feat(line): chat-based 6-digit linking codes

src/v1/common/__snapshots__/v1-route-input-contract.spec.ts.snap

@@ -1115,6 +1115,9 @@ exports[`V1 Route Input Contracts matches the full v1 request contract snapshot
     "/v1/line/link": {
       "delete": {},
     },
+    "/v1/line/link-code": {
+      "post": {},
+    },
     "/v1/line/link-start": {
       "post": {},
     },

src/v1/common/v1-route-input-contract.spec.ts

@@ -369,6 +369,7 @@
         'verifyWebhookSignature',
         'handleEvents',
         'createLinkNonce',
+        'createLinkCode',
         'unlink',
       ]),
     };
@@ -888,6 +889,18 @@
       name: 'POST /v1/line/link-start mints a nonce for the current user',
       url: '/v1/line/link-start',
     },
+    {
+      auth: true,
+      expectedCall: {
+        args: [MOCK_USER.sub],
+        method: 'createLinkCode',
+        service: 'line',
+      },
+      expectedStatus: 201,
+      method: 'post',
+      name: 'POST /v1/line/link-code mints a chat-linking code for the current user',
+      url: '/v1/line/link-code',
+    },
     {
       auth: true,
       expectedCall: {
@@ -1037,7 +1050,7 @@
   ];
 
   it.each(successCases)('$name', async (testCase) => {
     let req = request(app.getHttpServer())[testCase.method](testCase.url);
 
     if (testCase.auth) {
       req = req.set('Authorization', AUTH_HEADER);
@@ -1075,7 +1088,7 @@
   });
 
   it.each(rejectionCases)('$name', async (testCase) => {
     let req = request(app.getHttpServer())[testCase.method](testCase.url);
 
     if (testCase.auth) {
       req = req.set('Authorization', AUTH_HEADER);

src/v1/line/line.controller.ts

@@ -66,6 +66,18 @@ export class LineController {
     return this.lineService.createLinkNonce(user.sub);
   }
 
+  @Post('link-code')
+  @UseGuards(JwtAuthGuard)
+  @ApiBearerAuth()
+  @ApiOperation({
+    summary: 'Mint a 6-digit code the user sends to the LINE bot to link',
+  })
+  linkCode(
+    @CurrentUser() user: AuthenticatedUser,
+  ): Promise<{ code: string; expiresAt: string }> {
+    return this.lineService.createLinkCode(user.sub);
+  }
+
   @Delete('link')
   @UseGuards(JwtAuthGuard)
   @ApiBearerAuth()

src/v1/line/line.service.spec.ts

@@ -290,6 +290,61 @@ describe('LineService', () => {
       expect(apiClient.issueLinkToken).toHaveBeenCalledWith(LINE_USER);
     });
 
+    it('links the sender when an unbound user sends a valid 6-digit code', async () => {
+      const isLinkedLookup = chain({ data: null, error: null });
+      const profileUpdate = chain({ data: null, error: null });
+      const codeLookup = chain({
+        data: { nonce: '123456', user_id: 'user-1', expires_at: 'later' },
+        error: null,
+      });
+      const codeDelete = chain({ data: null, error: null });
+      const adminClient = buildAdminClient({
+        profiles: [isLinkedLookup, profileUpdate],
+        cw_line_link_nonces: [codeLookup, codeDelete],
+      });
+      const { service, apiClient } = createService({ adminClient });
+
+      await service.handleEvents([
+        {
+          type: 'message',
+          source: { userId: LINE_USER },
+          message: { type: 'text', text: ' 123456 ' },
+        },
+      ]);
+
+      expect(profileUpdate.calls).toContainEqual({
+        method: 'update',
+        args: [{ line_id: LINE_USER }],
+      });
+      expect(profileUpdate.calls).toContainEqual({
+        method: 'eq',
+        args: ['id', 'user-1'],
+      });
+      expect(apiClient.issueLinkToken).not.toHaveBeenCalled();
+      const [, messages] = apiClient.pushMessage.mock.calls[0];
+      expect(String(messages[0].text)).toContain('連携が完了');
+    });
+
+    it('replies invalid-code when the 6-digit code is unknown or expired', async () => {
+      const adminClient = buildAdminClient({
+        profiles: [chain({ data: null, error: null })],
+        cw_line_link_nonces: [chain({ data: null, error: null })],
+      });
+      const { service, apiClient } = createService({ adminClient });
+
+      await service.handleEvents([
+        {
+          type: 'message',
+          source: { userId: LINE_USER },
+          message: { type: 'text', text: '999999' },
+        },
+      ]);
+
+      expect(apiClient.issueLinkToken).not.toHaveBeenCalled();
+      const [, messages] = apiClient.pushMessage.mock.calls[0];
+      expect(String(messages[0].text)).toContain('無効か期限切れ');
+    });
+
     it('ignores messages from bound users', async () => {
       const adminClient = buildAdminClient({
         profiles: [chain({ data: { id: 'user-1' }, error: null })],
@@ -356,6 +411,29 @@ describe('LineService', () => {
       expect(row.nonce).toBe(nonce);
     });
 
+    it('createLinkCode invalidates prior codes and mints a 6-digit code', async () => {
+      const purgeExpired = chain({ data: null, error: null });
+      const purgeUser = chain({ data: null, error: null });
+      const insert = chain({ data: null, error: null });
+      const adminClient = buildAdminClient({
+        cw_line_link_nonces: [purgeExpired, purgeUser, insert],
+      });
+      const { service } = createService({ adminClient });
+
+      const { code, expiresAt } = await service.createLinkCode('user-1');
+
+      expect(code).toMatch(/^\d{6}$/);
+      expect(new Date(expiresAt).getTime()).toBeGreaterThan(Date.now());
+      expect(purgeUser.calls).toContainEqual({
+        method: 'eq',
+        args: ['user_id', 'user-1'],
+      });
+      const insertCall = insert.calls.find((c) => c.method === 'insert');
+      const row = (insertCall!.args[0] ?? {}) as Record<string, unknown>;
+      expect(row.nonce).toBe(code);
+      expect(row.user_id).toBe('user-1');
+    });
+
     it('unlink clears line_id for the current user', async () => {
       const profileUpdate = chain({ data: null, error: null });
       const adminClient = buildAdminClient({ profiles: [profileUpdate] });

src/v1/line/line.service.ts

@@ -5,26 +5,30 @@ import {
   UnauthorizedException,
 } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
-import { createHmac, randomBytes, timingSafeEqual } from 'crypto';
+import { createHmac, randomBytes, randomInt, timingSafeEqual } from 'crypto';
 import { SupabaseService } from '../../supabase/supabase.service';
 import { LineApiClient, type LineMessage } from './line-api.client';
 
 const APP_BASE_URL = 'https://app.cropwatch.io';
 const NONCE_TTL_MS = 10 * 60 * 1000;
 const UNIQUE_VIOLATION = '23505';
+const LINK_CODE_PATTERN = /^\d{6}$/;
+const LINK_CODE_INSERT_ATTEMPTS = 5;
 
 export interface LineWebhookEvent {
   type: string;
   source?: { type?: string; userId?: string };
   link?: { result?: string; nonce?: string };
+  message?: { type?: string; text?: unknown };
   [key: string]: unknown;
 }
 
 // Bilingual DM texts (ja first, matching the alert-email convention).
 const DM = {
   linkButtonAlt: 'CropWatchアカウント連携 / Link your CropWatch account',
+  // Buttons-template text is capped at 160 chars — keep this tight.
   linkButtonText:
-    'CropWatchアカウントと連携すると、アラートをLINEで受け取れます。\nLink your CropWatch account to receive alerts on LINE.',
+    'アプリの6桁コードをこのトークに送るか、下のボタンで連携できます。\nSend the 6-digit code from the app here, or tap the button.',
   linkButtonLabel: '連携する / Link',
   alreadyLinked:
     'このLINEアカウントは連携済みです。\nThis LINE account is already linked.',
@@ -34,6 +38,8 @@ const DM = {
     '連携に失敗しました。このトークにメッセージを送ると、新しい連携ボタンをお送りします。\nLink failed — send this chat any message to get a new link button.',
   linkedElsewhere:
     'このLINEアカウントは別のCropWatchアカウントに連携されています。\nThis LINE account is already linked to a different CropWatch user.',
+  codeInvalid:
+    'この連携コードは無効か期限切れです。アプリのプロフィールページで新しいコードを取得して、もう一度お送りください。\nThat linking code is invalid or expired. Get a new code from your profile page in the app and send it again.',
 } as const;
 
 @Injectable()
@@ -99,10 +105,8 @@ export class LineService {
         if (lineUserId) await this.handleAccountLink(lineUserId, event);
         return;
       case 'message':
-        // Recovery path: an unbound user's message re-issues the link button
-        // (the link token in the original DM expires after 10 minutes).
         if (lineUserId && !(await this.isLinked(lineUserId))) {
-          await this.sendLinkButton(lineUserId);
+          await this.handleUnboundMessage(lineUserId, event);
         }
         return;
       default:
@@ -118,38 +122,56 @@ export class LineService {
     await this.sendLinkButton(lineUserId);
   }
 
-  private async handleAccountLink(
+  // Primary linking path: the profile page shows a 6-digit code, the user
+  // sends it in chat. Works on every device/browser combination because the
+  // browser and LINE never have to share a session (the official
+  // account-link dialog breaks whenever the link escapes LINE's in-app
+  // browser). Non-code messages fall back to the account-link button.
+  private async handleUnboundMessage(
     lineUserId: string,
     event: LineWebhookEvent,
   ): Promise<void> {
-    if (event.link?.result !== 'ok' || !event.link.nonce) {
-      this.logger.warn(`LINE account link did not complete for ${lineUserId}`);
+    const text =
+      typeof event.message?.text === 'string' ? event.message.text.trim() : '';
+
+    if (!LINK_CODE_PATTERN.test(text)) {
+      await this.sendLinkButton(lineUserId);
       return;
     }
 
     const client = this.supabaseService.getAdminClient();
     const nowIso = new Date().toISOString();
 
-    const { data: nonceRow, error: nonceError } = await client
+    const { data: codeRow, error: codeError } = await client
       .from('cw_line_link_nonces')
       .select('nonce, user_id, expires_at')
-      .eq('nonce', event.link.nonce)
+      .eq('nonce', text)
       .gt('expires_at', nowIso)
       .maybeSingle();
 
-    if (nonceError) {
-      throw new Error(`Failed to look up link nonce: ${nonceError.message}`);
+    if (codeError) {
+      throw new Error(`Failed to look up link code: ${codeError.message}`);
     }
-    if (!nonceRow) {
-      this.logger.warn('LINE accountLink nonce missing or expired');
-      await this.pushText(lineUserId, DM.linkFailed);
+    if (!codeRow) {
+      await this.pushText(lineUserId, DM.codeInvalid);
       return;
     }
 
+    const row = codeRow as { nonce: string; user_id: string };
+    await this.bindProfile(lineUserId, row.user_id, row.nonce);
+  }
+
+  private async bindProfile(
+    lineUserId: string,
+    userId: string,
+    nonce: string,
+  ): Promise<void> {
+    const client = this.supabaseService.getAdminClient();
+
     const { error: updateError } = await client
       .from('profiles')
       .update({ line_id: lineUserId })
-      .eq('id', nonceRow.user_id);
+      .eq('id', userId);
 
     if (updateError) {
       if (updateError.code === UNIQUE_VIOLATION) {
@@ -159,12 +181,41 @@ export class LineService {
       throw new Error(`Failed to bind LINE account: ${updateError.message}`);
     }
 
-    await client
-      .from('cw_line_link_nonces')
-      .delete()
-      .eq('nonce', nonceRow.nonce);
+    await client.from('cw_line_link_nonces').delete().eq('nonce', nonce);
     await this.pushText(lineUserId, DM.linked);
-    this.logger.log(`Linked LINE account for user ${nonceRow.user_id}`);
+    this.logger.log(`Linked LINE account for user ${userId}`);
+  }
+
+  private async handleAccountLink(
+    lineUserId: string,
+    event: LineWebhookEvent,
+  ): Promise<void> {
+    if (event.link?.result !== 'ok' || !event.link.nonce) {
+      this.logger.warn(`LINE account link did not complete for ${lineUserId}`);
+      return;
+    }
+
+    const client = this.supabaseService.getAdminClient();
+    const nowIso = new Date().toISOString();
+
+    const { data: nonceRow, error: nonceError } = await client
+      .from('cw_line_link_nonces')
+      .select('nonce, user_id, expires_at')
+      .eq('nonce', event.link.nonce)
+      .gt('expires_at', nowIso)
+      .maybeSingle();
+
+    if (nonceError) {
+      throw new Error(`Failed to look up link nonce: ${nonceError.message}`);
+    }
+    if (!nonceRow) {
+      this.logger.warn('LINE accountLink nonce missing or expired');
+      await this.pushText(lineUserId, DM.linkFailed);
+      return;
+    }
+
+    const row = nonceRow as { nonce: string; user_id: string };
+    await this.bindProfile(lineUserId, row.user_id, row.nonce);
   }
 
   private async sendLinkButton(lineUserId: string): Promise<void> {
@@ -212,6 +263,40 @@ export class LineService {
     return { nonce };
   }
 
+  // 6-digit code for the chat-based linking path. Shares the nonce table:
+  // codes and account-link nonces never collide (different shapes), and both
+  // are single-use rows with a 10-minute expiry.
+  async createLinkCode(
+    userId: string,
+  ): Promise<{ code: string; expiresAt: string }> {
+    const client = this.supabaseService.getAdminClient();
+    const nowIso = new Date().toISOString();
+
+    await client.from('cw_line_link_nonces').delete().lt('expires_at', nowIso);
+    // A user re-requesting a code invalidates their previous one.
+    await client.from('cw_line_link_nonces').delete().eq('user_id', userId);
+
+    const expiresAt = new Date(Date.now() + NONCE_TTL_MS).toISOString();
+    for (let attempt = 1; attempt <= LINK_CODE_INSERT_ATTEMPTS; attempt += 1) {
+      const code = randomInt(100000, 1000000).toString();
+      const { error } = await client.from('cw_line_link_nonces').insert({
+        nonce: code,
+        user_id: userId,
+        expires_at: expiresAt,
+      });
+
+      if (!error) {
+        return { code, expiresAt };
+      }
+      if (error.code !== UNIQUE_VIOLATION) {
+        throw new Error(`Failed to store link code: ${error.message}`);
+      }
+      // Collision with another user's live code — regenerate.
+    }
+
+    throw new Error('Failed to allocate a unique link code');
+  }
+
   async unlink(userId: string): Promise<void> {
     // line_id is deliberately excluded from the PATCH-profile whitelist;
     // this service method is the only authenticated write path for it.