/**
 * Copyright (c) 2020 TypeFox GmbH. All rights reserved.
 * Licensed under the GNU Affero General Public License (AGPL).
 * See License-AGPL.txt in the project root for license information.
 */

import { injectable, inject } from "inversify";

export interface KeyMetadata {
    name: string,
    version: number
}

export interface Key {
    metadata: KeyMetadata,
    material: Buffer
}

export const KeyProvider = Symbol('KeyProvider');
export interface KeyProvider {
    getPrimaryKey(): Key;
    getKeyFor(metadata: KeyMetadata): Key;
}

export type KeyConfig = KeyMetadata & {
    /** base64 encoded */
    material: string,
    primary?: boolean
}

export const KeyProviderConfig = Symbol('KeyProviderConfig');
export interface KeyProviderConfig {
    keys: KeyConfig[]
}

@injectable()
export class KeyProviderImpl implements KeyProvider {

    static loadKeyConfigFromJsonString(configStr: string): KeyConfig[] {
        const keys = (JSON.parse(configStr) || []) as KeyConfig[];
        if (!Array.isArray(keys)
            || keys.length < 0
            || 1 !== keys.reduce((p, k) => k.primary ? p + 1 : p, 0)) {
            throw new Error('Invalid key config!');
        }
        return keys;
    }

    constructor(@inject(KeyProviderConfig) protected readonly config: KeyProviderConfig) {}

    protected get keys() {
        return this.config.keys
    }

    getPrimaryKey(): Key {
        const primaryKey = this.keys.find((key) => !!key.primary);
        if (!primaryKey) {
            throw new Error('No primary encryption key found!');
        }
        return this.configToKey(primaryKey);
    }

    getKeyFor(metadata: KeyMetadata): Key {
        const key = this.keys.find((k) => k.name === metadata.name && k.version === metadata.version);
        if (!key) {
            throw new Error(`No key found for metadata ${metadata.name}/${metadata.version}`);
        }
        return this.configToKey(key);
    }

    protected configToKey(config: KeyConfig): Key {
        return {
            metadata: {
                name: config.name,
                version: config.version
            },
            material: new Buffer(config.material, 'base64')
        };
    }
}