import { BadRequestException, Injectable } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { AuthUser } from '../auth/auth.types';
import { normalizeAiDescriptionHtml } from '../common/ai-html.util';
import {
  requestAiJsonCompletion,
  resolveAiProvider,
} from '../common/ai-provider.util';
import {
  BusinessProfileAiFillField,
  FillBusinessProfileFieldByAiDto,
} from './dto/business-profile-ai.dto';

@Injectable()
export class BusinessProfileAiService {
  constructor(private readonly config: ConfigService) {}

  async fillField(
    _businessIdRaw: string,
    dto: FillBusinessProfileFieldByAiDto,
    _actor: AuthUser,
  ) {
    const prompt = dto.prompt?.trim();
    if (!prompt || prompt.length < 10) {
      throw new BadRequestException('Prompt is required');
    }

    const nameEn = dto.nameEn?.trim() || '';
    const nameFa = dto.nameFa?.trim() || '';
    if (!nameEn && !nameFa) {
      throw new BadRequestException(
        'Enter a business name before using AI fill',
      );
    }

    const provider = resolveAiProvider(this.config);
    const isAbout = dto.field === BusinessProfileAiFillField.about;

    const systemPrompt = isAbout
      ? `You write short business abstracts for an Iranian B2B marketplace listing.
Return ONLY valid JSON: { "text": "..." }
Follow the user's instructions for language and tone.
Keep the abstract to 1–4 sentences. No HTML. No markdown.
Prefer a clear, professional, informative style about what the business does.
Never write sales CTAs, discounts, or vague praise.`
      : `You write business profile descriptions as HTML for an advanced rich-text editor on an Iranian marketplace.
Return ONLY valid JSON: { "html": "..." }
The "html" value must be a raw HTML fragment (real tags, not escaped entities, not markdown, not code fences).
Allowed tags only: p, ul, ol, li, strong, em, br.
Do not wrap in html/body/div. Do not include scripts, styles, classes, or attributes.
Follow the user's instructions for language and tone.
Prefer a professional, informative structure about the company, offerings, and strengths.
Never write sales CTAs, discounts, or vague marketing slogans.
Aim for 2–5 short paragraphs and optionally a bullet list.`;

    const userPrompt = JSON.stringify({
      instructions: prompt,
      business: {
        nameEn: nameEn || null,
        nameFa: nameFa || null,
        categories: dto.categories?.trim() || null,
      },
    });

    let content: string;
    try {
      content = await requestAiJsonCompletion(
        provider,
        systemPrompt,
        userPrompt,
        0.5,
      );
    } catch (err) {
      const message = err instanceof Error ? err.message : 'AI request failed';
      throw new BadRequestException(message);
    }

    let parsed: { text?: unknown; html?: unknown };
    try {
      parsed = JSON.parse(content) as { text?: unknown; html?: unknown };
    } catch {
      throw new BadRequestException('AI returned invalid JSON');
    }

    if (isAbout) {
      const text = String(parsed.text ?? '').trim();
      if (!text) {
        throw new BadRequestException('AI returned an empty abstract');
      }
      return { field: BusinessProfileAiFillField.about, text };
    }

    const html = normalizeAiDescriptionHtml(String(parsed.html ?? ''));
    if (!html) {
      throw new BadRequestException('AI returned an empty description');
    }
    return { field: BusinessProfileAiFillField.vision, html };
  }
}