/**
 * Default Dispatch Manager - Adapter Implementation
 *
 * Implements DispatchManager interface with in-memory queue
 * and dependency-ordered dispatch.
 *
 * This is the ADAPTER for the DispatchManager PORT.
 */

import type {
  EventBus,
  TaskQueuedEvent,
  TaskCompletedEvent,
  TaskBlockedEvent,
  TaskDispatchedEvent,
} from '../events/index.js';
import type { AgentManager, AgentResult, AgentInfo } from '../agent/types.js';
import type { TaskRepository } from '../db/repositories/task-repository.js';
import type { MessageRepository } from '../db/repositories/message-repository.js';
import type { AgentRepository } from '../db/repositories/agent-repository.js';
import type { InitiativeRepository } from '../db/repositories/initiative-repository.js';
import type { PhaseRepository } from '../db/repositories/phase-repository.js';
import type { PageRepository } from '../db/repositories/page-repository.js';
import type { Task, Phase } from '../db/schema.js';
import type { PageForSerialization } from '../agent/content-serializer.js';
import type { DispatchManager, QueuedTask, DispatchResult } from './types.js';
import { phaseBranchName, taskBranchName, isPlanningCategory, generateInitiativeBranch } from '../git/branch-naming.js';
import { buildExecutePrompt } from '../agent/prompts/index.js';
import { createModuleLogger } from '../logger/index.js';

const log = createModuleLogger('dispatch');

// =============================================================================
// Internal Types
// =============================================================================

/**
 * Internal representation of a blocked task.
 */
interface BlockedTask {
  taskId: string;
  reason: string;
}

// =============================================================================
// DefaultDispatchManager Implementation
// =============================================================================

/**
 * In-memory implementation of DispatchManager.
 *
 * Uses Map for queue management and checks task_dependencies table
 * for dependency resolution.
 */
export class DefaultDispatchManager implements DispatchManager {
  /** Internal queue of tasks pending dispatch */
  private taskQueue: Map<string, QueuedTask> = new Map();

  /** Blocked tasks with their reasons */
  private blockedTasks: Map<string, BlockedTask> = new Map();

  constructor(
    private taskRepository: TaskRepository,
    private messageRepository: MessageRepository,
    private agentManager: AgentManager,
    private eventBus: EventBus,
    private initiativeRepository?: InitiativeRepository,
    private phaseRepository?: PhaseRepository,
    private agentRepository?: AgentRepository,
    private pageRepository?: PageRepository,
  ) {}

  /**
   * Queue a task for dispatch.
   * Fetches task dependencies and adds to internal queue.
   * Checkpoint tasks are queued but won't auto-dispatch.
   */
  async queue(taskId: string): Promise<void> {
    // Fetch task to verify it exists and get priority
    const task = await this.taskRepository.findById(taskId);
    if (!task) {
      throw new Error(`Task not found: ${taskId}`);
    }

    // Get dependencies for this task from the repository
    const dependsOn = await this.taskRepository.getDependencies(taskId);

    const queuedTask: QueuedTask = {
      taskId,
      priority: task.priority,
      queuedAt: new Date(),
      dependsOn,
    };

    this.taskQueue.set(taskId, queuedTask);

    log.info({ taskId, priority: task.priority, isCheckpoint: this.isCheckpointTask(task) }, 'task queued');

    // Emit TaskQueuedEvent
    const event: TaskQueuedEvent = {
      type: 'task:queued',
      timestamp: new Date(),
      payload: {
        taskId,
        priority: task.priority,
        dependsOn,
      },
    };
    this.eventBus.emit(event);
  }

  /**
   * Get next dispatchable task.
   * Returns task with all dependencies complete, highest priority first.
   * Checkpoint tasks are excluded (require human action).
   */
  async getNextDispatchable(): Promise<QueuedTask | null> {
    const queuedTasks = Array.from(this.taskQueue.values());

    if (queuedTasks.length === 0) {
      return null;
    }

    // Filter to only tasks with all dependencies complete and not checkpoint tasks
    const readyTasks: QueuedTask[] = [];

    log.debug({ queueSize: queuedTasks.length }, 'evaluating dispatchable tasks');

    for (const qt of queuedTasks) {
      // Check dependencies
      const allDepsComplete = await this.areAllDependenciesComplete(qt.dependsOn);
      if (!allDepsComplete) {
        continue;
      }

      // Check if this is a checkpoint task (requires human action)
      const task = await this.taskRepository.findById(qt.taskId);
      if (task && this.isCheckpointTask(task)) {
        log.debug({ taskId: qt.taskId, type: task.type }, 'skipping checkpoint task');
        continue;
      }

      // Skip planning-category tasks (handled by architect flow)
      if (task && isPlanningCategory(task.category)) {
        log.debug({ taskId: qt.taskId, category: task.category }, 'skipping planning-category task');
        continue;
      }

      readyTasks.push(qt);
    }

    log.debug({ queueSize: queuedTasks.length, readyCount: readyTasks.length }, 'dispatchable evaluation complete');

    if (readyTasks.length === 0) {
      return null;
    }

    // Sort by priority (high > medium > low), then by queuedAt (oldest first)
    const priorityOrder: Record<string, number> = { high: 0, medium: 1, low: 2 };

    readyTasks.sort((a, b) => {
      const priorityDiff = priorityOrder[a.priority] - priorityOrder[b.priority];
      if (priorityDiff !== 0) {
        return priorityDiff;
      }
      return a.queuedAt.getTime() - b.queuedAt.getTime();
    });

    return readyTasks[0];
  }

  /**
   * Mark a task as complete.
   * Updates task status and removes from queue.
   *
   * @param taskId - ID of the task to complete
   * @param agentId - Optional ID of the agent that completed the task
   */
  async completeTask(taskId: string, agentId?: string): Promise<void> {
    const task = await this.taskRepository.findById(taskId);
    if (!task) {
      throw new Error(`Task not found: ${taskId}`);
    }

    // Store agent result summary on the task for propagation to dependent tasks
    await this.storeAgentSummary(taskId, agentId);

    await this.taskRepository.update(taskId, { status: 'completed' });

    // Remove from queue
    this.taskQueue.delete(taskId);

    log.info({ taskId }, 'task completed');

    // Emit TaskCompletedEvent
    const event: TaskCompletedEvent = {
      type: 'task:completed',
      timestamp: new Date(),
      payload: {
        taskId,
        agentId: agentId ?? '',
        success: true,
        message: 'Task completed',
      },
    };
    this.eventBus.emit(event);

    // Also remove from blocked if it was there
    this.blockedTasks.delete(taskId);
  }

  /**
   * Mark a task as blocked.
   * Updates task status and records block reason.
   */
  async blockTask(taskId: string, reason: string): Promise<void> {
    // Update task status to 'blocked'
    await this.taskRepository.update(taskId, { status: 'blocked' });

    // Record in blocked map
    this.blockedTasks.set(taskId, { taskId, reason });

    log.warn({ taskId, reason }, 'task blocked');

    // Remove from queue (blocked tasks aren't dispatchable)
    this.taskQueue.delete(taskId);

    // Emit TaskBlockedEvent
    const event: TaskBlockedEvent = {
      type: 'task:blocked',
      timestamp: new Date(),
      payload: {
        taskId,
        reason,
      },
    };
    this.eventBus.emit(event);
  }

  /**
   * Dispatch next available task to an agent.
   */
  async dispatchNext(): Promise<DispatchResult> {
    // Get next dispatchable task
    const nextTask = await this.getNextDispatchable();

    if (!nextTask) {
      log.debug('no dispatchable tasks');
      return {
        success: false,
        taskId: '',
        reason: 'No dispatchable tasks',
      };
    }

    // Find available agent (status='idle')
    const agents = await this.agentManager.list();
    const idleAgent = agents.find((a) => a.status === 'idle');

    if (!idleAgent) {
      log.debug('no available agents');
      return {
        success: false,
        taskId: nextTask.taskId,
        reason: 'No available agents',
      };
    }

    // Get task details
    const task = await this.taskRepository.findById(nextTask.taskId);
    if (!task) {
      return {
        success: false,
        taskId: nextTask.taskId,
        reason: 'Task not found',
      };
    }

    // Compute branch info for branch-aware spawning
    let baseBranch: string | undefined;
    let branchName: string | undefined;

    if (task.initiativeId && this.initiativeRepository) {
      try {
        if (isPlanningCategory(task.category)) {
          // Planning tasks run on project default branches — no initiative branch needed.
          // baseBranch and branchName remain undefined; ProcessManager uses per-project defaults.
        } else if (task.phaseId && this.phaseRepository) {
          // Execution task — ensure initiative has a branch
          const initiative = await this.initiativeRepository.findById(task.initiativeId);
          if (initiative) {
            let initBranch = initiative.branch;
            if (!initBranch) {
              initBranch = generateInitiativeBranch(initiative.name);
              await this.initiativeRepository.update(initiative.id, { branch: initBranch });
            }

            const phase = await this.phaseRepository.findById(task.phaseId);
            if (phase) {
              if (task.category === 'merge' || task.category === 'review') {
                // Merge/review tasks work directly on the phase branch
                baseBranch = initBranch;
                branchName = phaseBranchName(initBranch, phase.name);
              } else {
                baseBranch = phaseBranchName(initBranch, phase.name);
                branchName = taskBranchName(initBranch, task.id);
              }
            }
          }
        }
      } catch {
        // Non-fatal: fall back to default branching
      }
    }

    // Gather initiative context for the agent's input files
    let inputContext: import('../agent/types.js').AgentInputContext | undefined;
    if (task.initiativeId) {
      try {
        const initiative = await this.initiativeRepository?.findById(task.initiativeId);
        const phase = task.phaseId ? await this.phaseRepository?.findById(task.phaseId) : undefined;
        const context = await this.gatherInitiativeContext(task.initiativeId);

        inputContext = {
          initiative: initiative ?? undefined,
          task,
          phase: phase ?? undefined,
          phases: context.phases.length > 0 ? context.phases : undefined,
          tasks: context.tasks.length > 0 ? context.tasks : undefined,
          pages: context.pages.length > 0 ? context.pages : undefined,
        };
      } catch (err) {
        log.warn({ taskId: task.id, err }, 'failed to gather initiative context for dispatch');
      }
    }

    // Spawn agent with task (alias auto-generated by agent manager)
    let agent: AgentInfo;
    try {
      agent = await this.agentManager.spawn({
        taskId: nextTask.taskId,
        initiativeId: task.initiativeId ?? undefined,
        phaseId: task.phaseId ?? undefined,
        prompt: buildExecutePrompt(task.description || task.name),
        baseBranch,
        branchName,
        inputContext,
      });
    } catch (err) {
      const reason = `Spawn failed: ${err instanceof Error ? err.message : String(err)}`;
      log.error({ taskId: nextTask.taskId, err: reason }, 'agent spawn failed, blocking task');
      await this.blockTask(nextTask.taskId, reason);
      return { success: false, taskId: nextTask.taskId, reason };
    }

    log.info({ taskId: nextTask.taskId, agentId: agent.id }, 'task dispatched');

    // Update task status to 'in_progress'
    await this.taskRepository.update(nextTask.taskId, { status: 'in_progress' });

    // Remove from queue (now being worked on)
    this.taskQueue.delete(nextTask.taskId);

    // Emit TaskDispatchedEvent
    const event: TaskDispatchedEvent = {
      type: 'task:dispatched',
      timestamp: new Date(),
      payload: {
        taskId: nextTask.taskId,
        agentId: agent.id,
        agentName: agent.name,
      },
    };
    this.eventBus.emit(event);

    return {
      success: true,
      taskId: nextTask.taskId,
      agentId: agent.id,
    };
  }

  /**
   * Get current queue state.
   */
  async getQueueState(): Promise<{
    queued: QueuedTask[];
    ready: QueuedTask[];
    blocked: Array<{ taskId: string; reason: string }>;
  }> {
    const allQueued = Array.from(this.taskQueue.values());

    // Determine which are ready
    const ready: QueuedTask[] = [];
    for (const qt of allQueued) {
      const allDepsComplete = await this.areAllDependenciesComplete(qt.dependsOn);
      if (allDepsComplete) {
        ready.push(qt);
      }
    }

    return {
      queued: allQueued,
      ready,
      blocked: Array.from(this.blockedTasks.values()),
    };
  }

  // =============================================================================
  // Private Helpers
  // =============================================================================

  /**
   * Check if all dependencies are complete.
   */
  private async areAllDependenciesComplete(dependsOn: string[]): Promise<boolean> {
    if (dependsOn.length === 0) {
      return true;
    }

    for (const depTaskId of dependsOn) {
      const depTask = await this.taskRepository.findById(depTaskId);
      if (!depTask || depTask.status !== 'completed') {
        return false;
      }
    }

    return true;
  }

  /**
   * Check if a task is a checkpoint task.
   * Checkpoint tasks require human action and don't auto-dispatch.
   */
  private isCheckpointTask(task: Task): boolean {
    return task.type.startsWith('checkpoint:');
  }

  /**
   * Store the completing agent's result summary on the task record.
   */
  private async storeAgentSummary(taskId: string, agentId?: string): Promise<void> {
    if (!agentId || !this.agentRepository) return;
    try {
      const agentRecord = await this.agentRepository.findById(agentId);
      if (agentRecord?.result) {
        const result: AgentResult = JSON.parse(agentRecord.result);
        if (result.message) {
          await this.taskRepository.update(taskId, { summary: result.message });
        }
      }
    } catch (err) {
      log.warn({ taskId, agentId, err }, 'failed to store agent summary on task');
    }
  }

  /**
   * Gather initiative context for passing to execution agents.
   * Reuses the same pattern as architect.ts gatherInitiativeContext.
   */
  private async gatherInitiativeContext(initiativeId: string): Promise<{
    phases: Array<Phase & { dependsOn?: string[] }>;
    tasks: Task[];
    pages: PageForSerialization[];
  }> {
    const [rawPhases, deps, initiativeTasks, pages] = await Promise.all([
      this.phaseRepository?.findByInitiativeId(initiativeId) ?? [],
      this.phaseRepository?.findDependenciesByInitiativeId(initiativeId) ?? [],
      this.taskRepository.findByInitiativeId(initiativeId),
      this.pageRepository?.findByInitiativeId(initiativeId) ?? [],
    ]);

    // Merge dependencies into each phase as a dependsOn array
    const depsByPhase = new Map<string, string[]>();
    for (const dep of deps) {
      const arr = depsByPhase.get(dep.phaseId) ?? [];
      arr.push(dep.dependsOnPhaseId);
      depsByPhase.set(dep.phaseId, arr);
    }
    const phases = rawPhases.map((ph) => ({
      ...ph,
      dependsOn: depsByPhase.get(ph.id) ?? [],
    }));

    // Collect tasks from all phases (some tasks only have phaseId, not initiativeId)
    const taskIds = new Set(initiativeTasks.map((t) => t.id));
    const allTasks = [...initiativeTasks];
    for (const ph of rawPhases) {
      const phaseTasks = await this.taskRepository.findByPhaseId(ph.id);
      for (const t of phaseTasks) {
        if (!taskIds.has(t.id)) {
          taskIds.add(t.id);
          allTasks.push(t);
        }
      }
    }

    // Only include implementation tasks — planning tasks are irrelevant noise
    const implementationTasks = allTasks.filter(t => !isPlanningCategory(t.category));

    return { phases, tasks: implementationTasks, pages };
  }

}