const QUALITY_PROFILES = Object.freeze({
    source: Object.freeze({
        id: 'source',
        videoMode: 'copy'
    }),
    '1080p': Object.freeze({
        id: '1080p',
        videoMode: 'encode',
        maxResolution: '1080p',
        targetVideoBitrateKbps: 6000
    }),
    '720p': Object.freeze({
        id: '720p',
        videoMode: 'encode',
        maxResolution: '720p',
        targetVideoBitrateKbps: 3500
    }),
    '480p': Object.freeze({
        id: '480p',
        videoMode: 'encode',
        maxResolution: '480p',
        targetVideoBitrateKbps: 1500
    })
});

const QUALITY_MODES = Object.freeze(['auto', ...Object.keys(QUALITY_PROFILES)]);

function getAutomaticProfile(settings = {}) {
    const configuredResolution = settings.maxResolution;
    return QUALITY_PROFILES[configuredResolution] || QUALITY_PROFILES['1080p'];
}

function resolveQualityMode(qualityMode, settings = {}) {
    if (qualityMode === undefined || qualityMode === null || qualityMode === '') {
        return null;
    }

    if (!QUALITY_MODES.includes(qualityMode)) {
        const error = new Error(`Unsupported qualityMode: ${qualityMode}`);
        error.code = 'INVALID_QUALITY_MODE';
        throw error;
    }

    const profile = qualityMode === 'auto'
        ? getAutomaticProfile(settings)
        : QUALITY_PROFILES[qualityMode];

    return {
        qualityMode,
        mode: 'single',
        selectedProfile: profile.id,
        availableProfiles: QUALITY_MODES,
        sessionOptions: {
            videoMode: profile.videoMode,
            ...(profile.maxResolution && { maxResolution: profile.maxResolution }),
            ...(profile.targetVideoBitrateKbps && {
                targetVideoBitrateKbps: profile.targetVideoBitrateKbps
            }),
            // A manual downscale profile must not inherit a global upscaling setting.
            ...(profile.videoMode === 'encode' && { upscaleEnabled: false })
        }
    };
}

module.exports = {
    QUALITY_MODES,
    QUALITY_PROFILES,
    resolveQualityMode
};