/**
 * Session slice - manages session list state and pagination.
 */

import { api } from '@renderer/api';
import { createLogger } from '@shared/utils/logger';

import type { AppState } from '../types';
import type { Session } from '@renderer/types/data';
import type { StateCreator } from 'zustand';

const logger = createLogger('Store:session');

/**
 * Tracks the latest in-place refresh generation per project.
 * Used to guarantee last-write-wins under rapid file change events.
 */
const projectRefreshGeneration = new Map<string, number>();

// =============================================================================
// Slice Interface
// =============================================================================

export interface SessionSlice {
  // State
  sessions: Session[];
  selectedSessionId: string | null;
  sessionsLoading: boolean;
  sessionsError: string | null;
  // Pagination state
  sessionsCursor: string | null;
  sessionsHasMore: boolean;
  sessionsTotalCount: number;
  sessionsLoadingMore: boolean;
  // Pinned sessions
  pinnedSessionIds: string[];

  // Actions
  fetchSessions: (projectId: string) => Promise<void>;
  fetchSessionsInitial: (projectId: string) => Promise<void>;
  fetchSessionsMore: () => Promise<void>;
  resetSessionsPagination: () => void;
  selectSession: (id: string) => void;
  clearSelection: () => void;
  /** Refresh sessions list without loading states - for real-time updates */
  refreshSessionsInPlace: (projectId: string) => Promise<void>;
  /** Toggle pin/unpin for a session */
  togglePinSession: (sessionId: string) => Promise<void>;
  /** Load pinned sessions from config for current project */
  loadPinnedSessions: () => Promise<void>;
}

// =============================================================================
// Slice Creator
// =============================================================================

export const createSessionSlice: StateCreator<AppState, [], [], SessionSlice> = (set, get) => ({
  // Initial state
  sessions: [],
  selectedSessionId: null,
  sessionsLoading: false,
  sessionsError: null,
  // Pagination state
  sessionsCursor: null,
  sessionsHasMore: false,
  sessionsTotalCount: 0,
  sessionsLoadingMore: false,
  // Pinned sessions
  pinnedSessionIds: [],

  // Fetch sessions for a specific project (legacy - not paginated)
  fetchSessions: async (projectId: string) => {
    set({ sessionsLoading: true, sessionsError: null });
    try {
      const sessions = await api.getSessions(projectId);
      // Sort by createdAt (descending)
      const sorted = [...sessions].sort((a, b) => b.createdAt - a.createdAt);
      set({ sessions: sorted, sessionsLoading: false });
    } catch (error) {
      set({
        sessionsError: error instanceof Error ? error.message : 'Failed to fetch sessions',
        sessionsLoading: false,
      });
    }
  },

  // Fetch initial page of sessions (paginated)
  fetchSessionsInitial: async (projectId: string) => {
    set({
      sessionsLoading: true,
      sessionsError: null,
      sessions: [],
      sessionsCursor: null,
      sessionsHasMore: false,
      sessionsTotalCount: 0,
    });
    try {
      const { connectionMode } = get();
      const result = await api.getSessionsPaginated(projectId, null, 20, {
        includeTotalCount: false,
        prefilterAll: false,
        metadataLevel: connectionMode === 'ssh' ? 'light' : 'deep',
      });
      set({
        sessions: result.sessions,
        sessionsCursor: result.nextCursor,
        sessionsHasMore: result.hasMore,
        sessionsTotalCount: result.totalCount,
        sessionsLoading: false,
      });

      // Load pinned sessions after fetching session list
      void get().loadPinnedSessions();
    } catch (error) {
      set({
        sessionsError: error instanceof Error ? error.message : 'Failed to fetch sessions',
        sessionsLoading: false,
      });
    }
  },

  // Fetch more sessions (next page)
  fetchSessionsMore: async () => {
    const state = get();
    const { selectedProjectId, sessionsCursor, sessionsHasMore, sessionsLoadingMore } = state;

    // Guard: don't fetch if already loading, no more pages, or no project
    if (!selectedProjectId || !sessionsHasMore || sessionsLoadingMore || !sessionsCursor) {
      return;
    }

    set({ sessionsLoadingMore: true });
    try {
      const { connectionMode } = get();
      const result = await api.getSessionsPaginated(selectedProjectId, sessionsCursor, 20, {
        includeTotalCount: false,
        prefilterAll: false,
        metadataLevel: connectionMode === 'ssh' ? 'light' : 'deep',
      });
      set((prevState) => {
        // Deduplicate: pinned sessions fetched earlier may appear in paginated results
        const existingIds = new Set(prevState.sessions.map((s) => s.id));
        const newSessions = result.sessions.filter((s) => !existingIds.has(s.id));
        return {
          sessions: [...prevState.sessions, ...newSessions],
          sessionsCursor: result.nextCursor,
          sessionsHasMore: result.hasMore,
          sessionsLoadingMore: false,
        };
      });
    } catch (error) {
      set({
        sessionsError: error instanceof Error ? error.message : 'Failed to fetch more sessions',
        sessionsLoadingMore: false,
      });
    }
  },

  // Reset pagination state
  resetSessionsPagination: () => {
    set({
      sessions: [],
      sessionsCursor: null,
      sessionsHasMore: false,
      sessionsTotalCount: 0,
      sessionsLoadingMore: false,
      sessionsError: null,
    });
  },

  // Select a session and fetch its detail
  selectSession: (id: string) => {
    set({
      selectedSessionId: id,
      sessionDetail: null,
      sessionContextStats: null,
      sessionDetailError: null,
    });

    // Fetch detail for this session, passing the active tabId for per-tab data
    const state = get();
    const projectId = state.selectedProjectId;
    if (projectId) {
      const activeTabId = state.activeTabId ?? undefined;
      void state.fetchSessionDetail(projectId, id, activeTabId);
    } else {
      logger.warn('Cannot fetch session detail: no project selected');
    }
  },

  // Clear all selections
  clearSelection: () => {
    set({
      selectedProjectId: null,
      selectedSessionId: null,
      sessions: [],
      sessionDetail: null,
      sessionContextStats: null,
    });
  },

  // Refresh sessions list in place without loading states
  // Used for real-time updates when new sessions are added
  refreshSessionsInPlace: async (projectId: string) => {
    const currentState = get();

    // Only refresh if viewing this project
    if (currentState.selectedProjectId !== projectId) {
      return;
    }

    const generation = (projectRefreshGeneration.get(projectId) ?? 0) + 1;
    projectRefreshGeneration.set(projectId, generation);

    try {
      const { connectionMode } = get();
      const result = await api.getSessionsPaginated(projectId, null, 20, {
        includeTotalCount: false,
        prefilterAll: false,
        metadataLevel: connectionMode === 'ssh' ? 'light' : 'deep',
      });

      // Drop stale responses from older in-flight refreshes
      if (projectRefreshGeneration.get(projectId) !== generation) {
        return;
      }

      // Preserve pinned sessions that are beyond page 1
      const { pinnedSessionIds, sessions: prevSessions } = get();
      const newPageIds = new Set(result.sessions.map((s) => s.id));
      const pinnedSet = new Set(pinnedSessionIds);
      const pinnedToRetain = prevSessions.filter(
        (s) => pinnedSet.has(s.id) && !newPageIds.has(s.id)
      );

      // Update sessions without loading state
      set({
        sessions: [...result.sessions, ...pinnedToRetain],
        sessionsCursor: result.nextCursor,
        sessionsHasMore: result.hasMore,
        sessionsTotalCount: result.totalCount,
        // Don't touch sessionsLoading - keep it as-is
      });
    } catch (error) {
      logger.error('refreshSessionsInPlace error:', error);
      // Don't set error state - this is a background refresh
    }
  },

  // Toggle pin/unpin for a session (optimistic update)
  togglePinSession: async (sessionId: string) => {
    const state = get();
    const projectId = state.selectedProjectId;
    if (!projectId) return;

    const isPinned = state.pinnedSessionIds.includes(sessionId);
    const previousPinnedIds = state.pinnedSessionIds;

    // Optimistic: update UI immediately
    if (isPinned) {
      set({ pinnedSessionIds: previousPinnedIds.filter((id) => id !== sessionId) });
    } else {
      set({ pinnedSessionIds: [sessionId, ...previousPinnedIds] });
    }

    try {
      if (isPinned) {
        await api.config.unpinSession(projectId, sessionId);
      } else {
        await api.config.pinSession(projectId, sessionId);
      }
    } catch (error) {
      // Rollback on failure
      set({ pinnedSessionIds: previousPinnedIds });
      logger.error('togglePinSession error:', error);
    }
  },

  // Load pinned sessions from config for current project
  // Fetches missing pinned session data that may be beyond the paginated page
  loadPinnedSessions: async () => {
    const state = get();
    const projectId = state.selectedProjectId;
    if (!projectId) {
      set({ pinnedSessionIds: [] });
      return;
    }

    try {
      const config = await api.config.get();
      const pins = config.sessions?.pinnedSessions?.[projectId] ?? [];
      const pinnedIds = pins.map((p) => p.sessionId);
      set({ pinnedSessionIds: pinnedIds });

      // Determine which pinned sessions are missing from the loaded sessions array
      const currentSessions = get().sessions;
      const loadedIds = new Set(currentSessions.map((s) => s.id));
      const missingIds = pinnedIds.filter((id) => !loadedIds.has(id));

      if (missingIds.length > 0) {
        const missingSessions = await api.getSessionsByIds(projectId, missingIds);
        if (missingSessions.length > 0) {
          // Re-read sessions in case they changed during the async call
          const latestSessions = get().sessions;
          const latestIds = new Set(latestSessions.map((s) => s.id));
          const toAppend = missingSessions.filter((s) => !latestIds.has(s.id));
          if (toAppend.length > 0) {
            set({ sessions: [...latestSessions, ...toAppend] });
          }
        }
      }
    } catch (error) {
      logger.error('loadPinnedSessions error:', error);
      set({ pinnedSessionIds: [] });
    }
  },
});