/**
 * Execution Orchestrator
 *
 * Subscribes to task:completed events and orchestrates the post-completion
 * merge workflow:
 * - Task branch → Phase branch (on task completion)
 * - Phase branch → Initiative branch (when all phase tasks done)
 *
 * Supports two execution modes:
 * - YOLO: auto-merge everything
 * - Review per-phase: pause after each phase for diff review
 */

import type { EventBus, TaskCompletedEvent, PhasePendingReviewEvent, PhaseMergedEvent, TaskMergedEvent, PhaseQueuedEvent, AgentStoppedEvent } from '../events/index.js';
import type { BranchManager } from '../git/branch-manager.js';
import type { PhaseRepository } from '../db/repositories/phase-repository.js';
import type { TaskRepository } from '../db/repositories/task-repository.js';
import type { InitiativeRepository } from '../db/repositories/initiative-repository.js';
import type { ProjectRepository } from '../db/repositories/project-repository.js';
import type { DispatchManager, PhaseDispatchManager } from '../dispatch/types.js';
import type { ConflictResolutionService } from '../coordination/conflict-resolution-service.js';
import { phaseBranchName, taskBranchName } from '../git/branch-naming.js';
import { ensureProjectClone } from '../git/project-clones.js';
import { createModuleLogger } from '../logger/index.js';

const log = createModuleLogger('execution-orchestrator');

export class ExecutionOrchestrator {
  /** Serialize merges per phase to avoid concurrent merge conflicts */
  private phaseMergeLocks: Map<string, Promise<void>> = new Map();

  /** Coalesced dispatch scheduling state */
  private dispatchPending = false;
  private dispatchRunning = false;

  constructor(
    private branchManager: BranchManager,
    private phaseRepository: PhaseRepository,
    private taskRepository: TaskRepository,
    private initiativeRepository: InitiativeRepository,
    private projectRepository: ProjectRepository,
    private phaseDispatchManager: PhaseDispatchManager,
    private dispatchManager: DispatchManager,
    private conflictResolutionService: ConflictResolutionService,
    private eventBus: EventBus,
    private workspaceRoot: string,
  ) {}

  /**
   * Start listening for events that drive execution.
   */
  start(): void {
    this.eventBus.on<TaskCompletedEvent>('task:completed', (event) => {
      this.handleTaskCompleted(event).catch((err) => {
        log.error({ err: err instanceof Error ? err.message : String(err) }, 'error handling task:completed');
      });
    });

    // Kick off dispatch when phases are queued (e.g. user clicks Execute)
    this.eventBus.on<PhaseQueuedEvent>('phase:queued', () => this.scheduleDispatch());

    // Auto-complete task + re-dispatch when an agent finishes
    this.eventBus.on<AgentStoppedEvent>('agent:stopped', (event) => {
      this.handleAgentStopped(event).catch((err) => {
        log.error({ err: err instanceof Error ? err.message : String(err) }, 'error handling agent:stopped');
      });
    });

    log.info('execution orchestrator started');
  }

  // ---------------------------------------------------------------------------
  // Coalesced dispatch scheduler
  // ---------------------------------------------------------------------------

  /**
   * Schedule a dispatch cycle. Coalesces multiple rapid calls (e.g. from
   * synchronous EventEmitter) into a single async run.
   */
  private scheduleDispatch(): void {
    if (this.dispatchRunning) {
      this.dispatchPending = true;
      return;
    }
    this.runDispatchCycle().catch((err) =>
      log.error({ err: err instanceof Error ? err.message : String(err) }, 'dispatch cycle error'),
    );
  }

  private async handleAgentStopped(event: AgentStoppedEvent): Promise<void> {
    const { taskId, reason, agentId } = event.payload;

    // Auto-complete task for successful agent completions, not manual stops
    if (taskId && reason !== 'user_requested') {
      try {
        await this.dispatchManager.completeTask(taskId, agentId);
        log.info({ taskId, agentId, reason }, 'task auto-completed on agent stop');
      } catch (err) {
        log.warn(
          { taskId, agentId, reason, err: err instanceof Error ? err.message : String(err) },
          'failed to auto-complete task on agent stop',
        );
      }
    }

    this.scheduleDispatch();
  }

  private async runDispatchCycle(): Promise<void> {
    this.dispatchRunning = true;
    try {
      do {
        this.dispatchPending = false;
        // Dispatch all ready phases (each queues its tasks internally)
        while (true) {
          const result = await this.phaseDispatchManager.dispatchNextPhase();
          if (!result.success) break;
          log.info({ phaseId: result.phaseId }, 'auto-dispatched phase');
        }
        // Dispatch all ready tasks to idle agents
        while (true) {
          const result = await this.dispatchManager.dispatchNext();
          if (!result.success) break;
          log.info({ taskId: result.taskId, agentId: result.agentId }, 'auto-dispatched task');
        }
      } while (this.dispatchPending);
    } finally {
      this.dispatchRunning = false;
    }
  }

  /**
   * Handle a task:completed event.
   * Merges the task branch into the phase branch, then checks if all phase tasks are done.
   */
  private async handleTaskCompleted(event: TaskCompletedEvent): Promise<void> {
    const { taskId } = event.payload;

    const task = await this.taskRepository.findById(taskId);
    if (!task?.phaseId || !task.initiativeId) return;

    const initiative = await this.initiativeRepository.findById(task.initiativeId);
    if (!initiative?.branch) return;

    const phase = await this.phaseRepository.findById(task.phaseId);
    if (!phase) return;

    // Skip merge tasks — they already work on the phase branch directly
    if (task.category === 'merge') return;

    const initBranch = initiative.branch;
    const phBranch = phaseBranchName(initBranch, phase.name);
    const tBranch = taskBranchName(initBranch, task.id);

    // Serialize merges per phase
    const lock = this.phaseMergeLocks.get(task.phaseId) ?? Promise.resolve();
    const mergeOp = lock.then(async () => {
      await this.mergeTaskIntoPhase(taskId, task.phaseId!, tBranch, phBranch);
    });
    this.phaseMergeLocks.set(task.phaseId, mergeOp.catch(() => {}));
    await mergeOp;

    // Check if all phase tasks are done
    const phaseTasks = await this.taskRepository.findByPhaseId(task.phaseId);
    const allDone = phaseTasks.every((t) => t.status === 'completed');
    if (allDone) {
      await this.handlePhaseAllTasksDone(task.phaseId);
    }

    // Fill freed agent slot with next queued task
    this.scheduleDispatch();
  }

  /**
   * Merge a task branch into the phase branch for all linked projects.
   */
  private async mergeTaskIntoPhase(
    taskId: string,
    phaseId: string,
    taskBranch: string,
    phaseBranch: string,
  ): Promise<void> {
    const phase = await this.phaseRepository.findById(phaseId);
    if (!phase) return;

    const projects = await this.projectRepository.findProjectsByInitiativeId(phase.initiativeId);

    for (const project of projects) {
      const clonePath = await ensureProjectClone(project, this.workspaceRoot);

      // Only merge if the task branch actually exists (agents may not have pushed)
      const exists = await this.branchManager.branchExists(clonePath, taskBranch);
      if (!exists) {
        log.debug({ taskId, taskBranch, project: project.name }, 'task branch does not exist, skipping merge');
        continue;
      }

      const result = await this.branchManager.mergeBranch(clonePath, taskBranch, phaseBranch);

      if (!result.success && result.conflicts) {
        log.warn({ taskId, taskBranch, phaseBranch, conflicts: result.conflicts }, 'task merge conflict');
        await this.conflictResolutionService.handleConflict(taskId, result.conflicts, {
          sourceBranch: taskBranch,
          targetBranch: phaseBranch,
        });
        return;
      }

      log.info({ taskId, taskBranch, phaseBranch, project: project.name }, 'task branch merged into phase branch');
    }

    // Emit task:merged event
    const mergedEvent: TaskMergedEvent = {
      type: 'task:merged',
      timestamp: new Date(),
      payload: { taskId, phaseId, sourceBranch: taskBranch, targetBranch: phaseBranch },
    };
    this.eventBus.emit(mergedEvent);
  }

  /**
   * Handle all tasks in a phase being done.
   * YOLO mode: auto-merge phase → initiative.
   * Review mode: set phase to pending_review.
   */
  private async handlePhaseAllTasksDone(phaseId: string): Promise<void> {
    const phase = await this.phaseRepository.findById(phaseId);
    if (!phase) return;

    const initiative = await this.initiativeRepository.findById(phase.initiativeId);
    if (!initiative?.branch) return;

    if (initiative.executionMode === 'yolo') {
      await this.mergePhaseIntoInitiative(phaseId);
      await this.phaseDispatchManager.completePhase(phaseId);
      await this.phaseDispatchManager.dispatchNextPhase();
      this.scheduleDispatch();
    } else {
      // review_per_phase
      await this.phaseRepository.update(phaseId, { status: 'pending_review' as any });

      const event: PhasePendingReviewEvent = {
        type: 'phase:pending_review',
        timestamp: new Date(),
        payload: { phaseId, initiativeId: phase.initiativeId },
      };
      this.eventBus.emit(event);

      log.info({ phaseId, initiativeId: phase.initiativeId }, 'phase pending review');
    }
  }

  /**
   * Merge phase branch into initiative branch for all linked projects.
   */
  private async mergePhaseIntoInitiative(phaseId: string): Promise<void> {
    const phase = await this.phaseRepository.findById(phaseId);
    if (!phase) return;

    const initiative = await this.initiativeRepository.findById(phase.initiativeId);
    if (!initiative?.branch) return;

    const initBranch = initiative.branch;
    const phBranch = phaseBranchName(initBranch, phase.name);

    const projects = await this.projectRepository.findProjectsByInitiativeId(phase.initiativeId);

    for (const project of projects) {
      const clonePath = await ensureProjectClone(project, this.workspaceRoot);
      const result = await this.branchManager.mergeBranch(clonePath, phBranch, initBranch);

      if (!result.success) {
        log.error({ phaseId, phBranch, initBranch, conflicts: result.conflicts }, 'phase merge conflict');
        throw new Error(`Phase merge conflict: ${result.message}`);
      }

      log.info({ phaseId, phBranch, initBranch, project: project.name }, 'phase branch merged into initiative branch');
    }

    // Emit phase:merged event
    const mergedEvent: PhaseMergedEvent = {
      type: 'phase:merged',
      timestamp: new Date(),
      payload: { phaseId, initiativeId: phase.initiativeId, sourceBranch: phBranch, targetBranch: initBranch },
    };
    this.eventBus.emit(mergedEvent);
  }

  /**
   * Approve and merge a phase that's pending review.
   * Called from tRPC when user clicks approve in ReviewTab.
   */
  async approveAndMergePhase(phaseId: string): Promise<void> {
    const phase = await this.phaseRepository.findById(phaseId);
    if (!phase) throw new Error(`Phase not found: ${phaseId}`);
    if (phase.status !== 'pending_review') {
      throw new Error(`Phase ${phaseId} is not pending review (status: ${phase.status})`);
    }

    await this.mergePhaseIntoInitiative(phaseId);
    await this.phaseDispatchManager.completePhase(phaseId);
    await this.phaseDispatchManager.dispatchNextPhase();
    this.scheduleDispatch();

    log.info({ phaseId }, 'phase review approved and merged');
  }
}