packages: move sharing logic from web to core; reuse in web

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I26cb6848615a5788f2196fc1675bc22d6a6a6964

packages/core/package.json

@@ -16,5 +16,8 @@
   },
   "devDependencies": {
     "typescript": "^6.0.2"
+  },
+  "dependencies": {
+    "lzutf8": "^0.6.3"
   }
 }

packages/core/src/index.ts

@@ -1,2 +1,3 @@
 export * from './types';
 export * from './parser';
+export * from './share';

packages/core/src/share.ts

@@ -0,0 +1,47 @@
+import LZUTF8 from 'lzutf8';
+
+export type ShareState =
+  | { type: 'analysis'; data: Record<string, unknown>; name: string }
+  | {
+      type: 'compare';
+      left: Record<string, unknown>;
+      right: Record<string, unknown>;
+      leftName: string;
+      rightName: string;
+    };
+
+export function encodeShareUrl(state: ShareState): string {
+  const json = JSON.stringify(state);
+  const encoded = LZUTF8.compress(json, { outputEncoding: 'Base64' }) as string;
+  return encoded.replace(/\+/g, '-').replace(/\//g, '_').replace(/=/g, '');
+}
+
+export function decodeShareUrl(encoded: string): ShareState | null {
+  try {
+    let base64 = encoded.replace(/-/g, '+').replace(/_/g, '/');
+    const padLength = (4 - (base64.length % 4)) % 4;
+    base64 += '='.repeat(padLength);
+    const json = LZUTF8.decompress(base64, {
+      inputEncoding: 'Base64',
+      outputEncoding: 'String',
+    }) as string | null;
+    if (!json) {
+      return null;
+    }
+    const state = JSON.parse(json) as ShareState;
+    if (state.type === 'analysis') {
+      if (!state.data || !state.name) {
+        return null;
+      }
+    } else if (state.type === 'compare') {
+      if (!state.left || !state.right || !state.leftName || !state.rightName) {
+        return null;
+      }
+    } else {
+      return null;
+    }
+    return state;
+  } catch {
+    return null;
+  }
+}