import * as fs from 'fs'
import * as path from 'path'

import { AGENTS_SKILLS_DIR, CLAUDE_SKILLS_DIR } from './skills-common'
import {
  AGENTS_SKILLS_GITIGNORE,
  buildAgentsSkillsGitignore,
  buildClaudeSkillsGitignore,
  CLAUDE_SKILLS_GITIGNORE,
  listSkillNames,
  writeFileIfChanged
} from './skills-common'

/**
 * Ensures `.claude/skills/<skillName>` is a symlink pointing to
 * `../../.agents/skills/<skillName>` (relative to `.claude/skills/`).
 */
function ensureClaudeSkillSymlink(skillName: string): boolean {
  const agentsSkillDir = path.join(AGENTS_SKILLS_DIR, skillName)
  const claudeSkillDir = path.join(CLAUDE_SKILLS_DIR, skillName)
  const expectedTarget = path.join('..', '..', '.agents', 'skills', skillName)

  if (!fs.existsSync(agentsSkillDir)) {
    throw new Error(`.agents/skills/${skillName} is missing`)
  }

  let existing: fs.Stats | null = null
  try {
    existing = fs.lstatSync(claudeSkillDir)
  } catch (error) {
    const nodeError = error as NodeJS.ErrnoException
    if (nodeError.code !== 'ENOENT') {
      throw error
    }
  }

  if (existing !== null) {
    if (existing.isSymbolicLink()) {
      const currentTarget = fs.readlinkSync(claudeSkillDir)
      if (currentTarget === expectedTarget) {
        return false
      }
    }
    fs.rmSync(claudeSkillDir, { force: true, recursive: true })
  }

  fs.symlinkSync(expectedTarget, claudeSkillDir)
  return true
}

/**
 * Synchronizes skill infrastructure for all public skills:
 * - regenerates whitelist gitignore files
 * - syncs Claude-side SKILL.md files
 */
function main() {
  let skillNames: string[]
  try {
    skillNames = listSkillNames()
  } catch (error) {
    const message = error instanceof Error ? error.message : String(error)
    console.error(`skills:sync failed: ${message}`)
    process.exit(1)
  }

  const agentsGitignore = buildAgentsSkillsGitignore(skillNames)
  const claudeGitignore = buildClaudeSkillsGitignore(skillNames)

  const changedFiles: string[] = []
  const changedSkillFiles: string[] = []

  if (writeFileIfChanged(AGENTS_SKILLS_GITIGNORE, agentsGitignore)) {
    changedFiles.push('.agents/skills/.gitignore')
  }
  if (writeFileIfChanged(CLAUDE_SKILLS_GITIGNORE, claudeGitignore)) {
    changedFiles.push('.claude/skills/.gitignore')
  }
  for (const skillName of skillNames) {
    if (ensureClaudeSkillSymlink(skillName)) {
      changedSkillFiles.push(`.claude/skills/${skillName}`)
    }
  }

  if (changedFiles.length === 0 && changedSkillFiles.length === 0) {
    console.log(`skills:sync up-to-date (${skillNames.length} public skill${skillNames.length === 1 ? '' : 's'})`)
    return
  }

  const updatedCount = changedFiles.length + changedSkillFiles.length
  console.log(`skills:sync updated ${updatedCount} file${updatedCount === 1 ? '' : 's'}:`)
  for (const file of changedFiles) {
    console.log(`- ${file}`)
  }
  for (const file of changedSkillFiles) {
    console.log(`- ${file}`)
  }
}

main()