import * as git from "../git.ts"
import * as vm from "../vm.ts"
import { spinner } from "../spinner.ts"
import { die } from "../fmt.ts"
import { requireSession } from "./helpers.ts"

export async function action(branch: string) {
  const { session } = await requireSession(branch)
  const worktree = session.worktree

  if (await git.isDirty(worktree)) {
    die(`Branch "${branch}" has unsaved changes. Run "sandlot save ${branch}" first.`)
  }

  const main = await git.mainBranch(worktree)

  if (!await git.hasNewCommits(worktree)) {
    die(`Branch "${branch}" has no commits beyond ${main}.`)
  }

  const base = await git.mergeBase(main, "HEAD", worktree)
  const originalHead = await git.headRef(worktree)

  const spin = spinner("Squashing", branch)

  try {
    await git.resetSoft(base, worktree)

    spin.text = "Starting container"
    await vm.ensure((msg) => { spin.text = msg })

    spin.text = "Generating commit message"
    const diff = await git.diffStaged(worktree)

    if (!diff.trim()) {
      await git.resetSoft(originalHead, worktree)
      spin.fail("No changes after squash")
      return
    }

    const gen = await vm.claudePipe(
      diff,
      "Write a commit message summarizing all changes. Subject line: imperative mood, max 72 characters, no period. Add a blank line then a concise body with the key changes as bullet points. Output only the raw commit message, no quotes or markdown.",
    )

    const msg = (gen.exitCode === 0 && gen.stdout.trim()) || `squash ${branch}`
    await git.commit(msg, worktree)

    spin.succeed(`Squashed ${branch} into a single commit`)
  } catch (err) {
    const restored = await git.resetSoft(originalHead, worktree).then(() => true).catch(() => false)
    const message = err instanceof Error ? err.message : String(err)
    spin.fail(restored
      ? `Squash failed, changes restored: ${message}`
      : `Squash failed and rollback failed — check "git reflog" in the worktree: ${message}`)
    process.exit(1)
  }
}