/**
 * Git worktree management for external agent dispatch.
 *
 * Each dispatched task gets its own git worktree so the external agent
 * can modify files freely without touching the main working tree.
 * After the agent completes, we diff the worktree against HEAD and
 * queue the diff into pending_changes.
 */
import { sshExec } from './ssh.js';

const WORKTREE_BASE = '/tmp/booworktrees';

/**
 * Create a git worktree for a task on the host.
 * Returns the absolute path to the worktree directory.
 */
export async function createWorktree(
  projectPath: string,
  taskId: string,
  opts?: { signal?: AbortSignal },
): Promise<string> {
  const worktreePath = `${WORKTREE_BASE}/${taskId}`;
  const branchName = `task-${taskId}`;

  // Ensure the base directory exists
  await sshExec(`mkdir -p ${WORKTREE_BASE}`, { signal: opts?.signal });

  // Create the worktree with a new branch from HEAD
  const result = await sshExec(
    `git -C ${shellEscape(projectPath)} worktree add ${shellEscape(worktreePath)} -b ${shellEscape(branchName)} HEAD`,
    { signal: opts?.signal, timeoutMs: 30_000 },
  );

  if (result.exitCode !== 0) {
    throw new Error(`Failed to create worktree: ${result.stderr.trim() || result.stdout.trim()}`);
  }

  return worktreePath;
}

/**
 * Get the unified diff of changes made in the worktree vs the parent branch (HEAD).
 * Returns an empty string if there are no changes.
 */
export async function diffWorktree(
  worktreePath: string,
  projectPath: string,
  opts?: { signal?: AbortSignal },
): Promise<string> {
  // First, commit any uncommitted changes in the worktree so we can diff branches
  // Stage all changes
  const addResult = await sshExec(
    `cd ${shellEscape(worktreePath)} && git add -A`,
    { signal: opts?.signal, timeoutMs: 30_000 },
  );
  if (addResult.exitCode !== 0) {
    throw new Error(`Failed to stage worktree changes: ${addResult.stderr.trim()}`);
  }

  // Check if there are staged changes
  const statusResult = await sshExec(
    `cd ${shellEscape(worktreePath)} && git diff --cached --quiet`,
    { signal: opts?.signal, timeoutMs: 10_000 },
  );

  if (statusResult.exitCode === 0) {
    // No changes
    return '';
  }

  // Commit staged changes (needed to produce a clean branch diff)
  await sshExec(
    `cd ${shellEscape(worktreePath)} && git -c user.email=boocoder@local -c user.name=BooCoder commit -m "task changes" --allow-empty`,
    { signal: opts?.signal, timeoutMs: 15_000 },
  );

  // Diff the worktree branch against the parent commit (HEAD of main tree)
  const diffResult = await sshExec(
    `git -C ${shellEscape(projectPath)} diff HEAD...$(git -C ${shellEscape(worktreePath)} rev-parse HEAD)`,
    { signal: opts?.signal, timeoutMs: 60_000 },
  );

  if (diffResult.exitCode !== 0) {
    throw new Error(`Failed to diff worktree: ${diffResult.stderr.trim()}`);
  }

  return diffResult.stdout;
}

/**
 * Remove a worktree and its associated branch.
 * Best-effort — does not throw on failure (task may have already been cleaned up).
 */
export async function cleanupWorktree(
  projectPath: string,
  taskId: string,
): Promise<void> {
  const worktreePath = `${WORKTREE_BASE}/${taskId}`;
  const branchName = `task-${taskId}`;

  // Remove the worktree (--force handles dirty state)
  await sshExec(
    `git -C ${shellEscape(projectPath)} worktree remove ${shellEscape(worktreePath)} --force`,
    { timeoutMs: 15_000 },
  ).catch(() => {});

  // Delete the task branch
  await sshExec(
    `git -C ${shellEscape(projectPath)} branch -D ${shellEscape(branchName)}`,
    { timeoutMs: 10_000 },
  ).catch(() => {});
}

/** Minimal shell escape for paths (single-quote wrapping). */
function shellEscape(s: string): string {
  // Replace single quotes with escaped version, wrap in single quotes
  return "'" + s.replace(/'/g, "'\\''") + "'";
}