2 files changed, 95 insertions, 6 deletions

diff --git a/src/background/clients/FindClient.ts b/src/background/clients/FindClient.ts
index 863c5ad..b46b964 100644
--- a/src/background/clients/FindClient.ts
+++ b/src/background/clients/FindClient.ts
@@ -3,6 +3,8 @@ import * as messages from "../../shared/messages";
 export default interface FindClient {
   findNext(tabId: number, frameId: number, keyword: string): Promise<boolean>;
 
+  findPrev(tabId: number, frameId: number, keyword: string): Promise<boolean>;
+
   clearSelection(tabId: number, frameId: number): Promise<void>;
 }
 
@@ -20,6 +22,19 @@ export class FindClientImpl implements FindClient {
     return found;
   }
 
+  async findPrev(
+    tabId: number,
+    frameId: number,
+    keyword: string
+  ): Promise<boolean> {
+    const found = (await browser.tabs.sendMessage(
+      tabId,
+      { type: messages.FIND_PREV, keyword },
+      { frameId }
+    )) as boolean;
+    return found;
+  }
+
   clearSelection(tabId: number, frameId: number): Promise<void> {
     return browser.tabs.sendMessage(
       tabId,
diff --git a/src/background/operators/impls/FindPrevOperator.ts b/src/background/operators/impls/FindPrevOperator.ts
index 28238f6..822c386 100644
--- a/src/background/operators/impls/FindPrevOperator.ts
+++ b/src/background/operators/impls/FindPrevOperator.ts
@@ -7,14 +7,88 @@ import FramePresenter from "../../presenters/FramePresenter";
 
 export default class FindPrevOperator implements Operator {
   constructor(
-    _tabPresenter: TabPresenter,
-    _findRepository: FindRepository,
-    _findClient: FindClient,
-    _consoleClient: ConsoleClient,
-    _framePresenter: FramePresenter
+    private readonly tabPresenter: TabPresenter,
+    private readonly findRepository: FindRepository,
+    private readonly findClient: FindClient,
+    private readonly consoleClient: ConsoleClient,
+    private readonly framePresenter: FramePresenter
   ) {}
 
   async run(): Promise<void> {
-    throw new Error("not implemented");
+    const tab = await this.tabPresenter.getCurrent();
+    const tabId = tab?.id;
+    if (tabId == null) {
+      return;
+    }
+
+    const state = await this.findRepository.getLocalState(tabId);
+    if (state) {
+      // Start to find the keyword from the current frame which last found on,
+      // and concat it to end of frame ids to perform a wrap-search
+      //
+      //                ,- keyword should be in this frame
+      //                |
+      // [100, 101, 0, 100]
+      //   |
+      //   `- continue from frame id 100
+      //
+      const targetFrameIds = state.frameIds
+        .slice(state.framePos)
+        .concat(
+          state.frameIds.slice(0, state.framePos),
+          state.frameIds[state.framePos]
+        );
+
+      for (let i = targetFrameIds.length - 1; i >= 0; --i) {
+        const found = await this.findClient.findPrev(
+          tabId,
+          targetFrameIds[i],
+          state.keyword
+        );
+        if (found) {
+          this.findRepository.setLocalState(tabId, {
+            ...state,
+            framePos: (i + state.framePos) % state.frameIds.length, // save current frame position or first
+          });
+          return;
+        }
+        this.findClient.clearSelection(tabId, targetFrameIds[i]);
+      }
+
+      // The keyword is gone.
+      this.consoleClient.showError(
+        tabId,
+        "Pattern not found: " + state.keyword
+      );
+      return;
+    }
+
+    const keyword = await this.findRepository.getGlobalKeyword();
+    if (keyword) {
+      const frameIds = await this.framePresenter.getAllFrameIds(tabId);
+      for (const frameId of frameIds) {
+        await this.findClient.clearSelection(tabId, frameId);
+      }
+
+      for (let framePos = frameIds.length - 1; framePos >= 0; --framePos) {
+        const found = await this.findClient.findPrev(
+          tabId,
+          frameIds[framePos],
+          keyword
+        );
+        if (found) {
+          await this.findRepository.setLocalState(tabId, {
+            frameIds,
+            framePos,
+            keyword,
+          });
+          await this.consoleClient.showInfo(tabId, "Pattern found: " + keyword);
+          return;
+        }
+      }
+      this.consoleClient.showError(tabId, "Pattern not found: " + keyword);
+      return;
+    }
+    await this.consoleClient.showError(tabId, "No previous search keywords");
   }
 }