import { Injectable, Logger } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import Redis from 'ioredis';
import { ConversationEntry } from './types';

@Injectable()
export class MessagingConversationService {
    private readonly logger = new Logger(MessagingConversationService.name);
    private readonly redis: Redis;
    private readonly ttlSec = 24 * 60 * 60; // 24h — matches WhatsApp session window
    private readonly maxHistory = 20;

    constructor(config: ConfigService) {
        const redisUrl = config.get<string>('redis.url') ?? 'redis://localhost:6379';
        this.redis = new Redis(redisUrl);
    }

    private key(phone: string): string {
        return `wa:conv:${phone}`;
    }

    async getHistory(phone: string): Promise<ConversationEntry[]> {
        const raw = await this.redis.get(this.key(phone));
        if (!raw) return [];
        try {
            return JSON.parse(raw);
        } catch {
            return [];
        }
    }

    async addMessages(phone: string, entries: ConversationEntry[]): Promise<void> {
        const existing = await this.getHistory(phone);
        const updated = [...existing, ...entries].slice(-this.maxHistory);
        await this.redis.setex(this.key(phone), this.ttlSec, JSON.stringify(updated));
    }

    async clear(phone: string): Promise<void> {
        await this.redis.del(this.key(phone));
    }
}