diff --git a/src/aplication/Nfc.usecases.test.ts b/src/aplication/Nfc.usecases.test.ts
index 5f3c082..f6791db 100644
--- a/src/aplication/Nfc.usecases.test.ts
+++ b/src/aplication/Nfc.usecases.test.ts
@@ -1,18 +1,18 @@
 import { httpclient } from "config/httpclient.config.js";
 import { pgClient } from "config/pgclient.config.js";
 import type { ServerContext } from "domain/ServerContext.js";
-import test, { describe } from "node:test";
+import test, { describe, beforeEach } from "node:test";
 import { NfcUsecases } from "./Nfc.usecases.js";
+import type { NfcRepository } from "infrastructure/Nfc.repository.js";
 import assert from "node:assert";
 
-
-describe("NFC activation code", () => {
+describe("NFC activation code (Private methods)", () => {
     const serverContext: ServerContext = {
         PostgresClient: pgClient,
         HttpClient: httpclient
     }
 
-    const nfcUsecases = new NfcUsecases(serverContext)
+    const nfcUsecases = new NfcUsecases(serverContext, {} as NfcRepository)
 
     test("Should generate 8 digit codes", () => {
         // @ts-expect-error
@@ -43,3 +43,89 @@ describe("NFC activation code", () => {
         assert(validation == false)
     })
 })
+
+describe("NfcUsecases Unit Tests (Public methods with Mocks)", () => {
+    let mockNfcRepository: any;
+    let mockServerContext: ServerContext;
+    let nfcUsecases: NfcUsecases;
+
+    beforeEach(() => {
+        mockNfcRepository = {
+            findActivationCodes: test.mock.fn(),
+            createActivationCode: test.mock.fn(),
+        };
+
+        mockServerContext = {
+            PostgresClient: {} as any,
+            HttpClient: {} as any,
+        };
+
+        nfcUsecases = new NfcUsecases(mockServerContext, mockNfcRepository as unknown as NfcRepository);
+    });
+
+    describe("generateActivationLabel", () => {
+        const card_id = "test-card-id";
+
+        test("should return error if repository.findActivationCodes fails", async () => {
+            const expectedError = "Repository error";
+            mockNfcRepository.findActivationCodes.mock.mockImplementation(async () => ({
+                error: expectedError
+            }));
+
+            const usecase = nfcUsecases.generateActivationLabel();
+            const result = await usecase({ card_id });
+
+            assert.strictEqual(result.error, expectedError);
+            assert.strictEqual(mockNfcRepository.findActivationCodes.mock.callCount(), 1);
+        });
+
+        test("should reuse existing code if found and override is false", async () => {
+            const existingCode = "v1234567";
+            mockNfcRepository.findActivationCodes.mock.mockImplementation(async () => ({
+                data: [{ code_plain: existingCode }]
+            }));
+            mockNfcRepository.createActivationCode.mock.mockImplementation(async () => ({
+                data: { card_id, code_plain: existingCode }
+            }));
+
+            const usecase = nfcUsecases.generateActivationLabel();
+            const result = await usecase({ card_id, override: false });
+
+            assert.ok(result.data);
+            assert.strictEqual(result.data.code, existingCode);
+            assert.strictEqual(result.data.reused, true);
+            assert.strictEqual(result.data.overriden, false);
+
+            assert.strictEqual(mockNfcRepository.createActivationCode.mock.callCount(), 1);
+        });
+
+        test("should generate new code if no existing codes found", async () => {
+            mockNfcRepository.findActivationCodes.mock.mockImplementation(async () => ({
+                data: []
+            }));
+
+            const usecase = nfcUsecases.generateActivationLabel();
+            const result = await usecase({ card_id });
+
+            assert.ok(result.data);
+            assert.ok(result.data.code);
+            assert.strictEqual(result.data.reused, false);
+            assert.strictEqual(result.data.overriden, false);
+        });
+
+        test("should generate new code if override is true even if existing codes exist", async () => {
+            const existingCode = "v1234567";
+            mockNfcRepository.findActivationCodes.mock.mockImplementation(async () => ({
+                data: [{ code_plain: existingCode }]
+            }));
+
+            const usecase = nfcUsecases.generateActivationLabel();
+            const result = await usecase({ card_id, override: true });
+
+            assert.ok(result.data);
+            assert.notStrictEqual(result.data.code, existingCode);
+            assert.strictEqual(result.data.reused, false);
+            assert.strictEqual(result.data.overriden, true);
+        });
+    });
+});
diff --git a/src/aplication/Nfc.usecases.ts b/src/aplication/Nfc.usecases.ts
index 45007e4..28cefdc 100644
--- a/src/aplication/Nfc.usecases.ts
+++ b/src/aplication/Nfc.usecases.ts
@@ -1,12 +1,20 @@
 import type { ServerContext } from "domain/ServerContext.js";
 import { labelTemplate } from "./labelTemplate.js";
+import type { NfcRepository } from "infrastructure/Nfc.repository.js";
+import assert from "node:assert";
+import type { CodeGenerationResultDTO } from "domain/NfcDTOs.js";
+import type { Result } from "domain/Result.js";
 
 export class NfcUsecases {
     private ctx: ServerContext;
+    private nfcRepository: NfcRepository;
+
     constructor(
-        serverContext: ServerContext
+        serverContext: ServerContext,
+        nfcRepository: NfcRepository
     ) {
         this.ctx = serverContext
+        this.nfcRepository = nfcRepository
     }
 
     private getRandomDayOffset() {
@@ -69,16 +77,58 @@ export class NfcUsecases {
         return validationChar == testValidationChar
     }
 
+    /**
+    * Caso de uso principal, genera una etiqueta con un codigo de activación,
+    * si ya se ha generado uno para esa tarjeta se avisará.
+    * Se puede forzar generar uno nuevo.
+    */
     public generateActivationLabel() {
-        return () => {
+        return async (args: {
+            card_id: string,
+            override?: boolean,
+        }): Promise<Result<string, CodeGenerationResultDTO>> => {
+            const generatedCodes = await this.nfcRepository.findActivationCodes(args.card_id)
+
+            if (generatedCodes.error != undefined) {
+                console.error(generatedCodes.error)
+                return generatedCodes // Caso de error
+            }
+
+            if (generatedCodes.data.length > 0 && !args.override) {
+                // Ya se habia generado un codigo
+                assert(generatedCodes.data[0] != undefined)
+                const code = generatedCodes.data[0].code_plain
+                assert(code != undefined)
+
+                const label = labelTemplate(code)
+                this.nfcRepository.createActivationCode({
+                    cardId: args.card_id,
+                    code: code
+                })
+
+                return {
+                    data: {
+                        code: code,
+                        label: label,
+                        overriden: false,
+                        reused: true,
+                    }
+                }
+            }
+
             const codigo = this.generateActivationCode()
             const label = labelTemplate(codigo)
 
             // Introducir en la bdd
 
+            // Caso base: codigo limpio generado
             return {
-                code: codigo,
-                label: label
+                data: {
+                    code: codigo,
+                    label: label,
+                    overriden: args.override ?? false,
+                    reused: false
+                }
             }
         }
     }
diff --git a/src/domain/NfcRegistry.ts b/src/domain/NfcDTOs.ts
similarity index 70%
rename from src/domain/NfcRegistry.ts
rename to src/domain/NfcDTOs.ts
index b3bdb60..68323d7 100644
--- a/src/domain/NfcRegistry.ts
+++ b/src/domain/NfcDTOs.ts
@@ -26,3 +26,12 @@ export type ActivationLogDTO = {
     geo_location: string,
     created_at: Date,
 }
+
+export type CodeGenerationResultDTO = {
+    code: string,
+    label: string,
+    /** Si ya existia un codigo anterior pero se ha creado uno nuevo*/
+    overriden: boolean,
+    /** Si ya existia un código anterior y se ha reusado */
+    reused: boolean
+}
diff --git a/src/infrastructure/Nfc.repository.ts b/src/infrastructure/Nfc.repository.ts
index d4d7fc6..2943777 100644
--- a/src/infrastructure/Nfc.repository.ts
+++ b/src/infrastructure/Nfc.repository.ts
@@ -1,4 +1,4 @@
-import type { ActivationCodeDTO } from "domain/NfcRegistry.js";
+import type { ActivationCodeDTO } from "domain/NfcDTOs.js";
 import type { Result } from "domain/Result.js";
 import type { ServerContext } from "domain/ServerContext.js";
 import { constrainedMemory } from "node:process";