"""What a folder needs to be before Paperclip can give a task its own worktree.

A worktree is a git feature: Paperclip makes a directory and a branch per task
from the project's repository. A folder that is not a repository cannot have
one, and a repository with no commit has no branch to cut from. Both cases are
checked here, and neither is repaired without being asked.
"""

import os
import subprocess


def git(folder, *args, timeout=60):
    return subprocess.run(["git", "-C", folder] + list(args),
                          capture_output=True, text=True, timeout=timeout)


def is_repo(folder):
    if not os.path.isdir(folder):
        return False
    return git(folder, "rev-parse", "--is-inside-work-tree").stdout.strip() == "true"


def has_commit(folder):
    return git(folder, "rev-parse", "--verify", "HEAD").returncode == 0


def branch(folder):
    """The branch to cut task branches from: what is checked out, else main, else master."""
    out = git(folder, "symbolic-ref", "--short", "HEAD").stdout.strip()
    if out:
        return out
    for name in ("main", "master"):
        if git(folder, "rev-parse", "--verify", name).returncode == 0:
            return name
    return "main"


def untracked_and_modified(folder):
    out = git(folder, "status", "--porcelain").stdout.splitlines()
    return len([ln for ln in out if ln.strip()])


def has_ignored(folder):
    return os.path.isfile(os.path.join(folder, ".gitignore"))


def make_repo(folder, quiet=False):
    """git init, add everything, and one commit. Returns (ok, message)."""
    say = (lambda *_: None) if quiet else print
    steps = [
        ("init", ["init", "-b", "main"]),
    ]
    for label, args in steps:
        r = git(folder, *args)
        if r.returncode != 0:
            return False, "git %s failed: %s" % (label, (r.stderr or r.stdout).strip()[:200])
    if git(folder, "add", "-A").returncode != 0:
        return False, "git add failed"
    r = git(folder, "-c", "user.name=Paperclip Harness",
            "-c", "user.email=harness@localhost",
            "commit", "-q", "-m", "Initial commit, before any Paperclip task")
    if r.returncode != 0:
        detail = (r.stderr or r.stdout).strip()
        if "nothing to commit" in detail:
            return False, "the folder has no files to commit"
        return False, "git commit failed: %s" % detail[:200]
    say("  made a repository on branch %s, one commit" % branch(folder))
    return True, ""


STARTER = """# Paperclip puts each task's worktree inside this folder, at .paperclip/.
# It is a checkout of this repository, so it must never be committed.
.paperclip/

# Add your own patterns below, one per line. For example:
# evidence/
# .env
# *secret*
"""


def ensure_ignore(folder):
    """Make sure .gitignore exists and that it excludes .paperclip/.

    Returns (changed, note). The .paperclip entry is not a preference: without
    it the first commit takes the worktrees with it.
    """
    path = os.path.join(folder, ".gitignore")
    if not os.path.exists(path):
        with open(path, "w") as fh:
            fh.write(STARTER)
        return True, "wrote .gitignore, ignoring .paperclip/"
    with open(path) as fh:
        text = fh.read()
    for line in text.splitlines():
        line = line.strip().strip("/")
        if line == ".paperclip" or line.startswith(".paperclip/"):
            return False, ".gitignore already ignores .paperclip/"
    add = "" if text.endswith("\n") or not text else "\n"
    add += "\n# Paperclip's task worktrees; a commit must never take them.\n.paperclip/\n"
    with open(path, "a") as fh:
        fh.write(add)
    return True, "added .paperclip/ to the existing .gitignore"


def stage_all(folder):
    r = git(folder, "add", "-A")
    return r.returncode == 0


def commit_all(folder, message="Initial commit, before any Paperclip task"):
    """Commit what is staged. Returns (ok, message)."""
    r = git(folder, "-c", "user.name=Paperclip Harness",
            "-c", "user.email=harness@localhost",
            "commit", "-q", "-m", message)
    if r.returncode != 0:
        detail = (r.stderr or r.stdout).strip()
        if "nothing to commit" in detail:
            return False, "nothing to commit: the folder has no files git will take"
        return False, "git commit failed: %s" % detail[:200]
    return True, ""