import { Injectable, Logger } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import { generateObject } from 'ai';
import type { LanguageModel } from 'ai';
import { z } from 'zod';
import { createAiModel } from './ai-provider';

type LeadContext = {
    firstName?: string;
    lastName?: string;
    leadSource?: string;
    interestedService?: string;
    leadStatus?: string;
    contactAttempts?: number;
    createdAt?: string;
    campaignId?: string;
    activities?: { activityType: string; summary: string }[];
};

type EnrichmentResult = {
    aiSummary: string;
    aiSuggestedAction: string;
};

const enrichmentSchema = z.object({
    aiSummary: z.string().describe('1-2 sentence summary of who this lead is and their history'),
    aiSuggestedAction: z.string().describe('5-10 word suggested action for the agent'),
});

@Injectable()
export class AiEnrichmentService {
    private readonly logger = new Logger(AiEnrichmentService.name);
    private readonly aiModel: LanguageModel | null;

    constructor(private config: ConfigService) {
        this.aiModel = createAiModel(config);
        if (!this.aiModel) {
            this.logger.warn('AI not configured — enrichment uses fallback');
        }
    }

    async enrichLead(lead: LeadContext): Promise<EnrichmentResult> {
        if (!this.aiModel) {
            return this.fallbackEnrichment(lead);
        }

        try {
            const daysSince = lead.createdAt
                ? Math.floor((Date.now() - new Date(lead.createdAt).getTime()) / (1000 * 60 * 60 * 24))
                : 0;

            const activitiesText = lead.activities?.length
                ? lead.activities.map(a => `- ${a.activityType}: ${a.summary}`).join('\n')
                : 'No previous interactions';

            const { object } = await generateObject({
                model: this.aiModel!,
                schema: enrichmentSchema,
                prompt: `You are an AI assistant for a hospital call center.
An inbound call is coming in from a lead. Summarize their history and suggest what the call center agent should do.

Lead details:
- Name: ${lead.firstName ?? 'Unknown'} ${lead.lastName ?? ''}
- Source: ${lead.leadSource ?? 'Unknown'}
- Interested in: ${lead.interestedService ?? 'Unknown'}
- Current status: ${lead.leadStatus ?? 'Unknown'}
- Lead age: ${daysSince} days
- Contact attempts: ${lead.contactAttempts ?? 0}

Recent activity:
${activitiesText}`,
            });

            this.logger.log(`AI enrichment generated for lead ${lead.firstName} ${lead.lastName}`);
            return object;
        } catch (error) {
            this.logger.error(`AI enrichment failed: ${error}`);
            return this.fallbackEnrichment(lead);
        }
    }

    private fallbackEnrichment(lead: LeadContext): EnrichmentResult {
        const daysSince = lead.createdAt
            ? Math.floor((Date.now() - new Date(lead.createdAt).getTime()) / (1000 * 60 * 60 * 24))
            : 0;

        const attempts = lead.contactAttempts ?? 0;
        const service = lead.interestedService ?? 'general inquiry';
        const source = lead.leadSource?.replace(/_/g, ' ').toLowerCase() ?? 'unknown source';

        let summary: string;
        let action: string;

        if (attempts === 0) {
            summary = `First-time inquiry from ${source}. Interested in ${service}. Lead is ${daysSince} day(s) old with no previous contact.`;
            action = `Introduce services and offer appointment booking`;
        } else if (attempts === 1) {
            summary = `Returning inquiry — contacted once before. Interested in ${service} via ${source}. Lead is ${daysSince} day(s) old.`;
            action = `Follow up on previous conversation, offer appointment`;
        } else {
            summary = `Repeat contact (${attempts} previous attempts) for ${service}. Originally from ${source}, ${daysSince} day(s) old. Shows high interest.`;
            action = `Prioritize appointment booking — high-intent lead`;
        }

        return { aiSummary: summary, aiSuggestedAction: action };
    }
}