "${field.key}" may have at most 50 tags`;
      for (const tag of field.tags) {
        if (typeof tag !== 'string' || !tag.trim()) return `tags for "${field.key}" must be non-empty strings`;
        if (tag.length > 512) return `a tag in "${field.key}" exceeds 512 characters`;
      }
    }

    if (field.tagsDisabled !== undefined && typeof field.tagsDisabled !== 'boolean')
      return `tagsDisabled for "${field.key}" must be a boolean`;
  }
  return null;
}

/**
 * Back-fill any missing fieldIds (handles records saved before this feature).
 * Builtin fields get their canonical IDs; custom fields get fresh UUIDs.
 */
function ensureFieldIds(template) {
  const builtinById = Object.fromEntries(DEFAULT_TEMPLATE.map((f) => [f.key, f.fieldId]));
  return template.map((f) => ({
    ...f,
    fieldId: f.fieldId || (f.builtin ? builtinById[f.key] : uuidv4()),
    tags: f.tags ?? [],   // always return tags array (empty if not yet set)
  }));
}

// ── Experiment CRUD ────────────────────────────────────────────────────────────

// GET /api/experiments
router.get('/', async (req, res, next) => {
  try {
    const experiments = await prisma.experiment.findMany({
      orderBy: { created_at: 'desc' },
      include: { _count: { select: { animals: true } } },
    });
    res.json(experiments);
  } catch (err) { next(err); }
});

// GET /api/experiments/:id
router.get('/:id', async (req, res, next) => {
  try {
    const experiment = await prisma.experiment.findUnique({
      where: { id: req.params.id },
      include: { animals: true },
    });
    if (!experiment) return res.status(404).json({ error: 'Experiment not found' });
    experiment.template = ensureFieldIds(resolveTemplate(experiment.template));
    res.json(experiment);
  } catch (err) { next(err); }
});

// POST /api/experiments
router.post('/', experimentValidation, validateRequest, async (req, res, next) => {
  try {
    const { title } = req.body;
    const experiment = await prisma.experiment.create({ data: { title } });
    await prisma.auditLog.create({
      data: { table_name: 'experiments', record_id: experiment.id, action: 'CREATE', changes: { before: null, after: experiment } },
    });
    experiment.template = ensureFieldIds(resolveTemplate(experiment.template));
    res.status(201).json(experiment);
  } catch (err) { next(err); }
});

// PUT /api/experiments/:id
router.put(
  '/:id',
  auditMiddleware('experiments', prisma.experiment),
  experimentValidation,
  validateRequest,
  async (req, res, next) => {
    try {
      const { title } = req.body;
      const experiment = await prisma.experiment.update({ where: { id: req.params.id }, data: { title } });
      experiment.template = ensureFieldIds(resolveTemplate(experiment.template));
      res.json(experiment);
    } catch (err) { next(err); }
  }
);

// DELETE /api/experiments/:id
router.delete(
  '/:id',
  auditMiddleware('experiments', prisma.experiment),
  async (req, res, next) => {
    try {
      await prisma.experiment.delete({ where: { id: req.params.id } });
      res.status(204).send();
    } catch (err) { next(err); }
  }
);

// ── Subject-template validation ────────────────────────────────────────────────

function validateSubjectTemplate(template) {
  if (!Array.isArray(template)) return 'subject_info_template must be an array';
  if (template.length > 50) return 'subject_info_template may have at most 50 fields';

  const seenFieldIds = new Set();
  const seenKeys     = new Set();

  for (const field of template) {
    if (!field.fieldId || !UUID_RE.test(field.fieldId))
      return `each field must have a valid UUID fieldId (got: ${field.fieldId})`;
    if (seenFieldIds.has(field.fieldId)) return `duplicate fieldId "${field.fieldId}"`;
    seenFieldIds.add(field.fieldId);

    if (!field.key || typeof field.key !== 'string') return 'each field must have a string key';
    if (!/^[a-z0-9_]+$/.test(field.key)) return `key "${field.key}" must be lowercase alphanumeric/underscore only`;
    if (field.key.length > 64) return `key "${field.key}" must be ≤64 characters`;
    if (seenKeys.has(field.key)) return `duplicate key "${field.key}"`;
    seenKeys.add(field.key);

    if (!field.label || typeof field.label !== 'string' || !field.label.trim())
      return `field "${field.key}" must have a non-empty label`;
    if (field.label.length > 128) return `label for "${field.key}" must be ≤128 characters`;

    if (!VALID_TYPES.has(field.type)) return `field "${field.key}" type must be "text" or "textarea"`;
    if (typeof field.active !== 'boolean') return `field "${field.key}" must have a boolean active flag`;
    if (field.builtin !== false) return `subject field "${field.key}" must have builtin: false`;

    if (field.abbr !== undefined && field.abbr !== null) {
      if (typeof field.abbr !== 'string') return `abbr for "${field.key}" must be a string`;
      if (field.abbr.length > 10) return `abbr for "${field.key}" must be ≤10 characters`;
    }
    if (field.unit !== undefined && field.unit !== null) {
      if (typeof field.unit !== 'string') return `unit for "${field.key}" must be a string`;
      if (field.unit.length > 10) return `unit for "${field.key}" must be ≤10 characters`;
    }
    if (field.width !== undefined && field.width !== null) {
      if (!Number.isInteger(field.width) || field.width < 1 || field.width > 100)
        return `width for "${field.key}" must be an integer between 1 and 100`;
    }

    if (field.tags !== undefined) {
      if (!Array.isArray(field.tags)) return `tags for "${field.key}" must be an array`;
      if (field.tags.length > 50) return `field "${field.key}" may have at most 50 tags`;
      for (const tag of field.tags) {
        if (typeof tag !== 'string' || !tag.trim()) return `tags for "${field.key}" must be non-empty strings`;
        if (tag.length > 512) return `a tag in "${field.key}" exceeds 512 characters`;
      }
    }

    if (field.tagsDisabled !== undefined && typeof field.tagsDisabled !== 'boolean')
      return `tagsDisabled for "${field.key}" must be a boolean`;
  }
  return null;
}

// Upper bound on the stored UI-preference blob. Sized to comfortably hold the known
// fields plus a full hiddenSubjects list (≤500 UUIDs ≈ 20 KB) with headroom, while
// still guarding against a client persisting an arbitrarily large object.
const PLOT_CONFIG_MAX_BYTES = 64 * 1024;

// The blob is intentionally schema-loose (clients may add display keys over time);
// only hiddenSubjects is structurally validated since the backend reasons about it.
function validatePlotConfig(config) {
  if (config === null || typeof config !== 'object' || Array.isArray(config)) {
    return 'plot_config must be an object';
  }
  // req.body is already JSON-parsed, so stringify cannot throw here.
  if (Buffer.byteLength(JSON.stringify(config), 'utf8') > PLOT_CONFIG_MAX_BYTES) {
    return 'plot_config too large';
  }
  if ('hiddenSubjects' in config) {
    const hidden = config.hiddenSubjects;
    if (!Array.isArray(hidden) || hidden.length > 500 || !hidden.every((x) => typeof x === 'string')) {
      return 'hiddenSubjects invalid';
    }
  }
  return null;
}

// ── Template endpoints ─────────────────────────────────────────────────────────

// GET /api/experiments/:id/template
router.get('/:id/template', async (req, res, next) => {
  try {
    const experiment = await prisma.experiment.findUnique({
      where: { id: req.params.id },
      select: { id: true, template: true },
    });
    if (!experiment) return res.status(404).json({ error: 'Experiment not found' });
    res.json(ensureFieldIds(resolveTemplate(experiment.template)));
  } catch (err) { next(err); }
});

// PUT /api/experiments/:id/template
router.put('/:id/template', async (req, res, next) => {
  try {
    const experiment = await prisma.experiment.findUnique({ where: { id: req.params.id } });
    if (!experiment) return res.status(404).json({ error: 'Experiment not found' });

    const template = req.body;
    const validationError = validateTemplate(template);
    if (validationError) return res.status(422).json({ error: validationError });

    const before = ensureFieldIds(resolveTemplate(experiment.template));
    const updated = await prisma.experiment.update({
      where: { id: req.params.id },
      data: { template },
    });

    await prisma.auditLog.create({
      data: {
        table_name: 'experiments',
        record_id: experiment.id,
        action: 'UPDATE',
        changes: { before: { template: before }, after: { template } },
      },
    });

    res.json(template);
  } catch (err) { next(err); }
});

// GET /api/experiments/:id/subject-template
router.get('/:id/subject-template', async (req, res, next) => {
  try {
    const experiment = await prisma.experiment.findUnique({
      where: { id: req.params.id },
      select: { id: true, subject_info_template: true },
    });
    if (!experiment) return res.status(404).json({ error: 'Experiment not found' });
    const tmpl = Array.isArray(experiment.subject_info_template) ? experiment.subject_info_template : [];
    res.json(tmpl.map((f) => ({ ...f, tags: f.tags ?? [] })));
  } catch (err) { next(err); }
});

// PUT /api/experiments/:id/subject-template
router.put('/:id/subject-template', async (req, res, next) => {
  try {
    const experiment = await prisma.experiment.findUnique({ where: { id: req.params.id } });
    if (!experiment) return res.status(404).json({ error: 'Experiment not found' });

    const template = req.body;
    const validationError = validateSubjectTemplate(template);
    if (validationError) return res.status(422).json({ error: validationError });

    const updated = await prisma.experiment.update({
      where: { id: req.params.id },
      data: { subject_info_template: template },
    });

    await prisma.auditLog.create({
      data: {
        table_name: 'experiments',
        record_id: experiment.id,
        action: 'UPDATE',
        changes: { before: { subject_info_template: experiment.subject_info_template }, after: { subject_info_template: template } },
      },
    });

    res.json(template);
  } catch (err) { next(err); }
});

// PUT /api/experiments/:id/plot-config — persist UI display settings (no audit log)
router.put('/:id/plot-config', async (req, res, next) => {
  try {
    const experiment = await prisma.experiment.findUnique({ where: { id: req.params.id } });
    if (!experiment) return res.status(404).json({ error: 'Experiment not found' });

    const config = req.body;
    const validationError = validatePlotConfig(config);
    if (validationError) return res.status(422).json({ error: validationError });

    await prisma.experiment.update({
      where: { id: req.params.id },
      data: { plot_config: config },
    });
    res.json(config);
  } catch (err) { next(err); }
});

// GET /api/experiments/:id/calendar?field=<fieldId|builtinKey>
// Returns { field, days: { "YYYY-MM-DD": count } } where count = subjects with non-empty value that day.
router.get('/:id/calendar', async (req, res, next) => {
  try {
    const field = req.query.field ?? '';
    const cacheKey = `exp:${req.params.id}:cal:${field}`;

    const cached = cache.get(cacheKey);
    if (cached) return res.json(cached);

    const exp = await prisma.experiment.findUnique({ where: { id: req.params.id } });
    if (!exp) return res.status(404).json({ error: 'Experiment not found' });

    const BUILTIN_KEYS_SET = new Set(['experiment_description', 'vitals', 'treatment', 'notes']);
    const isBuiltin = BUILTIN_KEYS_SET.has(field);

    const statuses = await prisma.dailyStatus.findMany({
      where: { animal: { experiment_id: req.params.id } },
      select: {
        date: true,
        experiment_description: true,
        vitals: true,
        treatment: true,
        notes: true,
        custom_fields: true,
      },
    });

    const days = {};
    for (const s of statuses) {
      const value = isBuiltin ? s[field] : s.custom_fields?.[field];
      if (value !== null && value !== undefined && String(value).trim() !== '') {
        const dateKey = new Date(s.date).toISOString().slice(0, 10);
        days[dateKey] = (days[dateKey] || 0) + 1;
      }
    }

    const result = { field, days };
    cache.set(cacheKey, result);
    res.json(result);
  } catch (err) { next(err); }
});

// GET /api/experiments/:id/daily-statuses  — all statuses for all subjects, analysis_summary included
// ?date=YYYY-MM-DD  — filter to a single day
// ?analysisOnly=true  — only return statuses that have a saved analysis_summary (for charts)
router.get('/:id/daily-statuses', async (req, res, next) => {
  try {
    const date         = req.query.date ?? '';
    const analysisOnly = req.query.analysisOnly === 'true';
    const cacheKey     = `exp:${req.params.id}:ds:${analysisOnly ? '1' : '0'}:${date}`;

    const cached = cache.get(cacheKey);
    if (cached) return res.json(cached);

    const exp = await prisma.experiment.findUnique({ where: { id: req.params.id } });
    if (!exp) return res.status(404).json({ error: 'Experiment not found' });

    const where = { animal: { experiment_id: req.params.id } };
    if (date) {
      const d    = new Date(date + 'T00:00:00.000Z');
      const next = new Date(d); next.setUTCDate(next.getUTCDate() + 1);
      where.date = { gte: d, lt: next };
    }

    let statuses = await prisma.dailyStatus.findMany({
      where,
      select: {
        id: true,
        animal_id: true,
        date: true,
        analysis_summary: true,
        experiment_description: true,
        vitals: true,
        treatment: true,
        notes: true,
        custom_fields: true,
      },
      orderBy: { date: 'asc' },
    });

    // Prisma 5 has no clean IS NOT NULL filter for Json? fields; filter in JS.
    // The result is cached so this only runs once per cache period.
    if (analysisOnly) {
      statuses = statuses.filter((s) => s.analysis_summary !== null);
    }

    cache.set(cacheKey, statuses);
    res.json(statuses);
  } catch (err) { next(err); }
});

module.exports = router;