// src/rules-engine/rules-storage.service.ts

import { Injectable, Logger, OnModuleInit } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import Redis from 'ioredis';
import { readFileSync, writeFileSync, existsSync, mkdirSync } from 'fs';
import { dirname, join } from 'path';
import { randomUUID } from 'crypto';
import type { Rule, PriorityConfig } from './types/rule.types';
import { DEFAULT_PRIORITY_CONFIG } from './types/rule.types';

const RULES_KEY = 'rules:config';
const PRIORITY_CONFIG_KEY = 'rules:priority-config';
const VERSION_KEY = 'rules:scores:version';

@Injectable()
export class RulesStorageService implements OnModuleInit {
    private readonly logger = new Logger(RulesStorageService.name);
    private readonly redis: Redis;
    private readonly backupDir: string;

    constructor(private config: ConfigService) {
        this.redis = new Redis(config.get<string>('REDIS_URL') ?? 'redis://localhost:6379');
        this.backupDir = config.get<string>('RULES_BACKUP_DIR') ?? join(process.cwd(), 'data');
    }

    async onModuleInit() {
        // Restore rules from backup if Redis is empty
        const existing = await this.redis.get(RULES_KEY);
        if (!existing) {
            const rulesBackup = join(this.backupDir, 'rules-config.json');
            if (existsSync(rulesBackup)) {
                const data = readFileSync(rulesBackup, 'utf8');
                await this.redis.set(RULES_KEY, data);
                this.logger.log(`Restored ${JSON.parse(data).length} rules from backup`);
            } else {
                await this.redis.set(RULES_KEY, '[]');
                this.logger.log('Initialized empty rules config');
            }
        }

        // Restore priority config from backup if Redis is empty
        const existingConfig = await this.redis.get(PRIORITY_CONFIG_KEY);
        if (!existingConfig) {
            const configBackup = join(this.backupDir, 'priority-config.json');
            if (existsSync(configBackup)) {
                const data = readFileSync(configBackup, 'utf8');
                await this.redis.set(PRIORITY_CONFIG_KEY, data);
                this.logger.log('Restored priority config from backup');
            } else {
                await this.redis.set(PRIORITY_CONFIG_KEY, JSON.stringify(DEFAULT_PRIORITY_CONFIG));
                this.logger.log('Initialized default priority config');
            }
        }
    }

    // --- Priority Config ---

    async getPriorityConfig(): Promise<PriorityConfig> {
        const data = await this.redis.get(PRIORITY_CONFIG_KEY);
        return data ? JSON.parse(data) : DEFAULT_PRIORITY_CONFIG;
    }

    async updatePriorityConfig(config: PriorityConfig): Promise<PriorityConfig> {
        await this.redis.set(PRIORITY_CONFIG_KEY, JSON.stringify(config));
        await this.redis.incr(VERSION_KEY);
        this.backupFile('priority-config.json', config);
        return config;
    }

    // --- Rules CRUD ---

    async getAll(): Promise<Rule[]> {
        const data = await this.redis.get(RULES_KEY);
        return data ? JSON.parse(data) : [];
    }

    async getById(id: string): Promise<Rule | null> {
        const rules = await this.getAll();
        return rules.find(r => r.id === id) ?? null;
    }

    async getByTrigger(triggerType: string, triggerValue?: string): Promise<Rule[]> {
        const rules = await this.getAll();
        return rules.filter(r => {
            if (!r.enabled) return false;
            if (r.trigger.type !== triggerType) return false;
            if (triggerValue && 'request' in r.trigger && r.trigger.request !== triggerValue) return false;
            if (triggerValue && 'event' in r.trigger && r.trigger.event !== triggerValue) return false;
            return true;
        }).sort((a, b) => a.priority - b.priority);
    }

    async create(rule: Omit<Rule, 'id' | 'metadata'> & { createdBy?: string }): Promise<Rule> {
        const rules = await this.getAll();
        const newRule: Rule = {
            ...rule,
            id: randomUUID(),
            metadata: {
                createdAt: new Date().toISOString(),
                updatedAt: new Date().toISOString(),
                createdBy: rule.createdBy ?? 'system',
                category: this.inferCategory(rule.action.type),
                tags: [],
            },
        };
        rules.push(newRule);
        await this.saveRules(rules);
        return newRule;
    }

    async update(id: string, updates: Partial<Rule>): Promise<Rule | null> {
        const rules = await this.getAll();
        const index = rules.findIndex(r => r.id === id);
        if (index === -1) return null;
        rules[index] = {
            ...rules[index],
            ...updates,
            id,
            metadata: { ...rules[index].metadata, updatedAt: new Date().toISOString(), ...(updates.metadata ?? {}) },
        };
        await this.saveRules(rules);
        return rules[index];
    }

    async delete(id: string): Promise<boolean> {
        const rules = await this.getAll();
        const filtered = rules.filter(r => r.id !== id);
        if (filtered.length === rules.length) return false;
        await this.saveRules(filtered);
        return true;
    }

    async toggle(id: string): Promise<Rule | null> {
        const rule = await this.getById(id);
        if (!rule) return null;
        return this.update(id, { enabled: !rule.enabled });
    }

    async reorder(ids: string[]): Promise<Rule[]> {
        const rules = await this.getAll();
        const reorderedIds = new Set(ids);
        const reordered = ids.map((id, i) => {
            const rule = rules.find(r => r.id === id);
            if (rule) rule.priority = i;
            return rule;
        }).filter(Boolean) as Rule[];
        const remaining = rules.filter(r => !reorderedIds.has(r.id));
        const final = [...reordered, ...remaining];
        await this.saveRules(final);
        return final;
    }

    async getVersion(): Promise<number> {
        const v = await this.redis.get(VERSION_KEY);
        return v ? parseInt(v, 10) : 0;
    }

    // --- Internal ---

    private async saveRules(rules: Rule[]) {
        const json = JSON.stringify(rules, null, 2);
        await this.redis.set(RULES_KEY, json);
        await this.redis.incr(VERSION_KEY);
        this.backupFile('rules-config.json', rules);
    }

    private backupFile(filename: string, data: any) {
        try {
            if (!existsSync(this.backupDir)) mkdirSync(this.backupDir, { recursive: true });
            writeFileSync(join(this.backupDir, filename), JSON.stringify(data, null, 2), 'utf8');
        } catch (err) {
            this.logger.warn(`Failed to write backup ${filename}: ${err}`);
        }
    }

    private inferCategory(actionType: string): Rule['metadata']['category'] {
        switch (actionType) {
            case 'score': return 'priority';
            case 'assign': return 'assignment';
            case 'escalate': return 'escalation';
            case 'update': return 'lifecycle';
            default: return 'priority';
        }
    }
}