feat(orchestrator): MS23-P1-002 InternalAgentProvider (#719)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/orchestrator/src/api/agents/agent-tree.service.ts

@@ -1,11 +1,78 @@
 import { Injectable } from "@nestjs/common";
-import { PrismaService } from "../../prisma/prisma.service";
+import type { AgentSessionTree, Prisma } from "@prisma/client";
 import { AgentTreeResponseDto } from "./dto/agent-tree-response.dto";
+import { PrismaService } from "../../prisma/prisma.service";
+
+const DEFAULT_PAGE_LIMIT = 50;
+const MAX_PAGE_LIMIT = 200;
+
+interface SessionCursor {
+  spawnedAt: Date;
+  sessionId: string;
+}
+
+export interface AgentSessionTreeListResult {
+  sessions: AgentSessionTree[];
+  total: number;
+  cursor?: string;
+}
 
 @Injectable()
 export class AgentTreeService {
   constructor(private readonly prisma: PrismaService) {}
 
+  async listSessions(
+    cursor?: string,
+    limit = DEFAULT_PAGE_LIMIT
+  ): Promise<AgentSessionTreeListResult> {
+    const safeLimit = this.normalizeLimit(limit);
+    const parsedCursor = this.parseCursor(cursor);
+
+    const where: Prisma.AgentSessionTreeWhereInput | undefined = parsedCursor
+      ? {
+          OR: [
+            {
+              spawnedAt: {
+                lt: parsedCursor.spawnedAt,
+              },
+            },
+            {
+              spawnedAt: parsedCursor.spawnedAt,
+              sessionId: {
+                lt: parsedCursor.sessionId,
+              },
+            },
+          ],
+        }
+      : undefined;
+
+    const [sessions, total] = await Promise.all([
+      this.prisma.agentSessionTree.findMany({
+        where,
+        orderBy: [{ spawnedAt: "desc" }, { sessionId: "desc" }],
+        take: safeLimit,
+      }),
+      this.prisma.agentSessionTree.count(),
+    ]);
+
+    const nextCursor =
+      sessions.length === safeLimit
+        ? this.serializeCursor(sessions[sessions.length - 1])
+        : undefined;
+
+    return {
+      sessions,
+      total,
+      ...(nextCursor !== undefined ? { cursor: nextCursor } : {}),
+    };
+  }
+
+  async getSession(sessionId: string): Promise<AgentSessionTree | null> {
+    return this.prisma.agentSessionTree.findUnique({
+      where: { sessionId },
+    });
+  }
+
   async getTree(): Promise<AgentTreeResponseDto[]> {
     const entries = await this.prisma.agentSessionTree.findMany({
       orderBy: { spawnedAt: "desc" },
@@ -27,4 +94,53 @@ export class AgentTreeService {
 
     return response;
   }
+
+  private normalizeLimit(limit: number): number {
+    const normalized = Number.isFinite(limit) ? Math.trunc(limit) : DEFAULT_PAGE_LIMIT;
+    if (normalized < 1) {
+      return 1;
+    }
+
+    return Math.min(normalized, MAX_PAGE_LIMIT);
+  }
+
+  private serializeCursor(entry: Pick<AgentSessionTree, "spawnedAt" | "sessionId">): string {
+    return Buffer.from(
+      JSON.stringify({
+        spawnedAt: entry.spawnedAt.toISOString(),
+        sessionId: entry.sessionId,
+      }),
+      "utf8"
+    ).toString("base64url");
+  }
+
+  private parseCursor(cursor?: string): SessionCursor | null {
+    if (!cursor) {
+      return null;
+    }
+
+    try {
+      const decoded = Buffer.from(cursor, "base64url").toString("utf8");
+      const parsed = JSON.parse(decoded) as {
+        spawnedAt?: string;
+        sessionId?: string;
+      };
+
+      if (typeof parsed.spawnedAt !== "string" || typeof parsed.sessionId !== "string") {
+        return null;
+      }
+
+      const spawnedAt = new Date(parsed.spawnedAt);
+      if (Number.isNaN(spawnedAt.getTime())) {
+        return null;
+      }
+
+      return {
+        spawnedAt,
+        sessionId: parsed.sessionId,
+      };
+    } catch {
+      return null;
+    }
+  }
 }