/**
 * Validators - Input and data validation utilities
 * Provides functions for validating ONNX files, SafeTensors files, model data, and user inputs.
 * Requirements: 3.3, 9.3, 36.1, 36.3, 36.5
 */

const Validators = (function () {

  // ─── ONNX File Validation ─────────────────────────────────────────────────

  /**
   * ONNX protobuf magic bytes (first 2 bytes of a valid serialised protobuf
   * message with field 1 = irVersion).  We accept any non-empty ArrayBuffer
   * whose first byte is 0x08 (field 1, wire type 0 = varint) as a minimal
   * heuristic, since ONNX models always start with the irVersion field.
   *
   * A stricter check would require a full protobuf parse; this is intentionally
   * lightweight for a browser-side static app.
   */
  const ONNX_MAGIC_BYTE = 0x08;

  /**
   * Validate that a File object is a valid ONNX file.
   * Checks:
   *  1. The file has a .onnx extension (case-insensitive).
   *  2. The file is not empty.
   *
   * @param {File} file - Browser File object
   * @returns {{ valid: boolean, error?: string }}
   */
  function isValidOnnxFile(file) {
    if (!file) {
      return { valid: false, error: 'No file provided.' };
    }

    // Extension check
    const name = file.name || '';
    if (!name.toLowerCase().endsWith('.onnx')) {
      return {
        valid: false,
        error: `Invalid file type "${name}". Only .onnx files are accepted.`,
      };
    }

    // Empty file check
    if (file.size === 0) {
      return { valid: false, error: 'The file is empty.' };
    }

    return { valid: true };
  }

  /**
   * Validate the raw bytes of an ONNX file (ArrayBuffer).
   * Performs a lightweight magic-byte check.
   *
   * @param {ArrayBuffer} buffer
   * @returns {{ valid: boolean, error?: string }}
   */
  function isValidOnnxBuffer(buffer) {
    if (!(buffer instanceof ArrayBuffer) || buffer.byteLength === 0) {
      return { valid: false, error: 'Invalid or empty buffer.' };
    }
    const view = new Uint8Array(buffer, 0, Math.min(4, buffer.byteLength));
    if (view[0] !== ONNX_MAGIC_BYTE) {
      return {
        valid: false,
        error: 'File does not appear to be a valid ONNX model (unexpected header bytes).',
      };
    }
    return { valid: true };
  }

  // ─── SafeTensors File Validation ────────────────────────────────────────────

  /**
   * Validate that a File object is a valid SafeTensors file.
   * Checks:
   *  1. The file has a .safetensors extension (case-insensitive).
   *  2. The file is not empty.
   *
   * @param {File} file - Browser File object
   * @returns {{ valid: boolean, error?: string }}
   */
  function isValidSafeTensorsFile(file) {
    if (!file) {
      return { valid: false, error: 'No file provided.' };
    }

    // Extension check
    const name = file.name || '';
    if (!name.toLowerCase().endsWith('.safetensors')) {
      return {
        valid: false,
        error: `Invalid file type "${name}". Only .safetensors files are accepted.`,
      };
    }

    // Empty file check
    if (file.size === 0) {
      return { valid: false, error: 'The file is empty.' };
    }

    return { valid: true };
  }

  // ─── Model Data Validation ────────────────────────────────────────────────

  /**
   * Validate a parsed model data object returned by ONNXParser.
   * Ensures the required top-level fields are present and non-null.
   *
   * @param {Object} data - ParsedModel object
   * @returns {{ valid: boolean, error?: string }}
   */
  function isValidModelData(data) {
    if (!data || typeof data !== 'object') {
      return { valid: false, error: 'Model data is null or not an object.' };
    }

    const required = ['metadata', 'graph', 'inputs', 'outputs'];
    for (const field of required) {
      if (!(field in data) || data[field] == null) {
        return { valid: false, error: `Model data is missing required field: "${field}".` };
      }
    }

    if (!Array.isArray(data.inputs)) {
      return { valid: false, error: 'Model data "inputs" must be an array.' };
    }
    if (!Array.isArray(data.outputs)) {
      return { valid: false, error: 'Model data "outputs" must be an array.' };
    }

    return { valid: true };
  }

  // ─── Input / Search Validation ────────────────────────────────────────────

  /**
   * Validate a generic user input string.
   * Returns false for null/undefined; trims and checks length.
   *
   * @param {*} input
   * @param {{ minLength?: number, maxLength?: number, required?: boolean }} [opts]
   * @returns {{ valid: boolean, error?: string }}
   */
  function isValidInput(input, opts = {}) {
    const { minLength = 0, maxLength = 1000, required = false } = opts;

    if (input == null || input === '') {
      if (required) {
        return { valid: false, error: 'This field is required.' };
      }
      return { valid: true }; // empty is OK when not required
    }

    const str = String(input).trim();

    if (required && str.length === 0) {
      return { valid: false, error: 'This field cannot be blank.' };
    }
    if (str.length < minLength) {
      return { valid: false, error: `Input must be at least ${minLength} characters.` };
    }
    if (str.length > maxLength) {
      return { valid: false, error: `Input must not exceed ${maxLength} characters.` };
    }

    return { valid: true };
  }

  /**
   * Validate a search query string.
   * Allows empty strings (clears the filter); rejects excessively long ones.
   *
   * @param {string} query
   * @returns {{ valid: boolean, error?: string }}
   */
  function isValidSearchQuery(query) {
    return isValidInput(query, { maxLength: 200 });
  }

  /**
   * Validate a model path string (must be non-empty and end with .onnx or .safetensors).
   * @param {string} path
   * @returns {{ valid: boolean, error?: string }}
   */
  function isValidModelPath(path) {
    if (!path || typeof path !== 'string' || path.trim() === '') {
      return { valid: false, error: 'Model path must be a non-empty string.' };
    }
    const lower = path.toLowerCase();
    if (!lower.endsWith('.onnx') && !lower.endsWith('.safetensors')) {
      return { valid: false, error: 'Model path must point to an .onnx or .safetensors file.' };
    }
    return { valid: true };
  }

  // ─── Public API ───────────────────────────────────────────────────────────

  return {
    isValidOnnxFile,
    isValidOnnxBuffer,
    isValidSafeTensorsFile,
    isValidModelData,
    isValidInput,
    isValidSearchQuery,
    isValidModelPath,
  };
})();

// Export for global access in vanilla JS context
window.Validators = Validators;