GoogleAdmobConsentUtils.kt

import android.content.Context
import android.content.SharedPreferences
import android.content.pm.ApplicationInfo
import android.util.Log
import androidx.preference.PreferenceManager


//## HINT: https://stackoverflow.com/a/70324431
//## HINT: https://groups.google.com/g/google-admob-ads-sdk/c/InmLIbFm8Xg/m/h4fhgUwmAgAJ

// https://groups.google.com/g/google-admob-ads-sdk/c/InmLIbFm8Xg/m/HLKLt2B1AgAJ

// https://support.google.com/admob/answer/9760862#consent-policies describes the requirements for the different types of serving
// modes for EU traffic:
//
//- Personalized ads - Consent for purposes 1,3,4, Legitimate Interest for 2, 7, 9, 10
//- Non personalized ads - Consent for purpose 1, Legitimate Interest for 2, 7, 9, 10
//- Limited ads - No consent for purpose 1.

//## https://groups.google.com/g/google-admob-ads-sdk/   --> search for UMP

// Further sources:
// https://support.google.com/admanager/answer/9461778
//
// Purposes:
//   1  - Store and/or access information on a device
//   2  - Select basic ads
//   3  - Create a personalised ads profile
//   4  - Select personalised ads
//   5  - Create a personalised content profile
//   6  - Select personalised content
//   7  - Measure ad performance
//   8  - Measure content performance
//   9  - Apply market research to generate audience insights
//   10 - Develop and improve products
//
// Special purposes:
//   1 - Ensure security, prevent fraud, and debug
//   2 - Technically deliver ads or content
//
// Features:
//   1 - Match and combine offline data sources
//   2 - Link different devices
//   3 - Receive and send automatically sent device characteristics for identification
//
// Special features:
//   1 - Use precise geolocation data
//   2 - Actively scan device characteristics for identification


@Suppress("MagicNumber")
object GoogleAdmobConsentUtils {

    // https://github.com/InteractiveAdvertisingBureau/GDPR-Transparency-and-Consent-Framework/blob/master/TCFv2/IAB%20Tech%20Lab%20-%20CMP%20API%20v2.md#in-app-details
    // https://support.google.com/admob/answer/9760862?hl=en&ref_topic=9756841

    //## search here for Google: https://iabeurope.eu/vendor-list-tcf/
    private const val GOOGLE_TCF_VENDOR_ID: Int = 755

    private val Context.prefMngr: SharedPreferences get() = PreferenceManager.getDefaultSharedPreferences(this.applicationContext)

    //## IABTCF_PurposeConsents - A string of 0's and 1's up to 10 entries long indicating whether the user provided consent for the
    //##  10 different purposes
    private val SharedPreferences.purposeConsents get() = this.getString("IABTCF_PurposeConsents", "") ?: ""

    //## A string of 0s and 1s that is arbitrarily long, indicating whether a given vendor has been given consent for the previously
    //## mentioned purposes. Each vendor has an ID indicating their position in the string. For example Google's ID is 755, so if
    //## Google has been given consent then the 755th character in this string would be a "1". The full vendor list is available here:
    //## https://iabeurope.eu/vendor-list-tcf/
    private val SharedPreferences.vendorConsents get() = this.getString("IABTCF_VendorConsents", "") ?: ""

    //## A string of 0's and 1's up to 10 entries long indicating whether the app has legitimate interest for the 10 different purposes
    private val SharedPreferences.vendorLIs get() = this.getString("IABTCF_VendorLegitimateInterests", "") ?: ""

    //## Similar to the vendor consent string, except that it indicates if the vendor has legitimate interest for the previously
    //## indicated purposes.
    private val SharedPreferences.purposeLIs get() = this.getString("IABTCF_PurposeLegitimateInterests", "") ?: ""


    //  whether the user is in the EEA
    fun isGDPR(
        ctx: Context
    ): Boolean = ctx.prefMngr.getInt("IABTCF_gdprApplies", 0) == 1


    fun canShowAds(
        ctx: Context
    ): Boolean {
        val prefs: SharedPreferences = ctx.prefMngr

        val purposeConsents: String = prefs.purposeConsents
        val purposeLIs: String = prefs.purposeLIs

        val hasGoogleVendorConsent: Boolean = prefs.vendorConsents.hasAttribute(index = GOOGLE_TCF_VENDOR_ID)
        val hasGoogleVendorLI: Boolean = prefs.vendorLIs.hasAttribute(index = GOOGLE_TCF_VENDOR_ID)

        debug(
            ctx = ctx,
            debugStr = "canShowAds",
            consentForPurposes = listOf(1),
            hasConsentOrLegitimateInterestForPurposes = listOf(2, 7, 9, 10),
            purposeConsent = purposeConsents,
            purposeLI = purposeLIs,
            hasGoogleVendorConsent = hasGoogleVendorConsent,
            hasGoogleVendorLI = hasGoogleVendorLI
        )

        // Minimum required for at least non-personalized ads
        return hasConsentFor(
            purposes = listOf(1),
            purposeConsent = purposeConsents,
            hasVendorConsent = hasGoogleVendorConsent
        ) &&
            hasConsentOrLegitimateInterestFor(
                purposes = listOf(2, 7, 9, 10),
                purposeConsent = purposeConsents,
                purposeLI = purposeLIs,
                hasVendorConsent = hasGoogleVendorConsent,
                hasVendorLI = hasGoogleVendorLI
            )
    }


    fun canShowPersonalizedAds(
        ctx: Context
    ): Boolean {
        val prefs: SharedPreferences = ctx.prefMngr

        val purposeConsents: String = prefs.purposeConsents
        val purposeLIs: String = prefs.purposeLIs

        val hasGoogleVendorConsent: Boolean = prefs.vendorConsents.hasAttribute(index = GOOGLE_TCF_VENDOR_ID)
        val hasGoogleVendorLI: Boolean = prefs.vendorLIs.hasAttribute(index = GOOGLE_TCF_VENDOR_ID)

        debug(
            ctx = ctx,
            debugStr = "canShowPersonalizedAds",
            consentForPurposes = listOf(1, 3, 4),
            hasConsentOrLegitimateInterestForPurposes = listOf(2, 7, 9, 10),
            purposeConsent = purposeConsents,
            purposeLI = purposeLIs,
            hasGoogleVendorConsent = hasGoogleVendorConsent,
            hasGoogleVendorLI = hasGoogleVendorLI
        )

        return hasConsentFor(
            purposes = listOf(1, 3, 4),
            purposeConsent = purposeConsents,
            hasVendorConsent = hasGoogleVendorConsent
        ) &&
            hasConsentOrLegitimateInterestFor(
                purposes = listOf(2, 7, 9, 10),
                purposeConsent = purposeConsents,
                purposeLI = purposeLIs,
                hasVendorConsent = hasGoogleVendorConsent,
                hasVendorLI = hasGoogleVendorLI
            )
    }


    // Check if a binary string has a "1" at position "index" (1-based)
    private fun String.hasAttribute(
        index: Int
    ): Boolean = this.getOrNull(index - 1) == '1'


    // Check if consent is given for a list of purposes
    private fun hasConsentFor(
        purposes: List<Int>,
        purposeConsent: String,
        hasVendorConsent: Boolean
    ): Boolean = hasVendorConsent &&
        purposes.all { p: Int -> purposeConsent.hasAttribute(index = p) }


    // Check if a vendor either has consent or legitimate interest for a list of purposes
    private fun hasConsentOrLegitimateInterestFor(
        purposes: List<Int>,
        purposeConsent: String,
        purposeLI: String,
        hasVendorConsent: Boolean,
        hasVendorLI: Boolean
    ): Boolean = purposes.all { p: Int ->
        (hasVendorLI && purposeLI.hasAttribute(index = p)) ||
            (hasVendorConsent && purposeConsent.hasAttribute(index = p))
    }


    private fun debug(
        ctx: Context,
        debugStr: String,
        consentForPurposes: List<Int>,
        hasConsentOrLegitimateInterestForPurposes: List<Int>,
        purposeConsent: String,
        purposeLI: String,
        hasGoogleVendorConsent: Boolean,
        hasGoogleVendorLI: Boolean
    ) {
        val isDebuggable: Boolean = 0 != (ctx.applicationInfo.flags and ApplicationInfo.FLAG_DEBUGGABLE)
        if (!isDebuggable) return

        val purposes1: String = consentForPurposes.joinToString(separator = ", ") { purpose: Int ->
            val hasConsent: Boolean =
                hasConsentFor(purposes = listOf(purpose), purposeConsent = purposeConsent, hasVendorConsent = hasGoogleVendorConsent)
            return@joinToString "$purpose-$hasConsent"
        }

        val purposes2: String = hasConsentOrLegitimateInterestForPurposes.joinToString(separator = ", ") { purpose: Int ->
            val hasConsent: Boolean = hasConsentOrLegitimateInterestFor(
                purposes = listOf(purpose),
                purposeConsent = purposeConsent,
                purposeLI = purposeLI,
                hasVendorConsent = hasGoogleVendorConsent,
                hasVendorLI = hasGoogleVendorLI
            )
            return@joinToString "$purpose-$hasConsent"
        }

        val outStr: String = listOf(
            debugStr,
            "   hasGoogleVendorConsent: $hasGoogleVendorConsent",
            "   hasGoogleVendorLI: $hasGoogleVendorLI",
            "   hasConsent for purposes: $purposes1",
            "   hasConsentOrLegitimateInterest for purposes: $purposes2"
        ).joinToString(separator = "\n")

        Log.d("GoogleAdmobConsentUtils", outStr)
    }

}