Auto-fetch PayU payment link tokens

src/main/kotlin/com/android/trisolarisserver/controller/PayuPaymentLinksController.kt

@@ -23,6 +23,7 @@ import org.springframework.web.bind.annotation.RequestMapping
 import org.springframework.web.bind.annotation.RestController
 import org.springframework.web.client.RestTemplate
 import org.springframework.web.server.ResponseStatusException
+import java.time.OffsetDateTime
 import java.util.UUID
 
 @RestController
@@ -116,9 +117,11 @@ class PayuPaymentLinksController(
         }
         request.expiryDate?.trim()?.ifBlank { null }?.let { body["expiryDate"] = it }
 
+        val accessToken = resolveAccessToken(settings)
+        settingsRepo.save(settings)
         val headers = HttpHeaders().apply {
             contentType = MediaType.APPLICATION_JSON
-            set("Authorization", "Bearer ${settings.accessToken}")
+            set("Authorization", "Bearer $accessToken")
             set("merchantId", settings.merchantId)
         }
         val entity = HttpEntity(body, headers)
@@ -145,6 +148,60 @@ class PayuPaymentLinksController(
         }
     }
 
+    private fun resolveAccessToken(settings: com.android.trisolarisserver.models.payment.PayuPaymentLinkSettings): String {
+        val now = OffsetDateTime.now()
+        val existing = settings.accessToken?.trim()?.ifBlank { null }
+        val expiresAt = settings.tokenExpiresAt
+        if (existing != null && expiresAt != null && expiresAt.isAfter(now.plusSeconds(60))) {
+            return existing
+        }
+        val clientId = settings.clientId?.trim()?.ifBlank { null }
+        val clientSecret = settings.clientSecret?.trim()?.ifBlank { null }
+        if (clientId == null || clientSecret == null) {
+            throw ResponseStatusException(HttpStatus.BAD_REQUEST, "Payment link client credentials missing")
+        }
+        val tokenResponse = fetchAccessToken(settings.isTest, clientId, clientSecret)
+        settings.accessToken = tokenResponse.accessToken
+        settings.tokenExpiresAt = now.plusSeconds(tokenResponse.expiresIn.toLong())
+        return tokenResponse.accessToken
+    }
+
+    private data class TokenResponse(val accessToken: String, val expiresIn: Int)
+
+    private fun fetchAccessToken(isTest: Boolean, clientId: String, clientSecret: String): TokenResponse {
+        val url = if (isTest) {
+            "https://uat-accounts.payu.in/oauth/token"
+        } else {
+            "https://accounts.payu.in/oauth/token"
+        }
+        val form = org.springframework.util.LinkedMultiValueMap<String, String>().apply {
+            add("client_id", clientId)
+            add("client_secret", clientSecret)
+            add("grant_type", "client_credentials")
+            add("scope", "create_payment_links")
+        }
+        val headers = HttpHeaders().apply {
+            contentType = MediaType.APPLICATION_FORM_URLENCODED
+        }
+        val entity = HttpEntity(form, headers)
+        val response = restTemplate.postForEntity(url, entity, String::class.java)
+        val body = response.body ?: ""
+        if (!response.statusCode.is2xxSuccessful) {
+            throw ResponseStatusException(HttpStatus.BAD_GATEWAY, "PayU token request failed")
+        }
+        return try {
+            val node = objectMapper.readTree(body)
+            val token = node.path("access_token").asText(null)
+            val expiresIn = node.path("expires_in").asInt(0)
+            if (token.isNullOrBlank() || expiresIn <= 0) {
+                throw IllegalStateException("Token missing")
+            }
+            TokenResponse(token, expiresIn)
+        } catch (ex: Exception) {
+            throw ResponseStatusException(HttpStatus.BAD_GATEWAY, "PayU token parse failed")
+        }
+    }
+
     private fun extractPaymentLink(body: String): String? {
         if (body.isBlank()) return null
         return try {