import { mkdirSync, writeFileSync, readdirSync, existsSync, readFileSync } from 'node:fs'
import { join } from 'node:path'
import { PROJECT_ROOT, HOWL_CONFIG_DIR } from './config.js'
import { logger } from './logger.js'

const TEMPLATE_DIR = join(PROJECT_ROOT, 'agents', '_template')

export type CreateAgentArgs = {
  id: string
  displayName?: string
  description?: string
  location?: 'project' | 'config'
}

const ID_RE = /^[a-z0-9_-]{2,30}$/

export function listAgents(): Array<{ id: string; location: string; dir: string; description?: string }> {
  const out: Array<{ id: string; location: string; dir: string; description?: string }> = []
  const roots: Array<{ loc: string; base: string }> = [
    { loc: 'project', base: join(PROJECT_ROOT, 'agents') },
    { loc: 'config', base: join(HOWL_CONFIG_DIR, 'agents') },
  ]
  for (const { loc, base } of roots) {
    if (!existsSync(base)) continue
    for (const name of readdirSync(base)) {
      if (name.startsWith('_') || name.startsWith('.')) continue
      const dir = join(base, name)
      const yaml = join(dir, 'agent.yaml')
      if (!existsSync(yaml)) continue
      const body = readFileSync(yaml, 'utf8')
      const descMatch = /^description:\s*"?(.*?)"?\s*$/m.exec(body)
      out.push({ id: name, location: loc, dir, description: descMatch?.[1] })
    }
  }
  return out
}

export function createAgent(args: CreateAgentArgs): { dir: string } {
  if (!ID_RE.test(args.id)) {
    throw new Error(`agent id must match ${ID_RE}: got "${args.id}"`)
  }
  const location = args.location ?? 'project'
  const base = location === 'project' ? join(PROJECT_ROOT, 'agents') : join(HOWL_CONFIG_DIR, 'agents')
  const dir = join(base, args.id)
  if (existsSync(dir)) throw new Error(`agent already exists: ${dir}`)
  mkdirSync(dir, { recursive: true })

  const displayName = args.displayName ?? args.id
  const description = args.description ?? 'Specialist agent.'

  const claudeTemplate = readFileSync(join(TEMPLATE_DIR, 'CLAUDE.md'), 'utf8')
  const yamlTemplate = readFileSync(join(TEMPLATE_DIR, 'agent.yaml'), 'utf8')

  writeFileSync(
    join(dir, 'CLAUDE.md'),
    claudeTemplate
      .replace(/{{id}}/g, args.id)
      .replace(/{{displayName}}/g, displayName)
      .replace(/{{description}}/g, description)
  )
  writeFileSync(
    join(dir, 'agent.yaml'),
    yamlTemplate
      .replace(/{{id}}/g, args.id)
      .replace(/{{displayName}}/g, displayName)
      .replace(/{{description}}/g, description)
  )

  logger.info({ id: args.id, dir }, 'agent created')
  return { dir }
}