/**
 * @license
 * Copyright 2025 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

import { useCallback, useMemo, useEffect, useState } from 'react';
import { type PartListUnion } from '@google/genai';
import process from 'node:process';
import { UseHistoryManagerReturn } from './useHistoryManager.js';
import { useStateAndRef } from './useStateAndRef.js';
import {
  Config,
  GitService,
  Logger,
  logSlashCommand,
  SlashCommandEvent,
  ToolConfirmationOutcome,
} from '@google/gemini-cli-core';
import { useSessionStats } from '../contexts/SessionContext.js';
import { runExitCleanup } from '../../utils/cleanup.js';
import {
  Message,
  MessageType,
  HistoryItemWithoutId,
  HistoryItem,
  SlashCommandProcessorResult,
} from '../types.js';
import { LoadedSettings } from '../../config/settings.js';
import { type CommandContext, type SlashCommand } from '../commands/types.js';
import { CommandService } from '../../services/CommandService.js';
import { BuiltinCommandLoader } from '../../services/BuiltinCommandLoader.js';
import { FileCommandLoader } from '../../services/FileCommandLoader.js';
import { McpPromptLoader } from '../../services/McpPromptLoader.js';

/**
 * Hook to define and process slash commands (e.g., /help, /clear).
 */
export const useSlashCommandProcessor = (
  config: Config | null,
  settings: LoadedSettings,
  addItem: UseHistoryManagerReturn['addItem'],
  clearItems: UseHistoryManagerReturn['clearItems'],
  loadHistory: UseHistoryManagerReturn['loadHistory'],
  refreshStatic: () => void,
  onDebugMessage: (message: string) => void,
  openThemeDialog: () => void,
  openAuthDialog: () => void,
  openEditorDialog: () => void,
  toggleCorgiMode: () => void,
  setQuittingMessages: (message: HistoryItem[]) => void,
  openPrivacyNotice: () => void,
  toggleVimEnabled: () => Promise<boolean>,
  setIsProcessing: (isProcessing: boolean) => void,
  setGeminiMdFileCount: (count: number) => void,
) => {
  const session = useSessionStats();
  const [commands, setCommands] = useState<readonly SlashCommand[]>([]);
  const [shellConfirmationRequest, setShellConfirmationRequest] =
    useState<null | {
      commands: string[];
      onConfirm: (
        outcome: ToolConfirmationOutcome,
        approvedCommands?: string[],
      ) => void;
    }>(null);
  const [confirmationRequest, setConfirmationRequest] = useState<null | {
    prompt: React.ReactNode;
    onConfirm: (confirmed: boolean) => void;
  }>(null);

  const [sessionShellAllowlist, setSessionShellAllowlist] = useState(
    new Set<string>(),
  );
  const gitService = useMemo(() => {
    if (!config?.getProjectRoot()) {
      return;
    }
    return new GitService(config.getProjectRoot());
  }, [config]);

  const logger = useMemo(() => {
    const l = new Logger(config?.getSessionId() || '');
    // The logger's initialize is async, but we can create the instance
    // synchronously. Commands that use it will await its initialization.
    return l;
  }, [config]);

  const [pendingCompressionItemRef, setPendingCompressionItem] =
    useStateAndRef<HistoryItemWithoutId | null>(null);

  const pendingHistoryItems = useMemo(() => {
    const items: HistoryItemWithoutId[] = [];
    if (pendingCompressionItemRef.current != null) {
      items.push(pendingCompressionItemRef.current);
    }
    return items;
  }, [pendingCompressionItemRef]);

  const addMessage = useCallback(
    (message: Message) => {
      // Convert Message to HistoryItemWithoutId
      let historyItemContent: HistoryItemWithoutId;
      if (message.type === MessageType.ABOUT) {
        historyItemContent = {
          type: 'about',
          cliVersion: message.cliVersion,
          osVersion: message.osVersion,
          sandboxEnv: message.sandboxEnv,
          modelVersion: message.modelVersion,
          selectedAuthType: message.selectedAuthType,
          gcpProject: message.gcpProject,
        };
      } else if (message.type === MessageType.HELP) {
        historyItemContent = {
          type: 'help',
          timestamp: message.timestamp,
        };
      } else if (message.type === MessageType.STATS) {
        historyItemContent = {
          type: 'stats',
          duration: message.duration,
        };
      } else if (message.type === MessageType.MODEL_STATS) {
        historyItemContent = {
          type: 'model_stats',
        };
      } else if (message.type === MessageType.TOOL_STATS) {
        historyItemContent = {
          type: 'tool_stats',
        };
      } else if (message.type === MessageType.QUIT) {
        historyItemContent = {
          type: 'quit',
          duration: message.duration,
        };
      } else if (message.type === MessageType.COMPRESSION) {
        historyItemContent = {
          type: 'compression',
          compression: message.compression,
        };
      } else {
        historyItemContent = {
          type: message.type,
          text: message.content,
        };
      }
      addItem(historyItemContent, message.timestamp.getTime());
    },
    [addItem],
  );
  const commandContext = useMemo(
    (): CommandContext => ({
      services: {
        config,
        settings,
        git: gitService,
        logger,
      },
      ui: {
        addItem,
        clear: () => {
          clearItems();
          console.clear();
          refreshStatic();
        },
        loadHistory,
        setDebugMessage: onDebugMessage,
        pendingItem: pendingCompressionItemRef.current,
        setPendingItem: setPendingCompressionItem,
        toggleCorgiMode,
        toggleVimEnabled,
        setGeminiMdFileCount,
      },
      session: {
        stats: session.stats,
        sessionShellAllowlist,
      },
    }),
    [
      config,
      settings,
      gitService,
      logger,
      loadHistory,
      addItem,
      clearItems,
      refreshStatic,
      session.stats,
      onDebugMessage,
      pendingCompressionItemRef,
      setPendingCompressionItem,
      toggleCorgiMode,
      toggleVimEnabled,
      sessionShellAllowlist,
      setGeminiMdFileCount,
    ],
  );

  const ideMode = config?.getIdeMode();

  useEffect(() => {
    const controller = new AbortController();
    const load = async () => {
      const loaders = [
        new McpPromptLoader(config),
        new BuiltinCommandLoader(config),
        new FileCommandLoader(config),
      ];
      const commandService = await CommandService.create(
        loaders,
        controller.signal,
      );
      setCommands(commandService.getCommands());
    };

    load();

    return () => {
      controller.abort();
    };
  }, [config, ideMode]);

  const handleSlashCommand = useCallback(
    async (
      rawQuery: PartListUnion,
      oneTimeShellAllowlist?: Set<string>,
      overwriteConfirmed?: boolean,
    ): Promise<SlashCommandProcessorResult | false> => {
      setIsProcessing(true);
      try {
        if (typeof rawQuery !== 'string') {
          return false;
        }

        const trimmed = rawQuery.trim();
        if (!trimmed.startsWith('/') && !trimmed.startsWith('?')) {
          return false;
        }

        const userMessageTimestamp = Date.now();
        addItem(
          { type: MessageType.USER, text: trimmed },
          userMessageTimestamp,
        );

        const parts = trimmed.substring(1).trim().split(/\s+/);
        const commandPath = parts.filter((p) => p); // The parts of the command, e.g., ['memory', 'add']

        let currentCommands = commands;
        let commandToExecute: SlashCommand | undefined;
        let pathIndex = 0;
        const canonicalPath: string[] = [];

        for (const part of commandPath) {
          // TODO: For better performance and architectural clarity, this two-pass
          // search could be replaced. A more optimal approach would be to
          // pre-compute a single lookup map in `CommandService.ts` that resolves
          // all name and alias conflicts during the initial loading phase. The
          // processor would then perform a single, fast lookup on that map.

          // First pass: check for an exact match on the primary command name.
          let foundCommand = currentCommands.find((cmd) => cmd.name === part);

          // Second pass: if no primary name matches, check for an alias.
          if (!foundCommand) {
            foundCommand = currentCommands.find((cmd) =>
              cmd.altNames?.includes(part),
            );
          }

          if (foundCommand) {
            commandToExecute = foundCommand;
            canonicalPath.push(foundCommand.name);
            pathIndex++;
            if (foundCommand.subCommands) {
              currentCommands = foundCommand.subCommands;
            } else {
              break;
            }
          } else {
            break;
          }
        }

        if (commandToExecute) {
          const args = parts.slice(pathIndex).join(' ');

          if (commandToExecute.action) {
            if (config) {
              const resolvedCommandPath = canonicalPath;
              const event = new SlashCommandEvent(
                resolvedCommandPath[0],
                resolvedCommandPath.length > 1
                  ? resolvedCommandPath.slice(1).join(' ')
                  : undefined,
              );
              logSlashCommand(config, event);
            }

            const fullCommandContext: CommandContext = {
              ...commandContext,
              invocation: {
                raw: trimmed,
                name: commandToExecute.name,
                args,
              },
              overwriteConfirmed,
            };

            // If a one-time list is provided for a "Proceed" action, temporarily
            // augment the session allowlist for this single execution.
            if (oneTimeShellAllowlist && oneTimeShellAllowlist.size > 0) {
              fullCommandContext.session = {
                ...fullCommandContext.session,
                sessionShellAllowlist: new Set([
                  ...fullCommandContext.session.sessionShellAllowlist,
                  ...oneTimeShellAllowlist,
                ]),
              };
            }

            const result = await commandToExecute.action(
              fullCommandContext,
              args,
            );

            if (result) {
              switch (result.type) {
                case 'tool':
                  return {
                    type: 'schedule_tool',
                    toolName: result.toolName,
                    toolArgs: result.toolArgs,
                  };
                case 'message':
                  addItem(
                    {
                      type:
                        result.messageType === 'error'
                          ? MessageType.ERROR
                          : MessageType.INFO,
                      text: result.content,
                    },
                    Date.now(),
                  );
                  return { type: 'handled' };
                case 'dialog':
                  switch (result.dialog) {
                    case 'auth':
                      openAuthDialog();
                      return { type: 'handled' };
                    case 'theme':
                      openThemeDialog();
                      return { type: 'handled' };
                    case 'editor':
                      openEditorDialog();
                      return { type: 'handled' };
                    case 'privacy':
                      openPrivacyNotice();
                      return { type: 'handled' };
                    default: {
                      const unhandled: never = result.dialog;
                      throw new Error(
                        `Unhandled slash command result: ${unhandled}`,
                      );
                    }
                  }
                case 'load_history': {
                  await config
                    ?.getGeminiClient()
                    ?.setHistory(result.clientHistory);
                  fullCommandContext.ui.clear();
                  result.history.forEach((item, index) => {
                    fullCommandContext.ui.addItem(item, index);
                  });
                  return { type: 'handled' };
                }
                case 'quit':
                  setQuittingMessages(result.messages);
                  setTimeout(async () => {
                    await runExitCleanup();
                    process.exit(0);
                  }, 100);
                  return { type: 'handled' };

                case 'submit_prompt':
                  return {
                    type: 'submit_prompt',
                    content: result.content,
                  };
                case 'confirm_shell_commands': {
                  const { outcome, approvedCommands } = await new Promise<{
                    outcome: ToolConfirmationOutcome;
                    approvedCommands?: string[];
                  }>((resolve) => {
                    setShellConfirmationRequest({
                      commands: result.commandsToConfirm,
                      onConfirm: (
                        resolvedOutcome,
                        resolvedApprovedCommands,
                      ) => {
                        setShellConfirmationRequest(null); // Close the dialog
                        resolve({
                          outcome: resolvedOutcome,
                          approvedCommands: resolvedApprovedCommands,
                        });
                      },
                    });
                  });

                  if (
                    outcome === ToolConfirmationOutcome.Cancel ||
                    !approvedCommands ||
                    approvedCommands.length === 0
                  ) {
                    return { type: 'handled' };
                  }

                  if (outcome === ToolConfirmationOutcome.ProceedAlways) {
                    setSessionShellAllowlist(
                      (prev) => new Set([...prev, ...approvedCommands]),
                    );
                  }

                  return await handleSlashCommand(
                    result.originalInvocation.raw,
                    // Pass the approved commands as a one-time grant for this execution.
                    new Set(approvedCommands),
                  );
                }
                case 'confirm_action': {
                  const { confirmed } = await new Promise<{
                    confirmed: boolean;
                  }>((resolve) => {
                    setConfirmationRequest({
                      prompt: result.prompt,
                      onConfirm: (resolvedConfirmed) => {
                        setConfirmationRequest(null);
                        resolve({ confirmed: resolvedConfirmed });
                      },
                    });
                  });

                  if (!confirmed) {
                    addItem(
                      {
                        type: MessageType.INFO,
                        text: 'Operation cancelled.',
                      },
                      Date.now(),
                    );
                    return { type: 'handled' };
                  }

                  return await handleSlashCommand(
                    result.originalInvocation.raw,
                    undefined,
                    true,
                  );
                }
                default: {
                  const unhandled: never = result;
                  throw new Error(
                    `Unhandled slash command result: ${unhandled}`,
                  );
                }
              }
            }

            return { type: 'handled' };
          } else if (commandToExecute.subCommands) {
            const helpText = `Command '/${commandToExecute.name}' requires a subcommand. Available:\n${commandToExecute.subCommands
              .map((sc) => `  - ${sc.name}: ${sc.description || ''}`)
              .join('\n')}`;
            addMessage({
              type: MessageType.INFO,
              content: helpText,
              timestamp: new Date(),
            });
            return { type: 'handled' };
          }
        }

        addMessage({
          type: MessageType.ERROR,
          content: `Unknown command: ${trimmed}`,
          timestamp: new Date(),
        });
        return { type: 'handled' };
      } catch (e) {
        addItem(
          {
            type: MessageType.ERROR,
            text: e instanceof Error ? e.message : String(e),
          },
          Date.now(),
        );
        return { type: 'handled' };
      } finally {
        setIsProcessing(false);
      }
    },
    [
      config,
      addItem,
      openAuthDialog,
      commands,
      commandContext,
      addMessage,
      openThemeDialog,
      openPrivacyNotice,
      openEditorDialog,
      setQuittingMessages,
      setShellConfirmationRequest,
      setSessionShellAllowlist,
      setIsProcessing,
      setConfirmationRequest,
    ],
  );

  return {
    handleSlashCommand,
    slashCommands: commands,
    pendingHistoryItems,
    commandContext,
    shellConfirmationRequest,
    confirmationRequest,
  };
};