import { Injectable, Logger, OnModuleInit } from '@nestjs/common';
import { copyFileSync, existsSync, mkdirSync, readFileSync, writeFileSync } from 'fs';
import { dirname, join } from 'path';
import {
    DEFAULT_TELEPHONY_CONFIG,
    TELEPHONY_ENV_SEEDS,
    type TelephonyConfig,
} from './telephony.defaults';

const CONFIG_PATH = join(process.cwd(), 'data', 'telephony.json');
const BACKUP_DIR = join(process.cwd(), 'data', 'telephony-backups');

// File-backed telephony config. Replaces eight env vars (OZONETEL_*, SIP_*,
// EXOTEL_*). On first boot we copy whatever those env vars hold into the
// config file so existing deployments don't break — after that, the env vars
// are no longer read by anything.
//
// Mirrors WidgetConfigService and ThemeService — load on init, in-memory
// cache, file backups on every change.
@Injectable()
export class TelephonyConfigService implements OnModuleInit {
    private readonly logger = new Logger(TelephonyConfigService.name);
    private cached: TelephonyConfig | null = null;

    onModuleInit() {
        this.ensureReady();
    }

    getConfig(): TelephonyConfig {
        if (this.cached) return this.cached;
        return this.load();
    }

    // Public-facing subset for the GET endpoint — masks the Exotel API token
    // so it can't be exfiltrated by an unauthenticated reader. The admin UI
    // gets the full config via getConfig() through the controller's PUT path
    // (the new value is supplied client-side, the old value is never displayed).
    getMaskedConfig() {
        const c = this.getConfig();
        return {
            ...c,
            exotel: {
                ...c.exotel,
                apiToken: c.exotel.apiToken ? '***masked***' : '',
            },
            ozonetel: {
                ...c.ozonetel,
                agentPassword: c.ozonetel.agentPassword ? '***masked***' : '',
                adminPassword: c.ozonetel.adminPassword ? '***masked***' : '',
            },
        };
    }

    updateConfig(updates: Partial<TelephonyConfig>): TelephonyConfig {
        const current = this.getConfig();
        // Deep-ish merge — each top-level group merges its own keys.
        const merged: TelephonyConfig = {
            ozonetel: { ...current.ozonetel, ...(updates.ozonetel ?? {}) },
            sip: { ...current.sip, ...(updates.sip ?? {}) },
            exotel: { ...current.exotel, ...(updates.exotel ?? {}) },
            version: (current.version ?? 0) + 1,
            updatedAt: new Date().toISOString(),
        };
        // Strip the masked sentinel — admin UI sends back '***masked***' for
        // unchanged secret fields. We treat that as "keep the existing value".
        if (merged.exotel.apiToken === '***masked***') {
            merged.exotel.apiToken = current.exotel.apiToken;
        }
        if (merged.ozonetel.agentPassword === '***masked***') {
            merged.ozonetel.agentPassword = current.ozonetel.agentPassword;
        }
        if (merged.ozonetel.adminPassword === '***masked***') {
            merged.ozonetel.adminPassword = current.ozonetel.adminPassword;
        }
        this.backup();
        this.writeFile(merged);
        this.cached = merged;
        this.logger.log(`Telephony config updated to v${merged.version}`);
        return merged;
    }

    resetConfig(): TelephonyConfig {
        this.backup();
        const fresh = JSON.parse(JSON.stringify(DEFAULT_TELEPHONY_CONFIG)) as TelephonyConfig;
        this.writeFile(fresh);
        this.cached = fresh;
        this.logger.log('Telephony config reset to defaults');
        return fresh;
    }

    // First-boot bootstrap: if no telephony.json exists yet, seed it from the
    // legacy env vars. After this runs once the env vars are dead code.
    private ensureReady(): TelephonyConfig {
        if (existsSync(CONFIG_PATH)) {
            return this.load();
        }
        const seeded: TelephonyConfig = JSON.parse(
            JSON.stringify(DEFAULT_TELEPHONY_CONFIG),
        ) as TelephonyConfig;
        let appliedCount = 0;
        for (const seed of TELEPHONY_ENV_SEEDS) {
            const value = process.env[seed.env];
            if (value === undefined || value === '') continue;
            this.setNested(seeded, seed.path, value);
            appliedCount += 1;
        }
        seeded.version = 1;
        seeded.updatedAt = new Date().toISOString();
        this.writeFile(seeded);
        this.cached = seeded;
        this.logger.log(
            `Telephony config seeded from env (${appliedCount} env var${appliedCount === 1 ? '' : 's'} applied)`,
        );
        return seeded;
    }

    private load(): TelephonyConfig {
        try {
            const raw = readFileSync(CONFIG_PATH, 'utf8');
            const parsed = JSON.parse(raw);
            const merged: TelephonyConfig = {
                ozonetel: { ...DEFAULT_TELEPHONY_CONFIG.ozonetel, ...(parsed.ozonetel ?? {}) },
                sip: { ...DEFAULT_TELEPHONY_CONFIG.sip, ...(parsed.sip ?? {}) },
                exotel: { ...DEFAULT_TELEPHONY_CONFIG.exotel, ...(parsed.exotel ?? {}) },
                version: parsed.version,
                updatedAt: parsed.updatedAt,
            };
            this.cached = merged;
            this.logger.log('Telephony config loaded from file');
            return merged;
        } catch (err) {
            this.logger.warn(`Failed to load telephony config, using defaults: ${err}`);
            const fresh = JSON.parse(JSON.stringify(DEFAULT_TELEPHONY_CONFIG)) as TelephonyConfig;
            this.cached = fresh;
            return fresh;
        }
    }

    private setNested(obj: any, path: string[], value: string) {
        let cursor = obj;
        for (let i = 0; i < path.length - 1; i++) {
            if (!cursor[path[i]]) cursor[path[i]] = {};
            cursor = cursor[path[i]];
        }
        cursor[path[path.length - 1]] = value;
    }

    private writeFile(cfg: TelephonyConfig) {
        const dir = dirname(CONFIG_PATH);
        if (!existsSync(dir)) mkdirSync(dir, { recursive: true });
        writeFileSync(CONFIG_PATH, JSON.stringify(cfg, null, 2), 'utf8');
    }

    private backup() {
        try {
            if (!existsSync(CONFIG_PATH)) return;
            if (!existsSync(BACKUP_DIR)) mkdirSync(BACKUP_DIR, { recursive: true });
            const ts = new Date().toISOString().replace(/[:.]/g, '-');
            copyFileSync(CONFIG_PATH, join(BACKUP_DIR, `telephony-${ts}.json`));
        } catch (err) {
            this.logger.warn(`Telephony backup failed: ${err}`);
        }
    }
}