feat(build): add optional content-hash based build cache to skip rebuilding unchanged Dockerfiles

ts/classes.tsdockercache.ts

@@ -0,0 +1,117 @@
+import * as crypto from 'crypto';
+import * as fs from 'fs';
+import * as path from 'path';
+import * as plugins from './tsdocker.plugins.js';
+import * as paths from './tsdocker.paths.js';
+import { logger } from './tsdocker.logging.js';
+import type { ICacheData, ICacheEntry } from './interfaces/index.js';
+
+const smartshellInstance = new plugins.smartshell.Smartshell({
+  executor: 'bash',
+});
+
+/**
+ * Manages content-hash-based build caching for Dockerfiles.
+ * Cache is stored in .nogit/tsdocker_support.json.
+ */
+export class TsDockerCache {
+  private cacheFilePath: string;
+  private data: ICacheData;
+
+  constructor() {
+    this.cacheFilePath = path.join(paths.cwd, '.nogit', 'tsdocker_support.json');
+    this.data = { version: 1, entries: {} };
+  }
+
+  /**
+   * Loads cache data from disk. Falls back to empty cache on missing/corrupt file.
+   */
+  public load(): void {
+    try {
+      const raw = fs.readFileSync(this.cacheFilePath, 'utf-8');
+      const parsed = JSON.parse(raw);
+      if (parsed && parsed.version === 1 && parsed.entries) {
+        this.data = parsed;
+      } else {
+        logger.log('warn', '[cache] Cache file has unexpected format, starting fresh');
+        this.data = { version: 1, entries: {} };
+      }
+    } catch {
+      // Missing or corrupt file — start fresh
+      this.data = { version: 1, entries: {} };
+    }
+  }
+
+  /**
+   * Saves cache data to disk. Creates .nogit directory if needed.
+   */
+  public save(): void {
+    const dir = path.dirname(this.cacheFilePath);
+    fs.mkdirSync(dir, { recursive: true });
+    fs.writeFileSync(this.cacheFilePath, JSON.stringify(this.data, null, 2), 'utf-8');
+  }
+
+  /**
+   * Computes SHA-256 hash of Dockerfile content.
+   */
+  public computeContentHash(content: string): string {
+    return crypto.createHash('sha256').update(content).digest('hex');
+  }
+
+  /**
+   * Checks whether a build can be skipped for the given Dockerfile.
+   * Logs detailed diagnostics and returns true if the build should be skipped.
+   */
+  public async shouldSkipBuild(cleanTag: string, content: string): Promise<boolean> {
+    const contentHash = this.computeContentHash(content);
+    const entry = this.data.entries[cleanTag];
+
+    if (!entry) {
+      console.log(`[cache] ${cleanTag}:`);
+      console.log(`[cache]   Content hash: ${contentHash}`);
+      console.log(`[cache]   Stored hash:  (none)`);
+      console.log(`[cache]   Hash match:   no`);
+      console.log(`→ Building ${cleanTag}`);
+      return false;
+    }
+
+    const hashMatch = entry.contentHash === contentHash;
+    console.log(`[cache] ${cleanTag}:`);
+    console.log(`[cache]   Content hash: ${contentHash}`);
+    console.log(`[cache]   Stored hash:  ${entry.contentHash}`);
+    console.log(`[cache]   Image ID:     ${entry.imageId}`);
+    console.log(`[cache]   Hash match:   ${hashMatch ? 'yes' : 'no'}`);
+
+    if (!hashMatch) {
+      console.log(`→ Building ${cleanTag}`);
+      return false;
+    }
+
+    // Hash matches — verify the image still exists locally
+    const inspectResult = await smartshellInstance.exec(
+      `docker image inspect ${entry.imageId} > /dev/null 2>&1`
+    );
+    const available = inspectResult.exitCode === 0;
+    console.log(`[cache]   Available:    ${available ? 'yes' : 'no'}`);
+
+    if (available) {
+      console.log(`→ Skipping build for ${cleanTag} (cache hit)`);
+      return true;
+    }
+
+    console.log(`→ Building ${cleanTag} (image no longer available)`);
+    return false;
+  }
+
+  /**
+   * Records a successful build in the cache.
+   */
+  public recordBuild(cleanTag: string, content: string, imageId: string, buildTag: string): void {
+    this.data.entries[cleanTag] = {
+      contentHash: this.computeContentHash(content),
+      imageId,
+      buildTag,
+      timestamp: Date.now(),
+    };
+  }
+}