import type { LoggerService } from '@nestjs/common';

type LogLevel = 'error' | 'warn' | 'log' | 'debug';
const severity: Record<LogLevel, number> = {
    error: 0,
    warn: 1,
    log: 2,
    debug: 3,
};
// 按字段名递归脱敏，日志中不得出现会话、密码、密钥或授权头原文。
const sensitiveKeys = /authorization|cookie|password|secret|token|api[_-]?key/i;

export class AppLogger implements LoggerService {
    public constructor(private readonly minimumLevel: LogLevel) {}

    public log(message: unknown, context?: unknown): void {
        this.write('log', message, context);
    }

    public error(message: unknown, stack?: string, context?: unknown): void {
        this.write('error', message, { stack, context });
    }

    public warn(message: unknown, context?: unknown): void {
        this.write('warn', message, context);
    }

    public debug(message: unknown, context?: unknown): void {
        this.write('debug', message, context);
    }

    public verbose(message: unknown, context?: unknown): void {
        this.debug(message, context);
    }

    private write(level: LogLevel, message: unknown, context?: unknown): void {
        if (severity[level] > severity[this.minimumLevel]) return;
        const entry = {
            timestamp: new Date().toISOString(),
            level,
            message: typeof message === 'string' ? message : sanitize(message),
            context: sanitize(context),
        };
        // 每行独立 JSON，方便日志采集系统按字段索引 request_id、状态码等上下文。
        const output = JSON.stringify(entry);
        if (level === 'error') console.error(output);
        else console.log(output);
    }
}

function sanitize(value: unknown): unknown {
    if (Array.isArray(value)) return value.map(sanitize);
    if (value && typeof value === 'object') {
        return Object.fromEntries(
            Object.entries(value).map(([key, child]) => [
                key,
                sensitiveKeys.test(key) ? '[REDACTED]' : sanitize(child),
            ]),
        );
    }
    return value;
}