import { readdirSync, existsSync } from 'fs'
import { join } from 'path'
import { getPlansDir } from './config'
import { loadTaskFile, calculateStatus } from './prds'
import type { Task, TaskFile } from './prds'

export interface TaskFileStatus {
  filename: string
  feature: string
  completedCount: number
  totalCount: number
  nextTask: Task | null
}

/**
 * Get all task files in .plans/ directory
 */
export function listTaskFiles(): string[] {
  const plansDir = getPlansDir()
  if (!existsSync(plansDir)) {
    return []
  }

  const files = readdirSync(plansDir)
  return files.filter(file => file.startsWith('tasks-') && file.endsWith('.yml'))
}

/**
 * Find next task respecting dependencies
 * Returns first pending task where all dependencies are completed or cancelled
 */
export function findNextTask(taskFile: TaskFile): Task | null {
  if (!taskFile.tasks || taskFile.tasks.length === 0) {
    return null
  }

  // Find first pending task where all dependencies are satisfied
  for (const task of taskFile.tasks) {
    if (task.status === 'pending') {
      // Check if all dependencies are completed or cancelled
      const dependencies = task.dependencies || []
      const allDepsCompleted = dependencies.every(depId => {
        const depTask = taskFile.tasks.find(t => t.id === depId)
        return depTask && (depTask.status === 'completed' || depTask.status === 'cancelled')
      })

      if (allDepsCompleted) {
        return task
      }
    }
  }

  return null
}

/**
 * Get status for a single task file
 */
export async function getTaskFileStatus(taskFilename: string): Promise<TaskFileStatus | null> {
  const taskFile = await loadTaskFile(taskFilename)
  if (!taskFile) {
    return null
  }

  const { status, completedCount, totalCount } = calculateStatus(taskFile)

  // Skip fully completed files
  if (status === 'completed') {
    return null
  }

  const nextTask = findNextTask(taskFile)

  return {
    filename: taskFilename,
    feature: taskFile.feature,
    completedCount,
    totalCount,
    nextTask,
  }
}

/**
 * List all incomplete task files with their status
 */
export async function listIncompleteTaskFiles(): Promise<TaskFileStatus[]> {
  const taskFiles = listTaskFiles()
  const statusList = await Promise.all(taskFiles.map(file => getTaskFileStatus(file)))

  // Filter out null (completed files) and return
  return statusList.filter((s): s is TaskFileStatus => s !== null)
}