package com.myfatoorahreactnative.cardviewv3

import com.google.gson.Gson
import com.google.gson.JsonElement
import com.google.gson.JsonObject
import com.myfatoorah.sdk.v3.entity.callback.MFCallbackCard
import com.myfatoorah.sdk.v3.entity.payment.MFPaymentDetails
import com.myfatoorah.sdk.v3.entity.session.MFGetSessionData
import com.myfatoorah.sdk.v3.entity.session.MFSessionData
import com.myfatoorah.sdk.v3.views.MFV3PaymentResult
import com.myfatoorah.sdk.v3.views.MFV3VerifyResult

/**
 * MFV3Serializers - hand-serializes the V3 SDK result models into JSON strings with
 * PascalCase keys matching the JS interfaces in src/MFModels.tsx.
 *
 * The SDK models are Decodable-only and live in another module, so this builds
 * JsonObject trees by hand (with `type` discriminators for the result enums) instead
 * of reusing the V2 `handleReadableMap`/`convertJsonStringToUppercase` helpers, which
 * only flip key casing and can't add discriminators or flatten nested fields. Leaf
 * models whose @SerializedName already match the JS PascalCase contract still go
 * through Gson's `toJsonTree`.
 */
internal object MFV3Serializers {

  private val gson = Gson()

  //#region Public entry points

  fun session(session: MFSessionData): String =
    json(sessionObject(session))

  fun paymentResult(result: MFV3PaymentResult): String =
    json(paymentResultObject(result))

  fun verifyResult(result: MFV3VerifyResult): String =
    json(verifyResultObject(result))

  //#endregion

  //#region Result enums

  private fun paymentResultObject(result: MFV3PaymentResult): JsonObject = when (result) {
    is MFV3PaymentResult.Completed -> JsonObject().apply {
      addProperty("type", "completed")
      addTree("details", gson.toJsonTree(result.details))
    }

    is MFV3PaymentResult.CardCollected -> JsonObject().apply {
      addProperty("type", "cardCollected")
      addString("sessionId", result.sessionId)
      addTree("card", cardDetailsObject(result.card))
    }

    is MFV3PaymentResult.PendingBackendResolution -> JsonObject().apply {
      addProperty("type", "pendingBackendResolution")
      addString("paymentData", result.paymentData)
      addString("redirectionUrl", result.redirectionUrl)
      addString("paymentId", result.paymentId)
    }
  }

  private fun verifyResultObject(result: MFV3VerifyResult): JsonObject = when (result) {
    is MFV3VerifyResult.Verified -> JsonObject().apply {
      addProperty("type", "verified")
      addTree("session", getSessionDataObject(result.session))
    }

    is MFV3VerifyResult.PendingBackendResolution -> JsonObject().apply {
      addProperty("type", "pendingBackendResolution")
      addString("sessionId", result.sessionId)
      addString("redirectionUrl", result.redirectionUrl)
    }
  }

  //#endregion

  //#region Session (POST /v3/sessions)

  private fun sessionObject(s: MFSessionData): JsonObject = JsonObject().apply {
    addString("SessionId", s.sessionId)
    addString("SessionExpiry", s.sessionExpiry)
    addString("EncryptionKey", s.encryptionKey)
    addString("OperationType", s.operationType)
    addTree("Order", s.order?.let(gson::toJsonTree))
    addTree("Customer", s.customer?.let(gson::toJsonTree))
  }

  //#endregion

  //#region Card (COLLECT_DETAILS)
  // Hand-built because MFCallbackCard uses camelCase @SerializedName while the JS
  // contract (MFV3CardDetails) is PascalCase.

  private fun cardDetailsObject(c: MFCallbackCard?): JsonObject? {
    if (c == null) return null
    return JsonObject().apply {
      addString("Brand", c.brand)
      addString("PanHash", c.panHash)
      addString("Token", c.token)
      addString("Number", c.number)
      addString("NameOnCard", c.nameOnCard)
      addString("ExpiryYear", c.expiryYear)
      addString("ExpiryMonth", c.expiryMonth)
      addString("Issuer", c.issuer)
      addString("IssuerCountry", c.issuerCountry)
      addString("FundingMethod", c.fundingMethod)
      addString("ProductName", c.productName)
    }
  }

  //#endregion

  //#region Verify (GET /v3/sessions/{id})
  // Customer.Reference is flattened to top-level CustomerReference (mirrors iOS);
  // TransactionResult stays a nested object.

  private fun getSessionDataObject(d: MFGetSessionData): JsonObject = JsonObject().apply {
    addString("SessionExpiry", d.sessionExpiry)
    addProperty("IsUsed", d.isUsed)
    addString("OperationType", d.operationType)
    addTree("Order", d.order?.let(gson::toJsonTree))
    addString("CustomerReference", d.customer?.reference)
    addTree("Card", d.card?.let(gson::toJsonTree))
    addTree("TransactionResult", d.transactionResult?.let(gson::toJsonTree))
  }

  //#endregion

  //#region Helpers

  private fun JsonObject.addString(key: String, value: String?) {
    if (value != null) addProperty(key, value)
  }

  private fun JsonObject.addTree(key: String, tree: JsonElement?) {
    if (tree != null && !tree.isJsonNull) add(key, tree)
  }

  private fun json(obj: JsonObject): String =
    try {
      gson.toJson(obj)
    } catch (e: Exception) {
      "{}"
    }

  //#endregion
}