import { Injectable, Logger } from "@nestjs/common";

/**
 * Characters stripped from plate text during normalization.
 * These invisible Unicode code-points can sneak in via copy-paste
 * or OCR and break exact-match lookups against the plate letter map.
 */
const INVISIBLE_CHARS = [
  "\u200C", // Zero-Width Non-Joiner
  "\u200D", // Zero-Width Joiner
  "\u200E", // Left-to-Right Mark
  "\u200F", // Right-to-Left Mark
  "\uFEFF", // BOM / Zero-Width No-Break Space
];

const INVISIBLE_RE = new RegExp(`[${INVISIBLE_CHARS.join("")}]`, "g");

/**
 * Normalize a Persian license-plate character (or short text) so that
 * visually-identical Unicode variants collapse to the canonical form
 * used in the plate letter mapping.
 *
 * Steps (in order):
 * 1. NFKC normalization  — folds compatibility equivalents
 * 2. Strip invisible Unicode characters (ZWJ, ZWNJ, LTR/RTL marks, BOM)
 * 3. Convert Arabic ي (U+064A) → Persian ی (U+06CC)
 * 4. Trim leading/trailing whitespace
 */
export function normalizePlateText(text: string): string {
  if (!text) return text;

  let result = String(text);

  // 1. Unicode NFKC normalization
  result = result.normalize("NFKC");

  // 2. Remove invisible characters
  result = result.replace(INVISIBLE_RE, "");

  // 3. Arabic ي → Persian ی
  result = result.replace(/\u064A/g, "\u06CC");

  // 4. Trim whitespace
  result = result.trim();

  return result;
}

@Injectable()
export class PlateNormalizerService {
  private readonly logger = new Logger(PlateNormalizerService.name);

  /** @see module-level {@link normalizePlateText} */
  normalizePlateText(text: string): string {
    return normalizePlateText(text);
  }

  /**
   * Normalize a plate letter and, if it doesn't resolve in the given
   * mapping, log the raw Unicode code-points for debugging.
   *
   * @returns the numeric code from `mapping`, or `null` when the letter
   *          is unknown after normalization.
   */
  resolvePlateLetterCode(
    letter: string,
    mapping: Record<string, number>,
  ): number | null {
    const normalized = this.normalizePlateText(letter);

    const code = mapping[normalized];
    if (code !== undefined) return code;

    this.logger.debug(
      `Unknown plate letter: ${normalized} [${Array.from(normalized).map((c) => `U+${c.charCodeAt(0).toString(16).toUpperCase().padStart(4, "0")}`).join(", ")}]`,
    );
    return null;
  }
}