import { afterEach, describe, expect, it, vi } from "vitest";
import type { WorkspaceDescriptorPayload } from "@getpaseo/protocol/messages";
import { normalizeAgentSnapshot } from "@/utils/agent-snapshots";
import {
  normalizeProjectDescriptor,
  normalizeWorkspaceDescriptor,
  selectAgentTimelineState,
  useSessionStore,
} from "@/stores/session-store";
import { createUserMessage, type StreamItem } from "@/types/stream";
import { ReplicaCache, type ReplicaCacheStorage } from ".";

const SERVER_ID = "cached-host";
const LRU_SERVER_IDS = ["host-a", "host-b", "host-c"] as const;

class MemoryStorage implements ReplicaCacheStorage {
  readonly values = new Map<string, string>();
  writes = 0;

  async getItem(key: string): Promise<string | null> {
    return this.values.get(key) ?? null;
  }

  async setItem(key: string, value: string): Promise<void> {
    this.writes += 1;
    this.values.set(key, value);
  }

  async removeItem(key: string): Promise<void> {
    this.values.delete(key);
  }
}

function workspace(
  id = "workspace-1",
  projectId = "project-1",
  workspaceDirectory = "/repo/paseo",
): WorkspaceDescriptorPayload {
  return {
    id,
    projectId,
    projectDisplayName: "Paseo",
    projectRootPath: workspaceDirectory,
    workspaceDirectory,
    projectKind: "git",
    workspaceKind: "local_checkout",
    name: "main",
    status: "running",
    statusEnteredAt: "2026-07-18T08:00:00.000Z",
    activityAt: null,
    archivingAt: null,
    diffStat: null,
    scripts: [],
  };
}

function agent(id: string, workspaceId = "workspace-1", cwd = "/repo/paseo") {
  return {
    ...normalizeAgentSnapshot(
      {
        id,
        provider: "codex",
        cwd,
        workspaceId,
        model: null,
        createdAt: "2026-07-18T08:00:00.000Z",
        updatedAt: "2026-07-18T08:01:00.000Z",
        lastUserMessageAt: "2026-07-18T08:01:00.000Z",
        status: "idle",
        capabilities: {
          supportsStreaming: true,
          supportsSessionPersistence: true,
          supportsDynamicModes: true,
          supportsMcpServers: true,
          supportsReasoningStream: true,
          supportsToolInvocations: true,
        },
        currentModeId: null,
        availableModes: [],
        pendingPermissions: [],
        persistence: null,
        title: `Agent ${id}`,
        labels: {},
      },
      SERVER_ID,
    ),
    projectPlacement: {
      projectKey: cwd,
      projectName: cwd.split("/").at(-1) ?? cwd,
      workspaceName: workspaceId,
      checkout: {
        cwd,
        isGit: false as const,
        currentBranch: null,
        remoteUrl: null,
        worktreeRoot: null,
        isPaseoOwnedWorktree: false as const,
        mainRepoRoot: null,
      },
    },
  };
}

function message(id: string, text: string): StreamItem {
  return {
    kind: "assistant_message",
    id,
    text,
    timestamp: new Date("2026-07-18T08:02:00.000Z"),
    timelineCursor: { epoch: "epoch-1", seq: 12 },
  };
}

function seedSession(): void {
  const store = useSessionStore.getState();
  store.initializeSession(SERVER_ID, null);
  store.setAgents(SERVER_ID, new Map([["agent-1", agent("agent-1")]]));
  store.setWorkspaces(
    SERVER_ID,
    new Map([
      [
        "workspace-1",
        normalizeWorkspaceDescriptor({
          ...workspace(),
          workspaceKind: "worktree",
          worktreeSlug: "owned-worktree",
        }),
      ],
    ]),
  );
  store.setProjects(SERVER_ID, [
    normalizeProjectDescriptor({
      projectId: "project-1",
      projectKey: "remote:github.com/getpaseo/paseo",
      projectDisplayName: "Paseo",
      projectRootPath: "/repo/paseo",
      projectKind: "git",
    }),
    normalizeProjectDescriptor({
      projectId: "empty-project",
      projectDisplayName: "Empty project",
      projectRootPath: "/repo/empty",
      projectKind: "directory",
    }),
  ]);
  store.setFocusedAgentId(SERVER_ID, "agent-1");
  store.setAgentStreamTail(SERVER_ID, new Map([["agent-1", [message("message-1", "Cached")]]]));
  store.setAgentTimelineCursor(
    SERVER_ID,
    new Map([["agent-1", { epoch: "epoch-1", startSeq: 1, endSeq: 12 }]]),
  );
  store.setAgentTimelineHasOlder(SERVER_ID, new Map([["agent-1", true]]));
  store.setAgentAuthoritativeHistoryApplied(SERVER_ID, "agent-1", true);
}

function seedTimeline(serverId: string, text: string): void {
  const agentId = `agent-${serverId}`;
  const workspaceId = `workspace-${serverId}`;
  const workspaceDirectory = `/repo/${serverId}`;
  const store = useSessionStore.getState();
  store.initializeSession(serverId, null);
  store.setAgents(serverId, new Map([[agentId, agent(agentId, workspaceId, workspaceDirectory)]]));
  store.setWorkspaces(
    serverId,
    new Map([
      [
        workspaceId,
        normalizeWorkspaceDescriptor(
          workspace(workspaceId, `project-${serverId}`, workspaceDirectory),
        ),
      ],
    ]),
  );
  store.setFocusedAgentId(serverId, agentId);
  store.setAgentStreamTail(serverId, new Map([[agentId, [message(`message-${serverId}`, text)]]]));
}

afterEach(() => {
  vi.useRealTimers();
  const store = useSessionStore.getState();
  store.clearSession(SERVER_ID);
  for (const serverId of LRU_SERVER_IDS) store.clearSession(serverId);
});

describe("ReplicaCache", () => {
  it("persists focused replica changes without writing transient stream head updates", async () => {
    vi.useFakeTimers();
    const storage = new MemoryStorage();
    const cache = new ReplicaCache(storage);
    cache.setHosts([SERVER_ID]);
    seedSession();
    await cache.flush();
    cache.start();
    const writesBeforeStream = storage.writes;

    useSessionStore
      .getState()
      .setAgentStreamHead(SERVER_ID, new Map([["agent-1", [message("live", "Streaming")]]]));
    await vi.advanceTimersByTimeAsync(1_000);

    expect(storage.writes).toBe(writesBeforeStream);

    useSessionStore
      .getState()
      .setAgentStreamTail(SERVER_ID, new Map([["agent-1", [message("saved", "Committed")]]]));
    await vi.advanceTimersByTimeAsync(1_000);

    expect(storage.writes).toBe(writesBeforeStream + 1);
    cache.setHosts([]);
  });

  it("restores a displayable stale replica without claiming remote hydration", async () => {
    const storage = new MemoryStorage();
    const writer = new ReplicaCache(storage);
    writer.setHosts([SERVER_ID]);
    seedSession();
    await writer.flush();

    useSessionStore.getState().clearSession(SERVER_ID);

    const reader = new ReplicaCache(storage);
    reader.setHosts([SERVER_ID]);
    await reader.restore();

    const session = useSessionStore.getState().sessions[SERVER_ID];
    expect(session).toBeDefined();
    if (!session) throw new Error("Expected restored session");
    expect(session.client).toBeNull();
    expect(session.hasHydratedAgents).toBe(false);
    expect(session.hasHydratedWorkspaces).toBe(false);
    expect(session.hasWorkspaceDirectorySnapshot).toBe(true);
    expect(Array.from(session.agents.keys())).toEqual(["agent-1"]);
    expect(Array.from(session.workspaces.keys())).toEqual(["workspace-1"]);
    expect(Array.from(session.projects.keys())).toEqual(["project-1", "empty-project"]);
    expect(session.agents.get("agent-1")?.updatedAt).toBeInstanceOf(Date);
    expect(session.agents.get("agent-1")?.projectPlacement?.checkout.cwd).toBe("/repo/paseo");
    expect(session.workspaces.get("workspace-1")?.statusEnteredAt).toBeInstanceOf(Date);
    expect(session.workspaces.get("workspace-1")?.worktreeSlug).toBe("owned-worktree");
    expect(session.agentStreamTail.get("agent-1")).toEqual([message("message-1", "Cached")]);
    expect(session.agentAuthoritativeHistoryApplied).toEqual(new Map());
    expect(session.agentTimelineCursor).toEqual(new Map());
    expect(session.agentTimelineHasOlder).toEqual(new Map());
    expect(session.agentTimelineHasNewer).toEqual(new Map());
    expect(session.agentHistorySyncGeneration).toEqual(new Map());
    expect(selectAgentTimelineState(session, "agent-1")).toEqual({
      status: "painted",
      items: [message("message-1", "Cached")],
    });
  });

  it("persists the complete directory with only the focused timeline tail", async () => {
    const storage = new MemoryStorage();
    const cache = new ReplicaCache(storage);
    cache.setHosts([SERVER_ID]);
    seedSession();

    const store = useSessionStore.getState();
    store.setAgents(SERVER_ID, (agents) =>
      new Map(agents).set("agent-2", agent("agent-2", "workspace-2", "/repo/other")),
    );
    store.setWorkspaces(SERVER_ID, (workspaces) =>
      new Map(workspaces).set(
        "workspace-2",
        normalizeWorkspaceDescriptor(workspace("workspace-2", "project-2", "/repo/other")),
      ),
    );
    const secondTimeline = Array.from({ length: 60 }, (_, index) =>
      message(`message-${index}`, `Second ${index}`),
    );
    store.setAgentStreamTail(
      SERVER_ID,
      new Map([
        ["agent-1", [message("message-1", "First")]],
        ["agent-2", secondTimeline],
      ]),
    );
    store.setFocusedAgentId(SERVER_ID, "agent-2");
    await cache.flush();

    store.clearSession(SERVER_ID);
    const reader = new ReplicaCache(storage);
    reader.setHosts([SERVER_ID]);
    await reader.restore();

    const session = useSessionStore.getState().sessions[SERVER_ID];
    const timelines = session?.agentStreamTail;
    expect(Array.from(session?.agents.keys() ?? [])).toEqual(["agent-1", "agent-2"]);
    expect(Array.from(session?.workspaces.keys() ?? [])).toEqual(["workspace-1", "workspace-2"]);
    expect(Array.from(session?.projects.keys() ?? [])).toEqual([
      "project-1",
      "project-2",
      "empty-project",
    ]);
    expect(Array.from(timelines?.keys() ?? [])).toEqual(["agent-2"]);
    expect(timelines?.get("agent-2")).toEqual(secondTimeline.slice(-50));

    const persisted = JSON.parse(storage.values.get("@paseo:replica-cache") ?? "null") as {
      version: number;
      hosts: Array<{ timeline: Record<string, unknown> | null }>;
    };
    expect(persisted.version).toBe(5);
    expect(Object.keys(persisted.hosts[0]?.timeline ?? {}).sort()).toEqual(["agentId", "items"]);
  });

  it("persists reconciled rows without caching unreconciled local presentations", async () => {
    const storage = new MemoryStorage();
    const cache = new ReplicaCache(storage);
    cache.setHosts([SERVER_ID]);
    seedSession();
    const unreconciled = createUserMessage({
      clientMessageId: "client-pending",
      text: "Pending",
      timestamp: new Date("2026-07-18T08:01:00.000Z"),
    });
    const reconciled = createUserMessage({
      clientMessageId: "client-sent",
      messageId: "provider-sent",
      timelineCursor: { epoch: "epoch-1", seq: 11 },
      text: "Sent",
      timestamp: new Date("2026-07-18T08:01:30.000Z"),
    });
    useSessionStore
      .getState()
      .setAgentStreamTail(SERVER_ID, new Map([["agent-1", [unreconciled, reconciled]]]));

    await cache.flush();
    useSessionStore.getState().clearSession(SERVER_ID);
    await cache.restore();

    expect(useSessionStore.getState().sessions[SERVER_ID]?.agentStreamTail.get("agent-1")).toEqual([
      reconciled,
    ]);
  });

  it("persists monotonic directory cursors with the complete host replica", async () => {
    const storage = new MemoryStorage();
    const cache = new ReplicaCache(storage);
    cache.setHosts([SERVER_ID]);
    seedSession();
    await cache.flush();

    cache.writeDirectoryCheckpoint(SERVER_ID, {
      agents: { generation: "daemon-generation", afterSeq: 7 },
    });
    useSessionStore.getState().setAgents(SERVER_ID, (agents) => {
      const current = agents.get("agent-1");
      if (!current) throw new Error("Expected seeded agent");
      return new Map(agents).set("agent-1", { ...current, title: "Updated agent" });
    });
    await cache.flush();

    const reader = new ReplicaCache(storage);
    reader.setHosts([SERVER_ID]);
    await reader.restore();
    expect(reader.readDirectoryCheckpoint(SERVER_ID)).toEqual({
      agents: { generation: "daemon-generation", afterSeq: 7 },
    });
  });

  it("restores every registered host directory before any host reconnects", async () => {
    const storage = new MemoryStorage();
    const writer = new ReplicaCache(storage);
    writer.setHosts(LRU_SERVER_IDS);
    for (const serverId of LRU_SERVER_IDS) seedTimeline(serverId, `cached-${serverId}`);
    await writer.flush();
    for (const serverId of LRU_SERVER_IDS) useSessionStore.getState().clearSession(serverId);

    const reader = new ReplicaCache(storage);
    reader.setHosts(LRU_SERVER_IDS);
    await reader.restore();

    for (const serverId of LRU_SERVER_IDS) {
      const session = useSessionStore.getState().sessions[serverId];
      expect(Array.from(session?.agents.keys() ?? [])).toEqual([`agent-${serverId}`]);
      expect(Array.from(session?.workspaces.keys() ?? [])).toEqual([`workspace-${serverId}`]);
      expect(session?.hasHydratedAgents).toBe(false);
      expect(session?.hasHydratedWorkspaces).toBe(false);
      expect(session?.hasWorkspaceDirectorySnapshot).toBe(true);
    }
  });

  it("evicts the least recently written host when the cache exceeds its byte budget", async () => {
    const storage = new MemoryStorage();
    const cache = new ReplicaCache(storage, { maxBytes: 7_000 });
    cache.setHosts(LRU_SERVER_IDS.slice(0, 2));
    seedTimeline("host-a", "A".repeat(1_200));
    seedTimeline("host-b", "B".repeat(1_200));
    await cache.flush();

    seedTimeline("host-a", "A".repeat(1_201));
    await cache.flush();

    cache.setHosts(LRU_SERVER_IDS);
    seedTimeline("host-c", "C".repeat(1_200));
    await cache.flush();

    for (const serverId of LRU_SERVER_IDS) {
      useSessionStore.getState().clearSession(serverId);
    }
    const reader = new ReplicaCache(storage, { maxBytes: 7_000 });
    reader.setHosts(LRU_SERVER_IDS);
    await reader.restore();

    expect(Object.keys(useSessionStore.getState().sessions).sort()).toEqual(["host-a", "host-c"]);
  });

  it("rejects and clears version 4 cache data before overwriting it on flush", async () => {
    const storage = new MemoryStorage();
    storage.values.set(
      "@paseo:replica-cache",
      JSON.stringify({
        version: 4,
        hosts: [
          {
            serverId: SERVER_ID,
            agents: [],
            workspaces: [],
            emptyProjects: [],
            timeline: {
              agentId: "agent-1",
              items: [],
              cursor: { epoch: "poisoned", startSeq: 1, endSeq: 100 },
              hasOlder: false,
            },
          },
        ],
      }),
    );
    const cache = new ReplicaCache(storage);
    cache.setHosts([SERVER_ID]);

    await cache.restore();
    expect(storage.values.has("@paseo:replica-cache")).toBe(false);
    await cache.flush();

    expect(useSessionStore.getState().sessions[SERVER_ID]).toBeUndefined();
    expect(JSON.parse(storage.values.get("@paseo:replica-cache") ?? "null")).toEqual({
      version: 5,
      hosts: [],
    });
  });
});