export class AIResStreamParser {
  private buffer: string = '';
  private inCodeBlock: boolean = false;

  public parse(chunk: string): unknown {
    this.buffer += chunk;
    const clean = this.cleanBuffer(this.buffer);
    try {
      return JSON.parse(clean);
    } catch {
      return this.tryParsePartial(clean);
    }
  }

  private cleanBuffer(text: string): string {
    if (!this.inCodeBlock && text.includes('```json')) {
      this.inCodeBlock = true;
    }

    let content = text;
    if (this.inCodeBlock) {
      const startMatch = text.match(/```json\s*/);
      if (startMatch && startMatch.index !== undefined) {
        content = text.substring(startMatch.index + startMatch[0].length);
      }
    }

    content = content.replace(/```\s*$/, '');
    return content.trim();
  }

  private tryParsePartial(text: string): unknown {
    if (!text) return null;

    let braces = 0;
    let brackets = 0;
    let inString = false;
    let escaped = false;

    for (let i = 0; i < text.length; i++) {
      const char = text[i];
      if (escaped) {
        escaped = false;
        continue;
      }
      if (char === '\\') {
        escaped = true;
        continue;
      }
      if (char === '"') {
        inString = !inString;
        continue;
      }
      if (!inString) {
        if (char === '{') braces++;
        if (char === '}') braces--;
        if (char === '[') brackets++;
        if (char === ']') brackets--;
      }
    }

    if (braces < 0 || brackets < 0) return null;

    let fix = text;
    if (inString) fix += '"';

    const suffix = '}'.repeat(braces) + ']'.repeat(brackets);
    try {
      return JSON.parse(fix + suffix);
    } catch {
      /* incomplete JSON */
    }

    try {
      if (!fix.endsWith('"') && inString) fix += '"';
      return JSON.parse(fix + suffix);
    } catch {
      /* incomplete JSON */
    }

    return null;
  }
}