refactor: extract mattermost channel plugin to extension

Move mattermost channel implementation from core to extensions/mattermost plugin. Extract config schema, group mentions, normalize utilities, and all mattermost-specific logic (accounts, client, monitor, probe, send) into the extension. Update imports to use plugin SDK and local modules. Add channel metadata directly in plugin definition instead of using getChatChannelMeta. Update package.json with channel and install configuration.

extensions/mattermost/src/channel.ts

@@ -3,26 +3,42 @@ import {
   buildChannelConfigSchema,
   DEFAULT_ACCOUNT_ID,
   deleteAccountFromConfigSection,
-  getChatChannelMeta,
-  listMattermostAccountIds,
-  looksLikeMattermostTargetId,
   migrateBaseNameToDefaultAccount,
   normalizeAccountId,
-  normalizeMattermostBaseUrl,
-  normalizeMattermostMessagingTarget,
-  resolveDefaultMattermostAccountId,
-  resolveMattermostAccount,
-  resolveMattermostGroupRequireMention,
   setAccountEnabledInConfigSection,
-  mattermostOnboardingAdapter,
-  MattermostConfigSchema,
   type ChannelPlugin,
-  type ResolvedMattermostAccount,
 } from "clawdbot/plugin-sdk";
 
+import { MattermostConfigSchema } from "./config-schema.js";
+import { resolveMattermostGroupRequireMention } from "./group-mentions.js";
+import {
+  looksLikeMattermostTargetId,
+  normalizeMattermostMessagingTarget,
+} from "./normalize.js";
+import { mattermostOnboardingAdapter } from "./onboarding.js";
+import {
+  listMattermostAccountIds,
+  resolveDefaultMattermostAccountId,
+  resolveMattermostAccount,
+  type ResolvedMattermostAccount,
+} from "./mattermost/accounts.js";
+import { normalizeMattermostBaseUrl } from "./mattermost/client.js";
+import { monitorMattermostProvider } from "./mattermost/monitor.js";
+import { probeMattermost } from "./mattermost/probe.js";
+import { sendMessageMattermost } from "./mattermost/send.js";
 import { getMattermostRuntime } from "./runtime.js";
 
-const meta = getChatChannelMeta("mattermost");
+const meta = {
+  id: "mattermost",
+  label: "Mattermost",
+  selectionLabel: "Mattermost (plugin)",
+  detailLabel: "Mattermost Bot",
+  docsPath: "/channels/mattermost",
+  docsLabel: "mattermost",
+  blurb: "self-hosted Slack-style chat; install the plugin to enable.",
+  systemImage: "bubble.left.and.bubble.right",
+  order: 65,
+} as const;
 
 export const mattermostPlugin: ChannelPlugin<ResolvedMattermostAccount> = {
   id: "mattermost",
@@ -96,8 +112,7 @@ export const mattermostPlugin: ChannelPlugin<ResolvedMattermostAccount> = {
       return { ok: true, to: trimmed };
     },
     sendText: async ({ to, text, accountId, deps, replyToId }) => {
-      const send =
-        deps?.sendMattermost ?? getMattermostRuntime().channel.mattermost.sendMessageMattermost;
+      const send = deps?.sendMattermost ?? sendMessageMattermost;
       const result = await send(to, text, {
         accountId: accountId ?? undefined,
         replyToId: replyToId ?? undefined,
@@ -105,8 +120,7 @@ export const mattermostPlugin: ChannelPlugin<ResolvedMattermostAccount> = {
       return { channel: "mattermost", ...result };
     },
     sendMedia: async ({ to, text, mediaUrl, accountId, deps, replyToId }) => {
-      const send =
-        deps?.sendMattermost ?? getMattermostRuntime().channel.mattermost.sendMessageMattermost;
+      const send = deps?.sendMattermost ?? sendMessageMattermost;
       const result = await send(to, text, {
         accountId: accountId ?? undefined,
         mediaUrl,
@@ -144,11 +158,7 @@ export const mattermostPlugin: ChannelPlugin<ResolvedMattermostAccount> = {
       if (!token || !baseUrl) {
         return { ok: false, error: "bot token or baseUrl missing" };
       }
-      return await getMattermostRuntime().channel.mattermost.probeMattermost(
-        baseUrl,
-        token,
-        timeoutMs,
-      );
+      return await probeMattermost(baseUrl, token, timeoutMs);
     },
     buildAccountSnapshot: ({ account, runtime, probe }) => ({
       accountId: account.accountId,
@@ -256,7 +266,7 @@ export const mattermostPlugin: ChannelPlugin<ResolvedMattermostAccount> = {
         botTokenSource: account.botTokenSource,
       });
       ctx.log?.info(`[${account.accountId}] starting channel`);
-      return getMattermostRuntime().channel.mattermost.monitorMattermostProvider({
+      return monitorMattermostProvider({
         botToken: account.botToken ?? undefined,
         baseUrl: account.baseUrl ?? undefined,
         accountId: account.accountId,