import { Injectable, NotFoundException, BadRequestException, Inject, forwardRef } from '@nestjs/common';
import { FFBLangChainService } from '../../FFB/services/ffb-langchain.service';

import { MongoCoreService } from '../../mongo/mongo-core.service';
import { BlockRepository } from '../repositories/block.repository';
import { Block } from '../schemas/site.schema';
import { PhaseRepository } from '../repositories/phase.repository';
import { SiteRepository } from '../repositories/site.repository';
import { FFBProductionService } from '../../FFB/services/ffb-production.service';

@Injectable()
export class BlockService {
    private repo: BlockRepository;
    private phaseRepo: PhaseRepository;
    private siteRepo: SiteRepository;

    constructor(
        private readonly mongoCore: MongoCoreService,
        @Inject(forwardRef(() => FFBProductionService))
        private readonly ffbService: FFBProductionService,
        private readonly ffbLangChainService: FFBLangChainService,
    ) { }


    private async getRepos() {
        if (!this.repo) {
            const db = await this.mongoCore.getDb();
            this.repo = new BlockRepository(db);
            this.phaseRepo = new PhaseRepository(db);
            this.siteRepo = new SiteRepository(db);
            await this.repo.init();
            await this.phaseRepo.init();
            await this.siteRepo.init();
        }
        return { repo: this.repo, phaseRepo: this.phaseRepo, siteRepo: this.siteRepo };
    }

    async create(block: Block): Promise<Block> {
        const { repo, phaseRepo, siteRepo } = await this.getRepos();

        // 1. Validate Phase exists
        const phase = await phaseRepo.findById(block.phaseId);
        if (!phase) {
            throw new BadRequestException(`Phase with ID ${block.phaseId} does not exist.`);
        }

        // 2. Validate Site exists
        const site = await siteRepo.findById(phase.siteId);
        if (!site) {
            throw new BadRequestException(`Site with ID ${phase.siteId} (from Phase ${block.phaseId}) does not exist.`);
        }

        return repo.create(block);
    }

    async findAll(filter: Record<string, any> = {}): Promise<Block[]> {
        const { repo } = await this.getRepos();
        return repo.findAll(filter);
    }

    async findById(id: string): Promise<Block | null> {
        const { repo } = await this.getRepos();
        return repo.findById(id);
    }

    async update(id: string, update: Partial<Block>): Promise<void> {
        const { repo, phaseRepo, siteRepo } = await this.getRepos();

        const block = await repo.findById(id);
        if (!block) throw new NotFoundException('Block not found');

        if (update.phaseId) {
            // 1. Validate Phase exists
            const phase = await phaseRepo.findById(update.phaseId);
            if (!phase) throw new BadRequestException(`Phase with ID ${update.phaseId} does not exist.`);

            // 2. Validate Site exists
            const site = await siteRepo.findById(phase.siteId);
            if (!site) throw new BadRequestException(`Site with ID ${phase.siteId} (from Phase ${update.phaseId}) does not exist.`);
        }

        await repo.update(id, update);
    }

    async delete(id: string): Promise<void> {
        const { repo } = await this.getRepos();
        const block = await repo.findById(id);
        if (!block) throw new NotFoundException('Block not found');

        // Cascading Delete:
        // 1. Delete all FFB Production records referencing this block
        await this.ffbService.deleteMany({ 'block.id': id });

        // 2. Delete the block itself
        await repo.delete(id);
    }

    async generateDescription(data: { name: string, phaseName?: string, size?: number, numOfTrees?: number }): Promise<{ description: string }> {
        const prompt = `Write a realistic, professional description (2–4 sentences) for an oil palm plantation block named "${data.name}"${data.phaseName ? ` within phase "${data.phaseName}"` : ''}.${data.size ? ` It has a size of ${data.size} units` : ''}${data.numOfTrees ? ` and contains ${data.numOfTrees} trees` : ''}.

Choose 1-2 aspects from the following to incorporate naturally:
- Block health and maturity (e.g., trees at peak production age, healthy canopy development, consistent fruit set)
- Field accessibility (e.g., easily accessible by tractor paths, slightly sloped area requiring specialized harvesting tools)
- Environmental features (e.g., bordering primary forest, presence of natural irrigation channels, rich nutrient-holding soil)
- Monitoring and care (e.g., subject to intensive pest monitoring, recently fertilized, under strict irrigation schedule)

Guidelines:
- Maintain a grounded, operational tone.
- Do not mention the bullet points explicitly; weave them into the narrative.
- Ensure the length is exactly 2-4 sentences.

Description:`;
        const description = await this.ffbLangChainService.chatStateless(prompt);
        return { description: description.replace(/^Description:\s*/i, '').trim() };
    }
}