// Rules-as-data validator: `runRules` is generic over any rule list and any
// record list — it doesn't know anything about provinces/countries/
// encoding specifically. Each rule carries an `id`, a `level`
// (error/warn/info), a `when` guard, a `check`, a `message` builder, and a
// `note` explaining WHY the rule exists (rationale is mandatory so a future
// reader never has to guess whether a rule is load-bearing or someone's
// guess).
//
// A rule's `check` returning `true` means "this record is FINE" (no
// finding); returning `false` produces one finding. This mirrors how the
// concrete rules below read most naturally ("is the owner tag defined?"
// rather than "is the owner tag undefined?").

/**
 * @typedef {Object} Rule
 * @property {string} id
 * @property {'error'|'warn'|'info'} level
 * @property {(record: any, ctx: any) => boolean} when - whether this rule applies to this record at all
 * @property {(record: any, ctx: any) => boolean} check - true = OK, false = finding
 * @property {(record: any, ctx: any) => string} message
 * @property {string} note - rationale for why this rule exists
 */

/**
 * @typedef {Object} Finding
 * @property {string} id
 * @property {'error'|'warn'|'info'} level
 * @property {string} message
 * @property {string} [file]
 * @property {number} [line]
 * @property {number} [col]
 */

/**
 * @param {Rule[]} rules
 * @param {any[]} records
 * @param {any} ctx
 * @returns {Finding[]}
 */
export function runRules(rules, records, ctx = {}) {
  const findings = [];
  for (const rule of rules) {
    for (const record of records) {
      if (!rule.when(record, ctx)) continue;
      if (rule.check(record, ctx)) continue;

      const finding = { id: rule.id, level: rule.level, message: rule.message(record, ctx) };
      const position = locateRecord(record);
      if (position) Object.assign(finding, position);
      findings.push(finding);
    }
  }
  return findings;
}

// Records passed to runRules are usually { node, id, ... } shapes (a
// sugared or plain Node plus whatever metadata a caller attached) — if a
// `.node` with a `.raw`/`.file` is present, surface file:line:col
// automatically so individual rules never have to do this themselves.
function locateRecord(record) {
  const node = record?.node;
  if (!node) return null;
  try {
    const raw = node.raw;
    const file = node.file;
    if (!raw || !file) return null;
    return { file: file.path, line: raw.line, col: raw.col };
  } catch {
    return null;
  }
}

/**
 * Summarize findings by level, for the CLI's summary line.
 * @param {Finding[]} findings
 */
export function summarize(findings) {
  const summary = { error: 0, warn: 0, info: 0 };
  for (const f of findings) summary[f.level] += 1;
  return summary;
}

/**
 * Generic "does this ref field's value resolve in its defined-set" rule
 * generator, driven entirely by a registry's `refs` declaration — this is
 * what backs the error-level "owner-tag-defined" /
 * "culture-defined" / etc. checks for EVERY registry, without any
 * per-field rule being hand-written. One rule id per (registry, field)
 * pair is generated so CLI output can still group/report per field.
 *
 * Expects `ctx.definedSets` (from src/refs.mjs's buildDefinedSets) and
 * records shaped `{ node, id, field, value, target, ok }` — i.e. one
 * record PER (record, field, value) triple, matching the flat shape
 * `buildRefGraph`'s `forward` array already produces. This function
 * doesn't build that array itself (buildRefGraph does); it only turns
 * each entry into a rule check.
 *
 * @param {string} registryAs
 * @param {import('./registry.mjs').RegistryDescriptor} registry
 * @returns {Rule[]}
 */
export function refFieldRules(registry) {
  return Object.keys(registry.refs ?? {}).map((field) => ({
    id: `${registry.as}-${field}-defined`,
    level: 'error',
    when: (fwd) => fwd.registry === registry.as && fwd.field === field,
    check: (fwd) => fwd.ok,
    message: (fwd) => `${registry.as} ${fwd.id}: ${field} "${fwd.value}" is not a defined ${fwd.target}`,
    note: 'An undefined reference means the game silently drops the field at start — '
      + 'this is the exact shape of the write_country_support/write_history incident '
      + '(122+ provinces lost their owner when common/country_tags was not copied).',
  }));
}