/**
 * EPPP configuration validation — [E00-S04-T01] TypeBox/Ajv schema.
 *
 * Compiles the TypeBox `configSchema` with Ajv (the golden-tuple validator,
 * Technology-Stack §5.2/§7) and exposes `validateConfig`, the generic
 * schema-validation entry point: given an unknown value it reports whether
 * the value is a valid configuration and the Ajv error messages otherwise.
 *
 * This is deliberately NOT the E00-S04-T02 field-specific startup error:
 * `validateConfig` returns the raw schema-validation outcome (valid or not,
 * with the Ajv messages) and performs no startup wiring — the startup error
 * formatting (E00-S04-T02, `startup.ts`) and the environment adapter
 * (E00-S04-T04) build on this raw outcome in their own modules.
 */

import { Ajv } from 'ajv';

import { configSchema } from './schema.js';

/** Ajv instance for the config schema — `allErrors` reports every violation. */
const ajv = new Ajv({ allErrors: true });

/** The compiled validator — TypeBox schemas are JSON Schema, so Ajv compiles them directly. */
const validateConfigValue = ajv.compile(configSchema);

/** The outcome of validating a value against the config schema. */
export interface ConfigValidationResult {
  /** True when the value is a valid configuration. */
  valid: boolean;
  /** Ajv error messages, empty when `valid` is true. */
  errors: string[];
}

/**
 * Validates an unknown value against the config schema.
 *
 * @param value - the value to validate (typically the parsed config object)
 * @returns `{ valid: true, errors: [] }` for a valid configuration, or
 *   `{ valid: false, errors }` with the Ajv messages naming each violation
 *   (e.g. `"must have required property 'sessionSecret'"`).
 */
export function validateConfig(value: unknown): ConfigValidationResult {
  const valid = validateConfigValue(value);
  if (valid) {
    return { valid: true, errors: [] };
  }
  const errors = (validateConfigValue.errors ?? []).map((error) => error.message ?? 'invalid');
  return { valid: false, errors };
}