import { IBrowserOsDetector } from './IBrowserOsDetector';
import { OperatingSystem } from '../OperatingSystem';

export class DetectorBuilder {
    private readonly existingPartsInUserAgent = new Array<string>();
    private readonly notExistingPartsInUserAgent = new Array<string>();

    constructor(private readonly os: OperatingSystem) { }

    public mustInclude(str: string): DetectorBuilder {
        return this.add(str, this.existingPartsInUserAgent);
    }

    public mustNotInclude(str: string): DetectorBuilder {
        return this.add(str, this.notExistingPartsInUserAgent);
    }

    public build(): IBrowserOsDetector {
        if (!this.existingPartsInUserAgent.length) {
            throw new Error('Must include at least a part');
        }
        return {
            detect: (agent) => this.detect(agent),
        };
    }

    private detect(userAgent: string): OperatingSystem {
        if (!userAgent) {
            throw new Error('User agent is null or undefined');
        }
        if (this.existingPartsInUserAgent.some((part) => !userAgent.includes(part))) {
            return OperatingSystem.Unknown;
        }
        if (this.notExistingPartsInUserAgent.some((part) => userAgent.includes(part))) {
            return OperatingSystem.Unknown;
        }
        return this.os;
    }

    private add(part: string, array: string[]): DetectorBuilder {
        if (!part) {
            throw new Error('part is empty or undefined');
        }
        if (this.existingPartsInUserAgent.includes(part)) {
            throw new Error(`part ${part} is already included as existing part`);
        }
        if (this.notExistingPartsInUserAgent.includes(part)) {
            throw new Error(`part ${part} is already included as not existing part`);
        }
        array.push(part);
        return this;
    }
}