import { Injectable, computed, effect, inject, signal, type WritableSignal } from '@angular/core';
import type { ColumnKey, ConnectionConfig, FileEntry, SavedConnection } from '@shared/types';
import { fileKindKey } from './file-icons';
import { FocusService } from './focus.service';
import { formatMode, isRootPath, joinPath } from './format';
import { RpcService } from './rpc.service';
import { I18nService } from './i18n.service';
import { ToastService } from './toast.service';

export type Side = 'left' | 'right';
/** Any visible column sorts; Name is always available. */
export type SortKey = 'name' | ColumnKey;

/** Display string the text-based columns sort by. */
function sortText(entry: FileEntry, key: 'kind' | 'rights' | 'owner' | 'group'): string {
  if (key === 'kind') return fileKindKey(entry);
  if (key === 'rights') return formatMode(entry.mode);
  return (key === 'owner' ? entry.owner : entry.group) ?? '';
}

interface PanelDeps {
  rpc: RpcService;
  toast: ToastService;
}

export class PanelState {
  readonly sessionId = signal('local');
  /** Filesystem identity ("local" or resolvedIp:port) — self-copy guards use this. */
  readonly fsKey = signal('local');
  readonly title = signal('Local');
  readonly connecting = signal(false);
  /** Name shown in the "Connecting to X…" placeholder while connecting. */
  readonly connectingTo = signal<string | null>(null);
  readonly cwd = signal('');
  readonly entries = signal<FileEntry[]>([]);
  readonly loading = signal(false);
  /** True once an in-flight load has taken >300ms — drives the dim overlay. */
  readonly slowLoad = signal(false);
  /** Bumping this discards the result of any in-flight connect (cancel/supersede). */
  connectToken = 0;
  /** True once the user navigated or connected — a "pristine" panel is still at local home. */
  touched = false;

  /** Input on this panel is ignored while it's connecting or loading. */
  readonly busy = computed(() => this.connecting() || this.loading());
  readonly sortKey = signal<SortKey>('name');
  readonly sortAsc = signal(true);
  readonly cursor = signal(0);
  readonly selected = signal<ReadonlySet<string>>(new Set());
  /** Type-to-filter query; entries not matching are hidden (".." always stays). */
  readonly filter = signal('');

  /** Directories first, then the active sort column. ".." (parent) is pinned on top. */
  readonly sorted = computed(() => {
    const query = this.filter().toLowerCase();
    let list = [...this.entries()];
    if (query) {
      list = list.filter((e) => e.name.toLowerCase().includes(query));
    }
    const key = this.sortKey();
    const dir = this.sortAsc() ? 1 : -1;
    list.sort((a, b) => {
      const aDir = a.type === 'dir';
      const bDir = b.type === 'dir';
      if (aDir !== bDir) return aDir ? -1 : 1;
      let cmp = 0;
      if (key === 'size') cmp = a.size - b.size;
      else if (key === 'mtime') cmp = a.mtime - b.mtime;
      else if (key !== 'name') cmp = sortText(a, key).localeCompare(sortText(b, key));
      if (cmp === 0) {
        cmp = a.name.localeCompare(b.name, undefined, { numeric: true, sensitivity: 'base' });
        if (key === 'name') return cmp * dir;
      }
      return cmp * dir;
    });
    const cwd = this.cwd();
    if (cwd && !isRootPath(cwd)) {
      list.unshift({ name: '..', path: joinPath(cwd, '..'), type: 'dir', size: 0, mtime: 0, mode: 0 });
    }
    return list;
  });

  readonly selectedEntries = computed(() => {
    const names = this.selected();
    return this.sorted().filter((e) => names.has(e.name));
  });

  constructor(private deps: PanelDeps) {}

  async load(path: string | null): Promise<void> {
    if (path !== null) this.touched = true;
    this.loading.set(true);
    const slowTimer = setTimeout(() => this.slowLoad.set(true), 300);
    try {
      const res = await this.deps.rpc.request.listDir({ sessionId: this.sessionId(), path });
      if (!res.ok) {
        this.deps.toast.error(res.error);
        return;
      }
      this.cwd.set(res.path);
      this.entries.set(res.entries);
      this.cursor.set(0);
      this.selected.set(new Set());
      this.filter.set('');
    } finally {
      clearTimeout(slowTimer);
      this.slowLoad.set(false);
      this.loading.set(false);
    }
  }

  private refreshing = false;

  /**
   * Reload cwd, keeping cursor position and selection by name. `silent` (used by
   * auto-refresh) skips the loading/slowLoad flags — so no spinner, no dim
   * overlay, input never blocked — and touches no DOM, so scroll stays put.
   */
  async refresh(opts?: { silent?: boolean }): Promise<void> {
    const silent = opts?.silent ?? false;
    // a silent refresh must never fight the user or overlap itself
    if (silent && (this.refreshing || this.busy())) return;
    this.refreshing = true;
    // snapshot what we're listing; a silent refresh has no busy-block, so the
    // user can navigate mid-flight — discard the result if they did
    const forSession = this.sessionId();
    const forDir = this.cwd();
    const keepCursorName = this.sorted()[this.cursor()]?.name;
    const keepSelected = this.selected();
    if (!silent) this.loading.set(true);
    const slowTimer = silent ? null : setTimeout(() => this.slowLoad.set(true), 300);
    try {
      const res = await this.deps.rpc.request.listDir({
        sessionId: forSession,
        path: forDir,
      });
      if (this.sessionId() !== forSession || this.cwd() !== forDir) return;
      if (!res.ok) {
        if (!silent) this.deps.toast.error(res.error);
        return;
      }
      this.cwd.set(res.path);
      this.entries.set(res.entries);
      const names = new Set(res.entries.map((e) => e.name));
      this.selected.set(new Set([...keepSelected].filter((n) => names.has(n))));
      const idx = this.sorted().findIndex((e) => e.name === keepCursorName);
      this.cursor.set(idx >= 0 ? idx : Math.min(this.cursor(), Math.max(0, this.sorted().length - 1)));
    } finally {
      if (slowTimer) clearTimeout(slowTimer);
      if (!silent) {
        this.slowLoad.set(false);
        this.loading.set(false);
      }
      this.refreshing = false;
    }
  }

  open(entry: FileEntry): void {
    if (entry.type === 'file') return;
    // symlinks: try to open as a dir; the error toast covers file links
    void this.load(entry.path);
  }

  up(): void {
    if (!this.cwd()) return;
    void this.load(joinPath(this.cwd(), '..'));
  }

  /** Update the filter and park the cursor on the first real match. */
  setFilter(query: string): void {
    this.filter.set(query);
    const first = this.sorted().findIndex((e) => e.name !== '..');
    this.cursor.set(first >= 0 ? first : 0);
  }

  toggleSort(key: SortKey): void {
    if (this.sortKey() === key) {
      this.sortAsc.update((v) => !v);
    } else {
      this.sortKey.set(key);
      this.sortAsc.set(true);
    }
  }

  moveCursor(delta: number): void {
    const max = this.sorted().length - 1;
    if (max < 0) return;
    this.cursor.set(Math.max(0, Math.min(max, this.cursor() + delta)));
  }

  toggleSelect(name: string): void {
    if (name === '..') return;
    this.selected.update((prev) => {
      const next = new Set(prev);
      if (next.has(name)) next.delete(name);
      else next.add(name);
      return next;
    });
  }

  selectRange(fromIndex: number, toIndex: number): void {
    const [lo, hi] = fromIndex <= toIndex ? [fromIndex, toIndex] : [toIndex, fromIndex];
    const names = this.sorted()
      .slice(lo, hi + 1)
      .map((e) => e.name)
      .filter((n) => n !== '..');
    this.selected.update((prev) => new Set([...prev, ...names]));
  }

  selectAll(): void {
    this.selected.set(new Set(this.sorted().map((e) => e.name).filter((n) => n !== '..')));
  }

  clearSelection(): void {
    if (this.selected().size) this.selected.set(new Set());
  }
}

/** One tab: an independent left/right panel pair. */
export interface Workspace {
  id: number;
  left: PanelState;
  right: PanelState;
  activeSide: WritableSignal<Side>;
}

@Injectable({ providedIn: 'root' })
export class PanelsService {
  private readonly i18n = inject(I18nService);
  readonly workspaces = signal<Workspace[]>([]);
  readonly activeWorkspaceId = signal(0);
  readonly activeWorkspace = computed(() => {
    const list = this.workspaces();
    return list.find((w) => w.id === this.activeWorkspaceId()) ?? list[0];
  });
  private readonly focus = inject(FocusService);
  /** Bumped to tell the active panel to grab keyboard focus again (e.g. after a dialog closes). */
  readonly focusTick = this.focus.tick;

  private nextWorkspaceId = 1;

  constructor(
    private rpc: RpcService,
    private toast: ToastService,
  ) {
    this.newWorkspace();

    // a session died on its own — reset every panel bound to it, in any tab
    this.rpc.onSessionClosed((event) => {
      for (const workspace of this.workspaces()) {
        for (const panel of [workspace.left, workspace.right]) {
          if (panel.sessionId() === event.sessionId) {
            this.toast.error(
              this.i18n.t('toasts.disconnectedReason', {
                title: panel.title(),
                reason: event.reason,
              }),
            );
            this.resetToLocal(panel);
          }
        }
      }
    });

    // a watched local dir changed, or an editor saved a file — silently
    // refresh every panel showing that directory (no spinner, view preserved)
    this.rpc.onPathRefresh(({ sessionId, dir }) => {
      for (const panel of this.allPanels()) {
        if (panel.sessionId() === sessionId && panel.cwd() === dir) {
          void panel.refresh({ silent: true });
        }
      }
    });

    this.setupAutoRefresh();
  }

  /**
   * Auto-refresh the active tab's panels without disturbing the view. Local
   * panels are watched instantly via fs.watch (backend pushes pathRefresh);
   * remote panels have no change notification, so they're polled. Only the
   * active tab is watched/polled; switching tabs refreshes the new one at once.
   */
  private setupAutoRefresh(): void {
    // REMOTE_POLL_MS: also the cadence a future "auto-refresh interval" setting
    // would drive (see the commented breadcrumbs in settings).
    const REMOTE_POLL_MS = 3000;
    setInterval(() => {
      const ws = this.activeWorkspace();
      if (!ws) return;
      for (const panel of [ws.left, ws.right]) {
        if (panel.sessionId() !== 'local') void panel.refresh({ silent: true });
      }
    }, REMOTE_POLL_MS);

    // register the active tab's LOCAL dirs for fs.watch; re-runs when the active
    // tab changes or either panel navigates/(dis)connects
    effect(() => {
      const ws = this.activeWorkspace();
      const dirs = ws
        ? [ws.left, ws.right]
            .filter((p) => p.sessionId() === 'local' && p.cwd())
            .map((p) => p.cwd())
        : [];
      void this.rpc.request.setWatchedDirs({ dirs: [...new Set(dirs)] });
    });

    // switching tabs shows fresh data immediately instead of waiting a poll tick
    let lastActive = this.activeWorkspaceId();
    effect(() => {
      const id = this.activeWorkspaceId();
      if (id === lastActive) return;
      lastActive = id;
      const ws = this.activeWorkspace();
      if (ws) for (const panel of [ws.left, ws.right]) void panel.refresh({ silent: true });
    });
  }

  // ---- panels of the active workspace ----

  get(side: Side): PanelState {
    const workspace = this.activeWorkspace();
    return side === 'left' ? workspace.left : workspace.right;
  }

  activeSide(): Side {
    return this.activeWorkspace().activeSide();
  }

  setActiveSide(side: Side): void {
    this.activeWorkspace().activeSide.set(side);
  }

  active(): PanelState {
    return this.get(this.activeSide());
  }

  otherSide(side: Side): Side {
    return side === 'left' ? 'right' : 'left';
  }

  other(side: Side): PanelState {
    return this.get(this.otherSide(side));
  }

  /** Every panel across every workspace (for session-wide updates). */
  allPanels(): PanelState[] {
    return this.workspaces().flatMap((w) => [w.left, w.right]);
  }

  refocus(): void {
    this.focus.bump();
  }

  // ---- workspace (tab) management ----

  newWorkspace(): void {
    const deps = { rpc: this.rpc, toast: this.toast };
    const workspace: Workspace = {
      id: this.nextWorkspaceId++,
      left: new PanelState(deps),
      right: new PanelState(deps),
      activeSide: signal<Side>('left'),
    };
    this.workspaces.update((list) => [...list, workspace]);
    this.activeWorkspaceId.set(workspace.id);
    if (this.rpc.available) {
      // may be called during template rendering, where signal writes inside
      // load() are forbidden — defer past the render pass
      queueMicrotask(() => {
        void workspace.left.load(null);
        void workspace.right.load(null);
      });
    }
    this.refocus();
  }

  /** Close a tab; its remote sessions are disconnected. The last tab stays. */
  closeWorkspace(id: number): void {
    const list = this.workspaces();
    if (list.length <= 1) return;
    const index = list.findIndex((w) => w.id === id);
    if (index < 0) return;
    const workspace = list[index];

    for (const panel of [workspace.left, workspace.right]) {
      const sessionId = panel.sessionId();
      if (sessionId !== 'local') {
        void this.rpc.request.disconnect({ sessionId });
      }
    }

    this.workspaces.update((l) => l.filter((w) => w.id !== id));
    if (this.activeWorkspaceId() === id) {
      const neighbor = list[index + 1] ?? list[index - 1];
      this.activeWorkspaceId.set(neighbor.id);
    }
    this.refocus();
  }

  /**
   * Close every tab except one — the tab menu's "Close Other Tabs".
   *
   * Snapshot the ids FIRST: closeWorkspace mutates the list on every call, so
   * iterating the live signal would skip half of them. It also refuses the
   * last tab, which is exactly the wanted floor here.
   */
  closeOtherWorkspaces(id: number): void {
    for (const other of this.workspaces().map((w) => w.id)) {
      if (other !== id) this.closeWorkspace(other);
    }
    this.setActiveWorkspace(id);
  }

  /** Close every tab to the right of one, in visual order. */
  closeWorkspacesToRight(id: number): void {
    const list = this.workspaces();
    const index = list.findIndex((w) => w.id === id);
    if (index < 0) return;
    for (const target of list.slice(index + 1).map((w) => w.id)) {
      this.closeWorkspace(target);
    }
  }

  /**
   * Drop both of a tab's remote sessions, keeping the tab itself. Unlike
   * `disconnectPanel` this targets a tab by id, because the right-clicked tab
   * is not necessarily the active one.
   */
  async disconnectWorkspace(id: number): Promise<void> {
    const workspace = this.workspaces().find((w) => w.id === id);
    if (!workspace) return;
    for (const panel of [workspace.left, workspace.right]) {
      const sessionId = panel.sessionId();
      if (sessionId === 'local') continue;
      await this.rpc.request.disconnect({ sessionId });
      this.resetToLocal(panel);
    }
  }

  setActiveWorkspace(id: number): void {
    if (this.activeWorkspaceId() !== id) {
      this.activeWorkspaceId.set(id);
      this.refocus();
    }
  }

  /**
   * Open a stack: one tab per connection, left panel connecting (right stays
   * local, jumping to the connection's localDir when set). The first
   * connection reuses the current tab if it's pristine (local/local, never
   * navigated) instead of leaving a useless Local tab behind.
   */
  openStack(connections: SavedConnection[]): void {
    for (const [index, connection] of connections.entries()) {
      if (index > 0 || !this.workspaceIsPristine(this.activeWorkspace())) {
        this.newWorkspace();
      }
      // connectPanel resolves the panel synchronously (before awaiting), so
      // firing these back-to-back binds each connection to its own tab.
      // Remote goes right, local stays left — the commander convention.
      void this.connectPanel('right', connection, connection.name, connection.localDir);
    }
  }

  private workspaceIsPristine(workspace: Workspace): boolean {
    return [workspace.left, workspace.right].every(
      (p) => p.sessionId() === 'local' && !p.touched && !p.connecting(),
    );
  }

  /** Reorder a tab (drag & drop). Order is purely visual; ids stay stable. */
  moveWorkspace(id: number, toIndex: number): void {
    this.workspaces.update((list) => {
      const fromIndex = list.findIndex((w) => w.id === id);
      if (fromIndex < 0) return list;
      const next = [...list];
      const [moved] = next.splice(fromIndex, 1);
      next.splice(Math.max(0, Math.min(next.length, toIndex)), 0, moved);
      return next;
    });
  }

  cycleWorkspace(delta: 1 | -1): void {
    const list = this.workspaces();
    if (list.length < 2) return;
    const index = list.findIndex((w) => w.id === this.activeWorkspaceId());
    const next = list[(index + delta + list.length) % list.length];
    this.setActiveWorkspace(next.id);
  }

  /** Jump to a tab by visual position; negative counts from the end (⌘9 = last). */
  goToWorkspace(index: number): void {
    const target = this.workspaces().at(index);
    if (target) this.setActiveWorkspace(target.id);
  }

  /** Tab label: "Local" for a local/local pair, else the remote titles. */
  workspaceName(workspace: Workspace): string {
    const remoteTitles = [workspace.left, workspace.right]
      .filter((p) => p.sessionId() !== 'local')
      .map((p) => p.title());
    return remoteTitles.length ? remoteTitles.join(' ⇄ ') : this.i18n.t('common.local');
  }

  workspaceIsRemote(workspace: Workspace): boolean {
    return workspace.left.sessionId() !== 'local' || workspace.right.sessionId() !== 'local';
  }

  // ---- session binding ----

  /**
   * Connect a panel to a server; replaces (and disconnects) its previous remote
   * session. When the connection has a localDir and the workspace's other panel
   * is local and untouched, that panel jumps to the localDir.
   */
  async connectPanel(
    side: Side,
    config: ConnectionConfig,
    title: string,
    localDir?: string | null,
  ): Promise<boolean> {
    const workspace = this.activeWorkspace();
    const panel = workspace[side];
    const token = ++panel.connectToken;
    panel.connecting.set(true);
    panel.connectingTo.set(title);
    try {
      const res = await this.rpc.request.connect({ config });
      if (panel.connectToken !== token) {
        // cancelled or superseded while waiting — clean up the orphan session
        if (res.ok) void this.rpc.request.disconnect({ sessionId: res.sessionId });
        return false;
      }
      if (!res.ok) {
        this.toast.error(`${title}: ${res.error}`);
        return false;
      }
      const previous = panel.sessionId();
      if (previous !== 'local') {
        void this.rpc.request.disconnect({ sessionId: previous });
      }
      panel.sessionId.set(res.sessionId);
      panel.fsKey.set(res.fsKey);
      panel.title.set(title);
      panel.touched = true;
      const other = workspace[side === 'left' ? 'right' : 'left'];
      if (localDir && other.sessionId() === 'local' && !other.touched) {
        void other.load(localDir);
      }
      await panel.load(config.initialPath ?? res.homeDir);
      return true;
    } finally {
      if (panel.connectToken === token) {
        panel.connecting.set(false);
        panel.connectingTo.set(null);
      }
    }
  }

  /** Abort waiting on an in-flight connect; the panel keeps its previous state. */
  cancelConnect(side: Side): void {
    const panel = this.get(side);
    if (!panel.connecting()) return;
    panel.connectToken++;
    panel.connecting.set(false);
    panel.connectingTo.set(null);
  }

  async disconnectPanel(side: Side): Promise<void> {
    const panel = this.get(side);
    const sessionId = panel.sessionId();
    if (sessionId === 'local') return;
    await this.rpc.request.disconnect({ sessionId });
    this.resetToLocal(panel);
  }

  private resetToLocal(panel: PanelState): void {
    panel.sessionId.set('local');
    panel.fsKey.set('local');
    panel.title.set('Local');
    void panel.load(null);
  }
}