From baf78da79179812155355e3c053b06f7263879cc Mon Sep 17 00:00:00 2001
From: Travis Ralston <travpc@gmail.com>
Date: Mon, 30 Sep 2019 16:03:24 -0600
Subject: [PATCH] Support spec-level permalink parsing

---
 src/utils/permalinks/PermalinkConstructor.js  | 38 +++++++++++++++++++
 .../permalinks/SpecPermalinkConstructor.js    | 38 ++++++++++++++++++-
 2 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/src/utils/permalinks/PermalinkConstructor.js b/src/utils/permalinks/PermalinkConstructor.js
index 47d813390f..507f16f795 100644
--- a/src/utils/permalinks/PermalinkConstructor.js
+++ b/src/utils/permalinks/PermalinkConstructor.js
@@ -38,4 +38,42 @@ export default class PermalinkConstructor {
     isPermalinkHost(host: string): boolean {
         throw new Error("Not implemented");
     }
+
+    parsePermalink(fullUrl: string): PermalinkParts {
+        throw new Error("Not implemented");
+    }
+}
+
+// Inspired by/Borrowed with permission from the matrix-bot-sdk:
+// https://github.com/turt2live/matrix-js-bot-sdk/blob/7c4665c9a25c2c8e0fe4e509f2616505b5b66a1c/src/Permalinks.ts#L1-L6
+export class PermalinkParts {
+    roomIdOrAlias: string;
+    eventId: string;
+    userId: string;
+    groupId: string;
+    viaServers: string[];
+
+    constructor(roomIdOrAlias: string, eventId: string, userId: string, groupId: string, viaServers: string[]) {
+        this.roomIdOrAlias = roomIdOrAlias;
+        this.eventId = eventId;
+        this.groupId = groupId;
+        this.userId = userId;
+        this.viaServers = viaServers;
+    }
+
+    static forUser(userId: string): PermalinkParts {
+        return new PermalinkParts(null, null, userId, null, null);
+    }
+
+    static forGroup(groupId: string): PermalinkParts {
+        return new PermalinkParts(null, null, null, groupId, null);
+    }
+
+    static forRoom(roomIdOrAlias: string, viaServers: string[]): PermalinkParts {
+        return new PermalinkParts(roomIdOrAlias, null, null, null, viaServers || []);
+    }
+
+    static forEvent(roomId: string, eventId: string, viaServers: string[]): PermalinkParts {
+        return new PermalinkParts(roomId, eventId, null, null, viaServers || []);
+    }
 }
diff --git a/src/utils/permalinks/SpecPermalinkConstructor.js b/src/utils/permalinks/SpecPermalinkConstructor.js
index 5dd4a5a24e..e4cff798a7 100644
--- a/src/utils/permalinks/SpecPermalinkConstructor.js
+++ b/src/utils/permalinks/SpecPermalinkConstructor.js
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import PermalinkConstructor from "./PermalinkConstructor";
+import PermalinkConstructor, {PermalinkParts} from "./PermalinkConstructor";
 
 export const host = "matrix.to";
 export const baseUrl = `https://${host}`;
@@ -51,4 +51,40 @@ export default class SpecPermalinkConstructor extends PermalinkConstructor {
         if (!candidates || candidates.length === 0) return '';
         return `?via=${candidates.map(c => encodeURIComponent(c)).join("&via=")}`;
     }
+
+    // Heavily inspired by/borrowed from the matrix-bot-sdk (with permission):
+    // https://github.com/turt2live/matrix-js-bot-sdk/blob/7c4665c9a25c2c8e0fe4e509f2616505b5b66a1c/src/Permalinks.ts#L33-L61
+    parsePermalink(fullUrl: string): PermalinkParts {
+        if (!fullUrl || !fullUrl.startsWith(baseUrl)) {
+            throw new Error("Does not appear to be a permalink");
+        }
+
+        const parts = fullUrl.substring(`${baseUrl}/#/`.length).split("/");
+
+        const entity = parts[0];
+        if (entity[0] === '@') {
+            // Probably a user, no further parsing needed.
+            return PermalinkParts.forUser(entity);
+        } else if (entity[0] === '+') {
+            // Probably a group, no further parsing needed.
+            return PermalinkParts.forGroup(entity);
+        } else if (entity[0] === '#' || entity[0] === '!') {
+            if (parts.length === 1) {
+                return PermalinkParts.forRoom(entity, []);
+            }
+
+            // rejoin the rest because v3 events can have slashes (annoyingly)
+            const eventIdAndQuery = parts.length > 1 ? parts.slice(1).join('/') : "";
+            const secondaryParts = eventIdAndQuery.split("?");
+
+            const eventId = secondaryParts[0];
+            const query = secondaryParts.length > 1 ? secondaryParts[1] : "";
+
+            const via = query.split("via=").filter(p => !!p);
+
+            return PermalinkParts.forEvent(entity, eventId, via);
+        } else {
+            throw new Error("Unknown entity type in permalink");
+        }
+    }
 }