import {

Base64Url,

BitLength,

EncodingOptions,

SegmentEncoder,

SegmentSequence,

SemanticPreEncoder,

} from './encoder/index.js';

import {Segment, SegmentIDs} from './model/index.js';

import {IntEncoder} from './encoder/field/IntEncoder.js';

import {TCModel} from './TCModel.js';

/**

* Main class for encoding and decoding a

* TCF Transparency and Consent String

*/

export class TCString {

/**

* encodes a model into a TCString

*

* @param {TCModel} tcModel - model to convert into encoded string

* @param {EncodingOptions} options - for encoding options other than default

* @return {string} - base64url encoded Transparency and Consent String

*/

public static encode(tcModel: TCModel, options?: EncodingOptions): string {

let out = '';

let sequence: Segment[];

tcModel = SemanticPreEncoder.process(tcModel, options);

/**

* If they pass in a special segment sequence.

*/

if (Array.isArray(options?.segments)) {

sequence = options.segments;

} else {

sequence = new SegmentSequence(tcModel, options)[''+tcModel.version];

}

sequence.forEach((segment: Segment, idx: number): void => {

let dotMaybe = '';

if (idx < sequence.length - 1) {

dotMaybe = '.';

}

out += SegmentEncoder.encode(tcModel, segment) + dotMaybe;

});

return out;

}

/**

* Decodes a string into a TCModel

*

* @param {string} encodedTCString - base64url encoded Transparency and

* Consent String to decode - can also be a single or group of segments of

* the string

* @param {string} [tcModel] - model to enhance with the information. If

* none is passed a new instance of TCModel will be created.

* @return {TCModel} - Returns populated TCModel

*/

public static decode(encodedTCString: string, tcModel?: TCModel): TCModel {

const segments: string[] = encodedTCString.split('.');

const len: number = segments.length;

if (!tcModel) {

tcModel = new TCModel();

}

for (let i = 0; i < len; i ++) {

const segString: string = segments[i];

/**

* first char will contain 6 bits, we only need the first 3. In version 1

* and 2 of the TC string there is no segment type for the CORE string.

* Instead the first 6 bits are reserved for the encoding version, but

* because we're only on a maximum of encoding version 2 the first 3 bits

* in the core segment will evaluate to 0.

*/

const firstChar: string = Base64Url.decode(segString.charAt(0));

const segTypeBits: string = firstChar.substr(0, BitLength.segmentType);

const segment = SegmentIDs.ID_TO_KEY[IntEncoder.decode(segTypeBits, BitLength.segmentType).toString()];

SegmentEncoder.decode(segString, tcModel, segment);

}

return tcModel;

}

}