/** @module info */
/** @hidden */ 
import os = require('os');

import { StringValueMap } from 'pip-services4-commons-node';
import { ConfigParams } from '../config/ConfigParams';
import { IReconfigurable } from '../config/IReconfigurable';

/**
 * Context information component that provides detail information
 * about execution context: container or/and process.
 * 
 * Most often ContextInfo is used by logging and performance counters
 * to identify source of the collected logs and metrics.
 * 
 * ### Configuration parameters ###
 * 
 * - name:                     the context (container or process) name
 * - description:                human-readable description of the context
 * - properties:             entire section of additional descriptive properties
 * - ...
 * 
 * ### Example ###
 * 
 *     let contextInfo = new ContextInfo();
 *     contextInfo.configure(ConfigParams.fromTuples(
 *         "name", "MyMicroservice",
 *         "description", "My first microservice"
 *     ));
 *     
 *     context.name;            // Result: "MyMicroservice"
 *     context.contextId;        // Possible result: "mylaptop"
 *     context.startTime;        // Possible result: 2018-01-01:22:12:23.45Z
 *     context.uptime;            // Possible result: 3454345
 */
export class ContextInfo implements IReconfigurable {    
    private _name = "unknown";
    private _description: string = null;
    private _contextId: string = os.hostname(); // IdGenerator.nextLong();
    private _startTime: Date = new Date();
    private _properties: StringValueMap = new StringValueMap();

    /**
     * Creates a new instance of this context info.
     * 
     * @param name          (optional) a context name.
     * @param description     (optional) a human-readable description of the context.
     */
    public constructor(name?: string, description?: string) {
        this._name = name || "unknown";
        this._description = description || null;
    }

    /**
     * Configures component by passing configuration parameters.
     * 
     * @param config    configuration parameters to be set.
     */
    public configure(config: ConfigParams): void {
        this.name = config.getAsStringWithDefault("name", this.name);
        this.description = config.getAsStringWithDefault("description", this.description);        
        this.properties = config.getSection("properties");
    }
    
    /**
     * Gets the context name.
     * 
     * @returns the context name 
     */
    public get name(): string { return this._name; }

    /** 
     * Sets the context name.
     *  
     * @param value        a new name for the context.
     */
    public set name(value: string) { this._name = value || "unknown"; }
    
    /**
     * Gets the human-readable description of the context.
     * 
     * @returns the human-readable description of the context.
     */
    public get description(): string { return this._description; }

    /**
     * Sets the human-readable description of the context.
     * 
     * @param value a new human readable description of the context.
     */
    public set description(value: string) { this._description = value; }
    
    /**
     * Gets the unique context id.
     * Usually it is the current host name.
     * 
     * @returns the unique context id.
     */
    public get contextId(): string { return this._contextId; }

    /**
     * Sets the unique context id.
     * 
     * @param value a new unique context id.
     */
    public set contextId(value: string) { this._contextId = value; }
    
    /**
     * Gets the context start time.
     * 
     * @returns the context start time.
     */
    public get startTime(): Date { return this._startTime; }

    /**
     * Sets the context start time.
     * 
     * @param value a new context start time.
     */
    public set startTime(value: Date) { this._startTime = value || new Date(); }

    /**
     * Calculates the context uptime as from the start time.
     * 
     * @returns number of milliseconds from the context start time.
     */
    public get uptime(): number {
        return new Date().getTime() - this._startTime.getTime();
    }

    /**
     * Gets context additional parameters.
     * 
     * @returns a JSON object with additional context parameters.
     */
    public get properties(): any { return this._properties; }

    /** 
     * Sets context additional parameters.
     * 
     * @param properties     a JSON object with context additional parameters
    */
    public set properties(properties: any) {
        this._properties = StringValueMap.fromValue(properties);
    }
    
    /**
     * Creates a new ContextInfo and sets its configuration parameters.
     * 
     * @param config     configuration parameters for the new ContextInfo.
     * @returns a newly created ContextInfo
     */
    public static fromConfig(config: ConfigParams): ContextInfo {
        const result = new ContextInfo();
        result.configure(config);
        return result;
    }
}