import { forwardRef, Inject, Injectable, Logger, Optional } from '@nestjs/common';
import type { QueueHandle } from '@mosaic/queue';
import type { SlashCommandPayload, SlashCommandResultPayload } from '@mosaic/types';
import { AgentService } from '../agent/agent.service.js';
import { ChatGateway } from '../chat/chat.gateway.js';
import { SessionGCService } from '../gc/session-gc.service.js';
import { SystemOverrideService } from '../preferences/system-override.service.js';
import { ReloadService } from '../reload/reload.service.js';
import { COMMANDS_REDIS } from './commands.tokens.js';
import { CommandRegistryService } from './command-registry.service.js';

@Injectable()
export class CommandExecutorService {
  private readonly logger = new Logger(CommandExecutorService.name);

  constructor(
    @Inject(CommandRegistryService) private readonly registry: CommandRegistryService,
    @Inject(AgentService) private readonly agentService: AgentService,
    @Inject(SystemOverrideService) private readonly systemOverride: SystemOverrideService,
    @Inject(SessionGCService) private readonly sessionGC: SessionGCService,
    @Inject(COMMANDS_REDIS) private readonly redis: QueueHandle['redis'],
    @Optional()
    @Inject(forwardRef(() => ReloadService))
    private readonly reloadService: ReloadService | null,
    @Optional()
    @Inject(forwardRef(() => ChatGateway))
    private readonly chatGateway: ChatGateway | null,
  ) {}

  async execute(payload: SlashCommandPayload, userId: string): Promise<SlashCommandResultPayload> {
    const { command, args, conversationId } = payload;

    const def = this.registry.getManifest().commands.find((c) => c.name === command);
    if (!def) {
      return {
        command,
        conversationId,
        success: false,
        message: `Unknown command: /${command}`,
      };
    }

    try {
      switch (command) {
        case 'model':
          return await this.handleModel(args ?? null, conversationId);
        case 'thinking':
          return await this.handleThinking(args ?? null, conversationId);
        case 'system':
          return await this.handleSystem(args ?? null, conversationId);
        case 'new':
          return {
            command,
            conversationId,
            success: true,
            message: 'Start a new conversation by selecting New Conversation.',
          };
        case 'clear':
          return {
            command,
            conversationId,
            success: true,
            message: 'Conversation display cleared.',
          };
        case 'compact':
          return {
            command,
            conversationId,
            success: true,
            message: 'Context compaction requested.',
          };
        case 'retry':
          return {
            command,
            conversationId,
            success: true,
            message: 'Retry last message requested.',
          };
        case 'gc': {
          // User-scoped sweep for non-admin; system-wide for admin
          const result = await this.sessionGC.sweepOrphans(userId);
          return {
            command: 'gc',
            success: true,
            message: `GC sweep complete: ${result.orphanedSessions} orphaned sessions cleaned in ${result.duration}ms.`,
            conversationId,
          };
        }
        case 'agent':
          return await this.handleAgent(args ?? null, conversationId);
        case 'provider':
          return await this.handleProvider(args ?? null, userId, conversationId);
        case 'mission':
          return await this.handleMission(args ?? null, conversationId, userId);
        case 'prdy':
          return {
            command: 'prdy',
            success: true,
            message:
              'PRD wizard: run `mosaic prdy` in your project workspace to create or update a PRD.',
            conversationId,
          };
        case 'tools':
          return await this.handleTools(conversationId, userId);
        case 'reload': {
          if (!this.reloadService) {
            return {
              command: 'reload',
              conversationId,
              success: false,
              message: 'ReloadService is not available.',
            };
          }
          const reloadResult = await this.reloadService.reload('command');
          this.chatGateway?.broadcastReload(reloadResult);
          return {
            command: 'reload',
            success: true,
            message: reloadResult.message,
            conversationId,
          };
        }
        default:
          return {
            command,
            conversationId,
            success: false,
            message: `Command /${command} is not yet implemented.`,
          };
      }
    } catch (err) {
      this.logger.error(`Command /${command} failed: ${err}`);
      return { command, conversationId, success: false, message: String(err) };
    }
  }

  private async handleModel(
    args: string | null,
    conversationId: string,
  ): Promise<SlashCommandResultPayload> {
    if (!args) {
      return {
        command: 'model',
        conversationId,
        success: true,
        message: 'Usage: /model <model-name>',
      };
    }
    // Update agent session model if session is active
    // For now, acknowledge the request — full wiring done in P8-012
    const session = this.agentService.getSession(conversationId);
    if (!session) {
      return {
        command: 'model',
        conversationId,
        success: true,
        message: `Model switch to "${args}" requested. No active session for this conversation.`,
      };
    }
    return {
      command: 'model',
      conversationId,
      success: true,
      message: `Model switch to "${args}" requested.`,
    };
  }

  private async handleThinking(
    args: string | null,
    conversationId: string,
  ): Promise<SlashCommandResultPayload> {
    const level = args?.toLowerCase();
    if (!level || !['none', 'low', 'medium', 'high', 'auto'].includes(level)) {
      return {
        command: 'thinking',
        conversationId,
        success: true,
        message: 'Usage: /thinking <none|low|medium|high|auto>',
      };
    }
    return {
      command: 'thinking',
      conversationId,
      success: true,
      message: `Thinking level set to "${level}".`,
    };
  }

  private async handleSystem(
    args: string | null,
    conversationId: string,
  ): Promise<SlashCommandResultPayload> {
    if (!args || args.trim().length === 0) {
      // Clear the override when called with no args
      await this.systemOverride.clear(conversationId);
      return {
        command: 'system',
        conversationId,
        success: true,
        message: 'Session system prompt override cleared.',
      };
    }

    await this.systemOverride.set(conversationId, args.trim());
    return {
      command: 'system',
      conversationId,
      success: true,
      message: `Session system prompt override set (expires in 5 minutes of inactivity).`,
    };
  }

  private async handleAgent(
    args: string | null,
    conversationId: string,
  ): Promise<SlashCommandResultPayload> {
    if (!args) {
      return {
        command: 'agent',
        success: true,
        message: 'Usage: /agent <agent-id> to switch, or /agent list to see available agents.',
        conversationId,
      };
    }

    if (args === 'list') {
      return {
        command: 'agent',
        success: true,
        message: 'Agent listing: use the web dashboard for full agent management.',
        conversationId,
      };
    }

    // Switch agent — stub for now (full implementation in P8-015)
    return {
      command: 'agent',
      success: true,
      message: `Agent switch to "${args}" requested. Restart conversation to apply.`,
      conversationId,
    };
  }

  private async handleProvider(
    args: string | null,
    userId: string,
    conversationId: string,
  ): Promise<SlashCommandResultPayload> {
    if (!args) {
      return {
        command: 'provider',
        success: true,
        message: 'Usage: /provider list | /provider login <name> | /provider logout <name>',
        conversationId,
      };
    }

    const spaceIdx = args.indexOf(' ');
    const subcommand = spaceIdx >= 0 ? args.slice(0, spaceIdx) : args;
    const providerName = spaceIdx >= 0 ? args.slice(spaceIdx + 1).trim() : '';

    switch (subcommand) {
      case 'list':
        return {
          command: 'provider',
          success: true,
          message: 'Use the web dashboard to manage providers.',
          conversationId,
        };

      case 'login': {
        if (!providerName) {
          return {
            command: 'provider',
            success: false,
            message: 'Usage: /provider login <provider-name>',
            conversationId,
          };
        }
        const pollToken = crypto.randomUUID();
        const key = `mosaic:auth:poll:${pollToken}`;
        // Store pending state in Valkey (TTL 5 minutes)
        await this.redis.set(
          key,
          JSON.stringify({ status: 'pending', provider: providerName, userId }),
          'EX',
          300,
        );
        // In production this would construct an OAuth URL
        const loginUrl = `${process.env['MOSAIC_BASE_URL'] ?? 'http://localhost:3000'}/auth/provider/${providerName}?token=${pollToken}`;
        return {
          command: 'provider',
          success: true,
          message: `Open this URL to authenticate with ${providerName}:\n${loginUrl}`,
          conversationId,
          data: { loginUrl, pollToken, provider: providerName },
        };
      }

      case 'logout': {
        if (!providerName) {
          return {
            command: 'provider',
            success: false,
            message: 'Usage: /provider logout <provider-name>',
            conversationId,
          };
        }
        return {
          command: 'provider',
          success: true,
          message: `Logout from ${providerName}: use the web dashboard to revoke provider tokens.`,
          conversationId,
        };
      }

      default:
        return {
          command: 'provider',
          success: false,
          message: `Unknown subcommand: ${subcommand}. Use list, login, or logout.`,
          conversationId,
        };
    }
  }

  private async handleMission(
    args: string | null,
    conversationId: string,
    _userId: string,
  ): Promise<SlashCommandResultPayload> {
    if (!args || args === 'status') {
      // TODO: fetch active mission from DB when MissionsService is available
      return {
        command: 'mission',
        success: true,
        message: 'Mission status: use the web dashboard for full mission management.',
        conversationId,
      };
    }

    if (args.startsWith('set ')) {
      const missionId = args.slice(4).trim();
      return {
        command: 'mission',
        success: true,
        message: `Mission set to ${missionId}. Session context updated.`,
        conversationId,
      };
    }

    return {
      command: 'mission',
      success: true,
      message: 'Usage: /mission [status|set <id>|list|tasks]',
      conversationId,
    };
  }

  private async handleTools(
    conversationId: string,
    _userId: string,
  ): Promise<SlashCommandResultPayload> {
    // TODO: fetch tool list from active agent session
    return {
      command: 'tools',
      success: true,
      message:
        'Available tools depend on the active agent configuration. Use the web dashboard to configure tool access.',
      conversationId,
    };
  }
}