export interface RepoStatus {
  branch: string
  /** Number of commits ahead of upstream (undefined if no upstream) */
  ahead?: number
  /** Number of commits behind upstream (undefined if no upstream) */
  behind?: number
  /** True when there are uncommitted changes */
  dirty: boolean
}

/**
 * Parses `git status --short --branch` output into a RepoStatus.
 *
 * First line format:  ## main...origin/main [ahead N, behind M]
 * Remaining lines:    XY path  (presence means dirty)
 */
export function parseGitStatus(output: string): RepoStatus {
  const lines = output.trim().split('\n').filter(Boolean)

  let branch = 'unknown'
  let ahead: number | undefined
  let behind: number | undefined
  let dirty = false

  for (const line of lines) {
    if (line.startsWith('## ')) {
      const rest = line.slice(3)
      // "No commits yet on main" or "HEAD (no branch)"
      const trackMatch = rest.match(/^([^.]+)\.\.\.(\S+)/)
      if (trackMatch) {
        branch = trackMatch[1]
      } else {
        branch = rest.split(' ')[0]
      }
      const aheadMatch = rest.match(/ahead (\d+)/)
      const behindMatch = rest.match(/behind (\d+)/)
      if (aheadMatch) ahead = parseInt(aheadMatch[1], 10)
      if (behindMatch) behind = parseInt(behindMatch[1], 10)
    } else {
      // Any non-header line means there are changes
      dirty = true
    }
  }

  return { branch, ahead, behind, dirty }
}