from git import Repo
from git.exc import GitError
import hashlib
from SCons.Script import *

Import('env')

def _clone(env: Environment, repo_name: str, remote_url: str):
    repo_dir = os.path.join(env['CLONE_DIR'], 'git', repo_name, '_bare')
    try:
        repo = Repo(repo_dir)
        origin = repo.remotes['origin']
    except GitError:
        print(f'Initializing git repository at {repo_dir}.')
        repo = Repo.init(repo_dir, bare=True)
        origin = repo.create_remote('origin', remote_url)
    return repo, origin

def _git_branch(env: Environment, repo_name: str, remote_url: str, git_ref: str = 'main') -> dict:
    repo, origin = _clone(env, repo_name, remote_url)
    worktree_dir = os.path.join(env['CLONE_DIR'], 'git', repo_name, hashlib.shake_128(git_ref.encode('utf-8')).hexdigest(6)) # TODO: commit hash would be better, right? -> not if it's a branch!
    if not os.path.exists(worktree_dir):
        print(f'Checking out into {worktree_dir}.')
        origin.fetch(tags=True)
        os.makedirs(worktree_dir)
        repo.git.worktree('add', worktree_dir, git_ref)
    elif env['UPDATE_REPOSITORIES']:
        worktree_repo = Repo(worktree_dir)
        if not worktree_repo.head.is_detached:
            print(f'Updating git repository at {worktree_dir}')
            worktree_origin = worktree_repo.remotes['origin']
            worktree_origin.pull()
        else:
            print(f'Not updating git repository {worktree_dir} as it is not on a branch.')
    return {
        'checkout_root': worktree_dir
    }

def _git_tags(env: Environment, repo_name: str, remote_url: str, force_fetch: bool = False) -> 'list[str]':
    repo, origin = _clone(env, repo_name, remote_url)
    if force_fetch or env['UPDATE_REPOSITORIES']:
        origin.fetch(tags=True)
    return [t.name for t in repo.tags]

def _make_callable(val):
    if callable(val):
        return val
    else:
        return lambda env: val

def _git_recipe(env: Environment, globals: dict, repo_name, repo_url, cook_fn, versions = None, tag_pattern = None, tag_fn = None, ref_fn = None, dependencies: dict = {}) -> None:
    _repo_name = _make_callable(repo_name)
    _repo_url = _make_callable(repo_url)
    _tag_pattern = _make_callable(tag_pattern)
    versions_cb = versions and _make_callable(versions)

    def _versions(env: Environment, update: bool = False, options: dict = {}):
        if 'ref' in options:
            return [(0, 0, 0)] # no versions if compiling from a branch
        pattern = _tag_pattern(env)
        if pattern:
            tags = env.GitTags(repo_name = _repo_name(env), remote_url = _repo_url(env), force_fetch=update)
            result = []
            for tag in tags:
                match = pattern.match(tag)
                if match:
                    result.append(tuple(int(part) for part in match.groups() if part is not None))
            if len(result) == 0 and not update:
                return _versions(env, update=True)
            return result
        elif versions_cb:
            return versions_cb(env)
        else:
            return [(0, 0, 0)]

    def _dependencies(env: Environment, version) -> 'dict':
        return dependencies

    def _cook(env: Environment, version, options: dict = {}) -> dict:
        if 'ref' in options:
            git_ref = options['ref']
        elif tag_fn:
            git_ref = f'refs/tags/{tag_fn(version)}'
        else:
            assert ref_fn
            git_ref = ref_fn(env, version)
        repo = env.GitBranch(repo_name = _repo_name(env), remote_url = _repo_url(env), git_ref = git_ref)
        return cook_fn(env, repo)

    globals['versions'] = _versions
    globals['dependencies'] = _dependencies
    globals['cook'] = _cook

env.AddMethod(_git_branch, 'GitBranch')
env.AddMethod(_git_tags, 'GitTags')
env.AddMethod(_git_recipe, 'GitRecipe')
Return('env')