feat: reset (#146)

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<details>
  <summary>📦 Published PR as canary version: <code>Canary Versions</code></summary>
  <br />

  ✨ Test out this PR locally via:
  
  ```bash
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  npm install @dotinc/[email protected]
  # or 
  yarn add @dotinc/[email protected]
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  ```
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<!-- GITHUB_RELEASE PR BODY: canary-version -->

packages/ogre/src/repository.test.ts

@@ -24,7 +24,7 @@ test("reconstruction", async (t) => {
   t.is(
     repo.ref("refs/heads/main"),
     firstStep,
-    "main is pointing at wrong commit"
+    "main is pointing at wrong commit",
   );
   t.is(history.commits.length, 2, "incorrect # of commits");
 
@@ -37,7 +37,7 @@ test("reconstruction", async (t) => {
   t.is(
     sumChanges(history2.commits),
     changeEntries,
-    "incorrect # of changelog entries"
+    "incorrect # of changelog entries",
   );
 });
 
@@ -72,7 +72,7 @@ test("reconstruct with 2 commits", async (t) => {
   t.is(
     sumChanges(history2.commits),
     changeEntries,
-    "incorrect # of changelog entries"
+    "incorrect # of changelog entries",
   );
 });
 
@@ -107,6 +107,10 @@ test("diff is ok", async (t) => {
   t.is(
     diff.length,
     changeEntries,
-    `invalid # of change entries: ${JSON.stringify(diff)}`
+    `invalid # of change entries: ${JSON.stringify(diff)}`,
   );
 });
+
+// test("reset hard", async (t) => {
+//   // TODO: test reset feature
+// });

packages/ogre/src/repository.ts

@@ -59,6 +59,13 @@ export interface RepositoryObject<T extends { [k: string]: any }> {
   branch(): string;
 
   tag(tag: string): string;
+
+  /**
+   * Moves the HEAD and the branch to a specific shaish (commit or tag)
+   * @param mode hard - discard changes
+   * @param shaish
+   */
+  reset(mode?: "soft" | "hard", shaish?: string): void;
 }
 
 /**
@@ -89,7 +96,9 @@ export class Repository<T extends { [k: PropertyKey]: any }>
   private readonly original: T;
 
   data: T;
+
   private observer: Observer<T>;
+
   private readonly refs: Map<string, Reference>;
   private readonly commits: Commit[];
 
@@ -104,6 +113,32 @@ export class Repository<T extends { [k: PropertyKey]: any }>
     this.observer = observe(this.data);
   }
 
+  reset(
+    mode: "soft" | "hard" | undefined = "hard",
+    shaish: string | undefined = REFS_HEAD_KEY,
+  ): void {
+    if (mode === "hard") {
+      unobserve(this.data, this.observer);
+    }
+
+    const [commit] = shaishToCommit(shaish, this.refs, this.commits);
+    this.moveTo(commit);
+
+    const refs = refsAtCommit(this.refs, commit);
+    // reset only moves heads and not tags
+    const moveableRefs = refs.filter((r) =>
+      r.name.startsWith(headsRefPathPrefix),
+    );
+
+    for (const ref of moveableRefs) {
+      this.moveRef(ref.name, commit);
+    }
+
+    if (mode === "hard") {
+      this.observer = observe(this.data);
+    }
+  }
+
   branch(): string {
     const currentHeadRef = this.refs.get(REFS_HEAD_KEY);
     if (!currentHeadRef) {
@@ -145,20 +180,20 @@ export class Repository<T extends { [k: PropertyKey]: any }>
       const [commit, isRef, refKey] = shaishToCommit(
         shaish,
         this.refs,
-        this.commits
+        this.commits,
       );
       this.moveTo(commit);
       this.moveRef(
         REFS_HEAD_KEY,
-        isRef && refKey !== undefined ? refKey : commit
+        isRef && refKey !== undefined ? refKey : commit,
       );
     }
   }
 
   async commit(
     message: string,
     author: string,
-    amend?: boolean
+    amend?: boolean,
   ): Promise<string> {
     let parent = this.commitAtHead();
     if (amend && !parent) {
@@ -196,7 +231,7 @@ export class Repository<T extends { [k: PropertyKey]: any }>
     });
 
     const treeHash = Buffer.from(
-      compressSync(strToU8(JSON.stringify(this.data)), { level: 6, mem: 8 })
+      compressSync(strToU8(JSON.stringify(this.data)), { level: 6, mem: 8 }),
     ).toString("base64");
     const commit = {
       hash: sha,
@@ -307,7 +342,7 @@ export class Repository<T extends { [k: PropertyKey]: any }>
       throw new Error(
         `fatal: source type (${
           source instanceof Repository ? "Repository" : "History"
-        }) not implemented`
+        }) not implemented`,
       );
     }
 
@@ -374,7 +409,7 @@ export class Repository<T extends { [k: PropertyKey]: any }>
         throw new Error(`unreachable: HEAD not present`);
       }
       throw new Error(
-        `fatal: not a valid object name: '${getLastItem(headRef)}'`
+        `fatal: not a valid object name: '${getLastItem(headRef)}'`,
       );
     }
     this.refs.set(refKey, { name: name, value: headCommit.hash });
@@ -430,7 +465,7 @@ const traverseAndCollectChangelog = (commit: Commit, commitsList: Commit[]) => {
 const mapPath = (
   from: Commit,
   to: Commit,
-  commits: Commit[]
+  commits: Commit[],
 ): [isAncestor: boolean] => {
   let c: Commit | undefined = to;
   while (c !== undefined) {
@@ -451,7 +486,7 @@ const mapPath = (
 const commitAtRefIn = (
   ref: string,
   references: Map<string, Reference>,
-  commitsList: Commit[]
+  commitsList: Commit[],
 ) => {
   const reference = references.get(ref);
   if (!reference) {
@@ -477,6 +512,16 @@ const commitAtRefIn = (
   return undefined;
 };
 
+const refsAtCommit = (references: Map<string, Reference>, commit: Commit) => {
+  const list: Array<Reference> = [];
+  for (const [name, ref] of references.entries()) {
+    if (ref.value === commit.hash) {
+      list.push(ref);
+    }
+  }
+  return list;
+};
+
 /**
  * Accepts a shaish expression (e.g. refs (branches, tags), commitSha) and returns
  * - a commit of type Commit
@@ -486,7 +531,7 @@ const commitAtRefIn = (
 const shaishToCommit = (
   shaish: string,
   references: Map<string, Reference>,
-  commitsList: Commit[]
+  commitsList: Commit[],
 ): [commit: Commit, isRef: boolean, ref: string | undefined] => {
   let sha = shaish;
   let isRef = false;
@@ -557,7 +602,7 @@ export const validateRef = (name: string, oneLevel: boolean = true) => {
  * @param repository
  */
 export const printChangeLog = <T extends { [k: string]: any }>(
-  repository: RepositoryObject<T>
+  repository: RepositoryObject<T>,
 ) => {
   console.log("----------------------------------------------------------");
   console.log(`Changelog at ${repository.head()}`);