import { ref, watch, onBeforeUnmount, type Ref } from "vue";
import { invoke } from "@tauri-apps/api/core";
import { listen, type UnlistenFn } from "@tauri-apps/api/event";

export interface FileEntry {
  name: string;
  path: string;
  size: number;
  isDir: boolean;
  permissions: string;
  modTime: string;
}

export interface UseSftpReturn {
  currentPath: Ref<string>;
  entries: Ref<FileEntry[]>;
  isLoading: Ref<boolean>;
  followTerminal: Ref<boolean>;
  navigateTo: (path: string) => Promise<void>;
  goUp: () => Promise<void>;
  refresh: () => Promise<void>;
}

// Persist the last browsed path per session so switching tabs restores position
const sessionPaths: Record<string, string> = {};

/**
 * Composable that manages SFTP file browsing state.
 * Accepts a reactive session ID ref so it reinitializes on tab switch
 * without destroying the component.
 */
export function useSftp(sessionIdRef: Ref<string>): UseSftpReturn {
  const currentPath = ref("/");
  const entries = ref<FileEntry[]>([]);
  const isLoading = ref(false);
  const followTerminal = ref(true);

  let unlistenCwd: UnlistenFn | null = null;
  let currentSessionId = "";

  async function listDirectory(sessionId: string, path: string): Promise<FileEntry[]> {
    try {
      const result = await invoke<FileEntry[]>("sftp_list", { sessionId, path });
      return result ?? [];
    } catch (err) {
      console.error("SFTP list error:", err);
      return [];
    }
  }

  async function navigateTo(path: string): Promise<void> {
    if (!currentSessionId) return;
    isLoading.value = true;
    try {
      currentPath.value = path;
      sessionPaths[currentSessionId] = path;
      entries.value = await listDirectory(currentSessionId, path);
    } finally {
      isLoading.value = false;
    }
  }

  async function goUp(): Promise<void> {
    const parts = currentPath.value.split("/").filter(Boolean);
    if (parts.length <= 1) {
      await navigateTo("/");
      return;
    }
    parts.pop();
    await navigateTo("/" + parts.join("/"));
  }

  async function refresh(): Promise<void> {
    await navigateTo(currentPath.value);
  }

  async function switchToSession(sessionId: string): Promise<void> {
    if (!sessionId) {
      entries.value = [];
      return;
    }

    // Save current path for the old session
    if (currentSessionId) {
      sessionPaths[currentSessionId] = currentPath.value;
    }

    // Unlisten old CWD events
    if (unlistenCwd) {
      unlistenCwd();
      unlistenCwd = null;
    }

    currentSessionId = sessionId;

    // Restore saved path or default to root
    const savedPath = sessionPaths[sessionId] || "/";
    currentPath.value = savedPath;

    // Load the directory
    isLoading.value = true;
    try {
      entries.value = await listDirectory(sessionId, savedPath);
    } finally {
      isLoading.value = false;
    }

    // Listen for CWD changes on the new session
    try {
      unlistenCwd = await listen<string>(`ssh:cwd:${sessionId}`, (event) => {
        if (!followTerminal.value) return;
        const newPath = event.payload;
        if (newPath && newPath !== currentPath.value) {
          navigateTo(newPath);
        }
      });
    } catch {
      // Event listener setup failed — non-fatal
    }
  }

  // React to session ID changes
  watch(sessionIdRef, (newId) => {
    switchToSession(newId);
  }, { immediate: true });

  onBeforeUnmount(() => {
    if (currentSessionId) {
      sessionPaths[currentSessionId] = currentPath.value;
    }
    if (unlistenCwd) unlistenCwd();
  });

  return {
    currentPath,
    entries,
    isLoading,
    followTerminal,
    navigateTo,
    goUp,
    refresh,
  };
}