import {
  BadRequestException,
  Injectable,
  ServiceUnavailableException,
} from '@nestjs/common';
import { ConfigService } from '@nestjs/config';

export type NoteAiExtract = {
  nextAction: {
    title: string;
    description?: string;
    dueAt?: string | null;
  } | null;
  memoryItems: Array<{ content: string; category?: string }>;
  summary?: string;
};

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

  isEnabled(): boolean {
    return (
      this.config.get<string>('AI_ENABLED') === 'true' &&
      Boolean(this.config.get<string>('AI_API_KEY')?.trim())
    );
  }

  async extractFromNote(input: {
    body: string;
    title?: string | null;
    noteType?: string;
    personName?: string | null;
  }): Promise<NoteAiExtract> {
    const system = `You analyze CRM notes in Persian/Farsi and extract structured data.
Return ONLY valid JSON with this exact shape:
{
  "nextAction": { "title": string, "description"?: string, "dueAt"?: string|null } | null,
  "memoryItems": [{ "content": string, "category"?: string }],
  "summary"?: string
}
Rules:
- nextAction: one concrete follow-up task if the note implies action; otherwise null.
- dueAt: ISO 8601 date-time if a deadline is mentioned; otherwise null.
- memoryItems: durable facts about the customer (preferences, budget, decisions, family, objections) — NOT tasks.
- Keep text in Persian when the note is Persian.
- Do not invent facts not supported by the note.
- Maximum 5 memory items.`;

    const userParts = [
      input.title ? `Title: ${input.title}` : null,
      input.noteType ? `Type: ${input.noteType}` : null,
      input.personName ? `Customer: ${input.personName}` : null,
      `Note:\n${input.body.trim()}`,
    ].filter(Boolean);

    const raw = await this.completeJson<Partial<NoteAiExtract>>(
      system,
      userParts.join('\n'),
    );
    return this.normalizeExtract(raw);
  }

  async completeJson<T>(system: string, user: string): Promise<T> {
    if (!this.isEnabled()) {
      throw new ServiceUnavailableException('هوش مصنوعی فعال نیست');
    }

    const model = this.config.get<string>('AI_MODEL')?.trim() || 'gpt-4o-mini';
    const baseUrl =
      this.config.get<string>('AI_BASE_URL')?.trim() ||
      'https://api.openai.com/v1';
    const apiKey = this.config.get<string>('AI_API_KEY')!.trim();
    const timeoutMs = Number(this.config.get<string>('AI_TIMEOUT_MS') || 45000);

    const controller = new AbortController();
    const timer = setTimeout(() => controller.abort(), timeoutMs);

    try {
      const res = await fetch(`${baseUrl.replace(/\/$/, '')}/chat/completions`, {
        method: 'POST',
        headers: {
          Authorization: `Bearer ${apiKey}`,
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          model,
          temperature: 0.2,
          response_format: { type: 'json_object' },
          messages: [
            { role: 'system', content: system },
            { role: 'user', content: user },
          ],
        }),
        signal: controller.signal,
      });

      if (!res.ok) {
        const text = await res.text().catch(() => '');
        throw new ServiceUnavailableException(
          `خطا در ارتباط با مدل هوش مصنوعی (${res.status})${text ? `: ${text.slice(0, 200)}` : ''}`,
        );
      }

      const data = (await res.json()) as {
        choices?: Array<{ message?: { content?: string } }>;
      };
      const raw = data.choices?.[0]?.message?.content?.trim();
      if (!raw) {
        throw new BadRequestException('پاسخ مدل خالی بود');
      }

      return JSON.parse(raw) as T;
    } catch (err) {
      if (err instanceof BadRequestException || err instanceof ServiceUnavailableException) {
        throw err;
      }
      if (err instanceof SyntaxError) {
        throw new BadRequestException('پاسخ مدل قابل خواندن نبود');
      }
      if (err instanceof Error && err.name === 'AbortError') {
        throw new ServiceUnavailableException('زمان پاسخ مدل هوش مصنوعی تمام شد');
      }
      throw new ServiceUnavailableException('ارتباط با مدل هوش مصنوعی ناموفق بود');
    } finally {
      clearTimeout(timer);
    }
  }

  private normalizeExtract(raw: Partial<NoteAiExtract>): NoteAiExtract {
    const nextAction =
      raw.nextAction && typeof raw.nextAction === 'object'
        ? {
            title: String(raw.nextAction.title ?? '').trim().slice(0, 200),
            description: raw.nextAction.description
              ? String(raw.nextAction.description).trim().slice(0, 2000)
              : undefined,
            dueAt: raw.nextAction.dueAt
              ? String(raw.nextAction.dueAt).trim()
              : null,
          }
        : null;

    const memoryItems = Array.isArray(raw.memoryItems)
      ? raw.memoryItems
          .map((item) => ({
            content: String(item?.content ?? '').trim().slice(0, 500),
            category: item?.category
              ? String(item.category).trim().slice(0, 40)
              : undefined,
          }))
          .filter((item) => item.content.length > 0)
          .slice(0, 5)
      : [];

    const cleanedNext =
      nextAction && nextAction.title.length > 0 ? nextAction : null;

    return {
      nextAction: cleanedNext,
      memoryItems,
      summary: raw.summary ? String(raw.summary).trim().slice(0, 500) : undefined,
    };
  }
}